INFLUENCE OF EXPERIMENTAL PARAMETERS ON THE CHARACTERISTICS OF POLY(LACTIC ACID) NANOPARTICLES PREPARED BY A DOUBLE EMULSION METHOD

Nanoparticles were prepared by the double emulsion method (w/o/w), usi ng methylene chloride as an organic solvent and polyvinyl alcohol (PVA ) or human serum albumin (HSA) as a surfactant. Experimental parameter s such as the preparation temperature, the solvent evaporation method, the internal aqueous phase volume, the surfactant concentration and t he polymer molecular weight were investigated for particle size, the z eta potential, the residual surfactant percentage and the polydispersi ty index. Preparation parameters leading to particles with well-define d characteristics such as an average size around 200 nm and a polydisp ersity index lower than 0.1 were identified, The conditions were optim ized to ensure protein encapsulation: a cool temperature, a short proc essing time, a sufficient internal aqueous phase and careful washing. It appeared that the higher the surfactant concentration in the extern al aqueous phase was, the smaller the particles, the lower the polydis persity index and the higher the residual amount of surfactant were. F or PVA or HSA, the agreement between the convenient surfactant concent ration and its critical aggregation concentration could be emphasized. Otherwise, an increased polymer molecular weight led both to a slight ly decreased particle size and to a lower polydispersity index. Moreov er, multilayer adsorption of PVA which does not depend on Poly(lactic- acid) molecular weight was exhibited. Finally, the zeta potential resu lted from the polymer molecular weight and the residual PVA. (C) 1998 Elsevier Science B.V.