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-st abilized microparticles of the PLAGA-type by the evaporation solvent m ethod. It is shown that PLA50 oligomers prepared by polycondensation o f DL-lactic acid were able to emulsify an organic solution of high mol ecular weight PLA37.5GA25 (37.5% L-LA, 37.5% D-LA and 25% GA units) in salt-containing aqueous media. Resulting microspheres were characteri zed by SEC, DSC, SEM and by size measurements. In vitro degradation wa s investigated. The mechanism of degradation is driven by the rapid re lease of oligomeric materials. However, the degradation rate of the hi gh molecular weight components of the matrix was not greatly affected by the short-term presence of the oligomeric materials introduced as m atrix-like surfactant. As an example, surfactant-free progesterone-con taining microspheres were prepared by the solvent evaporation method.