NANOGEL NETWORKS AND BIOLOGICAL AGENT COMPOSITION THEREOF

Abstract: Copolymer networks having at least one cross-linked polyamine polymer fragment and at least one nonionic water-soluble polymer fragment, and compositions thereof, having at least one suitable biological agent.

Description: NANOGEL NETWORKS AND BIOLOGICAL AGENT COMPOSITION THEREOF Field of the Invention This invention is in the area of combinatorial drug delivery, or combinatorial formulation. Background of the Invention The conventional design of new drugs can be extremely difficult. For a new drug to be effective, it must be precisely matched to its molecular target. Moreover, once such a molecule is discovered, the new drug candidate must be soluble, bioavailable, nontoxic, and resistant to metabolic enzymes. Modifications to such a new molecule, necessary to satisfy these requirements, often have an adverse effect on the drug's therapeutic efficacy. Because of these complexities, conventional drug design can be a very costly, time- consuming process. Recent advances in combinatorial chemistry technology have provided improved throughput in the design of new molecules. These developments markedly reduce the time and cost necessary in designing a desired molecule. However, the problem of making such molecules soluble, bioavailable, resistant to metabolic enzymes, and capable of penetrating through membranes often remains unsolved. The drug delivery industry has addressed some of these problems by incorporating drugs in carriers. In the case of drug delivery assisted products, the time of development is shortened to approximately seven years, and the average cost is significantly decreased. Unfortunately, many drug delivery systems still have several serious limitations in view of the problems discussed above. Summary of the Invention This invention relates to combinatorial drug delivery, or combinatorial formulation. The invention reduces the time and cost required for creating desired drug compounds, which are not only immediately ready for clinical trial, but also possess a number of important characteristics increasing the probability of the ultimate success. In contrast to combinatorial chemistry, however, the invention does not discover new drug structures per se or alter the desirable drug characteristics, but instead provides optimal compositions of a desired drug solving the drug's problems relating to solubility, bioavailability, resistance to metabolic enzymes, toxicity, membrane transport, and site specific delivery. Using a biological agent molecule as a starting point, the invention identifies new composition with characteristics sought for the optimal performance of the selected molecule. Detailed Description of the Invention The invention thus relates to novel drug delivery and drug release systems that address the above problems. These systems involve new chemical molecules having polymer networks of cross-linked polyamine polymer fragments and nonionic polymer fragments. The dispersed polymer networks combine the properties of both polymer gels and colloidal particles. Polymer networks can be loaded by both low molecular mass and polymer biological agents including small molecules, oligo- and polysaccharides, polypeptides and proteins, polynucleotides such as RNA or DNA, and the like. The invention provides a method of identifying a biological agent composition of choice to create a composition that will render a biological agent soluble, bioavailable, resistant to metabolic enzymes, non-toxic, freely traveling through membranes and into cells, or having desired release characteristics in the body. By using polymer networks which differ in the length and structure of polymer fragments and preparing composition libraries, the invention has the ability to rapidly complex and identify the compositions of biological agents with the desired properties. The invention also relates to biological compositions of having polymer networks and biological agents. Dispersed polymer networks are capable of being transported in the body to a disease site, crossing biological barriers (including the blood-brain barrier and intestinal epithelium), entering cells, crossing cell membranes, and being transported to a target site inside a cell. These polymer network particles can be physically or chemically coupled with arge ng mo ecu es prov ng or s e spec c e very an recogn on n e body. The use of polymer fragments with dual functionality in polymer networks, such as polyamine polymers and nonionic water-soluble or water-swellable polymers, permits great variation in the properties of these systems by varying the lengths and/or chemical structure of the polymer fragments. This design of polymer network carriers provides for tremendous versatility of properties with simple chemical structures and permits optimized drug delivery and drug release for enhanced performance with a variety of drugs and drug delivery applications. Particularly, the longevity of circulation in the blood can be varied, biodistribution in the body can be varied to achieve site-specific drug delivery and release, and the rate of release can be varied from seconds to days and weeks, etc. This versatility of the polymer networks permits selection of drug compositions that are most efficient and safe {i.e., have the best "therapeutic index") for a very broad variety of drugs. This invention also provides for a method of identifying biological agent compositions that can be applied to pharmaceutics and biopharmaceutics diagnostics and imaging, immunology, veterinary, agriculture, and other areas where the properties of biological agents exhibited during interaction with a living organism or cell can be improved through formulation. Biological agents suitable for use in accordance with the invention include agents useful for diagnostics or imaging, or that can act on a cell, organ or organism to create a change in the functioning of the cell, organ or organism. This includes, but is not limited to pharmaceutical agents, genes, vaccines, herbicides and the like. The invention can be used in combination with high throughput screening of actual composition libraries, and can further utilize mathematical concepts, which have been found to be beneficial in combinatorial chemistry. Definitions As used herein, the terms below have the following meaning: Backbone: Used in graft copolymer nomenclature to describe the chain onto which the graft is formed. Biological agent: An agent that is useful for diagnosing or imaging or that can act on a cell, organ or organism, including but not limited to drugs (pharmaceuticals) to create a change in the functioning of the cell, organ or organism. Biological property: Any property of biological agent or biological agent composition that affects the action of this biological agent or biological agent composition during interaction with a biological system. Block copolymer: A combination of two or more chains of constitutionally or configurationally different features linked in a linear fashion. Branched polymer: A combination of two or more chains linked to each other, in which the end of at least one chain is bonded at some point along the other chain. Chain: A polymer molecule formed by covalent linking of monomeric units. Composition library: Plurality of compositions of biological agents with polymer networks. Configuration: Organization of atoms along the polymer chain, which can be interconverted only by the breakage and reformation of primary chemical bonds. Conformation: Arrangements of atoms and substituents of the polymer chain brought about by rotations about single bonds. Conterminous: At both ends or at points along the chain. Conterminous link: A polymer cross-link in which a polymer chain is linked at both ends to the same or constitutionally or configurationally different chain or chains. Copolymer: Polymer that is derived from more than one species of monomer. Cross-link: A structure bonding two or more polymer chains together. Dendrimer: Regularly branched polymer in which branches start from one or more centers. Dispersion: Particulate matter distributed throughout a continuous medium. Drug candidate: A substance with biological activity potentially useful for therapy. Interpenetrating network: An intimate combination of at least two polymer networks at least one of which is synthesized in the immediate presence of the other. Graft copolymer: A combination of two or more chains of constitutionally or configurationally different features, one of which serves as a backbone main chain, and at least one of which is bonded at some points along the backbone and constitutes a side chain. Homopolvmer: Polymer that is derived from one species of monomer. Link: A covalent chemical bond between two atoms, including bond between two monomeric units, or between two polymer chains. Nanogel: A polymer network dispersion with sub- micron particle size. Network: A three-dimensional polymer structure, where all the chains are connected through cross-links. Network basis: plurality of cross-linked polymer networks differing in at least one of the polymer fragment constitutional, configurational or conformational feature. Parent database: Computer database containing information on known polymer networks. Polymer blend: An intimate combination of two or more polymer chains of constitutionally or configurationally different features, which are not bonded to each other. Polymer fragment: A portion of polymer molecule in which the monomeric units have at least one constitutional or configurational feature absent from adjacent portions. Repeating unit: Monomeric unit linked into a polymer chain. Semi-interpenetrating: Used herein to describe an intimate combination of at least one non cross-linked polymer and at least one polymer network at least one of which is synthesized in the immediate presence of the other. Side chain: The grafted chain in a graft copolymer. Star block copolymer: Three or more chains of different constitutional or configurational features linked together at one end through a central moiety. Star polymer: Three or more chains linked together at one end through a central moiety. Surfactant: Surface active agent that is adsorbed at interface. Virtual library: A list of polymer networks potentially useful with the biological agent. In a preffered embodiment, the invention relates to networks of cross- linked polymer fragments wherein the fragments comprise: (a) at least one polycation fragment which is a cationic homopolymer or copolymer comprising at least three cationic amino acids or at least three aminoalkylene monomers, said monomers being selected from the group consisting of at least one of: (/) at least one tertiary amino monomer of the formula: A. and the quaternary salts of said tertiary amino monomer, and (/ ' /) at least one secondary amino monomer of the formula: B. and the acid addition and quaternary salts of said secondary amino monomer, in which: R 1 is hydrogen, alkyl of 2 to 8 carbon atoms, an A monomer, or a B monomer; each of R 2 and R 3 , taken independently of the other, is the same or different straight or branched chain alkanediyl group of the formula: "( Z H 22 ) in which z has a value of from 2 to 8; R 4 is hydrogen satisfying one bond of the depicted geminally bonded carbon atom; and R 5 is hydrogen, alkyl of 2 to 8 carbon atoms, an A monomer, or a B monomer; R 6 is hydrogen, alkyl of 2 to 8 carbon atoms, an A monomer, or a B monomer; R 7 is a straight or branched chain alkanediyl group of the formula: — (C 2 zH n ;2z in which z has a value of from 2 to 8; and R 8 is hydrogen, alkyl of 2 to 8 carbon atoms, an A monomer, or a B monomer; and (b) at least one nonionic homopolymer or copolymer comprising at least three the same or different repeating units containing at least one atom selected from the group consisting of oxygen and nitrogen. The invention provides fine dispersions of the networks with a sub-micron range of particle size ("nanogels"). This invention further provides biological compositions comprising the nanogel networks of cross-linked polymer fragments defined herein ("polymer networks") and a suitable biological agent or agents. The polycation and nonionic polymer fragments independently of each other can be linear polymers, randomly branched polymers, block copolymers, graft copolymers, star polymer, star block copolymer, dendrimers or have other architecture including but not limited to combinations of the above listed structures. The degree of polymerization of the polycation and nonionic polymer fragments is between about 20 and about 100,000. More preferably, the degree of polymerization is between about 30 and about 10,000, still more preferably, between about 30 and about 1 ,000. The preferred polycation fragments forming the polymer networks include but are not limited to polyamines (e.g., spermine, polyspermine, polyethyleneimine, polypropyleneimine, polybutileneimine, polypentyleneimine, polyhexyleneimine and copolymers thereof), copolymers of tertiary amines and secondary amines, partially or completely quatemized amines, polyvinyl pyridine and the quaternary ammonium salts of said polycation fragments. These preferred polycation fragments also include aliphatic, heterocyclic or aromatic ionenes (Rembaum et al. Polymer letters, 1968, 6; 159; Tsutsui, T., Development in ionic polymers-2, Wilson A.D. and Prosser, H.J. (eds.) Applied Science Publishers, London, new York, vol. 2, pp. 167-187, 1986). Particularly preferred polycation fragments comprise a plurality of cationic repeating units of formula -N-R 0 , wherein R° is a straight chain aliphatic group of 2 to 6 carbon atoms, which may be substituted. Each -NHR°- repeating unit in an polycation fragment can be the same or different from another -NHR°- repeating unit in the fragment. The polycation fragments in the polymer networks of the invention can be branched. For example, polyspermine-based copolymers are branched. The cationic fragment of these copolymers was synthesized by condensation of 1 ,4-dibromobutane and N-(3-aminopropyl)-1 ,3- propanediamine. This reaction yields highly branched polymer products with primary, secondary, and tertiary amines. An example of branched polycations are products of the condensation reactions between polyamines containing at least 2 nitrogen atoms and alkyl halides containing at least 2 halide atoms (including bromide or chloride). In particular, the branched polycations are produced as a result of polycondensation. An example of this reaction is the reaction between N-(3-aminiopropyl)-1 ,3-propanediamine and 1 ,4- dibromobutane, producing polyspermine. Another example of a branched polycation is polyethyleneimine represented by the formula: (NHCH 2 CH 2 ) x [N(CH 2 CH 2 )CH 2 CH 2 ] y Additionally, dendrimers, for example, polyamidoamines or poiypropyleneimines of various generations (Tomalia et al. Angew. Chem., Int. Ed. Engl. 29:138 (1990)) can be also used as polycation fragments in the current invention. The polycation fragments have several positively ionizable groups and a net positive charge at physiologic pH. Preferably, the polycation fragments will have at least about 3 positive charges at physiologic pH, more preferably, at 25 least about 6, still more preferably, at least about 12. Also preferred are polymers or fragments that, at physiologic pH, can present positive charges with about a distances between the charges of about 2 A to about 1θA. The distances established by ethtyleneimine, aminopropylene, aminobutylene, aminopentylene and aminohehhylene repeating units, or by mixtures of at least two of the group including ethyleneimine, aminopropylene, aminobutilene, aminopentylene and aminohexylene repeating units are most preferred. Accordingly, for instance, polycationic fragments that utilize a (NCH 2 CH 2 ), (NCH 2 CH 2 CH 2 ), (NCH 2 CH 2 CH 2 CH 2 ), (NCH 2 CH 2 CH 2 CH 2 CH 2 ), and (NCH 2 CH 2 CH 2 CH 2 CH 2 CH 2 ) repeating unit, or a mixture of at least two of the group including (NCH 2 CH 2 ), (NCH 2 CH 2 CH 2 ), (NCH 2 CH 2 CH 2 CH 2 ), (NCH 2 CH 2 CH 2 CH 2 CH 2 ), and (NCH 2 CH 2 CH 2 CH 2 CH 2 CH 2 ) repeating units, are preferred. Polycation fragments comprising a -N-R 0 - repeating unit are also preferred. R° is preferably an ethylene, propylene, butylene, pentylene, or hexylene which can be modified. In a preferred embodiment, in at least one of the repeating units, R° includes a DNA intercalating group such as an ethidium bromide group. Such intercalating groups can increase the affinity of the polymer for nucleic acid. Preferred substitutions on R° include alkyl of 1-6 carbons, hydroxy, hydroxyalkyl, wherein the alkyl has 1-6 carbon atoms, alkoxy having 1-6 carbon atoms, an alkyl carbonyl group having 2-7 carbon atoms, alkoxycarbonyl wherein the alkoxy has 1-6 carbon atoms, alkoxycarbonylalkyl wherein the alkoxy and alkyl each independently has 1-6 carbon atoms, alkylcarboxyalkyl wherein each alkyl group has 1-6 carbon atoms, aminoalkyl wherein the alkyl group has 1-6 carbon atoms, alkylamino or dialkylamino where each alkyl group independently has 1-6 carbon atoms, mono- or di- alkylaminoalkyl wherein each alkyl independently has 1-6 carbon atoms, chloro, chloroalkyl wherein the alkyl has from 1-6 carbon atoms, fluoro, fluoroalkyl wherein the alkyl has from 1-6 carbon atoms, cyano, or cyano alkyl wherein the alkyl has from 1-6 carbon atoms or a carboxyl group. More preferably, R° is ethylene, propylene or butylene. It is preferred that nonionic polymer fragments comprise water-soluble polymers, which are nontoxic and nonimmunogenic. The preferred nonionic polymer fragment is a polyethylene oxide, a copolymer of ethylene oxide and propylene oxide, a polysaccharide, a polyacrylamide, a polygycerol, a polyvinylalcohol, a polyvinyl-pyrrolidone, a polyvinylpyridine N-oxide, a copolymer of vinylpyridine N-oxide and vinylpyridine, a polyoxazoline, or a polyacroylmorpholine or the derivatives thereof. The following nonionic polymer fragments are particularly preferred: a block copolymer of or in which each of m and j has a value of from 3 to about 50,000,000. In one preferred embodiment of the present invention the nonionic polymer fragments are the block copolymers of ethylene oxide and propylene oxide having the formulas: HO- H 2 O- -CH 2 CH 2 O-f-H x (I) OO CH, CH, HO- CHCH 2 O- -CH 2 CH 2 O- -CHCH 2 O- Η y (III) or, R 1 R , 1 p2 r r H[OCH 2 CH 2 ].- [OCHCH]. [CHCHO].- [CH 2 CH 2 0] j H \ H[OCH 2 CH 2 ] - [O [CH 2 CH 2 0] . H (IV) H H (IV-A) in which x, y, z, i and j have values from about 2 to about 800, preferably from about 5 to about 200, more preferably from about 5 to about 80, and wherein for each R 1 , R 2 pair, one is hydrogen and the other is a methyl group. Formulas (I) through (III) are oversimplified in that, in practice, the orientation of the isopropylene radicals within the B block will be random. This random orientation is indicated in formula (IV), which is more complete. Such poly(oxyethylene)-poly(oxypropylene) compounds have been described by Santon, Am. Perfumer Cosmet. 72(4):54-58 (1958); Schmolka, Loc. cit. 82(7):25 (1967); Schick, Non-ionic Surfactants, pp. 300-371 (Dekker, NY, 1967). A number of such compounds are commercially available under such generic trade names as "poloxamers", "pluronics" and "synperonics." Pluronic polymers within the B-A-B formula are often referred to as "reversed" pluronics, "pluronic R" or "meroxapol". The "polyoxamine" polymer of formula (IV) is available from BASF (Wyandotte, Ml) under the tradename Tetronic™. The order of the polyoxyethylene and polyoxypropylene blocks represented in formula (XVII) can be reversed, creating Tetronic R™, also available from BASF. See, Schmolka, J. Am. Oil Soc, 59:110 (1979). Polyoxypropylene- polyoxyethylene block copolymers can also be designed with hydrophilic blocks comprising a random mix of ethylene oxide and propylene oxide repeating units. To maintain the hydrophilic character of the block, ethylene oxide will predominate. Similarly, the hydrophobic block can be a mixture of ethylene oxide and propylene oxide repeating units. Such block copolymers are available from BASF under the tradename Pluradot™. The diamine-linked pluronic of formula (IV) can also be a member of the family of diamine-linked polyoxyethylene-polyoxypropylene polymers of formula: (V) wherein the dashed lines represent symmetrical copies of the polyether * extending off the second nitrogen, R is an alkylene of 2 to 6 carbons, a - cycloalkylene of 5 to 8 carbons or phenylene, for R 1 and R 2 , either (a) both are hydrogen or (b) one is hydrogen and the other is methyl, for R 3 and R 4 either (a) both are hydrogen or (b) one is hydrogen and the other is methyl, if both of R 3 and R 4 are hydrogen, then one R 5 and R 6 is hydrogen and the other is methyl, and if one of R 3 and R 4 is methyl, then both of R 5 and R 6 are hydrogen. Those of ordinary skill in the art will recognize, in light of the discussion herein, that even when the practice of the invention is confined for example, to poly(oxyethylene)-poly(oxypropylene) compounds, the above exemplary formulas are too confining. Thus, the units making up the first block need not consist solely of ethylene oxide. Similarly, not all of the second type block need consist solely of propylene oxide units. Instead, the blocks can incorporate monomers other than those defined in formulas (I) - (V), so long as the parameters of this first embodiment are maintained. Thus, in the simplest of examples, at least one of the monomers in hydrophilic block might be substituted with a side chain group as previously described. The term "link" used herein means covalent bond between two atoms, including bond between two monomeric units, or between two polymer chains. The term "cross-link" used herein means a structure bonding two or more polymer chains together. The polymer network of the current invention can be produced by covalent linkage of one polymer fragment to at least two other polymer fragments having the same or different structure. The linkage of the polymer fragments in the networks can be conterminous, i.e., polymer cross¬ link in which a polymer chain is linked at both ends to the same or constitutionally or configurationally different chain or chains. The conterminous polymer networks can be produced by covalently cross-linking the polycation fragments by nonionic fragments or pendant groups or vise versa cross-linking the nonionic fragments by the polycation fragments. For example, the polymer networks can be synthesized by reacting polyoxyethylene having reactive groups at two ends with primary amino groups of polyethyleneimine. Another example is covalent attachment of polyspermine to polyvinylalcohol chains having activated pendant hydroxyl groups. The network can also be obtained by cross-linking the pendant groups of polymer fragments. For example, linking the pendant amino groups of polylysine to the pendant hydroxyl groups of polyvinylalcohol can produce such network. The networks can also combine conterminous and non-conterminous linkage. Such network can be produced, for example, by linking primary and secondary amino groups of polyethyleneimine and polyvinylalcohol. Without wishing to limit this invention to a particulate theory it is believed that the polymer networks of the current invention can also be interpenetrating or semi-interpenetrating and can non- covalently trap polymers and other molecules present during their synthesis. Those of ordinary skill in the art will recognize, in light of the discussion herein, that numerous types of polymer network architecture described in literature can be used in the current invention. See, for example, Sperling, Introduction to Physical Polymer Science, 2d Edition. Johen Wiley, New York, 1992. Polymer gels can be synthesized by co-polymerization of the monomers that form the polycation and nonionic polymer fragments or polymerization of the monomer that forms one polymer fragment in the presence of another fragment. Numerous examples of such synthesis are available in the literature. For example, polymerizing epoxides with polyalkylenepolyamines produced polymer beads, see U.S. Patent No. 4,189,539. Cationic microgel dispersions were produced by cross-linking polyepoxide-amine reaction products with polyepoxide cross-linking agent, see U.S. Patent No. 5,096,556. Carboxylic acid containing microgel particles were prepared by polymerizing in aqueous emulsion a monomer mixture containing carboxylic acid monomers and vinyl monomers, see U.S. Patent No. 4,560,714. Another approach to synthesizing polymer network involves cross-linking of pre-formed polymer fragments. For example, cross-linked polymer gels or films were prepared by cross-linking homopolymers and copolymers of acrylamide, N-substituted acrylamine or N-substituted methacrylamide with polyamines or polyols. See U.S. Patent No. 5,280,078. Linking can be accomplished by a number of reactions, many of which have been described generally in conjugate chemistry, in particular, for synthesizing block and graft copolymers, and various polymer conjugates. See, for example, Seymour et al. In Self-Assembling Complexes for Gene Delivery. From Laboratory to Clinical Trial, Kabanov et al. (eds.), John Wiley, Chichester (1998); U.S. Patent Nos. 5,593,658, 5,567,410, and 5,656,611. These reactions can involve, for example, a terminal or pendant hydroxyl group on one polymer fragment, e.g. R 5 -O-(C 2 H 4 O)-H, in which R 5 is hydrogen or a blocking group such as alkyl, and an appropriate group on another polymer fragment, the two being joined directly or indirectly; i.e., through a third component. Alternatively a terminal or pendant group can be converted to some other functional group, as for example amino, which then is allowed to react with either with the next polymer fragment or another linking component. The linking group thus may be formed either by reactively involving a terminal or pendant group of a polymer fragment or by replacing the terminal or pendant group. For example, a carboxylic acid group can be activated as with N,N'- dicyclohexylcarbodiimide and then allowed to react with an amino or hydroxy group to form an amide or ether respectively. Anhydrides and acid chlorides will produce the same links with amines and alcohols. Alcohols can be activated by carbonyldiimidazole and then linked to amines to produce urethane linkages or activated to produce ethers or esters. Alkyl halides can be converted to amines or allowed to react with an amine, diamines, alcohols, or diol. A terminal or pendant hydroxy group can be oxidized to form the corre- sponding aldehyde or ketone. This aldehyde or ketone then is allowed to react with a precursor carrying a terminal or pendant amino group to form an imine which, in turn, is reduced, as with sodium borohydrate to form the secondary amine. See Kabanov et al., J. Contr. Release, 22:141 (1992); Meth. Enzymol. XLVII, Hirs & Timasheff, Eds., Acad. Press, 1977. The linkage thereby formed is the group -NH-, replacing the terminal or pendant hydroxyl group of the polymer fragment. Alternatively, a terminal or pendant hydroxyl group on the polymer can be allowed to react with bromoacetyl chloride to form a bromoacetyl ester which in turn is allowed to react with an amine precursor to form the -NH-CH 2 -C(O)- linkage. Immobilized Enzymes, Berezin et al. (eds.), MGU, Moscow, 1976, i.e., -NH-CH 2 -C(0)-. The bromoacetyl ester of a polymer fragment also can be allowed to react with a diaminoalkane of the formula NH 2 -C Q H 2c? -NH 2 which in turn is allowed to react with an carboxy group on another polymer fragment, or an activated derivative thereof such as an acid chloride or anhydride. The bromoacetyl ester also can be allowed to react with a cyanide salt to form a cyano intermediate. See e.g., Sekiguchi et al., J. Biochem., 85, 75 (1979); Tuengler et al., Biochem. Biophys. Ada, 484, 1 (1977); Browne et al. BBRC, 67, 126 (1975); and Hunter et al., JACS 84, 3491 (1962). This cyano intermediate then can be converted to an imido ester, for instance by treatment with a solution of methanol and hydrogen chloride, which is allowed to reacted with a amine precursor to form a -NH-C(NH 2 + )CH 2 C(0)- linkage. A terminal or pendant hydroxyl group also can be allowed to react with 1 , 1 '-carbonyl-jb/s- imidazole and this intermediate in turn allowed to react with an amino precursor to form a -NH-C(O)0- linkage. See Bartling er a/., Nature 243, 342 (1973). A terminal or pendant hydroxyl also can be allowed to react with a cyclic anhydride such as succinic anhydride to yield a half-ester which, in turn, is allowed to react with a precursor having terminal or pendant amino group using conventional condensation techniques for forming peptide bonds such as dicyclohexylcarbodiimide, diphenylchlorophosphonate, or 2-chloro-4,6- dimethoxy-1 ,3,5-triazine. See e.g., Means et al., Chemical Modification of Proteins, Holden-Day (1971). Thus formed is the -NHC(0)(CH 2 ) (7 C(0)0- linkage. A terminal or pendant hydroxyl group also can be allowed to react with 1 ,4- butanediol diglycidyl ether to form an intermediate having a terminal or pendant epoxide function linked to the polymer through an ether bond. The terminal or pendant epoxide function, in turn, is allowed to react with an amino precursor. Pitha et al., Eur. J. Biochem., 94:11 (1979); Elling and Kula, Biotech. Appl. Biochem., 13:354 (1991); Stark and Holmberg, Biotech. Bioeng., 34:942 (1989). Halogenation of a terminal or pendant hydroxyl group permits subsequent reaction with an alkanediamine such as 1 ,6-hexanediamine. The resulting product then is allowed to react with carbon disulfide in the presence of potassium hydroxide, followed by the addition of proprionyl chloride to generate a isothiocyanate which in turn is allowed to react with an amino precursor to yield a -N-C(S)-N-(CH 2 ) 6 -NH- linkage. See Means et al., Chemical Modification of Proteins, Holden-Day (1971). The polymer chain terminating in an amino group also can be treated with phosgene and then another polymer fragment containing amino group to form an urea linkage. See Means et al., Chemical Modification of Proteins, Holden-Day (1971). The polymer fragment terminating in an amino group also can be treated with dimethyl ester of an alkane dicarboxylic acid and the product allowed to react with an amino precursor to produce a -N-C(NH 2 + )-(CH 2 ) 4 -C(NH 2 + )-N- linkage. See Lowe et al., Affinity Chromatography, Wiley & Sons (1974). The polymer fragment terminating in an amino group also can be allowed to react with an alkanoic acid or fluorinated alkanoic acid, preferably an activated derivative thereof such as an acid chloride or anhydride, to form a linking group -CONH-. Alternatively an amino precursor can be treated with an α,ω- diisocyanoalkane to produce a -NC(0)NH(CH 2 ) 6 NHC(0)-N- linkage. See Means et al. Chemical Modification of Proteins, Holden-Day (1971). Some linking groups thus can simply involve a simple functional group while others may comprise a spacer unit such as a polymethylene chain between two func¬ tional groups. When the linking group comprises such a polymethylene chain, it can have as few as two methylene units but preferably contains more; e.g., six or more methylene units. The above descriptions exemplify typical strategies for the formation of linkages between the fragments of the polymer networks of the current invention. These procedures parallel those, which are known to form conjugates of biologically active agents and other agents, including the general conjugation met ods described by Means et al., Chemical Modification of Proteins, Holden-Day (1971); Glazer et al., Chemical Modification of Proteins, Elsevier, New York (1975J; Immunotechnology Catalog & Handbook, Pierce Chemical Co.; and Polyethylene Glycol Derivatives Catalog, Shearwater Polymers, Inc. (1994). It also will be appreciated that linkages which are not symmetrical, such as -CONH- or - NHCOO-, can be present in the reverse orientation; e.g., -NHCO- and -OCONH-, respectively. The size of the polymer networks is one major parameter determining their usefulness in biological compositions. After administration in the body large particles are eliminated by the reticuloendothelial system and cannot be easily transported to the disease site (see, for example, Kabanov et al., J. Contr. Release, 22, 141 (1992); Volkheimer. Pathologe 14: 247 (1993); Kwon and Kataoka, Adv. Drug. Del. Rev. 16:295 (1995). Also, the transport of large particles in the cell and intracellular delivery is limited or insignificant. See, e.g., Labhasetwar et al. Adv. Drug Del. Res. 24:63 (1997). It was demonstrated that aggregated cationic species with a size from 500 nm to over 1 μm are ineffective in cell transfection, see Kabanov et al., Self-Assembling Complexes for Gene Delivery. From Laboratory to Clinical Trial, Kabanov et al. (eds.), John Wiley, Chichester (1998) and references cited. Large particles, particularly, those positively charged exhibit high toxicity in the body, in part due to adverse effects on liver and embolism. See e.g., Volkheimer. Pathologe 14:247 (1993); Khopade et al Pharmazie 51 :558 (1996); Yamashita et al., Vet. Hum. Toxicol., 39:71 (1997). Nanogel polymer networks are nontoxic, can enter into small capillaries in the body, transport in the body to a disease site, cross biological barriers (including but not limited to the blood-brain barrier and intestinal epithelium), absorb into cell endocytic vesicles, cross cell membranes and transport to the target site inside the cell. The particles in that size range are believed to be more efficiently transferred across the arterial wall compared to larger size microparticles, see Labhasetwar et al., Adv. Drug Del. Res. 24:63 (1997). Without wishing to be bound by any particular theory it is also believed that because of high surface to volume ratio, the small size is essential for successful targeting of such particles using targeting molecules. Further, it is also believed the nanogel size ranges are preferred for the optimal performance of the polymer networks in the combinatorial formulations. The preferred range of the size of nanogel networks is from about 20 nm to about 600 nm, more preferred from about 50 nm to about 250 nm, still more preferred from about 70 nm to about 150 nm. While not wishing to be bound by any specific theory, it is further believed that nanogel particles shall have these sizes in a swollen state in aqueous solutions. The preferred range of size of the nanogel networks of the current invention is much less that that of the previously described dispersed and water-swollen cationic microgels and beads can be produced. See, for example, U.S. Patent Nos. 4,189,539 and 5,096,556. It is also believed that maintaining the particle size distribution in the preferred range and thorough purification from larger particles is essential for the efficiency and safety of the nanogel networks. It is recognized that useful properties of the nanogel networks are determined solely by their size and structure and are independent of the method used for their preparation. Therefore, this invention is not limited to a certain synthesis or purification procedures, but rather encompasses new and novel chemical entities useful in biological agent compositions. Those of ordinary skill in the art will recognize, in light of the discussion herein, that even when the practice of the invention is confined, for example, to certain nanogel networks there are numerous methods of particle preparation and dispersion that will yield the nanogel networks with the desired characteristics. Thus any method resulting in nanogel species with the desired characteristics is suitable for preparation of the polymer networks and biological agent compositions thereof. Many such useful methods can be found in nanotechnologies and nanoparticle chemistry. See, for example, Hrkach et al. Biomaterials, 18:27 (1997). Nanoparticles and nanospheres can be synthesized in aqueous and non-aqueous emulsions under the appropriate conditions and then separated by size exclusion chromatography, membrane filtration, ultracentrifugation or similar technique. See, for example, Bertling, et al., Appl. Biochem., 13, 390 (1991); Lukowski et al., Int. J. Pharm., 84, 23 (1992); Pirker er a/., Int. J. Pharm., 128, 189 (1996); Peracchia, et al. J. Contr. Re/., 46, 223 (1997); Zobel et al. Antisense Nucl. Acid Drug Dev. 7, 483 (1997); Ferdous, et al. J. Contr. Rel. 50, 71 (1998); and literature cited. The "water-in- oil" and "oil-in-water" microemulsions as well as normal and reverse surfactant micelles have proven to be particularly useful for preparation of particles with the preferred size distribution. See, for example, Abakumova, et al., Dokl. Acad. Nauk SSSR, 283, 136 (1985); Khmelnitsky, et al., Eur. J. Biochem., 210, 751 (1992). Methods of nanoparticle preparation include but are not limited to emulsification-solvent evaporation technique, multiple emulsion solvent evaporation technique, phase inversion, coacervation, salting out, spray drying, emulsion and micro-emulsion polymerization, and the like. See Labhasetwar, In Self-Assembling Complexes for Gene Delivery. From Laboratory to Clinical Trial, Kabanov et al. (eds.), John Wiley, Chichester (1998). By varying conditions of reaction, including the type and dispersity of the media, addition of surfactants, temperature, and ratio of reagents the size of the particles can be controlled. Various nanoparticles were proposed recently as versatile carriers for pharmaceutical agents. See, e.g., Sharma et al. Oncology Research 8, 281 (1996); Zobel et al. Antisense Nucl. Acid Drug Dev. 7, 483 (1997); de Verdiere et al. Br. J. Cancer 76, 198 (1997); Hussein et al. Pharm. Res. 14, 613 (1997); Alyautdin et al. Pharm. Res. 14, 325 (1997); Hrkach et al. Biomaterials, 18, 27 (1997); Torchilin, J. Microencapsulation 15, 1 (1988); Labhasetwar, Self- Assembling Complexes for Gene Delivery. From Laboratory to Clinical Trial, Kabanov et al. (eds.), John Wiley, Chichester (1998); and literature cited. The nanoparticle chemistries provide for a wide spectrum of rigid polymer structures, which are suitable for the encapsulation of drugs, drug delivery and controlled release. Some major problems of these carriers include aggregation, low drug loading capacity and restricted control of the drug release kinetics. Due to their unique architecture, nanogel polymer networks combine properties of cross-linked polymer gels and dispersed colloidal particles. They are porous materials that can be loaded with a variety of biological agents, including small molecules and polymers, at a very high biological agent to polymer network ratio. The immobilization of the biological agents in the nanogel networks proceed in the whole volume of the network rather on its surface and under certain conditions can be accompanied by the micro- collapse of the network providing for additional masking and protection of the biological agent. Nanogel networks of the current invention are soluble and do not aggregate after complete neutralization of the polycation charges. The loading capacity of nanogel networks can be as high as several grams or several dozen grams per one gram of the polymer network. This is much higher compared to the loading capacity achieved with nanoparticles. See, Labhasetwar et al. Adv. Drug Del. Res. 24:63 (1997). In contrast to conventional drug delivery particles such as nanoparticles (which usually have to be prepared in the presence of the biological agent) the polymer network is loaded with the biological agent after this network its synthesized. This greatly simplifies the preparation and use of the biological agent composition of this invention and permits using same batches of nanogel network with many different biological agents and compositions. The combination of the polycation and nonionic fragments including hydrophobic-hydrophilic block copolymers enables formulating the nanogel networks with a broader range of biological agents compared to most other particulate drug delivery and controlled release systems. Also, combination of polycation and nonionic polymer fragments in the polymer networks of the current invention provides for much greater versatility and property range compared to conventional drug delivery systems. The possibility to change the structure and porosity of nanogel networks by changing the polymer fragment structure is unprecedented for any particulate delivery system. Also, due to the small size the polymeric species can be transported in the body to a disease site, cross biological barriers including but not limited to the blood-brain barrier and intestinal epithelium, enter cells, cross cell membranes and be transported to the target site inside cell. It is further believed that the combination of the useful properties of nanogel network is unique and unmatched by other delivery systems in this size range. It will in some circumstances be desirable to incorporate in the nanogel networks of the current invention, by noncovalent association or covalent conjugation, targeting molecules. See for example, Kabanov et al., J. Controlled Release, 22:141 (1992), the contents of which are hereby incorporated by reference. The term "targeting molecule" refers to any molecule, atom, or ion linked to the polymer networks of the current invention that enhance binding, transport, accumulation, residence time, bioavailability or modify biological activity of the polymer networks or biologically active compositions of the current invention in the body or cell. The targeting molecule will frequently comprise an antibody, fragment of antibody or chimeric antibody molecules typically with specificity for a certain cell surface antigen. It could also be, for instance, a hormone having a specific interaction with a cell surface receptor, or a drug having a cell surface receptor. For example, glycolipids could serve to target a polysaccharide receptor. It could also be, for instance, enzymes, lectins, and polysaccharides. Low molecular mass ligands, such as folic acid and derivatives thereof are also useful in the context of the current invention. The targeting molecules can also be polynucleotide, polypeptide, peptidomimetic, carbohydrates including polysaccharides, derivatives thereof or other chemical entities obtained by means of combinatorial chemistry and biology. Targeting molecules can be used to facilitate intracellular transport of the particles of the invention, for instance transport to the nucleus, by using, for example, fusogenic peptides as targeting molecules described by Soukchareun et al., Bioconjugate Chem., 6, 43, (1995) or Arar et al., Bioconjugate Chem., 6, 43 (1995), caryotypic peptides, or other biospecific groups providing site-directed transport into a cell (in particular, exit from endosomic compartments into cytoplasm, or delivery to the nucleus). Included within the scope of the invention are compositions comprising the polymer networks of the current invention and a suitable targeting molecule. The targeting molecule can be covalently linked to any of the polymer fragments of the polymer networks identified herein, including cationic and nonionic polymer fragments. For instance, the targeting molecule can be linked to the free-terminal or pendant groups of the nonionic fragments of the particles of the invention. Such targeting molecules can be linked to the terminal or pendant -OH end group of the polymer fragments, and the terminal or pendant -NH 2 group of the polymers, or the terminal or pendant -COOH end group of the polymers or the like. It will in some circumstances be desirable to incorporate targeting molecules through ligand-receptor construct, in which (/) the ligand molecule is any chemical entity (e.g., molecule, atom or ion) capable of specific binding with the receptor molecule, (/ ' /) the receptor molecule is any chemical capable of specific binding to the ligand molecule, (///) the ligand or receptor molecules or both the ligand and receptor molecules are incorporated in the polymer networks of the current invention or targeting molecules or both polymer networks and targeting molecules, by noncovalent association or covalent conjugation, so that after mixing targeting molecules and polymeric species with ligand and receptor molecules attached to them or adding either free ligand or receptor or both ligand and receptor to the mixture of targeting molecules and polymer networks, the targeting molecule become attached to the polymer networks ad a result of binding between the ligand and receptor. Useful examples of such construct are the constructs using biotin as the ligand and avidin or streptavidin as the receptor. For example, biotin or the derivative thereof can be covalently linked to the polymer networks of the current invention and avidin (or streptavidin) can be covalently linked to the targeting molecule. Alternatively, biotin can be linked to both the polymer networks and targeting molecule and the latter can be linked through avidin, which has four biotin-binding centers. Additionally, more complex constructs comprising biotin and avidin can be used for incorporating targeting molecules in polymer networks of the current invention. In a preferred embodiment, the invention provides for the polymer networks with biotin molecules or derivatives thereof linked to at least one polycation or nonionic polymer fragment of both polycation and nonionic polymer fragments. Those of ordinary skill in the art will recognize, in light of the discussion herein, that even when the practice of the invention is confined for example, to biotin- avidin or biotin-streptavidin constructs or the similar constructs, there are numerous ways available providing for the design of the ligand-receptor constructs with the desired characteristics pursuant to this invention. Such constructs, for example, can comprise ligands and/or receptors that are polynucleotide, polypeptide, peptidomimetic, carbohydrates including polysaccharides, derivatives thereof or other chemical entities obtained by means of combinatorial chemistry and biology. The targeting molecules that can be associated with the polymer networks of the current invention can also have a targeting group having affinity for a cellular site and a hydrophobic group. Such targeting molecules can provide for the site specific delivery and recognition in the body. The targeting molecule will spontaneously associate with the particles and be "anchored" thereto through the hydrophobic group. These targeting adducts will typically comprise about 1% or less of the polymers in a final composition. In the targeting molecule, the hydrophobic group can be, among other things, a lipid group such as a fatty acyl group. Alternately, it can be an ionic or nonionic homopolymer, copolymer, block copolymer, graft copolymer, dendrimer or other natural or synthetic polymer. The use of the polymer fragments with dual nonionic and cationic functionality in polymer networks of the current invention permits varying of the properties of these systems by changing the lengths and/or chemical structure of these polymer fragments within a very broad range. This design of polymer networks allows for tremendous versatility of properties with simple chemical structures and permits optimization of drug delivery and drug release systems for enhanced performance with a variety of drugs and drug delivery situations. Particularly, the longevity of circulation in blood can be varied from very long circulating network dispersions to dispersions rapidly accumulating in organs. Biodistribution can be varied to achieve site-specific drug delivery and release, and the rate or release can be varied from seconds to days and weeks, etc. The versatility of these polymer networks permits selecting biological agent compositions that are most efficient and safe {i.e., have best "therapeutic index") for a very broad variety of biological agents. Therefore, this invention also provides for a method of identifying biological agent compositions that can be useful in pharmaceutics and biopharmaceutics, diagnostics and imaging, immunology, veterinary, agriculture, and other areas where the properties of biological agents exhibited during interaction with a living organism or cell can be improved by formulation. Due to the complex relationship between the biological properties and biological agent compositions, the current methods for discovery and optimization of a useful biological agent composition is often time-consuming and requires numerous trials. In one embodiment, therefore, the invention provides for a rational combinatorial method for identifying a useful biological agent composition by determining which copolymer of the basis possesses the desired properties with a certain biological agent. The present invention thus relates to a method of identifying a biological agent composition of choice comprising: (a) preparing a plurality of polymer networks, said networks differing in at least one of the polymer fragment constitutional, configurational or conformational feature; (b) preparing compositions of polymer networks with a biological agent; (c) testing at least some said compositions of said polymer networks with a biological agent for biological properties using at least one of the following: a cell model, animal, plant or other biological model; measurement of a chemical or physical property in a test tube; or a theoretical model, and (d) identifying said compositions with desired biological properties. The terms "preparing a plurality of polymer networks" and "preparing compositions of polymer networks" are used in the broad sense to include design of theoretical models for computational analysis. This includes mixing of the biological agent and the carrier under specific conditions of solvent composition, concentration, pH, temperature and the like as well as creation of a parent database of polymer networks and databases on biological agents alone, including but not limited to chemical structure and biological properties. The invention does not require that all or any polymer networks are synthesized, or that all or any of biological agent compositions are actually formulated. The plurality of polymer networks can be constructed "on paper" and then tested in a computer database. Similarly, the compositions of the polymer networks with biological agents can be presented as a database. Such databases can contain information on the structure of polymer networks, constitution, architecture and properties of the polymer fragments, properties of biological agent compositions, including physicochemical properties, biological activity, mechanism of action, disease target, initial screening results, and known or expected problems to their use. The term "biological property" as used herein means any property of biological agent or biological agent composition that affects the action of this biological agent or biological agent composition during interaction with a biological system. This includes, but is not limited to solubility, stability, mechanical properties, spectral properties, binding with plasma proteins, DNA, RNA, specific receptors, enzymes or other molecules, resistance to metabolic enzymes, chemical stability, toxicity, membrane transport, transport into, out, within and across target cells, tissues or organs, bioavailability, pharmacokinetics, site specific delivery, specific enzymatic activities, activation or suppression of gene expression, total DNA, RNA and protein biosynthesis, cell proliferation and differentiation, apoptosis, hormone and polypeptide secretion; bioavailability, pharmacokineticts, pharmacodynamics, efficacy, toxicity, therapeutic index and the like. The term "testing" (of the compositions) as used herein refers to evaluation of the useful properties of the compositions. Testing can be done using a variety of computational methods, so that part of or all process of the identification can be carried out or simulated virtually {i.e., by computer). Typically testing of the compositions involves evaluation of the biological property of the compositions using a screening assay. The plurality of polymer networks of the current invention is termed the "network basis." The plurality of compositions of these polymer networks with a biological agent is termed the "composition library." The ability of the polymer networks of the invention to capture and release biological agents, interact with various systems of cell and organism affecting biological properties or otherwise interact modifying the biological response with respect to a certain biological agent depends on the lengths (number of repeating units) of the polycation and nonionic fragments, their structure, and conformation. The invention proposes that within a basis of the polymer networks there will be at least one chemical entity that will form with a certain biological agent a composition with desired biological properties. Screening Assays and Composition Identification. The screening assays of this invention are analytical tests, useful in characterizing and selecting biological agent compositions by sorting them for "positive" and "negative" compositions according to the initially defined criteria. Normally, one or more screening assays are required to identify a preferable biological agent composition. Depending upon the task, varieties of in vitro cell-free and cell-based, as well as in vivo screening assays can be used to select preferred biological agent compositions. This includes physico-chemical tests such as the characterization of solubility, stability, size, rheology, mechanics, spectral properties, release kinetics, binding with plasma proteins, DNA, RNA, specific receptors, enzymes or other molecules, chemical stability, transport-related tests such as analyses of transport into, out of, within, and through target cells, tissues or organs, functional tests such as analyses of specific enzymatic activities, activation or suppression of gene expression, total DNA, RNA and protein biosynthesis, cell proliferation and differentiation assays, apoptosis analysis, hormone and polypeptide secretion assays; in vivo pharmacological tests, such as pharmaco-kineticts, bioavailability, pharmacodynamics of biological agent, its efficacy, toxicity and therapeutic index. Since composition libraries are screened in accordance with the invention, high-throughput and ultra-high-throughput screening assays are preferred. Depending upon the specific properties of the biological agent and obstacles to biological agent use, various combinations of the screening assays can be applied to identify a biological agent composition. Many biological agents have limited solubility in aqueous solutions. Therefore, they often cannot be administered at required doses in the body without specifically selected and optimized delivery systems for improving biological agent solubility. In one embodiment, composition libraries are generated and screened to improve biological agent solubility in aqueous solutions. In the related screening system, solubility of the biological agent alone is determined and compared to that of a biological agent formulated with the selected carriers. A variety of methods can be used to determine the biological agent solubility including but not limiting light absorption, fluorescent, spectrophotometry, circular dichroism, calorimetry, NMR, ESR, chromatography; mass spectrometry and the like. One of the most common problems related to the limited performance of biological agents is their insufficient stability, which is often related to their high sensitivity to metabolic enzymes. Such enzymes include proteases, nucleases, redox enzymes, transferases, etc. In one preferred embodiment, composition libraries are generated and screened to protect biological agent from degradation by metabolic enzymes. The screening can include treatment of the biological agent with isolated enzymes, their combinations or enzymatic complexes existing in isolated fractions of cells or tissues, followed by analysis of the native biological agent level in the analyzed sample. The screening can also be based on the biological agent administration in a whole organism followed by sampling and analysis of the native biological agent level in the sample, or by continuous monitoring of the native biological agent level in the body. Verity of methods could be used for detection of the native biological agent level including but not limiting HPLC, LC-MS, GC-MS, radioisotope methods, NMR, various bioassays, etc. Another common obstacle that limits biological agent effectiveness is insufficient circulation time in the body due to clearance of the biological agent by the reticuloendothelial system. According to the present invention, the composition libraries can be prepared and screened to reduce the biological agent clearance. The screening methods can be based upon direct measurement of the biological agent binding with serum proteins such as albumin, low density and ultralow density lipopolyproteins, and the like. Also, these screening methods can use the analysis of the biological agent phagocytosis by isolated cell populations such as macrophages, polymorphonulear cells, etc. The screening can also be based on biological agent administration in a whole organism followed by sampling and analysis of the native biological agent level in the sample, or by continuos monitoring of the native biological agent level in the body. Combinations of the above procedures can also be used. Reduced efficacy of the biological agent is also often caused by its low bioavailability. For example, most polypeptides and proteins, polynucleotides, as well as many low molecular weight pharmaceutical drugs are not effective when administered orally. An important factor that limits oral bioavailability of the above pharmaceutical agents is their reduced adsorption through small intestinal epithelial tissue. According to the present invention, the composition libraries of such biological agents can be prepared and screened to increase biological agent oral bioavailability. The screening methods include, but are not limited to the measurement of the biological agent transport across polarized epithelial cell monolayers, for example, Caco-2 or Caco-4 cell monolayers. Another bioavailability-related problem is low efficacy of central nervous system agents, which caused by limited transport of the agents across brain microvessel endothelial tissue that is also known as blood brain barrier (BBB). Composition libraries can be generated and screened for compositions that increase biological agent transport across BBB. The screening methods for this assay can be based on the measurement of the biological agent transport across polarized endothelial cell monolayers, such as primary bovine brain microvessel endothelial cells (BBMEC), human primary and immortalized brain microvessel endothelial cells, etc. The bioavailability screening procedures also include administration of the biological agent in a whole organism followed by sampling and analysis of the native biological agent level in the sample, or by continuos monitoring of the native biological agent level in the body. Combinations of the above procedures can also be used. Depending on the nature of the biological agent, the efficacy of its transport can be measured by various methods including but not limited to fluorescence, absorption or other spectroscopy, radioisotope methods, various bio- or immunoassays, etc. Biological activity of many biological agents is often significantly reduced due to insufficient efficacy of the biological agent transport through the cell membrane. To resolve this problem, composition libraries can be generated and screened for compositions that can improve biological agent transmembraneous properties. Verity of screening methods can be used to evaluate the efficacy of biological agent transport through the membrane. These methods include but not limited by those based on analysis of the biological agent transport across artificial membranes such as lipid bilayers and liposomes, analysis of the biological agent uptake in cells including, cell lines, primary cell cultures, bacterial strains and isolates, etc. Depending on the biological agent nature, the efficacy of its transport can be measured by various methods including but not limited fluorescent, absorption or other spectroscopy, radioisotope methods, various bio- or immunoassays, etc. The libraries of biological agent composition can be also screened using direct measurement of the biological agent biological activity. Depending on the biological agent properties, verity of screening methods can be used to analyze biological agent biological effect. For example, for many anticancer agents apoptosis assays, such as TONEL staining; proliferation assays, such as thymidine DNA incorporation rate analysis, MTT, XTT and colony formation assays can be used to evaluate efficacy of the selected compositions. Cell adhesion based methods could be used for evaluation of immune modulating compositions. Depending on the nature of the biological agent, more specific screening methods could be used to evaluate efficacy of the biological agent compositions including but not limiting analyses of activity of specific enzymes that are known to be direct or indirect targets for particular biological agent; analysis of signal transduction events (such as tyrosine phosphorylation, association or dissociation of SH2 and/or SH3 signaling proteins, changes in second messenger levels, etc.) that are involved in the biological agent mechanism of action; analyses of specific gene expression (by using hybridization, RT-PCR and/or protein expression assays) that known to involved in the biological agent mechanism of action. In general, any assay that relates to biological activity, transport, pharmacokinetics, stability or other useful property of a biological agent and composition thereof can be used to screen composition libraries for the best performing composition with pre-selected biological agent. The screening and identification of the biological agent compositions pursuant this invention can use a virtual library. Without wishing to be limited to any particular computational analysis, the use of the virtual library is exemplified as follows. The starting information for identifying the desired biological agent composition includes (i) the drug structure, (ii) the database of available polymer fragments for synthesis of polymer networks, and (iii) accumulated data on polymer networks, if available. The starting data also includes the selection of desirable biological properties, which identify the preferred biological agent composition for the given biological agent. New polymer networks are virtually assembled by combining structures of polymer fragments stored in computer database. The combination is subjected to the rules of the bond formation as if a new compound is synthesized as a result of a chemical reaction yielding a polymer network of a specific molecular architecture. A plurality of virtually designed network is a virtual network base. The physicochemical and biological properties of each network of this base is then predicted in relation to its specific constitutional, configurational, or conformational features using the properties of separate polymer fragments and or model polymer networks that were actually synthesized and characterized in the experiment. The properties of the isolated polymer fragments include but are not limited to chemical structures of the repeating units, lengths, QSAR parameters derived from the structures, physicochemical and biological parameters available from experiments or derived from experimental data. Exemplary properties of polymer fragments include molecular weight, volume, surface, hydrophobicity, hydration energy, partitioning coefficients, ionization degree, etc. The prediction of the polymer network property can be based on any known or expected relationship between the properties of the polymer fragments and the polymer network property. Without wishing to be limited to a particulate theory, it is believed that interpolation or extrapolation of any previously accumulated data on properties of polymer networks gives the predicted values. At this stage, the data on the experimentally determined biological properties of the compositions of the biological agent, for example, drug candidate, and actually synthesized model polymer networks are used in the computerized analysis. The predicted properties of the polymer networks and their compositions with biological agents are then compared to the desired values, and the score of fit is calculated. Finally, the virtual polymer networks from the base are classified according their score, and the best compositions are identified. Without wishing to be limited by a particular theory, it is believed that possible elements in the identification of the biological agent composition with desired properties include but are not limited to parent databases comprising a large variety of chemical templates, exploratory virtual library of carriers, computational analysis predicting chemical and physical properties of biological agent compositions, validated polymer network chemistries (including solid- phase and solution-phase chemistries) and high throughput screening. The results of screening are analyzed to determine the compositions with the desired properties. The analysis includes review and classification of the data obtained from testing composition using high throughput screening or otherwise to drawing conclusions from the classified data. Analysis identifies the compositions with desired biological properties answering to a set of criteria questions including but not limited to the following: (/) is any of composition good enough to be a final product {ii) do the data from testing support creation of new library for new testing cycle, and the like. The computational analysis includes the use of computer program, which analyzes structures of new polymer networks in the virtual library, predicts their interaction with the drug candidate and selects the most promising compositions. Biological agents The polymer networks and compositions of this invention are useful in pharmaceutics and biopharmaceutics, diagnostics and imaging, immunology, veterinary, agriculture, and other areas where the properties of biological agents exhibited during interaction with a living organism or cell can be improved by formulation. The biological agent of this invention is an agent that is useful for diagnostics or imaging or that can act on a cell, organ or organism to create a change in the functioning of the cell, organ or organism, including but not limited to pharmaceutical drugs, immunoadjuvants, vaccines genes, herbicides and the like. Such biological agents are represented by wide variety of agents that are used in diagnostics, therapy, immunization or otherwise are applied to combat human and animal disease. Such agents include but are not limited to nucleic acids, polynucleotides, antibacterial agents, antiviral agents, antifungal agents, antiparasitic agents, tumoricidal or anti-cancer agents, proteins, toxins, enzymes, hormones, neurotransmitters, glycoproteins, immunoglobulins, immunomodulators, dyes, radiolabels, radio- opaque compounds, fluorescent compounds, polysaccharides, cell receptor binding molecules, anti-inflammatories, anti-glaucomic agents, mydriatic compounds and local anesthetics. Special classes of biological agents that can be used in this invention include pharmaceutical drugs. Many drugs are rapidly cleared from the body or are degraded by the body's defense mechanisms. These problems, plus toxic side effects, seriously limit drug efficacy by reducing time available to the drug to reach its target and by limiting the amount of drug which can safely be given to the patient. In addition many drugs do not readily penetrate tissues or effectively seek out and concentrate in appropriate cells to maximize their therapeutic effect. The use of the biological agent compositions pursuant to this invention permits to significantly improve therapeutic drugs by decreasing in their side effects, and increase in therapeutic action. The biological agents with which the present compositions can be used include but are not limited to non-steroidal anti-inflammatories such as indomethacin, salicylic acid acetate, ibuprofen, sulindac, piroxicam, and naproxen, antiglaucomic agents such as timolol or pilocarpine, neurotransmit- ters such as acetylcholine, anesthetics such as dibucaine, neuroleptics such as the phenothiazines (for example compazine, thorazine, promazine, chlorpromazine, acepromazine, aminopromazine, perazine, prochlorperazine, trifluoperazine, and thioproperazine), rauwolfia alkaloids (for example, resperine and deserpine), thioxanthenes (for example chlorprothixene and tiotixene), butyrophenones (for example haloperidol, moperone, trifluoperidol, timiperone, and droperidol), diphenylbutylpiperidines (for example pimozde), and benzamides (for example sulpiride and tiapride); tranquilizers such as glycerol derivatives (for example mephenesin and methocarbamol), propanediols (for example meprobamate), diphenylmethane derivatives (for example orphenadrine, benzotrapine, and hydroxyzine), and benzodiazepines (for example chlordiazepoxide and diazepam); hypnotics (for example zolpdem and butoctamide); beta-blockers (for example propranolol, acebutonol, metoprolol, and pindolol); antidepressants such as dibenzazepines (for example, imipramine), dibenzocycloheptenes (for example, amtiriptyline), and the tetracyclics (for example, mianserine); MAO inhibitors (for example phenelzine, iproniazid, and selegeline); psychostimulants such as phenylehtylamine derivatives (for example amphetamines, dexamphetamines, fenproporex, phentermine, amfeprramone, and pemoline) and dimethylamino- ethanols (for example clofenciclan, cyprodenate, aminorex, and mazindol); GABA-mimetics (for example, progabide); alkaloids (for example codergocrine, dihydroergocristine, and vincamine); anti-Parkinsonism agents (for example L- dopamine and selegeline); agents utilized in the treatment of Altzheimer's disease, cholinergics (for example citicoline and physostigmine); vasodilators (for example pentoxifyline); and cerebro active agents (for example pyritinol and meclofenoxate). These agents include also DNA topoisomerase inhibitors (including type I and type II), brain and tumor imaging agents, free radical scavenger drugs, anticoagulants, ionotropic drugs, and neuropeptides such as endorphins. The biological agent compositions also can be used advantageously with anti-neoplastic agents such as paclitaxel, daunorubicin, doxorubicin, carminomycin, 4'-epiadriamycin, 4-demethoxy-daunomycin, 11- deoxydaunorubicin, 13-deoxy-daunorubicin, adriamycin-14-benzoate, adriamycin-14-actanoate, adriamycin-14-naphthaleneacetate, vinblastine, vincristine, mitomycin C, N-methyl mitomycin C, bleomycin A 2 , dideazatetrahydrofolic acid, aminopterin, methotrexate, cholchicine and cisplatin, antibacterial agents such as aminoglycosides including gentamicin, antiviral compounds such as rifampicin, 3'-azido-3'-deoxythymidine (AZT), and acylovir; antifungal agents such as azoles including fluconazole, macrolides such as amphotericin B, and candicidin; anti-parastic compounds such as antimonials. These biological agents include without limitation vinca alkaloids, such as vincristine and vinblastine, mitomycin-type antibiotics, such as mitomycin C and N-methyl mitomycin, bleomycin-type antibiotics such as bleomycin A 2 , antifolates such as methotrexate, aminopterin, and dideaza¬ tetrahydrofolic acid, taxanes, anthracycline antibiotics and others. The compositions also can utilize a variety of polypeptides such as antibodies, toxins such as diphtheria toxin, peptide hormones, such as colony stimulating factor, and tumor necrosis factors, neuropeptides, growth hormone, erythropoietin, and thyroid hormone, lipoproteins such as μ-lipoprotein, proteoglycans such as hyaluronic acid, glycoproteins such as gonadotropin hormone, immunomodulators or cytokines such as the interferons or interleukins, hormone receptors such as the estrogen receptor. The compositions also can be used with enzyme inhibiting agents such as reverse transcriptase inhibitors, protease inhibitors, angiotensin converting enzymes, 5μ-reductase, and the like. Typical of these agents are peptide and nonpeptide structures such as finasteride, quinapril, ramipril, lisinopril, saquinavir, ritonavir, indinavir, nelfinavir, zidovudine, zalcitabine, allophenylnorstatine, kynostatin, delaviridine, b/s-tetrahydrofuran ligands (see, for example Ghosh et al., J. Med. Chem. 1996, 39:3278), and didanosine. Such agents can be administered alone or in combination therapy; e.g., a combination therapy utilizing saquinavir, zalcitabine, and didanosine, zalcitabine, and zidovudine. See, for example, Collier et al., Antiviral Res. 1996, 29:99. Included among the suitable biological agents are viral genomes and viruses (including the lipid and protein coat). This accounts for the possibility of using our invention with a variety of viral vectors in gene delivery (e.g. retroviruses, adenoviruses, herpes-virus, Pox-virus) used as complete viruses of their parts. See, for example, Hodgson, Biotechnology, 1995, 13: 222. The suitable biological agents include oxygen transporters (e.g., porphines, porphirines and their complexes with metal ions), coenzymes and vitamins (e.g., NAD/NADH, vitamins B12, chlorophylls), and the like. The suitable biological agents further include the agents used in diagnostics visualization methods, such as magnetic resonance imaging (e.g., gadolinium (III) diethylenetriamine pentaacetic acid), and may be a chelating group (e.g., diethylenetriamine pentaacetic acid, triethylenetriamine pentaacetic acid, ethylenediamine-tetraacetic acid, 1 ,2-diaminocyclo-hexane- N,N,N',N'-tetraaceticacid, N,N'-di(2-hydroxybenzyl) ethylene diamine), N-(2- hydroxyethyl) ethylene diamine triacetic acid and the like). Such biological agent may further include an alpha-, beta-, or gamma-emitting radionuclide (e.g., galliun 67, indium 111 , technetium 99). The suitable biological agents are also iodine containing radiopaque molecules. The biological agent may also be a diagnostic agent, which may include a paramagnetic or superparamagnetic element, or combination of paramagnetic element and radionuclide. The paramagnetic elements include but are not limited to gadolinium (III), dysporsium (III), holmium (III), europium (III) iron (III) or manganese (II). The invention can be also used to identify useful fibrinolitic compositions with enzymes such as streptokinase, urokinase, tissue plasminogen activator or other fibrinolitic enzyme that is effective in dissolving blood clots and reestablishing and maintaining blood flow through trombosed coronary or other blood vessels. Also this invention is used to identify useful compositions for treating burns, circulatory diseases in which there is an acute impairment of circulation, in particular, microcirculation, respiratory distress syndrome, as well as compositions for reducing tissue damage during angioplasty procedures. Further, the compositions identified using this invention including these to treat myocardial damage, ischemic tissue, tissue damaged by reperfusion injury, stroke, sickle cell anemia and hypothermia. These compositions are especially useful for treating vascular obstructions caused by abnormal cells which is an often complication during malaria and leukemia and are suitable as a perfusion medium for transplantation of organs. This invention is also suitable for identifying the compositions of antiinfective compounds, as well as modulators of immune response, and improved adjuvants, antigenes and vaccines. The adjuvants suitable for use in this invention include but are not limited to adjuvants of mineral, bacterial, plant, synthetic or host product origin. The suitable mineral adjuvants include aluminum compounds such as aluminum particles and aluminum hydroxide. The suitable bacterial adjuvants include but are not limited to muramyl dipeptides, lipid A, Bordetella pertussis, Freund's Complete Adjuvant, lipopolysaccharides and its various derivatives, and the like. The suitable adjuvants include without limitation small immunogenes, such as synthetic peptide of malaria, polysaccharides, proteins, bacteria and viruses. The antigenes that can be used in the present invention are compounds which, when introduced into a mammal will result in formation of antibodies. The suitable antigens include but are not limited to natural, recombinant, or synthetic products derived from viruses, bacteria, fungi, parasites and other infectious agents, as well as autoimmune disease, hormones or tumor antigens used in prophylactic or therapeutic vaccines. These antigens include components produced by enzymatic cleavage or can be compounds produced by recombinant DNA technique. Viral antigens include but are not limited to HIV, rotavirus, influenza, foot and mouth disease, herpes simplex, Epstein Barr virus, Chicken pox, pseudorabies, rabies, hepatitis A, hepatitis B, hepatitis C, measles, distemper, Venezuelan equine encephalomyelitis, Rota virus, polyoma tumor virus, Feline leukemia virus, reovirus, respiratory synticial virus, Lassa fever virus, canine parvovirus, bovine pappiloma virus, tick borne encephalitis, rinderpest, human rhinovirus species, enterovirus species, Mengo virus, paramixovirus, avian infectious bronchitis virus. Suitable bacterial antigens include but are not limited to Bordetella pertussis, Brucella abortis, Escherichia coli, salmonella species, salmonella typhi, streptococci, cholera, shigella, pseudomonas, tuberculosis, leprosy and the like. Also suitable antigens include infections such as Rocky mountain spotted fever and thyphus, parasites such as malaria, schystosomes and trypanosomes, and fungus such as Cryptococcus neoformans. The protein and peptide antigens include subunits of recombinant proteins (such as herpes simplex, Epstein Barr virus, hepatitis B, pseudorabies, flavivirus, Denge, yellow fever, Neissera gonorrhoeae, malaria, trypanosome surface antigen, alphavirus, adenovirus and the like), proteins (such as diphteria toxoid, tetanus toxoid, meningococcal outer membrane protein, streptococcal M protein, hepatitis B, influenza hemagglutinin and the like), synthetic peptides (e.g. malaria, influenza, foot and mouth disease virus, hepatitis B, hepatitis C). Suitable polysaccharide and oligosaccharide antigens originate from pneumococcus, haemphilis influenza, neisseria meningitides, Pseudomonas aeruginosa, Klebsiella pneumoniae, pneumococcus. Surfactant-containing compositions The invention also provides compositions comprising polymer network and at least one surfactant. Surfactants are useful for improving solubility of biological agents, changing properties (e.g. particle size, aggregation stability, bioavailability, cell transport) of the polymer networks and compositions of the current invention, improving shelf life and the like. Without wishing to limit this invention to a particulate theory it is believed that surfactants can alter the conformation of the polymer fragments by interacting with them. Such alteration occurs during interaction of the polycation fragments of the polymer networks with anionic surfactants resulting in the collapse of these fragments and condensation of the nanogel particles. For example, the polyoxyethylene-polyethyleneimine networks interact with sodium dodecylsulfate. Another example is interaction of nonionic and ionic amphiphilic surfactants with nonionic fragments, e.g. polyoxyethylene-polyoxypropylene fragments. Also anionic surfactants can interact with nonionic fragments, e.g. alkylsufates interacting with polyoxyethylene. The addition of surfactant to the polymer network containing compositions can be used to vary in a controllable manner the porosity and stability of the network, adjust the size of the nanogel particles, and modify variety of properties of the polymer networks and the biological agent compositions thereof that are relevant to the effects on a living organism or cell. In this respect the surfactants can be used in the context of the embodiment of present invention providing the combinatorial method of identifying a biological agent composition. In this case the polymer networks can be mixed with one or several surfactants at the same or different concentrations to provide the network basis in which the conformation of the polymer fragments differ from each other as a result of the interactions with the said surfactants. The surfactants are defined herein in a most general sense as surface active agents that are adsorbed at interface (see, for example, Martin, Physical Pharmacy, 4 th edn., p. 370 et seq., Lea & Febiger, Philadelphia, London, 1993). These surface active agents in particular decrease the surface tension at the air-water interface in aqueous solutions (see, for example, Martin, Physical Pharmacy, 4 th edn., p. 370 et seq., Lea & Febiger, Philadelphia, London, 1993) and include without limitation micelle forming amphiphiles, soaps, lipids, surface active drugs and other surface active biological agents, and the like (see, for example, Martin, Physical Pharmacy, 4 th edn., Lea & Febiger, Philadelphia, London, 1993; Marcel Dekker, New York, Basel, 1979; Atwood and Florence, J. Pharm. Pharmacol. 1971 , 23:242S; Atwood and Florence, J. Pharm. Sci. 1974, 63:988; Florence and Attwood, Physicochemical Principles of Pharmacy, 2 nd edn., p.180 et seq., Chapman and Hall, New York, 1988; Hunter, Introduction to Modern Colloid Science, p. 12 et seq., Oxford University Press, Oxford, 1993). The surfactant can be (/) cationic (including those used in various transfection cocktails), {ii) nonionic (e.g., Pluronic or Tetronic), {Hi) zwitterionic (including betains and phospholipids), or (/V) anionic (e.g., salts of fatty acids). The cationic surfactants that can be used in the present biological agent compositions include but are not limited to primary amines (e.g., hexylamine, heptylamine, octylamine, decylamine, undecylamine, dodecylamine, pentadecyl amine, hexadecyl amine, oleylamine, stearylamine, diamino- propane, diaminobutane, diaminopentane, diaminohexane, diaminoheptane, diaminooctane, diaminononane, diaminodecane, diaminododecane), seconda¬ ry amines (e.g., N,N-distearylamine), tertiary amines (e.g., N,N',N'- polyoxyethylene(10)-N-tallow-1 ,3-diaminopropane), quaternary amine salts {e.g., dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, alkyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, benzalkonium chloride, cetyldimethylethylammonium bromide, dimethyldioctadecyl ammonium bromide, methylbenzethonium chloride, decamethonium chloride, methyl mixed trialkyl ammonium chloride, methyl trioctylammonium chloride), 1 ,2-diacyl-3-(trimethylammonio)propane (acyl group = dimyristoyl, dipalmitoyl, distearoyl, dioleoyl), 1 ,2-diacyl-3-(dimethy- lammonio)propane (acyl group = dimyristoyl, dipalmitoyl, distearoyl, dioleoyl), 1 ,2-dioleoyl-3-(4'-trimethylammonio) butanoyl-sn-glycerol, 1 ,2-dioleoyl-3- succinyl-sπ-glycerol choline ester, cholesteryl (4'-trimethylammonio) butanoate), N-alkyl pyridinium and quinaldinium salts (e.g., cetylpyridinium halide, N-alkylpiperidinium salts, dialkyldimetylammonium salts, dicationic bolaform electrolytes (C 12 Me 6 ; C 12 Bu 6 ), dialkylglycetylphosphorylcholine, lysolecithin), cholesterol hemisuccinate choline ester, lipopolyamines (e.g., dioctadecylamidoglycylspermine (DOGS), dipalmitoyl phosphatidylethanol- amidospermine (DPPES), N'-octadecylsperminecarboxamide hydroxytrifluoro¬ acetate, N',N"-dioctadecylsperminecarboxamide hydroxytrifluoroacetate, N'- nonafluoropentadecylosperminecarboxamide hydroxytrifluoroacetate, N',N"- dioctyl(sperminecarbonyl)glycinamide hydroxytrifluoroacetate, N'-(heptadeca- fluorodecyl)-N'-(nonafluoropentadecyl)-sperminecarbonyl)glycinamede hydroxytrifluoroacetate, N'-[3,6,9-trioxa-7-(2'-oxaeicos-11 '-enyl)heptaeicos-18- enyl]sperminecarboxamide hydroxytrifluoroacetate, N'-(1 ,2-dioleoyl-sπ-glycero- 3-phosphoethanoyl)spermine carboxamide hydroxytrifluoroacetate) (see, for example, Behr et. al., Proc. Natl. Acad. Sci. 1989, 86:6982; Remy et al., Bioconjugate Chem. 1994, 5:647), 2,3-dio!eyloxy-N-[2(spermine-carboxa- mido)ethyl]-N,N-dimethyl-1-propanaminiumtrifluoroacetate (DOSPA) (see, for example, Ciccarone et al., Focus 1993, 15:80), N I N l ,N ll l N lll -tetramethyl- N,N , l N ll I N l,l -tetrapalmitylspermine (TM-TPS) (Lukow et al., J. Virol. 1993, 67:4566), N-[1-(2,3-dioleyloxy)propyl]-N,N,N-trimethylamonium chloride (DOTMA) (see, for example, Feigner, et al., Proc. Natl. Acad. Sci. USA 1987, 84:7413; Ciccarone et al., Focus 1993, 15:80), dimethyl dioctadecylammonium bromide (DDAB) (see, for example, Whitt et al., Focus 1991, 13:8), 1 ,2- dioleoyl-3-dimethyl-hydroxyethyl ammonium bromide (DORI) (see, for example, Feigner et al., J. Biol. Chem. 1994, 269:2550), 1 ,2-dioleyloxypropyl-3-dimethyl- hydroxyethyl ammonium bromide (DORIE) (see, for example, Feigner et al., J. Biol. Chem. 1994, 269:2550), 1 ,2-dioleyloxypropyl-3-dimethyl-hydroxypropyl ammonium bromide (DORIE-HP) (see, for example, Feigner et al., J. Biol. Chem. 1994, 269:2550), 1 ,2-dioleyloxypropyl-3-dimethyl-hydroxybutyl ammonium bromide (DORIE-HB) (see, for example, Feigner et al., J. Biol. Chem. 1994, 269:2550), 1 ,2-dioleyloxypropyl-3-dimethyl-hydroxypentyl ammonium bromide (DORIE-HPe) (see, for example, Feigner et al., J. Biol. Chem. 1994, 269:2550), 1 ,2-dimyristyloxypropyl-3-dimethyl-hydroxyethyl ammonium bromide (DMRIE) (see, for example, Feigner et al., J. Biol. Chem. 1994, 269:2550), 1 ,2-dipalmitoyloxypropyl-3-dimethyl-hydroxyethyl ammonium bromide (DPRIE) (see, for example, Feigner et al., J. Biol. Chem. 1994, 269:2550), 1 ,2-distearoyloxypropyl-3-dimethyl-hydroxyethyl ammonium bromide (DSRIE) (see, for example, Feigner et al., J. Biol. Chem. 1994, 269:2550), N,N-dimethyl-N-[2-(2-methyl-4-(1 ,1 ,3,3-tetramethylbutyl)-phenoxy]- ethoxy)ethyl]-benzenemethanaminium chloride (DEBDA), N-[1-(2,3- dioleyloxy)propyl]-N,N,N,-trimethylammonium methylsulfate (DOTAB), lipopoly- L(or D)-lysine (see, for example, Zhou, et al., Biochim. Biophys. Acta 1991 , 1065:8), poly(L (or D)-lysine conjugated to N-glutarylphosphatidylethanolamine lysine (see, for example, Zhou, et al., Biochim. Biophys. Acta 1991 , 1065:8), didodecyl glutamate ester with pendant amino group (C 12 GluPhC n N + ) (see, for example, Behr, Bioconjugate Chem. 1994, 5:382), ditetradecyl glutamate ester with pendant amino group (C 14 GluC n N + ) (see, foe example, Behr, Bioconjugate Chem. 1994, 5:382), 9-(N',N"-dioctadecylglycinamido)acridine (see, for example, Remy et al., Bioconjugate Chem. 1994, 5:647), ethyl 4-[[N-[3- bis(octadecylcarbamoyl)-2-oxapropylcarbonyl]glycinamido]pyrrole-2-carbox- amido]-4-pyrrole-2-carboxylate (see, for example, Remy et al., Bioconjugate Chem. 1994, 5:647), N',N'-dioctadecylornithylglycinamide hydroptrifluoroacetate (see, for example, Remy et al., Bioconjugate Chem. 1994, 5:647), cationic derivatives of cholesterol (e.g., cholesteryl-3β-oxysuccin- amidoethylenetrimethylammonium salt, cholesteryl-3β-oxysuccinamido- ethylenedimethylamine, cholesteryl-3β-carboxyamidoethylenetrimethyl- ammonium salt, cholesteryl-3β-carboxyamidoethylenedimethylamine, 3β[N- (N'.N'-dimethylaminoetane-carbomoyl] cholesterol) (see, for example, Singhal and Huang, In Gene Therapeutics, Wolff, Ed., p. 118 et seq., Birkhauser, Boston, 1993), pH-sensitive cationic lipids (e.g., 4-(2,3-bis-palmitoyloxy-propyl)- 1 -methyl-1 H-imidazole, 4-(2,3-bis-oleoyloxy-propyl)-1 -methyl-1 H-imidazole, cholesterol-(3-imidazol-1-yl propyl) carbamate, 2,3-bis-palmitoyl-propyl-pyridin- 4-yl-amine) and the like (see, for example, Budker, et al. Nature Biotechnology 1996, 14:760). Especially useful in the context of gene delivery and other applications are the compositions with the mixtures of cationic surfactant and nonionic surfactants including but not limited to dioloeoyl phosphatidylethanolamine (DOPE), dioleoyl phosphatidylcholine (DOPC) (see, for example, Feigner, et al., Proc. Natl. Acad. Sci. USA 1987; Singhal and Huang, In Gene Therapeutics, Wolff, Ed., p. 118 et seq., Birkhauser, Boston, 1993). This includes, in particular, commercially available cationic lipid compositions including but not limited to LipofectAMINE™, Lipofectine , DMRIE-C, CellFICTIN™, LipofectACE™, Transfectam reagents (see, for example, Ciccarone et al., Focus 1993, 15:80; Lukow et al., J. Virol. 1993, 67:4566; Behr, Bioconjugate Chem. 1994, 5:382; Singhal and Huang, In Gene Therapeutics, Wolff, Ed., p. 118 et seq., Birkhauser, Boston, 1993; GIBCO- BRL Co.; Promega Co., Sigma Co) and other cationic lipid compositions used for transfection of cells (see, for example, Feigner et al., J. Biol. Chem. 1994, 269:2550; Budker, et al. Nature Biotechnology 1996, 14:760). The anionic surfactants that can be used in the present biological agent compositions include but are not limited to alkyl sulfates, alkyl sulfonates, fatty acid soap including salts of saturated and unsaturated fatty acids and derivatives (e.g., arachidonic acid, 5,6-dehydroarachidonic acid, 20- hydroxyarachidonic acid, 20-trifluoro arachidonic acid, docosahexaenoic acid, docosapentaenoic acid, docosatrienoic acid, eicosadienoic acid, 7,7-dimethyl- 5,8-eicosadienoic acid, 7,7-dimethyl-5,8-eicosadienoic acid, 8,11-eicosadiynoic acid, eicosapentaenoic acid, eicosatetraynoic acid, eicosatrienoic acid, eicosatriynoic acid, eladic acid, isolinoleic acid, linoelaidic acid, linoleic acid, linolenic acid, dihomo-γ-linolenic acid, γ-linolenic acid, 17-octadecynoic acid, oleic acid, phytanic acid, stearidonic acid, 2-octenoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, undecelenic acid, lauric acid, myristoleic acid, myristic acid, palmitic acid, palmitoleic acid, heptadecanoic acid, stearic acid, nonanedecanoic acid, heneicosanoic acid, docasanoic acid, tricosanoic acid, tetracosanoic acid, c/s-15-tetracosenoic acid, hexacosanoic acid, heptacosanoic acid, octacosanoic acid, triocantanoic acid), salts of hydroxy-, hydroperoxy-, polyhydroxy-, epoxy- fatty acids (see, for example, Ingram and Brash, Lipids 1988, 23:340; Honn et al., Prostaglandins 1992, 44:413; Yamamoto, Free Radic. Biol. Med. 1991 , 10:149; Fitzpatrick and Murphy, Pharmacol. Rev. 1989, 40:229; Muller et al., Prostaglandins 1989, 38:635; Falgueyret et al., FEBS Lett. 1990, 262:197; Cayman Chemical Co., 1994 Catalog, pp. 78-108), salts of carboxylic acids (e.g., valeric acid, trans- 2,4-pentadienoic acid, hexanoic acid, frat.s-2-hexenoic acid, rat.s-3-hexenoic acid, 2,6-heptadienoic acid, 6-heptenoic acid, heptanoic acid, pimelic acid, suberic acid, sebacicic acid, azelaic acid, undecanedioic acid, decanedicarboxylic acid, undecanedicarboxyiic acid, dodecanedicarboxylic acid, hexadecanedioic acid, docasenedioic acid, tetracosanedioic acid, agaricic acid, aleuritic acid, azafrin, bendazac, benfurodil hemisuccinate, benzylpenicillinic acid, p-(benzylsulfonamido)benzoic acid, biliverdine, bongkrekic acid, bumadizon, caffeic acid, calcium 2-ethylbutanoate, capobenic acid, carprofen, cefodizime, cefmenoxime, cefixime, cefazedone, cefatrizine, cefamandole, cefoperazone, ceforanide, cefotaxime, cefotetan, cefonicid, cefotiam, cefoxitin, cephamycins, cetiridine, cetraric acid, cetraxate, chaulmoorgic acid, chlorambucil, indomethacin, protoporphyrin IX, protizinic acid), prostanoic acid and its derivatives (e.g., prostaglandins) (see, for example, Nelson et al., C&EN 1982, 30-44; Frolich, Prostaglandins, 1984, 27:349; Cayman Chemical Co., 1994 Catalog, pp. 26-61), leukotrienes and lipoxines (see for example, Samuelsson et al., Science 1987, 237:1171 ; Cayman Chemical Co., 1994 Catalog, pp. 64-75), alkyl phosphates, O- phosphates (e.g., benfotiamine), alkyl phosphonates, natural and synthetic lipids (e.g., dimethylallyl pyrophosphate ammonium salt, S-famesylthioacetic acid, farnesyl pyrophosphate, 2-hydroxymyristic acid, 2-fluorpalmitic acid, inositoltrphosphates, geranyl pyrophosphate, geranygeranyl pyrophosphate, α- hydroxyfarnesyl phosphonic acid, isopentyl pyrophoshate, phosphatidylserines, cardiolipines, phosphatidic acid and derivatives, lysophosphatidic acids, sphingolipids and like), synthetic analogs of lipids such as sodium-dialkyl sulfosuccinate (e.g., Aerosol OT ), n-alkyl ethoxylated sulfates, n-alkyl monothiocarbonates, alkyl- and arylsulfates (asaprol, azosulfamide, p- (benzylsulfona ideo)benzoic acid, cefonicid, CHAPS), mono- and dialkyl dithiophosphates, N-alkanoyl-N-methylglucamine, perfluoroalcanoate, cholate and desoxycholate salts of bile acids, 4-chloroindoleacetic acid, cucurbic acid, jasmonic acid, 7-epi jasmonic acid, 12-oxo phytodienoic acid, traumatic acid, tuberonic acid, abscisic acid, acitertin, and the like. Preferred cationic and anionic surfactants also include fluorocarbon and mixed fluorocarbon-hydrocarbon surfactants. See, for example, Mukerjee, P. Coll. Surfaces A: Physicochem. Engin. Asp. 1994, 84: 1 ; Guo et al. J. Phys. Chem., 1991 , 95: 1829; Guo et al. J. Phys. Chem., 1992, 96: 10068. The list of such surfactants that are useful in current inventions includes but is not limited to the salts of perfluorocarboxylic acids (e.g., pentafluoropropionic acid, heptafluorobutyric acid, nonanfluoropentanoic acid, tridecafluoroheptanoic acid, pentadecafluorooctanoic acid, heptadecafluorononanoic acid, nonadecafluorodecanoic acid, perfluorododecanoic acid, perfluorotetradecanoic acid, hexafluoroglutaric acid, perfluoroadipic acid, perfluorosuberic acid, perfluorosebacicic acid), double tail hybrid surfactants (C m F 2m+ ι)(C n H 2n+1 )CH-OSO 3 Na (see, for example, Guo et al. J. Phys. Chem.1992, 96: 6738, Guo et al. J. Phys. Chem 992, 96: 10068; Guo et al. J. Phys. Chem .1992, 96: 10068), fluoroaliphatic phosphonates, fluoroaliphatic sulphates, and the like) The biological agent compositions of this invention may additionally contain nonionic or zwitterionic surfactants including but not limited to phospholipids (e.g. phosphatidylethanolamines, phosphatidylglycerols, phosphatidylinositols, diacyl phosphatidyl-cholines, di-O-alkyl phosphatidylcholines, platelet- activating factors, PAF agonists and PAF antagonists, lysophosphatidylcholines, lysophosphatidylethanolamines, lysophosphatidylglycerols, lysophosphatidylinositols, lyso-platelet-activating factors and analogs, and the like), saturated and unsaturated fatty acid derivatives (e.g., ethyl esters, propyl esters, cholesteryl esters, coenzyme A esters, nitrophenyl esters, naphtyl esters, monoglycerids, diglycerids, and triglycerids, fatty alcohols, fatty alcohol acetates, and the like), lipopolysaccharides, glyco- and shpingolipids (e.g. ceramides, cerebrosides, galactosyldiglycerids, gangliosides, lactocerebrosides, lysosulfatides, psychosines, shpingomyelins, sphingosines, sulfatides), chromophoric lipids (neutral lipids, phospholipids, cerebrosides, sphingomyelins), cholesterol and cholesterol derivatives, n-alkylphenyl polyoxyethylene ether, n-alkyl polyoxy¬ ethylene ethers (e.g., Triton™), sorbitan esters (e.g. Span™), polyglycol ether surfactants (Tergitol™), polyoxyethylenesorbitan (e.g., Tween™), polysorbates, polyoxyethylated glycol monoethers (e.g., Brij™, polyoxylethylene 9 lauryl ether, polyoxylethylene 10 ether, polyoxylethylene 10 tridecyl ether), lubrol, copolymers of ethylene oxide and propylene oxide (e.g., Pluronic™, Pluronic R ™, Teronic™, Pluradot™), alkyl aryl polyether alcohol (Tyloxapol™), perfluoroalkyl polyoxylated amides, N,N-bis[3-D-gluconamidopropyl]cholamide, decanoyl-N-methylglucamide, n-decyl α-D-glucopyranozide, n-decyl β-D-gluco¬ pyranozide, n-decyl β-D-maltopyranozide, n-dodecyl β-D-glucopyranozide, n- undecyl β-D-glucopyranozide, n-heptyl β-D-glucopyranozide, n-heptyl β-D- thioglucopyranozide, n-hexyl β-D-glucopyranozide, n-nonanoyl β-D- glucopyranozide 1-monooleyl-rac-glycerol, nonanoyl-N-methylglucamide, n- dodecyl α-D-maltoside, n-dodecyl β-D-maltoside, N,N-bis[3-gluconamidepropyl- ]deoxycholamide, diethylene glycol monopentyl ether, digitonin, heptanoyl-N- methylglucamide, heptanoyl-N-methylglucamide, octanoyl-N-methylglucamide, n-octyl β-D-glucopyranozide, n-octyl α-D-glucopyranozide, n-octyl β-D- thiogalactopyranozide, n-octyl β-D-thioglucopyranozide, betaine (R 1 R 2 R 3 N + R'C0 2 " , where R 1 R 2 R 3 R' hydrocarbon chains), sulfobetaine (R 1 R 2 R 3 N + R'S0 3 " ), phoshoplipids (e.g. dialkyl phosphatidylcholine), 3-[(3- cholamidopropyl)-dimethylammonio]-2-hydroxy-1-propanesulfonate, 3-[(3-chol- amidopropyl)-dimethylammonio]-1-propanesulfonate, N-decyl-N,N-dimethyl-3- ammonio-1-propanesulfonate, N-dodecyl-N,N-dimethyl-3-ammonio-1-propane- sulfonate, N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate, N- octadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate, N-octyl-N,N-dimethyl- 3-ammonio-1-propanesulfonate, N-tetradecyl-N,N-dimethyl-3-ammonio-1- propanesulfonate, and dialkyl phosphatitidyl-ethanolamine. Polymer Blends The polymer networks and the compositions thereof can be blended with various natural and synthetic polymers to improve stability, bioavailability, shelf-life and other properties that are relevant to the effects on the living organism and cell. Such natural and synthetic polymers can be cationic, anionic or nonionic include but are not limited to homopolymers, copolymers, block copolymers, graft copolymers or dendrimers of ethylene oxide, propylene oxide, butylene oxide, carbohydrates, acrylamide, acrylic esters, methacrylamide, N-(2-hydroxypropyl)methacrylamide, vinyl alcohol, vinyl pyrrolidone, vinyltriazole, vinylpyridine and its N-oxide, ortho esters, amino acids, nucleic acids, acrylic acid, methacrylic acid, heparin, phosphate, malic acid, lactic acid, carboxylated dextran, alkylene imine, ethyleneimine, amidoamines, vinylpyridinium salts, ionenes methacrylates, dimethylaminoethyl methacrylate, trimethylamonioethyl methacrylate and the like. The polymer networks and compositions thereof can be administered orally, topically, rectally, vaginally, by pulmonary route by use of an aerosol, or parenterally, i.e. intramuscularly, subcutaneously, intraperitoneallly or intravenously. The polymer networks and compositions thereof can be administered alone, or it can be combined with a pharmaceutically-acceptable carrier or excipient according to standard pharmaceutical practice. For the oral mode of administration, the polymer networks and compositions thereof can be used in the form of tablets, capsules, lozenges, troches, powders, syrups, elixirs, aqueous solutions and suspensions, and the like. In the case of tablets, carriers that can be used include lactose, sodium citrate and salts of phosphoric acid. Various disintegrants such as starch, and lubricating agents such as magnesium stearate, sodium lauryl sulfate and talc, are commonly used in tablets. For oral administration in capsule form, useful diluents are lactose and high molecular weight polyethylene glycols. When aqueous suspensions are required for oral use, the polymer networks and compositions thereof can be combined with emulsifying and suspending agents. If desired, certain sweetening and/or flavoring agents can be added. For parenteral administration, sterile solutions of the polymer networks and compositions thereof are usually prepared, and the pH of the solutions are suitably adjusted and buffered. For intravenous use, the total concentration of solutes should be controlled to render the preparation isotonic. For ocular administration, ointments or droppable liquids may be delivered by ocular delivery systems known to the art such as applicators or eye droppers. Such compositions can include mucomimetics such as hyaluronic acid, chondroitin sulfate, hydroxypropyl methylcellulose or poly(vinyl alcohol), preservatives such as sorbic acid, EDTA or benzylchronium chloride, and the usual quantities of diluents and/or carriers. For pulmonary administration, diluents and/or carriers will be selected to be appropriate to allow the formation of an aerosol. The following examples will serve to further typify the nature of the invention but should not be construed as a limitation on the scope thereof, which is defined solely by the appended claims. EXAMPLE 1 Synthesis of nanogel networks from polyethyleneimine and polyfethylene glycol) A. Bis-carbonyldiimidazole-activated poly(ethylene glycol) was synthesized by treating poly(ethylene glycol), M.W. 4,600, (Aldrich) with 10-fold excess of 1 ,1 '-carbonyldiimidazole. A solution of 1.8 g (10 mmol) of 1 ,1'- carbonyldimidazole in 10 ml of anhydrous acetonitrile is added in small portions to 8.0 g (1 mmol) of poly(ethylene glycol) in 20 ml of anhydrous acetonitrile with constant stirring. Reaction was carried out in for 17 hrs at 40°C. Then the reaction mixture was diluted by water and dialyzed against water for 24 hrs. Products were obtained after lyophilization as white solids with near quantitative yields. B. "Emulsion-evaporation" technique was used for the synthesis of Nanogel I. 2.4 g of bis-activated poly(ethylene glycol), MW 4,800 was dissolved in 10 ml of of dichloromethane and suspended into 200 ml of water. To the intensively stirred suspension 80 ml of 2% solution of polyethyleneimine, MW 25,000, (Aldrigh) in water was added dropwise. The resulting milky suspension was then sonicated for 30 min at 25°C in ultrasonic cleaner water bath at 80 W. Dichloromethane was removed by rotor evaporation in vacuo at 40°C, and the suspension became transparent during this procedure. Solution was left for 17 hrs at 4°C for cross-linking reaction to complete and large debris were separated by centrifugation for 5 min at 12,000g. Resulting suspension of Nanogel I particles was separated by gel- permeation chromatography. EXAMPLE 2 Synthesis of nanogel networks from polyethyleneimine and polv(ethylene glycol) Following the procedure of Example 1 but substituting 2.4 g of bis- activated poly(ethylene glycol), MW 4,800 for 4.1 g of bis-activated poly(ethylene glycol), MW 8,000 there is obtained Nanogel II. EXAMPLE 3 Synthesis of nanogel networks from polyethyleneimine, Pluronic F38 and poly(ethylene glycol) A. 24g (3 mmol) of Pluronic F38 (BASF Co.) were dried by co-evaporation with anhydrous pyridine in vacuo and dissolved in 50 ml of anhydrous acetonitrile. Then 0.51g (1.5 mmol) of 4,4'-dimethoxytrityl chloride in 30 ml of anhydrous pyridine was added to this solution dropwise under continuous stirring during 30 min. The mixture was allowed to stand for additional 2 h at room temperature, then the solvents were evaporated in vacuo. The residue was dissolved in 50 ml of dichloromethane, extracted with 5% sodium bicarbonate (2x30 ml), and applied on the Silicagel column (3x45 cm, 40-60 μm). Stepwise elution with dichloromethane-methanol solutions separated a slightly yellow mono-4,4'-dimethoxytrityl-derivative of Pluronic F38 with an yield about 75-85%. The side product of the reaction (10-15 % yield) was the bis- 4,4'-dimethoxytrityl-derivative of Pluronic F38. B. 1.5 g of mono-4,4'-dimethoxytrityl-derivative of Pluronic F38 obtained in A was activated by 0.25g of 1 ,1 '-carbonyldiimidazole in 10 ml of anhydrous acetonitrile for 3 hrs at room temperature. The solvent was evaporated in vacuo, the residue redissolved in water and dialyzed through Membra-Cel MD- 25-03.5 membrane with cutoff 3500 Da against water. Desalted solution was concentrated in vacuo and then reacted with polyethyleneimine, Mw. 2,000, (Aldrich) in methanol-water solution for 24 h at room temperature at a molar ratio of Pluronic F38 to free amino groups of polyethyleneimine 0.3:1.0. The conjugate obtained was purified by gel-permeation column chromatography on Sephadex-50 (fine) (Pharmacia) in water and then by reverse phase chromatography on semi-preparative column (Vydac C18 5 μm, 10 mm x 25 cm) in acetonitrile concentration gradient. This yields a grafted polyethyleneimine block copolymer at 40% yield in which 9% of free amino groups are substituted with Pluronic F38 as determined by fluorescamine method as described by Weigele et al. (J. Amer. Chem. Soc, 1972, 94:5927). C. 50 ml of 6% solution of bis-activated poly(ethylene glycol), MW 4,800, obtained as described in Part A of Example 1 was added to 3% solution of Pluronic F38-polyethyleneimine (MW 2 kDa) conjugate in 100 ml of 0.2 M sodium bicarbonate, pH 9. After 30 min incubation at the room temperature under constant stirring the mixture was charged to semi-permeable membrane bag, cutoff 3,500 and dialyzed against water for 17 hrs at 25°C. Nanogel III suspension was concentrated in vacuo and was fractionated by gel-permeation chromatography. EXAMPLE 4 Synthesis of nanogel networks from polyethyleneimine. Pluronic F123 and polv(ethylene glycol) Nanogel IV is obtained by following the procedure of Example 3 but substituting 2.4g of bis-activated poly(ethylene glycol), MW 4,800 for 1.7g of bis-activated poly(ethylene glycol), MW 1 ,700 and 1.5g of mono-4,4'- dimethoxytrityl-derivative of Pluronic F38 for the same amount of mono-4,4'- dimethoxytrityl-derivative of Pluronic F123. EXAMPLE 5 Fractionation of nanogel particles and size determination Suspensions of the nanogel particles obtained in Examples 1-4 were each concentrated in vacuo and redissolved in 0.1 M ammonium acetate, pH 7, to prepare solutions containing ca. 0.25g of crude product/ml. 10 ml of each nanogel solution was applied on the column (2.5 x 85 cm) with Sepharose CL- 2B and eluted by 0.1 M ammonium acetate, pH 7, at flow rate 1 ml/min. A refractive index detector was used to visualize the eluted products. High- molecular weight products were collected and concentrated in vacuo then redissolved in water and lyophilized. The dimensions of the nanogel particles were determined after resuspension using "ZetaPlus" Zeta Potential Analyzer (Brookhaven Instrument Co.) with 15 mV solid state laser operated at a laser wavelength of 635 nm and equipped with the Multi Angle Option. The results of the particle purification using gel-filtration were compared with those of ultracentrifugation and dialysis. Ultracentrifugation as a method of separation of nanogels from reaction solution was used only for Nanogel 1. Recovery of high-molecular weight material by this method was quite a low (about 7-12%), presumably because of low density and hydrophility of synthesized gels. Typically, only large particles (ca. 310 nm) could be separated from suspension during centrifugation at 45,000 g for 1 hr. Dialysis in semi-permeable membrane bags with cutoff up to 50 kDa did not permit the complete removal of lower-molecular weight components of reaction mixture. Only preparative gel-permeation chromatography was able to produce pure and easily analyzed polymeric fractions. In the Nanogel II preparation, the first peak (6 ml/tube, fractions 9-14) contained 0.1 g; the second peak (fractions 15-24) contained 1.05 g; and the third peak (fractions 25-30) contained 1.09 g of polymeric products. Chemical analysis of peaks 2 and 3 resulted in the following nitrogen content: 9.52% (peak 2) and 9.1% (peak 3). Molecular ratio of poly(ethylene glycol) to polyethyleneimine determined from the nitrogen content data for the peak 2 equaled 7.5. Particle sizes were 224 nm (peak 1), 119 nm (peak 2) and 26 nm (peak 3). Total content of chargeable nitrogen measured by potentiometric titration was equal to 3.3 μmol/mg for the peak (peak 2). In the Nanogel III preparation, peak 1 (5 ml/tube, fractions 22-27) contained 1.5 g, and peak 2 (fraction 28-33) contained 0.8 g of polymeric products. Chemical analysis of peak 1 resulted in % nitrogen 13.02, which corresponds to poly(ethylene glycol)/Pluronic F38 to polyethyleneimine ratio of 1.5. Particle size was 254 nm (peak 1) and 236 nm (peak 2). Total content of chargeable nitrogen in peak 1 measured by potentiometric titration was equal 4.9 μmol/mg. In the Nanogel IV preparation, one main peak was obtained containing particles with the average effective diameter of 33 nm. Transition electron microphotographs obtained for nanogel samples using uranyl acetate staining showed mainly spherical particles with highly developed surface and size distribution in the range from 0.08 (Nanogel III and IV) to 0.22-0.29 (Nanogel I and II). EXAMPLE 6 Preparation of NanoGel compositions with sodium dodecylsulfate A suspension of Nanogel 1 was prepared in phosphate buffer pH 7.4 by sonication of 1 mg/ml Nanogel 1 sample for 30 min at 25°C. 50 mM solution of sodium dodecylsulfate was added dropwise to the suspension of Nanogel 1. The particle size at various charge ratios: Z. /+ = [surfactant]/[chargeable nitrogen] was measured using "ZetaPlus" Zeta Potential Analyzer (Brookhaven Instrument Co.) with 15 mV solid state laser operated at a laser wavelength of 635 nm. Before each measurement the Nanogel 1 suspension was incubated for 10 min. at 25°C. The results at different Z /+ are as follows: a After 48 hour incubation. At the charge neutralization point (Z /+ = 1) a clear suspension was obtained with no sign of aggregation and with effective diameter ca. 125 nm, which is 2.5 times less than initial non-loaded Nanogel 1 particles. The particle size at Z /+ = 1 did not change after 48 h incubation. EXAMPLE 7 Preparation and characterization of nanogel compositions with oligonucleotide 10 mg/ml suspension of Nanogel II (peak 2) described in Example 5 was obtained by resuspension of lyophilized Nanogel II sample in phosphate buffered saline (PBS), sonication for 30 min at 25°C and filtration through 0.45 urn disposable filter. Oligonucleotide solutions were prepared at 8-10 mg/ml concentration in PBS and filtered through 0.22 urn disposable filter. The calculated volume of the polynucleotide solution was added dropwise into the stirred suspension of Nanogel II (peak 2) to obtain 10 uM stock solution and final mixture was incubated for 1 hr at 37°C. The particle size at various charge ratios Z /+ = [phosphate]/[chargeable nitrogen] was measured using "ZetaPlus" Zeta Potential Analyzer (Brookhaven Instrument Co.). The results are as follows: The nanogel particles are formed with effective diameter ca. 80 to 160 nm. Minimal size is observed at Z. /+ = 0.4. The nanogel loading capacity with respect to oligonucleotide was ca. 80 to 160 nmol/mg (ca. 0.8 to mg/mg). EXAMPLE 8 Preparation and characterization of nanogel compositions with DNA Salmon sperm DNA solution (1 mg/ml) was prepared in PBS and filtered through 0.22 um disposable filter. The calculated volume of this solution was added dropwise at constant stirring to the suspension of Nanogel II (peak 2) prepared as described in Example 7. Incubation for 4 hrs at 37°C or 17 hrs at 4°C was necessary to reach the maximum loading of 0.5-0.7 mg of DNA per mg of Nanogel II. The final suspensions were filtered through 0.45 um disposable filter. The particles were formed with effective diameter 240-270nm as determined using "ZetaPlus" Zeta Potential Analyzer (Brookhaven Instrument Co.). EXAMPLE 9 Preparation and characterization of nanogel compositions with insulin Insulin solution (1 mg/ml) was prepared in 50 mM sodium bicarbonate, pH 8.5, and filtered through 0.22 um disposable filter. The calculated volume of this solution was added dropwise to the Nanogel I suspension prepared as described in Example 7. The mixture was incubated for 1-17 hrs at 4°C and the particle size was measured using "ZetaPlus" Zeta Potential Analyzer (Brookhaven Instrument Co.). The nanogel loading capacity with respect to insulin was ca. 0.25 to 0.3 mg/mg. Loaded Nanogels I were condensed up to effective diameter 112 nm at the maximum insulin loading. Further condensation of loaded nanogel particles was observed when the pH was decreased from pH 7 to pH 2; at pH 2 the particle effective diameter was ca. 95 nm. EXAMPLE 10 Blending of nanogel with polvacrylic acid One percent aqueous solution of the polyacrylic acid sodium salt, MW 30,000, (Aldrich) was prepared and filtered through 0.22 μm disposable filter. This solution was added dropwise to the Nanogel I suspension prepared as described in the Example 7. This resulted in the the condensation of loaded nanogel particles with the effective diameter of the particles reaching 1 10-120 nm as determined using "ZetaPlus" Zeta Potential Analyzer (Brookhaven Instrument Co.). The oligonucleotide and insulin loaded nanogel particles prepared as described in examples 7 and 9 respectively were used in these experiments. EXAMPLE 1 1 Cvtotoxicitv of nanogels particles Cytotoxicity of free and oligonucleotide-loaded nanogel particles was determined using confluent KBv monolayers were grown in DMEM supplemented with 10% fetal bovine serum and 1g/ml vinblastine. Cells were treated by Nanogel II (peak II) and Nanogel II (peak II) loaded with phosphorothioate oligonucleotide 20-mer at Z = 2 every 12-hours for 48 hours. After the treatment the cells were cultivated another 48 hours at 37°C and 5% C0 2 . After that, the drug cytotoxic activity was determined using the MTT (3- (4,5-dimethylthiazol-2-yl)2,5-diphenyl tetrazolium bromide) assay (Ferrari, et al., J. Immunol. Methods 131 , 165, 1990). In a control experiment it was shown that oligonucleotide alone does not produce cytotoxic effect at the concentrations used in nanogel formulations. The results were as follows: The cytotoxicity of the nanogel thus decreases after loading with oligonucleotide. EXAMPLE 12 Cytotoxicity of nanogels particles Cytotoxicity of the Nanogel I and Nanogel II particles was compared using confluent KBv monolayers were grown in DMEM supplemented with 10% fetal bovine serum and 1 ug/ml vinblastine. Cells were treated by Nanogel I and Nanogel II every 12-hours for 48 hours. After the treatment the cells were cultivated another 48 hours at 37°C and 5% C0 2 . Next, the drug cytotoxic activity was determined using the MTT (3-(4,5-dimethylthiazol-2-yl)2,5-diphenyl tetrazolium bromide) assay (Ferrari, et al., J. Immunol. Methods 131 , 165, 1990). The results were as follows: Nanogel I, having larger particle size (310 nm), is thus also more toxic compared to Nanogel II having smaller particle size (120 nm). EXAMPLE 13 Transport of nanogel loaded with oligonucleotide in Caco-2 cells The effects of nanogels on the transport of oligonucleotides in cells were characterized using the monolayers of human intestinal epithelum Caco-2, which are commonly used as an in vitro model of the intestinal barrier for oral delivery (Nerurkar et al., Pharm. Res., 1996, 13: 528). A 1 % suspension of the Nanogel II (peak 2) was loaded with the fluorecein-labeled oligonucleotide phosphorothioate 20-mer at Z = 2 in PBS solution. KBV cell monolayers were grown on polycarbonate membrane filters and then placed in "Side-by-Side" diffusion chambers. Samples containing 0.02% loaded Nanogel II suspension were placed into the donor chamber and the transport across cell monolayers was measured at 37°C by sampling the solution in the reciever chamber at various time intervals. The oligonucleotide concentration in the reciever chamber was determined determined by measuring fluorescence of the cell lysates with a Shimadzu RF5000 fluorescent spectrophotometer (488 nm excitation; 510 nm emission). The oligonucleotide transport in the Nanogel II formulation was increased ca. 20 times compared to the transport of the free oligonucleotide. Maximum transport increase was observed during the first 60 min (11.5% compared to 0.5% for free oligonucleotide). Quantitation of the oligonucleotide using HPLC-analysis with UV-detection has given the similar results. Integration of HPLC peaks corresponding to the main oligonucleotide its degradation products in the receiver chamber after 6 hour incubation allowed to determine degradation of the oligonucleotide in the Nanogel II formulation. The results were as follows: Incorporation of oligonucleotides into the nanogel formulation results in increased protection against nuclease degradation in Caco-2 cells. EXAMPLE 14 Effect of oligonucleotides in nanogels on cells The multidrug resistant KBv cell line (vinblastine resistant human epidermoid carcinoma) which expresses high levels of glycoprotein P (P-gp) efflux pump (Gervasoni, et al. Cancer Research, 1991 , 51 , 4955) can be used to evaluate the effects of the antisense oligonucleotides in nanogel formulations on rhodamine 123. Rhodamine 123 is a specific probe for the effects on the P-gp efflux system, which is commonly used for evaluation of the P-gp efflux function in cancer and normal cells (Jancis, et al., Mol. Pharmacol. 1993, 43, 51 ; Lee, et al., Mol. Pharmacol., 1994, 46, 627). Phosphorothioate antisense oligonucleotide 20-mer, TCCTCCATTGCGGTCCCCTT, complementary to sites 435-454 of the human mdrl-mRNA were used in the experiments on KBv cell cultures. Cells were treated with 0.2-2 uM free oligonucleotide or oligonucleotide in the Nanogel II (peak 2) (Z. /+ = 0.5, Z. /+ = 0.7) suspensions every 12-hours for 48 hours, and then allowed to grow for another 24 hours at 37°C and 5% C0 2 . The cells were then washed by the fresh medium and rhodamine 123 uptake in the cells was studied using the following protocol. The uptake of rhodamine 123 in KBv cell monolayers in presence and absence of the block copolymers is examined at 37°C over a period of 60 minutes. The culture media was removed from the KBv monolay¬ ers and replaced with an assay buffer having the following composition: NaCI (122 mM), NaHC0 3 (25 mM), glucose (10 mM), KCI (3 mM), MgS04 (1.2 mM), K 2 HP0 4 (0.4 mM), CaCI 2 (1.4 mM) and HEPES (10 mM). After a thirty-minute pre-incubation at 37°C, the assay buffer is removed from the monolayers and 3.2 μM rhodamine in the assay buffer is added to the monolayers for 90 min¬ utes. The medium was then removed and cell monolayers were washed three times with 0.5 ml ice-cold PBS. The KBv monolayers were solubilized in 1.0% Triton X-100 (0.5 ml) and aliquots removed for determining cell-associated rhodamine fluorescence and protein content. Rhodamine 123 fluorescence was determined at λex = 488 nm and λem = 550 nm using a Shimadzu 5000 spectrophotometer. Protein content was determined using the Pierce BCA method. The concentration of rhodamine in the KBv lyzate solution was quantitatively determined by construction of standard curves. The results are as follows: The results with rhodamine 123 are indicative of the effects of the oligonucleotide incorporated into nanogel on the P-gp efflux system in multidrug resistant cells.

Claims: What is Claimed 1. A polymer network comprising a plurality of cross-linked polymer fragments wherein the polymer fragments comprise: (a) at least one polycationic fragment which is a cationic homopolymer or copolymer comprising at least three cationic amino acids or at least three aminoalkylene monomers, the monomers being selected from the group consisting of at least one of: (0 at least one tertiary amino monomer of the formula: A. and the quaternary salts of the tertiary amino monomer, and (/ ' /) at least one secondary amino monomer of the formula: B. and the acid addition and quaternary salts of the secondary amino monomer, in which 1 R is hydrogen, alkyl of 2 to 8 carbon atoms, an A monomer, or a B monomer; 2 3 each of R and R , taken independently of the other, is the same or different straight or branched chain alkanediyl group of the formula: (C H 2z ) in which z has a value of from 2 to 8; R is hydrogen satisfying one bond of the depicted geminally bonded carbon atom; and 5 R is hydrogen, alkyl of 2 to 8 carbon atoms, an A monomer, or a B monomer; R is hydrogen, alkyl of 2 to 8 carbon atoms, an A monomer, or a B monomer; R is a straight or branched chain alkanediyl group of the formula- -(C Z H in which z has a value of from 2 to 8; and o R is hydrogen, alkyl of 2 to 8 carbon atoms, an A monomer, or a B monomer; and (b) at least one nonionic homopolymer or copolymer comprising at least three of the same or different repeating units containing at least one atom selected from the group consisting of oxygen and nitrogen 2. The polymer network according to claim 1 wherein the network size is between about 20 nm and about 600 nm. 3 The polymer network according to claim 1 wherein the network size is between about 50 nm and about 250 nm. 4. The polymer network according to claim 1 wherein the network size is between about 70 nm and about 150 nm. 5 A composition comprising the polymer network of claim 1 and a biological agent 6 The composition according to claim 5 wherein the biological agent is selected from the group consisting of polynucleotides, viral vectors, and viruses 7 The composition according to claim 5 wherein the biological agent is selected from the group consisting of peptides and proteins 8 The composition according to claim 5 wherein the biological agent is selected from the group consisting of immunoglobulins, immunomodulators, immunoadjuvants, immunogens, antigens, and vaccines 9 The composition according to claim 5 wherein the biological agent is selected from the group consisting of dyes, radiolabels, radio-opaque compounds, and fluorescent compounds 10 A pharmaceutical composition comprising the polymer network according to claim 1 and a pharmaceutically acceptable carrier 11. A composition comprising the polymer network of claim 1 and a targeting molecule. 12. A method of immunizing an organism comprising administering to said organism an effective amount of a polymer network according to claim 1 , and a biological agent. 13. A method of treating an organism in need of treatment comprising administering to said organism an effective amount of the polymer network composition of claim 1 and a biological agent. 14. A method of identifying a desired cross-linked polymer network comprising: (a) preparing a plurality of cross-linked polymer fragment networks according to claim 1 ; and (b) preparing a plurality of compositions of polymer networks with a biological agent; (c) testing at least one of said cross-linked polymer networks a biological agent for desired biological properties; and (d) identifying said compositions with desired biological properties.

Inventors: KABANOV ALEXANDER V, VINOGRADOV SERGEY V, KABANOV, ALEXANDER, V., VINOGRADOV, SERGEY, V.
Applicants: KABANOV ALEXANDER V, SUPRATEK PHARMA INC, VINOGRADOV SERGEY V, KABANOV, ALEXANDER, V., SUPRATEK PHARMA, INC., VINOGRADOV, SERGEY, V.
Application year: 1999
Main classification: A61K9
IPC codes: A61K9, A61K31, A61K35, A61K38, A61K39, A61K45, A61K47, A61K48, A61K51, C08G73, C08L79, C08L89, C08L101