Physicochemical properties and adsorption state of aluminum adjuvants with different processes in vaccines

Aluminum salts are by far the most widely used adjuvants for human vaccines, showing acceptable safety and efficacy. Previous studies have shown that each aluminum adjuvant have different charges and morphologies, but whether the manufacturing and production processes affects the physicochemical properties of aluminum adjuvant has not yet been reported. In this study, we explored the physical and chemical properties of different aluminum adjuvants and Hib, sIPV antigens through particle size, zeta potential and morphological characteristics. The adsorption rate and efficacy were also investigated. The results showed that the preparation process had an impact on the physical and chemical properties of aluminum adjuvants, including differences in the particle size，zeta potential and morphological structure. Hib vaccine had larger particle size than sIPV vaccine with different aluminum adjuvants in the process of vaccine preparation. In addition, by measuring the adsorption rate, increasing the concentration of phosphate or Aluminum phosphate (AP) can improve the adsorption rate of Hib, but Aluminium hydroxide (AH) and amorphous aluminum hydroxyphosphate sulfate (AAHS) adjuvants are not affected. In vivo result showed that increasing the adsorption rate of Hib could enhance the Hib-IgG antibody titers. In conclusion, this study provides a reference for the application of adjuvants in vaccines by studying the physicochemical properties and adsorption conditions of different aluminum adjuvants and antigens.