FUNCTIONALITY OF PROTECTIVE COLLOIDS AFFECTING THE FORMATION, SIZE UNIFORMITY AND MORPHOLOGY OF DRUG-FREE POLYLACTIC ACID MICROSPHERES

Drug-free polylactic acid (PLA) microspheres were prepared by an emuls ification-solvent evaporation technique using different types of prote ctive colloids. The influence of five types of hydrophilic prolymers ( polysaccharides, proteins, synthetic cellulose derivatives, synthetic nonionic polymers and surfactants) on the formation, size uniformity a nd morphology of PLA microspheres was investigated. Four characteristi c functions (surface activity, viscosity, electric charge and interfac ial film formation) of the hydrophilic polymer aqueous solutions were used to evaluate the efficacy of these protective colloids used. The r esults indicate that these four functions were the key parameters to a chieve the formation of PLA microspheres. The best protective colloid should have high surface activity, optimum viscosity, adequate electri c charge, and form an interfacial film to give a higher recovery, bett er size uniformity and smoother topography of the PLA microspheres.