NANOPARTICLE-BASED DRUG DELIVERY SYSTEMS

Nanoparticles are colloidal polymer particles of a size below 1-mu-m that are used as carriers for drugs as well as for vaccines. The drugs or antigens may be entrapped in the polymer matrix in particulate form or in the form of a solid solution, or they may be bound to the particle surface by adsorption. In certain cases, the drug also can be bound covalently to the polymer. The drug or antigen may be present during polymerization or may be added to previously produced particles. A number of preparation methods exist for the manufacture of nanoparticles. These methods include emulsion polymerization, interfacial polymerization, solvent evaporation, and denaturation or desolvation of natural proteins or carbohydrates. After intravenous injection, nanoparticles like other colloidal drug carriers accumulate in the reticuloendothelial system. This uptake into the reticuloendothelial system can be reduced and the body distribution altered by coating with certain materials such as surfactants. Another way of altering the body distribution is the incorporation of magnetite particles into the nanoparticles and subsequent targeting with a magnetic field. Other administration routes for nanoparticles include intramuscular or subcutaneous injection, peroral, and ocular administration. Parenteral administration of a number of cytostatic drugs or antibiotics leads to an enhanced efficacy or reduced toxicity of these drugs, or to both, thus resulting in an improvement of the therapeutic index by binding to nanoparticles. The binding of vincamine and especially insulin to nanoparticles resulted in an enhancement of the bioavailability after peroral administration. The elimination rate of nanoparticles from the eye is considerably slower than that of aqueous eyedrop solutions. Probably for this reason, the miosis time and the duration of the intraocular pressure reduction were considerably prolonged after binding of pilocarpine to polycyanoacrylate nanoparticles. The retention of nanoparticles was greater in inflamed than in normal eyes, indicating a potential for targeting to inflamed tissue. Poly(methyl methacrylate) nanoparticles are powerful adjuvants for some antigens. These nanoparticles improved the antibody response and the protection against challenge with life virus in comparison to the classical adjuvant aluminium hydroxide using influenza as a model antigen. In addition, the duration of these effects as well as the stability against heat inactivation was improved.