Development and physicochemical, toxicity and immunogenicity assessments of recombinant hepatitis B surface antigen (rHBsAg) entrapped in chitosan and mannosylated chitosan nanoparticles: as a novel vaccine delivery system and adjuvant.

In this study chitosan nanoparticles (CS NPs) and mannosylated chitosan nanoparticles (MCH NPs) loaded with recombinant hepatitis B surface antigen (rHBsAg) was synthesized as a vaccine delivery system and assessed toxically and immunologically. The physicochemical properties of the nanoparticles (NPs) were determined by methods including scanning electron microscope (SEM) and dynamic light scattering (DLS). The morphology of the NPs was semi spherical and the average diameter of the loaded CS and MCH NPs was found to be 189 and 239 nm, respectively. The release studies showed that after the initial burst, both of the loaded NPs provided a continuous and slow release of the antigens. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed concentration and time dependent toxicity profile for both formulations, but rHBsAg loaded CS nanoparticle showed higher toxicity due to smaller particle size and larger zeta potential. Abnormal toxicity test (ATT) results showed no signs of toxicity in mice and guinea-pigs treated with loaded MCHNPs. Stability test for six months showed acceptable changes in size, surface charge, and antigenicity for loaded MCH nanoparticles. Finally, in vivo immunogenicity study revealed greater adjuvant capability of MCH nanoparticles than others formulations. Our results showed MCH NPs can be used as a controlled and targeted vaccine delivery system.