Effect of atmospheric cold plasma on structure, activity, and reversible assembly of the phytoferritin

Ferritin is characterized by a shell-like structure and a reversible self-assembly property. In this study, atmospheric cold plasma (ACP) was applied to red bean seed ferritin (RBF) to prepare an ACP-treated RBF (ACPF). Results indicated that the ACP treatment retained the shell-like structure of ferritin but reduced the α-helix/β-sheet contents and thermal stability. Iron oxidative deposition and release activities were also markedly changed. The ACPF could be disassembled at pH 4.0 and then assembled into an intact ferritin cage when pH was increased to 7.0, which was a more benign transition condition than that of the traditional method (pH 2.0/7.0 transition). By using this assembly routine, curcumin was successfully encapsulated within the ACPF with a size distribution of 12 nm. Moreover, the encapsulation ratio of curcumin in the ACPF reached 12.7% (w/w). This finding can be used to expand the application of ACP and improve the functionalization of the ferritin.