ATP stabilised and sensitised calcium phosphate nanoparticles as effective adjuvants for a DNA vaccine against cancer.

Cancer vaccines based on DNA encoding oncogenes have shown great potential in preclinical studies. However, the efficacy of DNA vaccines is limited by their weak immunogenicity because of low cellular internalisation and insufficient activation of dendritic cells (DCs). Calcium phosphate (CP) nanoparticles (NPs) are biodegradable vehicles with low toxicity and high loading capacity of DNA but suffer from stability issues. Here we employed adenosine triphosphate (ATP) as a dual functional agent, i.e. stabiliser for CP and immunological adjuvant, and applied the ATP-modified CP (ACP) NPs to the DNA vaccine. ACP NP-enhanced cellular uptake and improved transfection efficiency of DNA vaccine, and further showed the ability to activate DCs that are critical for them to prime T cells in cancer immunotherapy. As a result, a higher level of antigen-specific antibody with stronger tumour growth inhibition was achieved in mice immunised with the ACP-DNA vaccine. Overall, this one-step synthesised ACP NPs are an efficient nano-delivery system and nano-adjuvant for cancer DNA vaccines.