Adsorption/desorption of human serum albumin at the surface of poly(lactic acid) nanoparticles prepared by a solvent evaporation process.

Biocompatible and biodegradable nanoparticles of poly(lactic acid) (100% L-lactic units = PLA) were prepared by an emulsion, microfluidization, and solvent evaporation method using human serum albumin (HSA) as a surface agent. A radiolabeling technique was employed to quantify the serum albumin bound to the nanoparticles and to measure its desorption kinetics in various media at 22 degrees C and 37 degrees C (phosphate buffer pH 7.4, serum albumin 40 g/L in phosphate buffer pH 7.4 and fetal calf serum). The amount of serum albumin bound to the nanoparticles was found to be a linear function of 1/D (where D is the nanoparticle mean diameter) and was related to the total developed area of the nanoparticles. The adsorption/desorption behavior of serum albumin at the surface of the nanoparticles suggested a multilayer adsorption model. Moreover, a part of the serum albumin molecules was irreversibly bound regardless of the incubation conditions. Consequently, the classical Langmuirian theories of equilibria could not be applied.