Quantitative analysis of polyvinyl alcohol on the surface of poly(D, L-lactide-co-glycolide) microparticles prepared by solvent evaporation method: effect of particle size and PVA concentration.

Polyvinyl alcohol (PVA) is an emulsion stabilizer that is used in the solvent evaporation method for poly(D,L-lactide-co-glycolide) (PLG) microparticles preparation. In this study, the surface binding of PVA on PLG microparticles was quantitatively examined by employing gel permeation chromatography. The PVA binding can affect hydrophobicity and digestibility of the microparticle surface. GPC analysis detected the presence of PVA bound on the microparticle surfaces in an irreversible manner. The PVA content per weight of microparticle increased with the specific surface area as the particle size decreased. The surface PVA density, which is the PVA content per unit surface area of microparticle, changed with particle size in a biphasic manner. In the size range larger than 1 microm, the surface PVA density increased from 0.8 mg/m2 to 2.2 mg/m2 as the particle size decreased. But below 1 microm, the surface PVA density remained unchanged at about 1.8 mg/m2. The surface PVA density of PLG microparticles prepared in different PVA concentrations (0.1, 1, 5, 10% w/v) showed similar values and size dependency, indicating that the PVA concentration of the continuous phase did not affect the surface PVA density of PLG microparticles. These data suggest that the influence of the surface PVA layer would be larger in the smaller particles, but be independent of the PVA concentration of the continuous phase in the manufacturing process.