SELECTIVELY BINDING AND MAGNETICALLY RESPONSIBLE NANOPARTICLES

Abstract: The present application relates to a particle with a superparamagnetic core. Synthetic peptides or carbohydrates, capable of binding to targets such as tissues or organs, are arranged on the surface of the particles. The particles can be used for treatment of cancer, infections, metabolic disorders, disorders related to the immune system and genetic diseases. In one embodiment, drug or effector molecules may be bound to the surface of the particles.

Description: SELECTIVELY BINDING AND MAGNETICALLY RESPONSIBLE NANOPARTICLES The present invention relates to magnetically responsible particles which are applicable for medical use. BACKGROUND OF THE INVENTION The main component m commercially available mag- netically responsible particles m most cases consists of ferrite/magnetite (a special type of iron oxide having magnetic properties, i.e. its relative magnetic permeability is very high) . The particles contain a super- paramagnetic core which can be enclosed m or mixed with a polymer, such as dextran or protein, or surrounded by an outer monolayer or bilayer of amphiphatic molecules, such as fatty acids or derivates thereof. This outer coating consisting of polymer or amphiphatic molecules prevents che superparamagnetic core from aggregating with other adjacent cores and forming larger particles which have undesired permanent -magnetic properties (1) . The outer coating has been used for chemical association of other molecules, for instance, receptors and antibodies, to the surface of the magnetically responsible particles, which thus obtain selectively binding properties. Presently, magnetically responsible particles, m the size of ten nanometres up to a few micrometres, with modified surfaces are commercially available for various purposes, such as preparation of RNA, synthesis of cDNA libraries on solid phase, protein purification, carriers m lmmunologic analyses, ion exchange and affinity chro- matography and purification of cells, viruses, organelles and proteins (2, 3) . Such particles have also recently proved to be usable as markers m lmmunologic analyses (1) . Development of magnetically responsible particles m the size of one to a few hundred nanometres is m progress, since such particles are sufficiently small to form stable colloidal aqueous solutions, so-called ferrofluids which can be used for injection m humans and animals. A suitably constructed particle with optimal properties as to selectivity, biocompatibility and toxicity offers the possibility of recognising and binding to different targets (such as tissues or organs) m an organism, which enables the development of new powerful drugs against e.g. cancer. It is already known that the advantage of using mag- netically responsible particles m connection with therapy is that toxicity can be produced directly (heating of the core) or indirectly (thermal activation via the core of thermoactivatable toxic molecules which are bound to the coating) when the particles are exposed to an applied magnetic field. By associating special recognition molecules to the coating of the magnetically responsible particle, the particles can be concentrated m vivo m a target . The type of molecules which are capable of specifically rec- ognismg and binding to other biomolecules can, for instance, be a receptor, a receptor ligand, an enzyme or an antibody. In the applications described m the literature, use is primarily made of antibodies which are directly bound to the magnetically responsible particles to be able to target said particles (4, 5) . However, when the size of the magnetically responsible particles is m the nanometre range (one to a few hundred nanometres) there may be problems m associating one or more native proteins to the limited surface with- out getting undesirable mtermolecular interactions (e.g. steric blocking of active sites) or an undesirable increase of the particle size (destabilises the colloidal properties, undesirable aggregation and obstructed passage through biological structures and membranes) . To ensure the provision of the colloidal stability of ferrofluids, the particle size of the recognition molecule should not exceed 10 nm, whereas a protein has an average size of 2-10 nm (6) . SUMMARY OF THE INVENTION The invention relates to a magnetically responsible particle comprising a superparamagnetic core and an outer coating which contains at least one type of synthetic or partially synthetic molecules having at least one recognition function. Preferably, the particle has a diameter of 10 nm or less. At least one of the constituents included m the core suitably consists of at least one metal or a derivative thereof, such as an oxide. In one embodiment of the particle, the core and the coating do not form separate units but constitute a chemically homogeneous mass. The synthetic or partially synthetic molecules, for instance, consist of a peptide having a length of 1 to 30 ammo acids or of a carbohydrate polymer having a length of 1 to 30 carbohydrate units. The particle according to the present invention can be used as a therapeutic agent combination with an alternating homogeneous magnetic field or gradient magnetic field for treating different types of diseases. Examples of diseases are cancer, fungal and bacterial infections, protozoan infections, virus infections, metabolic disorders, immune defence diseases and genetically related diseases . The therapeutic effect of the particle can be fur- ther enhanced by modifying its surface with one or more effector molecules comprising, inter alia, cytostatics, toxins, enzymes, heavy metals, biocompatibility promoting substances, substances which facilitate the transport of the particle through vascular walls and tissues. The particle according to the invention can also be used as a subcomponent m bioassay. BRIEF DESCRIPTION OF THE DRAWING Fig. 1 is a schematic drawing of the particle according to the present invention. DETAILED DESCRIPTION OF THE INVENTION The particle according to the invention utilises synthetic peptides instead of proteins to circumvent the above-mentioned problems. By starting from short (1-30 ammo acids which corresponds to 1-10 % of a native protein) synthetic or partially synthetic peptides, which have been selected by computer design or from a synthetic peptide library using the target cell or the target molecule as a reference, the problems when using native proteins are circumvented. Further advantages of a synthetic or semisynthetic peptide is the increase stability for which these peptides can also be selected, because the binding activity of the recognition molecule is not as sensitive during production and handling as, for instance, an antibody. The synthetic or partially synthetic peptides can be replaced by selectively binding synthetic or partially synthetic carbohydrate-based polymers, which consist of 1-30 identical or different carbohydrate units. Patent Specification US 4,323,056 (Borelli et al) (7) discloses ferromagnetic particles designed for cancer therapy. These particles contain a magnetically responsible core incorporated a ceramic material, which is derivatised with tumour-specifIC ions, antibodies and/or similar bioactive molecules directed towards the tumour. However, the present invention use is not at all made of native proteins or defined bioactive molecules, which makes the particles described herein unique. The magnetically responsible particle and a possible configuration are illustrated Fig. 1. The magnetically responsible core 1 m the particle mainly consists of magnetite (iron oxide) . Furthermore, the particle is covered with an outer layer 2 consisting of a derivatised polymer (Dextran) or a monolayer or alternatively a bi- layer of derivatised fatty acids. The choice of the type (number of ammo acid or carbohydrate units and sequence) of ligand 3 to be used for the deπvatisation is individually adjusted for each application of the magneti- cally responsible particle, whose therapeutic effect can be further enhanced by further modifying its surface with one or more effector molecules 4. The manufacturing process of magnetically responsible particles containing a synthetic polypetide with recognition function for HIV virus is described m Example I. Naturally, it is not difficult for the one skilled m the art to modify the formula by using alternative libraries or computer designs for the construction of the polypeptide, or alternatively to choose other targets than HIV virus, such as cells, bacteria, viruses, fungi, protozoa. Other alternatives consist m replacing the polypeptide by other artificial recognition molecules or using other metal salts, alternatively replacing Dextran by other polymers or fatty acids. It is, of course, also possible to replace the NaI0 4 -coupling method by other prior-art coupling techniques. The invention will be described m more detail by means of the following non-limitmg Example. EXAMPLE 1 Manufacture of magneti cally responsibl e parti cl es wi th affini ty to HIV virus . HIV virus protein capsids are adsorbed according to standard procedure protocol (8) (which is provided by the manufacturer) to wells microtitre plates. Subse- quently, 10 11 colony forming units (cfu) of an M13-phage library are added, with a DNA fragment inserted m the pill gene of 36 randomised base pairs, TBS with 1 mg/ml of bovme serum albumin. After 1 h incubation at 37°C, the wells are thoroughly washed with TBS-contammg 1 mg/ml of bovme serum albumin Selected bacteriophages are eluated by adding a solution with pH 2.2 containing 1 mg/ml of bovme serum albumin and 0.1 N HCl . The eluate is permitted to infect E. coli cells according to standard procedure protocols. Selected clones are DNA se- quenced by means of standard procedure protocols, after which 100 μig of synthetic polypeptide with affinity to HIV virus is produced preparatively . A solution containing 100 mM FeCl 2 , 150 mM FeCl 3 and 6% Dextran (having a molecular weight of 70,000 g/mol) is precipitated in a beaker by adding 28% NH 3 . The precipitation takes place at 50°C and is allowed to continue for 3 h. Subsequently, the solution is centrifuged (5500 rpm) for 50 min and finally dialysed against distilled water with a dialysis tubing (MWCO 70 kDa) . The final product is a brownish solution containing magnetically responsible particles with an approximate diameter of 10 nm. 1 mg NaI0 4 is added to 1 ml of the brownish solution containing the magnetically responsible particles. The solution is allowed to stand for 20 min at 75°C, whereby the hydroxyl groups on the Dextran coating of the particles are activated. The synthetic polypeptide is added and the mixture is incubated over night, amino groups on the synthetic polypeptide binding covalently to the activated hydroxyl groups on the Dextran coating of the particles. Then blocking is performed with 10 mM glycine over night. The reaction mixture is dialysed against distilled water and evaporated, which finally results in a brown powder containing magnetically responsible particles (10 nm) having affinity to HIV virus. REFERENCES 1. Larsson, K. Kriz, K. and Kriz, D. Magnetic transducers in Biosensors and Bioassays . Analysis, No. 7, 1999. 2. Jordan, A., Wust P., Scholz R., Faehling H., Krause J. & Felix R. Magnetic Fluid Hyperthermia, 569-597, in Scientific and Clinical Applications of Magnetic Carriers, edited by Hafeli U. , Schutt W., Teller J. and Zborowski _M. Plenum. Press 1997.. 3. Mosbach, K. and Kriz, D. Framstallning and anvandning av magnetiskt paverkbara polymerpartiklar. Swedish Patent Application SE 9400938-8. 4. Sestier C, Da Silva M.F., Sabolovic D., Roger J. & Pons J.N. Surface modification of superparamagnetic nano- particles (Ferrofluid) studied with particle electropho- resis: Application to the specific targeting of cells. Electrophoresis, 19, 1220-1226, 1998. 5. Halbreich A., Roger J., Pons J.N., Geldwerth D., Da Silva M.F., Roudier M. & Bacri J.C. Biomedical applica- tions of maghemite ferrofluid. Biochimie, 80, 379-90, 1998. 6. Mathews C.K., & van Holde K.E., BIOCHEMISTRY, The Benj amin/Cummings Publishing Company, 1990. 7. Borelli N.F., Luderer A.A. & Panzarino J. N. Radio frequency induced hyperthermia for tumor therapy. US Patent No. 4,323,056, 1982. 8. Scott J.K. & Smith G.P. Biopanning . Science, 249, 386- 390, 1990.

Claims: CLAIMS 1. A magnetically responsible particle, c h a r - a c t e r i s e d in that it comprises a superparamagnetic core and an outer coating which contains at least one type of synthetic or partially synthetic molecules with at least one recognition function. 2. A particle as claimed in claim 1, c h a r a c -_ t e r i s e d in that its diameter is 10 nm or less. 3. A particle as claimed in claim 1 or 2 , c h a r a c t e r i s e d in that at least one of the constituents included in the core consists of at least one metal or a derivative thereof, such as an oxide. 4. A particle as claimed in any one of claims 1-3, c h a r a c t e r i s e d in that the core and the coating do not form separate units but constitute a chemically homogeneous mass. 5. A particle as claimed in any one of claims 1-4, c h a r a c t e r i s e d in that the synthetic or partially synthetic molecules consist of a peptide having a length of 1 to 30 amino acids. 6. A particle as claimed in any one of claims 1-5, c h a r a c t e r i s e d in that the synthetic or par- tially synthetic molecules consist of a carbohydrate polymer having a length of 1 to 30 carbohydrate units. 7. A particle as claimed in any one of claims 1-6 for use as a therapeutic agent in combination with an alternating homogeneous magnetic field or gradient mag- netic field for treating different types of diseases. 8. A particle as claimed in claim 7 intended for treating cancer, fungal and bacterial infections, protozoan infections, virus infections, metabolic disorders, immune defence diseases and genetically related diseases. 9. A particle as claimed in claim 7 or 8, c h a r a c t e r i s e d in that the therapeutic effect of the particle has been further enhanced by modifying its sur- face with one or more effector molecules comprising, inter alia, cytostatics, toxins, enzymes, heavy metals, biocompatibility promoting substances, substances which facilitate the transport of the particle through vascular walls and tissues. 10. A particle as claimed in any one of claims 1-6, for use as a subcomponent in bioassay.

Inventors: FREDRIKSSON SARAH, KRIZ DARIO, FREDRIKSSON, SARAH, KRIZ, DARIO
Applicants: EUROP I OF SCIENCE AB, FREDRIKSSON SARAH, KRIZ DARIO, EUROPEAN INSTITUTE OF SCIENCE AB, FREDRIKSSON, SARAH, KRIZ, DARIO
Application year: 2000
Main classification: G01N33
IPC codes: A61N2