Intracellular uptake of chitosan nanoparticle-based vaccines

Particle-based delivery systems are a promising approach to enhance antigen-specific immunity for use in vaccines. Chitosan, a natural polysaccharide derived from the exoskeletons of crustaceans, shows great potential as a vaccine carrier due to its favorable properties as a biomaterial, including biocompatibility and biodegradability. In this study, the intracellular uptake of chitosan nanoparticles is explored and compared to that of other commonly used particle-based delivery vehicles, such as poly (lactic-co-glycolic acid) (PLGA). Fluorescein isothiocyanate-labeled bovine serum albumin (FITC-BSA) was used as a model protein antigen and encapsulated in both chitosan particles via precipitation-coacervation and PLGA particles via double emulsion solvent evaporation. Fluorescence microscopy images showed that, when co-incubated with dendritic cells, all cells were found to internalize FITC-BSA-chitosan nanoparticles. Additionally, punctate fluorescence in the cytoplasm indicated that at least some of the particles were within endosomes at early (less than 24 hour) time points. Furthermore, flow cytometry results showed chitosan particles to have a greater uptake (74%) by dendritic cells compared to PLGA particles (32%) or soluble protein (43%) at early time points (1 hour)