Metal-polyphenol nanoshells for enhancing the thermostability of a single viral vaccine†

Vaccines are essential to preventing infectious diseases, but their thermal instability leads to heavy reliance on cold chains. Physical encapsulation is the simplest and most effective strategy to increase the thermostability of vaccines. However, traditional mineralized coatings are strictly dependent on the properties of the substrate surface and synthesis conditions. Considering the instability and low surface charge density of vaccines, we developed a facile and robust approach for the protection of a single viral vaccine, tobacco mosaic virus (TMV), through metal-polyphenol networks of tannic acid (TA) and Fe^III, which significantly improved the thermostability of the viral vaccine by strengthening its conformational rigidity. We found that the formed TA-Fe^III nanoshells drastically enhanced the thermostability of the viral vaccine at a high temperature of 100 °C and in long-term storage at 37 °C. Additionally, the TA-Fe^III nanoshell did not destroy viral RNA, had excellent biocompatibility and was easily synthesized on the vaccine surface within seconds. This easy, low cost and substrate-independent approach makes the TA-Fe^III nanoshell a potential candidate for vaccine applications.