Immunization with functionalized carbon nanotubes enhances the antibody response against mode antigen ovalbumin

Carbon nanotubes (CNTs) have attracted considerable attention because of their potential application as a new nonvehicle. We have covalently conjugated the mode antigen ovalbumin (OVA) to functionalized multi-walled carbon nanotubes. Herein, we explored the underlying theoretical mechanisms of CNTs' immunological adjuvant characterization. In vitro, the efficiency of cellular uptake of MWCNT-OVA into DC2.4 cells was improved over that of pure-antigen OVA. The costimulators (CD40/86), the major histocompatibility complex MHCII molecules, and the CD11c molecules were found to be upregulated. Further in vivo experiments established that the MWCNT-OVA group enhanced the IL-1β, TNF-α, and IL-6 cytokine secretion, suggesting that MWCNT reinforced the immune response using different cytokine pathways. Anti-OVA antibodies after inoculation of MWCNT-OVA into mice were measured. The medium dose of MWCNTs conjugated with OVA induced the highest level of OVA-specific antibodies at day 82 and have a synergistic effect with the commercial Freund's adjuvant. MWCNTs-KLH-MC-LR also induced higher levels of MC-LR-specific antibody than did KLH-MC-LR. MWCNTs also could activate the complement system which is closely related with humoral immunity. These results suggested that MWCNTs enhance the immune response and show excellent inherent characteristics to be applied as an adjuvant.