Modification of biodegradable poly(malate) and poly(lactic-co-glycolic acid) microparticles with low molecular polyethylene glycol.

Poly(lactic-co-glycolic acid) microparticles (PLGA-MP) and cross-linked poly(malate) microparticles (PMAL-MP) were prepared by solvent/extraction and polycondensation, respectively. Microparticles were modified with polyethylene glycol (PEG 400) which lowered the drug loading of PMAL-MP, but did not influence the loading of PLGA-MP. The drug release from PMAL-PEG-MP occurred by initial degradation to oligomeric fractions, followed by further hydrolysis of oligomers to free drug (dipyridamole). The complete release was achieved for 22 days, whereas the release from non-modified PMAL-MP took 38 days. The drug release from PLGA-PEG-MP was characterized with an initial burst effect, followed by slower release during 26 days. Thus, the modification with PEG could be used to achieve appropriate release of the selected antithrombotic drug.