Nanogels, nanometer-sized hydrogels with three-dimensional networks, are useful biomaterials for delivery of bioactive molecules (e.g., drug, protein, and nucleic acid) into the targeted tissues. Pullulan, which is a polysaccharide long-chain polymer, forms self-assembled nanogels by introducing cholesterol groups. The cholesteryl group-bearing pullulan (CHP) nanogels are capable of incorporating vaccine antigen in the hydrogels in vitro, and releasing it while keeping its antigenicity and immunogenicity in vivo. One practical advantage of using the CHP nanogels is that the further beneficial properties can be freely added on their original characters. For example, cationic type CHP (cCHP) nanogels, which are bioengineered by adding amine groups to CHP nanogels, enables us to deliver vaccine antigen into the negatively charged nasal epithelium efficiently following nasal administration, resulting in effective uptaking of the antigen by nasal dendritic cells that possesses important roles in inducing the antigen-specific immune responses in nasal mucosa. In this chapter, we review the immunobiological characteristics of cCHP nanogels as potential antigen delivery vehicles for nasal vaccine.
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