PREPARATION AND DEGRADATION OF SURFACTANT-FREE PLAGA MICROSPHERES

PLA oligomers which have an amphiphilic surfactant-like structure with a polar head and a long hydrophobic tail were used to prepare self-stabilized microparticles of the PLAGA-type by the evaporation solvent method. It is shown that PLA50 oligomers prepared by polycondensation of DL-lactic acid were able to emulsify an organic solution of high molecular weight PLA37.5GA25 (37.5% L-LA, 37.5% D-LA and 25% GA units) in salt-containing aqueous media. Resulting microspheres were characterized by SEC, DSC, SEM and by size measurements. In vitro degradation was investigated. The mechanism of degradation is driven by the rapid release of oligomeric materials. However, the degradation rate of the high molecular weight components of the matrix was not greatly affected by the short-term presence of the oligomeric materials introduced as matrix-like surfactant. As an example, surfactant-free progesterone-containing microspheres were prepared by the solvent evaporation method.