Mechanistic study of the uptake of wheat germ agglutinin-conjugated PLGA nanoparticles by A549 cells

The purpose of this study was to evaluate the extent and mechanism of uptake of wheat germ agglutinin-conjugated PLGA nanoparticles by A549 cells. PLGA nanoparticles of 150 nm were prepared by a solvent diffusion method and covalently conjugated to FITC-WGA (fWGA) or FITC-bovine serum albumin (fBSA) by a two-step carbodiimide method. Uptake of fWGA-PLGA and fBSA-PLGA nanoparticles by confluent A549 cells was quantified by fluorometry. A549 cellular uptake of fWGA-PLGA nanoparticles at 2 h, 37degreesC was 5.02-fold that of fBSA-PLGA nanoparticles at a loading concentration of 2.65 mg/mL. The difference in uptake between the two types of nanoparticles was increased to 7.84-fold at a higher loading concentration of 5.3 mg/mL, but was reduced to 2.07-fold by lowering the uptake temperature to 4degreesC. Coincubation with 5 mg/mL of unlabeled WGA negated the differential uptake of fwGA-PLGA nanoparticles at 4degreesC, suggesting that the nanoparticles interacted with a specific WGA-binding receptor on the cell membrane. Internalization of the fwGA-PLGA nanoparticles by the A549 cells was confirmed by confocal microscopy. Filipin (1 mug/mL), a known inhibitor of caveolae, reduced the 1-h uptake of the nanoparticles by 75%. Surface modification of PLGA nanoparticles with WGA significantly enhanced its endocytosis by A549 cells by a receptor-mediated, caveola-dependent pathway. (C) 2004 Wiley-Liss, Inc. and the American Pharmacists Association.