Novel polymer‐grafted starch microparticles for mucosal delivery of vaccines

Recent studies have demonstrated that systemic and mucosal administration of soluble antigens in biodegradable microparticles can potentiate antigen‐specific humoral and cellular immune responses. However, current microparticle formulations are not adequate for all vaccine antigens, necessitating the further development of microparticle carrier systems. In this study, we developed a novel microparticle fabrication technique in which human serum albumin (HSA) was entrapped in starch microparticles grafted with 3‐(triethoxysilyl)‐propyl‐terminated polydimethylsiloxane (TS‐PDMS), a biocompatible silicone polymer. The immunogenicity of HSA was preserved during the microparticle fabrication process. Following intraperitoneal immunization of mice, TS‐PDMS‐grafted microparticles (MP) dramatically enhanced serum IgG responses compared with ungrafted MP and soluble HSA alone (P < 0.001). When delivered orally, both TS‐PDMS‐grafted and ungrafted microparticles elicited HSA‐specific IgA responses in gut secretions, in contrast to orally administered soluble antigen. Indeed, TS‐PDMS‐grafted microparticles stimulated significantly stronger serum IgG (P < 0.005) and IgA (P < 0.001) responses compared with those elicited by ungrafted microparticles. These findings indicate that TS‐PDMS‐grafted starch microparticles have potential as systemic and mucosal vaccine delivery vehicles.