Chitosan/calcium phosphates nanosheet as a vaccine carrier for effective cross-presentation of exogenous antigens.

Chitosan/calcium phosphate nanosheet as a promising antigen carrier was prepared via the direct mixture of modified chitosan, PBS and CaCl. Specifically, chitosan was modified with catechol groups, and its water solubility under neutral conditions was improved. Then, nanosheet was formed by mixing modified chitosan and PBS followed by addition of CaCl. Antigen was entrapped into the nanosheet via coprecipitation during its preparation. The nanosheet composed of CaHPO·2HO crystals, was internalized by dendritic cells (DCs) via macropinocytosis with enhanced efficiency. The antigen endosomal escape induce by nanosheet was successful observed with intracellular Lysotracker and Lamp-1 staining. Moreover, DCs activation was triggered by the nanosheet along with the up-regulated expression of co-stimulation marker and production of Th1-type cytokines. More importantly, cross-presentation of antigens achieved by the nanosheet was markedly increased when compared to free antigen. Therefore, chitosan/calcium phosphate nanosheet could be used as a vaccine carrier for effective cross-presentation of exogenous antigens.