Programmed nanoparticle-loaded microparticles for effective antigen/adjuvant delivery

A microscale vaccine containing SiO_(2)nanoparticles loaded in CaC〇3 microparticles was constructed using the co-precipitation method.The antigen ovalbumin(OVA)was covalently conjugated with SiO_(2)nanoparticles,and these nanoparticles and CpG were co-encapsulated into CaCO_(3)microparticles,generating a vaccine with a size of approximately 5.2μm.Scanning electron microscopy(SEM),energy-dispersive X-ray(EDX),elemental mapping,and Fourier transform infrared(FTIR)analyses confirmed the successful preparation of the microscale vaccine;the vaccine had good storage stability without sustained antigen release,and negligible cytotoxicity to dendritic cells(DCs)and macrophages.Compared to SiO_(2)nanoparticles,the microscale vaccine can significantly improve antigen/adjuvant uptake.DCs internalized the entire microscale vaccine into lysosomes via macropinocytosis,and an increase in antigen endo/lysosomal escape was observed by confocal User scanning microscopy(CLSM).Specifically,DCs pulsed with the vaccine were fully mature,expressing high levels of costimulatory molecules(CD40,CD80,and CD86),MHCⅡ,and MHCⅠand secreting high levels of proinflammatory cytokines(IL-12,TNF-α,IL-1β,and IL-6).In addition,the vaccine had good in vivo biocompatibility,could protect the antigen from rapid degradation,and increased the retention time in lymph nodes.SiO_(2)nanoparticles-in-CaCO_(3)microparticles were an excellent carrier for antigen and adjuvant delivery.Hopefully,this study can provide some information on the design of microscale carriers for vaccine delivery systems.