Abstract: We hypothesize that calcium phosphate (CAP) coated polysaccharide as vaccine adjuvant can improve the transmission efficiency as well as enhance immune response.In this study,unpurified polysaccaride krestins (PSK) was treated in traditional craft.PSK was then oxidized by sodium periodate to obtain a multi-aldehyde product.PSK-aldehyde was reacted with pamidronate (PA) to obtain Pa-modified PSK (PSK-PA) and the products were identified by infrared spectrum (IR).PSK-PA was used to synthesize CAP nanoparticles by co-precipitation method.The size and PDI was used to optimize the formulation of the nanoparticle.The morphology of nanoparticles was observed using scanning electron microscope (SEM).Subsequently,ovalbumin (OVA),used as a model antigen,was loaded into the nanoparticles to examine the cytotoxicity on RAW264.7.The uptake of PSK-CAP-OVA-FITC loaded nanoparticle was investigated on RAW264.7 by fluorescent microscopy.The average diameter of the nanoparticles was about 100 nm with a PDI less than 0.3 indicating a homogeneous dispersion.Interestingly,the toxicity of PSK-CAP-OVA nanoparticles was significantly reduced when compared to the free PA.Additionally,we observed that Raw264.7 cell preferentially uptake the PSK-CAP-OVA nanoparticles compared to that of the free OVA.In conclusion,PSK-CAP nanoparticles can provide a reference for future studies on immune adjuvants.

Key words: PSK, calcium phosphate nanoparticles, vaccine adjuvant, OVA, nanoparticle characterization