A novel oral protein delivery system with enhanced intestinal penetration and improved antigen stability based on chitosan (CS) nanoparticles and antigen-cyclodextrin (CD) inclusion complex was prepared by a precipitation/coacervation method. Ovalbumin (OVA) as a model antigen was firstly encapsulated by cyclodextrin, either β-cyclodextrin (β-CD) or carboxymethyl-hydroxypropyl-β-cyclodextrin (CM-HP-β-CD) and formed OVA-CD inclusion complexes, which were then loaded to chitosan nanoparticles to form OVA loaded β-CD/CS or CM-HP-β-CD/CS nanoparticles with uniform particle size (836.3 and 779.2 nm, respectively) and improved OVA loading efficiency (27.6% and 20.4%, respectively). In vitro drug release studies mimicking oral delivery condition of OVA loaded CD/CS nanoparticles showed low initial releases at pH 1.2 for 2 h less than 3.0% and a delayed release which was below to 30% at pH 6.8 for further 72 h. More importantly, after oral administration of OVA loaded β-CD/CS nanoparticles to Balb/c mice, OVA-specific sIgA levels in jejunum of OVA loaded β-CD/CS nanoparticles were 3.6-fold and 1.9-fold higher than that of OVA solution and OVA loaded chitosan nanoparticles, respectively. In vivo evaluation results showed that OVA loaded CD/CS nanoparticles could enhance its efficacy for inducing intestinal mucosal immune response. In conclusion, our data suggested that CD/CS nanoparticles could serve as a promising antigen-delivery system for oral vaccination.
Conclusion
A novel oral protein delivery system, OVA-loaded CD/CS nanoparticles, was successfully prepared by a precipita- tion/coacervation method with enhanced oral absorption, penetration and improvement of OVA stability from cyclodex- trin and chitosan. The formation of OVA-CD inclusion com- plexes was verified by molecular docking. OVA loaded CD/CS nanoparticles had uniform particle size and exhibited higher OVA encapsulation efficiency and slower drug release rate in vitro. More importantly, in vivo evaluation results showed OVA loaded CD/CS nanoparticles could enhance its efficacy in in- ducing intestinal mucosal immune response. Thus, we con- sider that CD/CS nanoparticles can be used as a promising oral antigen delivery system to improve the immunogenicity of oral protein delivery.
