INTERNALIZATION OF POLY(D,L-LACTIC ACID) NANOPARTICLES BY ISOLATED HUMAN-LEUKOCYTES AND ANALYSIS OF PLASMA-PROTEINS ADSORBED ONTO THE PARTICLES

The objective of this work was to investigate the interactions of poly (D,L-lactic acid) nanoparticles prepared by a recently developed salti ng-out process, with lymphocytes and monocytes isolated from healthy h uman donors. Nanoparticles were labeled with a hydrophobic fluorescent dye and incubated with lymphocytes and monocytes, and their uptake wa s followed by flow cytometry in the presence and absence of plasma. Pl asma protein adsorption increased nanoparticle uptake by monocytes, wh ereas a decrease of cellular binding of the nanoparticles to lymphocyt es was noted. The cellular uptake for both cell types consisted in a p assive adsorption and in an energy-requiring process, because the cell s became 2-3 times more fluorescent when the incubation temperature wa s increased from 4 to 37 degrees C. When nanoparticles were coated wit h polyethylene glycol 20,000, uptake by monocytes decreased by 43 and 78% in phosphate-buffered saline and plasma, respectively; a similar d ecrease in nanoparticle uptake was observed for lymphocytes. Two-dimen sional gel electrophoresis was performed to identify the plasma opsoni ns adsorbed onto the nanoparticle surface. Protein mappings for uncoat ed and polyethylene glycol-coated nanoparticles differed for two spot series. These spots, not yet clearly identified, may represent specifi c apolipoproteins involved in the metabolism of human lipoproteins, in dicating the possible involvement of specific receptors in the uptake of the nanoparticles. (C) 1994 John Wiley and Sons, Inc.