In vivo self-assembly of an intact functional cage protein: Intracellular generation of chimeric ferritins without disassembly-involved damage

Ferritin (Fn) is an attractive nano-biomaterial with a hollow structure. Functional chimeric cage-protein Fns (chimera-Fn) can be designed by combining two different monomer subunits. However, unavoidable damage is induced by the severe disassembly conditions required for preparing the Fn monomer. Here, a biocompatible method using a designed dual-expression vector to obtain chimera-Fns without a damage-inducing process is described. Fn monomer and silica-forming peptide (Kpt)-fused Fn monomer are expressed simultaneously and assembled within host-cells to form chimera-Fn of Kpt. Characteristic analysis showed that the chimera-Fns obtained intracellularly were composed of the two monomers in a ratio of 1:1. Morphological and functional analyses determined that the intracellularly-generated chimera-Fns had more intact forms and bioactive functions compared with those produced by chemical-involved disassembly and reassembly. This is the first report about the in vivo self-assembly of chimera-Fn with intact function and hold promise in designing functional templates for various nanomaterial preparations.