Patent Description:
Water insoluble polymers of biological origin, e.g. polysaccharides, such as chitosan, comprise compounds containing active amine or carboxyl groups susceptible to formation of peptide bond.

Chitosan is a linear polysaccharide, composed of β-(<NUM>-<NUM>)-linked D-glucosamine and N-acetyl-D-glucosamine units. It can be produced from animal or fungal chitin and has multiple applications e.g. in the cosmetic industry and medicine.

In the prior art classical peptide synthesis in the solid phase has been used. Resins for peptide synthesis according to the Fmoc/SPPS protocol, conditions for attaching the first amino acid to the resin and for elongation of the peptide by means of generating the peptide bond are known in the prior art.

<CIT> discloses a method of peptide synthesis on chilosan. However classical synthesis and an additional binding molecule between the amino group of chitosan and the first amino acid of the peptide are used.

There was no disclosure in the prior art of a use of fully biodegradable biopolymer, such as chitosan, as resin for attaching modifiers with formation of a direct peptide bond between chitosan and the modifier molecule. Under conditions applicable for classical peptide synthesis the reaction takes a long time and gives no satisfactory yield.

<CIT> discloses incorporation of biologically active components into chitosan layer(s) while coating metal-made medical devices. However, in this method biomolecules are added as a separate coating layer, without forming specific covalent bonds.

Methods derived from classical peptide synthesis in the solid phase for obtaining chitosan derivatives involve many inconveniences, e.g. low yields and long reaction times.

<NPL>, describe the method of preparing chitosan and glutathione conjugates and the product obtained by this method. The method of preparing chitosan and glutathione conjugates is based on a reaction carried out for <NUM> hours, using EDC. The conjugates are used as a reactive oxygen scavenger in myocardial infarction. As results from the used method for obtaining the chitosan derivative, this document relates in fact to the chitosan chloride derivatives but not a chitosan derivative, wherein said chitosan is modified with glutathione with the formation of a peptide bond. The chloride per se and its derivatives are known as skin irritating agent. Thus those derivatives are of no use according to the application on skin. The method leading to chloride derivative is of no use for the present invention.

<NPL> discloses a chitosan-glutathione derivative, which is also obtained with the use of completely different method and is different derivative then disclosed in the pending application. As detailed in Table I of Kafedjiiski K. the method described therein yields a derivative, which contains a mixture of GSH thiol and disulfide, with the excess of the latter. The method comprises use of EDAC and NHS reagents and <NUM> hours are necessary to complete the reaction. Use of such reagents in the method leads to the formation of extremely harmful by-products, so it is evident that the final derivative also comprises such harmful by-products. Moreover, the yield of their process is very low, providing less than <NUM> GSH per <NUM> of chitosan, which is contaminated with ca. <NUM> of GSSG. Thus, it is clear for the person skilled in the art, that Kafedjiiski K. discloses different "chitosan-glutathione derivative" then the chitosan derivative of the present invention. Contrary to the present application is also use of the derivative, since this document is focusing on maintaining the GSH permeation enhancing properties. This is in direct opposition to the idea of the present invention, where the derivative is used as a barrier, in order to stop penetration of the metal ions to the skin or to entrap the ions in purification of the wastes.

The method according to <NPL> is similar to that described in Kafedjiiski K. , but the reaction takes even more time i.e. <NUM> hours. Thus, the obtained GSII-chitosan derivative must be analogous to the derivative of Kafedjiiski K. and the final product is also contaminated. In fact Koo et al. focuses on chitosan-glutathione nanoparticles as a system for GSH delivery to the living organisms and to maintain the GSH antioxidant activity based on its radical scavenging activity. Thus the use of the method for obtaining GSH-chitosan derivative is completely out of the field of the present invention. Similarly, <CIT> relates also to the chitosan-glutathione derivative obtained with the use of EDC and NHS with reaction lasting <NUM> hours.

Even though <CIT> relates to the method with the use of HBTU, HOBT and DIPEA, but does not relate to use of microwaves for the reaction. The method according to <CIT> comprises attaching a bifunctional linker molecule to the free amino groups of the chitosan, prior to the step of attaching the first amino acid. Thus, <CIT> relates to the different method then the present invention.

Use of the microwaves for N-alkylation was described in <CIT>. However this document does not relate to peptide bond formation and not for obtaining a glutathione-chitosan derivative. The method according to <CIT> differs from the method according to the present invention by the reagents and conditions used, such as temperature <NUM><NUM>C and <NUM> Watts vs. <NUM> according to the method of the pending application. Even more important is that according to the method described in <CIT> the same yield is obtained with and without use of microwaves. In result the skilled person would not see any advantage with using microwaves for N-alkylation of chitosan, and would even not try to use microwaves in peptide bond formation. A person skilled in the art will easily recognize that conditions needed for the reaction in <CIT> are analogous to those used for destruction of peptide bonds in biochemical practice.

None of the document of the prior art discloses free of toxic impurities chitosan derivatives with glutathione and a method for obtaining thereof. Also, there is no document disclosing or suggesting use of microwaves in combination with either DCC and HOPfp or HBTU, HOBT and DIPEA activators in a mild condition such as temperature <NUM> or lower and time reaction <NUM> minutes or shorter for obtaining a peptide bond between chitosan and another molecule.

Use of chitosan for treatment of skin irritation caused by various factors is known from the prior art. <CIT> describes the use of dermatological preparation containing <NUM>% chitosan hydrochloride for prevention and treatment of platinosis. <CIT>) relates to a method of protecting the skin from contact with an allergen or toxin comprising applying to the skin of a subject sensitized to said allergenic agent, prior to contact with said skin, a polysaccharide selected from chitosan polymers and chitosan derivatives. This document neither mentions an antigen being a metal, nor a possibility of application of chitosan derivatives, in which their amino group would be engaged in a peptide bond. Further, <CIT> discloses chitosan coating of metal-made medical devices to make them biocompatible and to prevent irritation of the organism with metal ions derived from these devices.

The most frequent nickel allergy manifestation is contact dermatitis caused by response related to Th lymphocytes (type IV hypersensitivity). Nickel is one of the most frequent allergens. More than <NUM>% of population of developed European countries (e.g. Germany, United Kingdom, Italy) suffers nickel allergy. In Poland <NUM>% of <NUM>-<NUM> year old girls suffer from nickel allergy [<NPL>; <NPL>]. The importance of the problem is stressed by the fact that the EU Directive <NUM>/<NUM>/EC regulates the allowed amount of nickel released from jewelry and common use objects.

Therefore, there is an urgent need for the development of effective protection against allergy to metals, especially allergy to heavy metals, in particular to nickel.

The invention disclosed herein solves the problem of a synthetic method that provides sufficient efficacy for industrial application of the obtained derivatives, as well as solves the problem of a delivery on an industrial scale of active molecules based on safe, nontoxic, biodegradable compounds, such as chitosan.

The subject of the invention is defined in the attached set of claims.

Herein disclosed is an insoluble polymer derivative containing reactive amine or carboxyl groups, modified by a modifier molecule with the use of formation of a peptide bond. Preferably, the polymer is a poly/oligosaccharide, preferably chitosan. The peptide bond is present between the amine group of a subunit of poly(<NUM>-deoxy-<NUM>-aminoglucose) and one of the available carboxyl groups of a modifier molecule. Preferably, the modifier molecule containing the carboxyl group is selected from carboxylic acids, amino acids, amino acid analogues, dipeptides, tripeptides, tetrapeptides, longer peptides, peptidomimetics, proteins and protein mimetics or any mixture thereof.

Disclosed is also a method of synthesis of a derivative of an insoluble polymer, in which peptide bonds are formed between the amine or carboxyl groups of units of the biopolymer containing reactive amine or carboxyl groups, and the available carboxyl or amine groups of the modifier molecules being attached.

The disclosed method comprises forming a peptide bond between the amine group of a unit of poly(<NUM>-deoxy-<NUM>-aminoglucose) wherein the peptide bond between the polymer and the modifier molecule is formed in the field of microwaves.

The step of obtaining the Fmoc protected peptide molecule can be omitted.

As disclosed, the preferred method comprises:.

DCC and HOPfp or HBTU, HOBT and DIPEA are used as preferred activators. Preferably, the processing with microwaves is continued for <NUM>-<NUM> minutes. Nevertheless, even longer times are also included in the disclosure, as far as they lead to the peptide hond formation.

The method for synthesis comprises chitosan as the biopolymer and the modifier molecule is selected from at least one of carboxylic acids, amino acids, amino acid analogues, dipeptides, tripeptides, tetrapeptides, longer peptides, peptidomimetics, proteins or protein mimetics, preferably the tripeptide molecule is glutathione.

Disclosed is also a cosmetic or pharmaceutic composition containing the biopolymer derivative according to the invention. The composition is in a form of ointment, cream, lotion. The composition is used in medicine, medicinal products or cosmetic products.

Disclosed is also a composition for use in preventing symptoms of allergy caused by heavy metals, preferably palladium, cobalt, chromium and gold, most preferably nickel.

Preferably, the composition contains an additional biopolymer, preferably a biopolymer being a metal binding protein.

Moreover, disclosed is a chitosan derivative for use in preventing symptoms of skin allergy caused by contact with metals, preferably with heavy metals, most preferably with nickel.

Disclosed is also a matrix for attaching modifier molecules, containing the biopolymer derivative according to the invention.

Disclosed is the use of a chitosan derivative and/or chitosan for preventing symptoms of allergy caused by heavy metals, preferably for preventing symptoms of allergy caused by nickel. Preferably the composition contains an additional biopolymer, preferably a biopolymer being a metal binding protein.

Further, disclosed is a method for purification of industrial and domestic waste wherein the biopolymer derivative according to the invention is contacted with said waste to entrap the pollutants and said biopolymer derivative with entrapped pollutant is resolved. Disclosed is also a method for recovery of metals wherein the material containing metal ion is contacted with the biopolymer derivative according to the invention. Thus, disclosed is the use of a biopolymer derivative according to the invention for purification of industrial and domestic waste and/or recovery of metals.

The term "insoluble biopolymer" denotes all chemical compounds of biological origin consisting of units (mers), these compounds contain active amine or carboxyl groups susceptible for the formation of peptide bonds. These compounds are principally water insoluble. Cellulose and chitosan are examples of insoluble biopolymers.

The term "modifier molecule" relates to the molecule that is able to form a peptide bond with chitosan or other biopolymer molecule having carboxyl or amine moieties.

The term "peptidomimetics" or "protein mimetics" relates to a modification or cyclization of linear peptides or proteins. The examples of peptidomimetics comprise amide bond surrogates, peptidosulfonamides, phosphonopeptides, oligourcas, depsides, depsipeptides, and peptidoids.

Chitosan is practically insoluble in water and organic solvents suitable for peptide synthesis, but it is chemically active, thus enabling its use as matrix for attaching organic molecules, e.g. peptides.

Disclosed is the modification of chitosan with molecules containing carboxylic groups suitable for the formation of peptide bonds under classical conditions of formation of peptide bonds and in the field of microwaves. Examples of such molecules include carboxylic acids, amino acids, amino acid analogues, dipeptides, tripeptides, tetrapeptides, longer peptides, peptidomimetics, proteins or protein mimetics or any mixture thereof.

By means of selection of an appropriate modifier molecule it is possible to obtain desired properties of a biopolymer being modified. For example, by attaching the molecule of glutathione - a tripeptide forming complexes with metal ions- to a monomeric unit of the polymer, it is possible to significantly increase the ability of chitosan to chelate metal ions. The selection of appropriate modifiers may affect a number of properties of the biopolymer, such as its solubility, the pH value after its suspension in water, as well as its fungicidal and bactericidal properties.

The method of synthesis of chitosan modified with glutathione according to the disclosure employs the commercially available chitosan or another insoluble biopolymer characterized by the presence of reactive amine or carboxyl groups and the modifier molecule, e.g. peptide.

In the method of synthesis of chitosan modified with glutathione according to the disclosure, peptide bonds are formed between the amine groups of poly(<NUM> deoxy-<NUM>-aminoglucose) molecule, where <NUM>-deoxy-<NUM>-aminoglucose is a monomer forming the structure of chitosan, and one of available carboxyl groups of glutathione, according to the synthetic strategy designed for the purpose of this invention and under optimized conditions. Fmoc-glutathione is used in the reaction, with the amine function group protected according to the procedure described in Example <NUM>. The procedure applied for the formation of the peptide bond is described in Example <NUM>.

The coupling reaction in the field of microwaves was used in the method as disclosed, to synthesize new derivatives. Microwaves additionally activate amine groups of the biopolymer, and also facilitate access of modifier molecules to function groups of the polymer by influencing its structure.

The microwaves play an essential role in the method of peptide bond formation as disclosed. The generation of the peptide bond in the field of microwaves significantly increased the reaction yield (by a factor of <NUM>, from <NUM>% to <NUM>%) and at the same time reduced the reaction time (from <NUM> minutes to <NUM> minutes). It also helps avoid a difficult and expensive step of protecting the amine group of the modifier molecule.

In the first step of reaction the biopolymer is strongly activated in the field of microwaves, which makes its function groups much more active than the function groups of the modifier. Next, the coupling of the modifier molecules with appropriate function groups of the biopolymer and attaching the modifier molecule to the matrix is conducted. The formation of di- tri- or even polymeric products composed of molecules of unprotected modifier is a possible side reaction. Such reaction was prevented by previous activation of the biopolymer, which privileged the reaction of the biopolymer with the modifier molecule. This activation made it possible to avoid protecting the amine group of the modifier molecule with fluorenylmetoxycarbonyl chloride, thus eliminating two reaction steps: protecting the amine group and removing the protection after the coupling reaction. This results in a significant reduction of reaction cost and also provides a green chemistry aspect to the invention. The environmentally hazardous fluorenylmetoxycarbonyl chloride is not used any more in the reaction, which is conducted with the use of a biocompatible polymer, biodegradable modifiers, popular activators and volatile solvents.

The biopolymer - chitosan is a nontoxic compound, and thus its use, even on an industrial scale, does not evoke environmental pollution. Biocompatibility is an important property of this polymer. Its further advantages are high adhesivity and absorptivity, high chemical reactivity and ability to chelate metal ions, resulting from the presence of an amine group in each of its units (mers). In an aqueous environment it interacts with metal ions forming coordination bonds. Due to its ability to assume many spatial conformations, this polymer can also enclose metal ions within its structure. A clear advantage of chitosan is also its property to serve as a nontoxic and envirommentally friendly matrix for attaching modifier molecules.

The manipulation of properties of a biopolymer, in particular those regarding the increase of metal binding strength and/or selectivity opens up a wide field of various applications of modified biopolymers, c. in cosmetic industry, pharmacy and environmental protection.

Disclosed herein is attaching glutathione to chitosan. Preferably, the synthesis is performed with the use of field of microwaves. An appropriate reaction vessel and a microwave reactor can be used for this purpose. Chitosan is processed with microwaves for the period of time sufficient for the activation of function groups of the polymer, preferably for <NUM>-<NUM> minutes, at <NUM>-<NUM> and power P-<NUM>-<NUM> W.

Preferably, the function groups of chitosan are activated with DCC and I-IOPfp. Also preferably, activation of function groups is followed by contacting chitosan with glutathione which is not protected by Fmoc and the resulting reaction mixture is again processed with microwaves for a required period of time in an appropriate temperature. Chitosan is processed with microwaves at least twice. Preferably, the exposure to microwaves lasts for <NUM>-<NUM> minutes, power is in the range of <NUM>-<NUM> W and the reaction occurs at <NUM>-<NUM>. The product can be recovered according to standard procedures, such as centrifugation and lyophilization.

As disclosed, attaching of glutathione to chitosan in the field of microwaves is performed with the use of HBTU, HOBT and DIPEA. The time of exposure, power and temperature are selected to activate the chitosan function groups.

The product present in a form of suspension is centrifuged and the supernatant is decanted. The obtained modified biopolymer is washed at least once, preferably two or three times with fresh portions of DMF and centrifuged. Preferably, this procedure is repeated with methylene chloride.

Attaching of bacitracin or ticarcillin to chitosan in the field of microwaves is performed with the use of HBTU, HOBT and DIPEA.

Disclosed herein, modified chitosan captures metal ions, preferably of nickel or other heavy metals.

The method as disclosed is explained on the basis of the specific examples in more detail on Figures wherein:.

Examples are provided herein below. However, the disclosed and claimed invention is to be understood to not be limited in its application to the specific experimentation, results and laboratory procedures. Rather, the Examples are simply provided as one of various embodiments and are meant to be exemplary, not exhaustive.

In a <NUM> three-necked flask <NUM> of glutathione (<NUM> mmoles) was dissolved in a mixture of <NUM> of dioxane and <NUM> of <NUM>% NaCO<NUM> under anaerobic conditions. The flask fitted with a dropping funnel, stirring magnet, argon balloon and a bubbler was mounted over a magnetic stirrer. <NUM> of Fmoc-Cl (<NUM> mmoles) was dissolved in <NUM> of dioxane and added dropwise slowly over <NUM> minutes. The reaction was kept in the ice bath during addition. Then, the ice bath was removed. The reaction was allowed to proceed for <NUM> hours under argon, while monitoring its progress by ESI-MS. Next, the solution was acidified to pH≈<NUM>. The precipitate formed was separated on a Schott funnel. The remaining solution was evaporated until a significant amount of precipitate formed. This precipitate was separated on a Schott funnel and washed with distilled water. Fmoc-glutathione was obtained, having molecular mass <NUM>/mole (<FIG>).

<NUM> of chitosan was placed in a reaction vessel for solid state peptide synthesis. <NUM> of Fmoc-glutathione (<NUM> mol equivalents) was dissolved in <NUM> of DMF. To this solution <NUM> (<NUM> mol equivalents) of HBTU, <NUM> (<NUM> mol equivalents) of HOBt and <NUM> (<NUM> mol equivalents) of DIPEA were added. The reagents were mixed together and added to the reaction vessel containing chitosan. The mixture was allowed to react for <NUM> hours on a laboratory shaker. This procedure was repeated three times. Next, the solution was filtered off and the remaining biopolymer was washed three times with DMF. In order to remove the Fmoc protecting group from glutathione, a <NUM>% solution of piperidine in DMF was added twice, followed by shaking for <NUM> minutes. Following the Fmoc group removal, the biopolymer was washed three times with DMF. The DMF solution was sucked up and the biopolymer with glutathione was suspended in distilled water and lyophilized. The reaction yield determined by elemental analysis Y<<NUM>%.

To a reaction vessel for solid state peptide synthesis <NUM> of chitosan suspended in <NUM> of <NUM>:<NUM> DMF:H<NUM>O mixture was added and processed with microwaves (t=<NUM> minutes, P=<NUM> W, T=<NUM>). <NUM> of HOPfp and <NUM> of DCC were dissolved in <NUM> of <NUM>:<NUM> DMF:H<NUM>O mixture and added to the reaction vessel. The resulting mixture of chitosan with the activators was processed with microwaves (t=<NUM> minutes, P=<NUM> W, T=<NUM>), which activated the function groups of the polymer. Next, <NUM> of glutathione (free molecule, not protected with Fmoc) in <NUM> of DMF was added to the vessel and subjected twice to the microwaves (t=<NUM> minutes, P=<NUM> W, T<<NUM>). The suspension was added to a centrifugation vessel and centrifuged. The supernatant was decanted. The obtained modified biopolymer was suspended three times in fresh portions of DMF, and then centrifuged and decanted. This procedure was repeated with the use of methylene chloride. After these three washes with methylene chloride the precipitation was frozen in liquid nitrogen and lyophilized. The lyophilized precipitate was washed three times with distilled water and lyophilized again. Elemental analysis revealed the presence of sulfur, and therefore the presence of glutathione attached to the polymer. The reaction yield determined by elemental analysis Y = <NUM>%.

To a reaction vessel for solid state peptide synthesis <NUM> of chitosan suspended in <NUM> of DMF was added and subjected to the action of microwaves (t=<NUM> minutes, P=<NUM> W, T=<NUM>). <NUM> HBTU, <NUM> HOBT and <NUM> DIPEA in <NUM> of DMF were added to the reaction vessel. The resulting mixture of chitosan with the activators was subjected to the action of microwaves (t=<NUM> minutes, P=<NUM> W, T=<NUM>), which activated the function groups of the polymer. Next, <NUM> of glutathione (free molecule, not protected with Fmoc) in <NUM> of DMF was added to the vessel and subjected twice to the action of microwaves (t=<NUM> minutes, P=<NUM> W, T<<NUM>). The suspension was added to a centrifugation vessel and centrifuged. The supernatant was decanted. The obtained modified biopolymer was suspended three times in fresh portions of DMF, and then centrifuged and decanted. This procedure was repeated with the use of methylene chloride. After these three washes with methylene chloride the precipitation was frozen in liquid nitrogen and lyophilized. The lyophilized precipitate was washed three times with distilled water and lyophilized again. The reaction yield determined by elemental analysis Y = <NUM>%.

<NUM> of chitosan suspended in <NUM> of DMF was placed in a reaction vessel for solid state peptide synthesis and subjected to the action of microwaves (t=<NUM> minutes, P=<NUM> W, T=<NUM>). <NUM> HBTU, <NUM> HOBT and <NUM> DIPEA in <NUM> of DMF was added to the reaction vessel, The resulting mixture of chitosan with the activators was processed with microwaves (t=<NUM> minutes, P=<NUM> W, T=<NUM>), thus activating the function groups of the polymer. Next, <NUM> of bacitracin dissolved in <NUM> of <NUM>:<NUM> DMF:H<NUM>O mixture was added to the vessel and subjected twice to the action of microwaves (t=<NUM> minutes, P=<NUM> W, T<<NUM>). The suspension was transferred to a centrifugation vessel and centrifuged. The supernatant was decanted. The obtained modified biopolymer was suspended three times in fresh portions of DMF, and then centrifuged and decanted. This procedure was repeated with the use of methylene chloride. After these three washes with methylene chloride the precipitation was frozen in liquid nitrogen and lyophilized. The lyophilized precipitate was washed three times with distilled water and lyophilized again. The reaction yield determined by elemental analysis Y = <NUM>%.

<NUM> of chitosan suspended in <NUM> of DMF was placed in a reaction vessel for solid state peptide synthesis and subjected to the action of microwaves (t=<NUM> minutes, P=<NUM> W, T=<NUM>). <NUM> HBTU, <NUM> HOBT and <NUM> DIPEA in <NUM> of DMF was added to the reaction vessel. The resulting mixture of chitosan with the activators was processed with microwaves (t=<NUM> minutes, P=<NUM> W, T=<NUM>), thus activating the function groups of the polymer. Next, <NUM> of ticarcillin dissolved in <NUM> of <NUM>:<NUM> DMF:H<NUM>O mixture was added to the vessel and subjected twice to the action of microwaves (t=<NUM> minutes, P=<NUM> W, T<<NUM>). The suspension was transferred to a centrifugation vessel and centrifuged. The supernatant was decanted. The obtained modified biopolymer was suspended three times in fresh portions of DMF, and then centrifuged and decanted. This procedure was repeated with the use of methylene chloride. After these three washes with methylene chloride the precipitation was frozen in liquid nitrogen and lyophilized. The lyophilized precipitate was washed three times with distilled water and lyophilized again. The reaction yield determined by elemental analysis Y = <NUM>%.

A <NUM> portion of unmodified commercially available chitosan and a <NUM> portion of glutathione modified chitosan obtained according to the invention were dispensed separately into two test tubes, followed by the addition of l ml of <NUM> nickel(II) chloride solution. A discoloration of pale green nickel(II) chloride solution was observed, accompanied by a change of the polymer color, to green for the unmodified chitosan, and to brown for the glutathione modified chitosan (<FIG>). The precipitate settled at the bottom of the test tube, leaving a clear colorless supernatant above. The Ni(II) content in the supernatant was determined by spectrophotometry, using its colored DTT complexes. The change of Ni(II) concentration in solution is illustrated on <FIG>.

In a vessel composed of three elements, designed for the purpose of this experiment and made with a 3D printer, two layers of dialysis membrane were mounted. The vessel was placed in a <NUM> beaker containing <NUM> of deionized water and a magnetic stirrer. The setup was placed on a magnetic stirrer and used as control experiment. In two further identical vessels <NUM> of commercially available chitosan or <NUM> of glutathione modified chitosan according to the invention was placed between the membrane layers. <NUM> of a <NUM> solution of nickel(II) chloride was placed in the inner cylinder of each vessel, and the vessels were placed in <NUM> beakers containing <NUM> of deionized water each. All setups were stirred for <NUM> hours, thus allowing for diffusion of Ni<NUM>+ ions across the dialysis membranes and across the layer of chitosan or modified chitosan present between the membranes, respectively. Then, the Ni<NUM>+ concentrations present in water solutions in each of the beakers were determined. Both polymers demonstrated barrier action with the metal ion concentration detected nearly <NUM> times tower than that in the control. The results in the last column of Table <NUM> were calculated on the basis of reaction yield Y = <NUM>% given in Example <NUM>.

The above Table <NUM> clearly shows that the presence of the chitosan derivative causes a significant reduction of diffusion of Ni<NUM>+ ions to solution and the chitosan derivative is over <NUM>% more potent than chitosan itself in capturing Ni<NUM>+. A cosmetic composition containing the chitosan derivative according to the invention as active component has analogous properties, limiting the access of sensitizing ions after placing the composition on the skin.

A use of a new agent (glutathione modified chitosan) provides for effective and simple recovery of metals from water solutions. The use of any desired modifier molecule of chitosan provides an opportunity for controlling the metal chelation properties of the biopolymer, while preserving its biocompatibility and nontoxicity.

The use of chitosan or other biocompatible biopolymer susceptible for attaching modifier molecules, such as of antibiotics used for treatment of dermatitis provides a basis for obtaining new materials for dermatological use.

Claim 1:
A chitosan derivative, wherein said chitosan is modified with glutathione with the formation of a peptide bond, to form chitathione, a compound having peptide bonds between amine groups of units of poly(<NUM>-deoxy-<NUM>-aminoglucose) and available carboxyl groups of glutathione, for use in preventing symptoms of skin allergy caused by the contact with metals, especially heavy metals, in particular nickel.