Effects of plasma proteins on degradation properties of poly(L-lactide) microcapsules.

The degradation rate of poly(L-lactide) microcapsules in an aqueous medium was accelerated by the addition of albumin, gamma-globulins, and fibrinogen. These proteins form adsorption layers on the surface of poly(L-lactide) microcapsules. At the interface between the microcapsules and the adsorbed protein layers, the value of the electric potential is expected to increase in magnitude, i.e., become highly negative compared with that at the interface between the microcapsules and the bulk buffer solution containing no plasma protein. This potential increase causes an increase in H+ concentration at that interface, which may result in an acceleration of the hydrolytic degradation rate of poly(L-lactide) microcapsules. Also, the presence of plasma proteins can increase the solubility of poly(L-lactide), causing the poly(L-lactide) molecules to exist in an expanded form. This effect may also accelerate the degradation of poly(L-lactide) microcapsules.