Effect of wheat germ agglutinin density on cellular uptake and toxicity of wheat germ agglutinin conjugated PEG-PLA nanoparticles in Calu-3 cells.

Wheat germ agglutinin (WGA) modified PEG-PLA nanoparticles (WGA-NP) have demonstrated its potential for enhancing delivery of peptides into brain following intranasal administration. However, the effect of ligand density is less well known. WGA density may affect nanoparticles uptake in nasal epithelial cells through ligand-receptor interactions, and the damage to nasal tissue since WGA showed cytotoxicity to cells in a dose-dependent manner. In this study, the effect of WGA density on WGA-NP was studied with regard to both the uptake and toxicity in vitro, using Calu-3 cells, which express a number of N-acetylglucosamine on their cell surface. Nanoparticles containing different WGA ligand densities were prepared by controlling the molar ratio of thiolated WGA to maleimide-PEG-PLA (WGA/maleimide) and particles properties were examined. With the increase of WGA/maleimide ratio, the particle size, WGA density and the hemoagglutination increased, while the conjugation efficiency decreased. The in vitro study showed markedly enhanced endocytosis of WGA-NP compared to NP in Calu-3 cells and significant inhibition of uptake in the presence of chitin. Cytotoxicity of WGA-NP increased gradually with the increase of molar ratio of WGA to maleimide, nanoparticles concentration and incubation time. WGA-NP showed the highest efficiency of uptake and a mild cytotoxicity when the molar ratio of WGA to maleimide was 1:10. These results suggest that WGA density plays an important role in both cellular uptake and toxicity of WGA-NP via a receptor-mediated mechanism. Therefore, to achieve a more rational approach of drug delivery system design, the surface density of the targeting moiety on the nanoparticles surface should be considered.