Design of silaffin-fused ferritin and its silica-coated form as a new drug delivery agent

Ferritin (FT), an iron storage and transport protein found in most living organisms, comprises 24 subunits with interior and exterior diameters of 8 and 12 nm, respectively. FT without iron has the capacity to load many... [ view full abstract ]

Ferritin (FT), an iron storage and transport protein found in most living organisms, comprises 24 subunits with interior and exterior diameters of 8 and 12 nm, respectively. FT without iron has the capacity to load many types of metals or small molecules into its interior; thus, FT nanocages have attracted much attention as an ideal drug delivery system (DDS). In order to design FT as a more efficient agent for DDS, FT with silica-forming ability was developed by fusion of the silaffin peptide (Sp) found in diatom with FT at its N-terminus. In such newly-designed fusion protein(Sp-FT), the N-terminal SP is exposed on the surface of the designed FT and can mediate the silica deposition on the surface to generate silica-coated protein (SiO₂/Sp-FT). To investigate the potential of Sp-FT as DDS agent, the release pattern of drug was analyzed. Doxorubicin (Dox), the model drug, was loaded into cage interior by re-assembly of Sp-FT, then was coated additionally with silica matrix by Sp-mediated silicification. The loading amount of Dox by SiO₂/Sp-FT was larger than that of FT. Moreover, the release of loaded Dox was controlled and retarded by the silica-coated matrix. These results showed that the designed SiO₂/Sp-FT is favorable agent for DDS. Moreover, the Sp-FT provides a biocompatible and eco-friendly manufacturing process for the preparation of silica nanoparticles with drug compared to conventional production methods. Therefore, SiO₂/Sp-FT, new silica-protein composite particles developed here is advantageous for applications in the biological and medical fields.