2022 Volume 30 Pages 93-103
We have succeeded in producing nanoparticles consisting solely of intact high-molecular-weight sericin protein, which has molecular weight comparable to that of the native state. Such intact sericin was obtained from the “Sericin Hope” silkworm variety bred in Japan. Nanoparticles were prepared using a so-called anti-solvent diffusion method by which the aqueous solution of intact sericin was added dropwise to ethanol (EtOH). Morphological transmission electron microscopy (TEM) observations were performed of nanoparticle sericin dispersed in the 75% EtOH aqueous solution, which is a mixed solution produced by dropping an aqueous solution of sericin onto EtOH. Effect of the concentration of dropped sericin on particle size was evaluated using dynamic light scattering (DLS) measurements. The particle size became uniform at concentrations lower than 1.0 wt%. For concentrations <1.0 wt%, the average size of nanoparticles was 10–30 nm, and lower concentrations were associated with larger nanoparticles. Nanoparticle-dispersed EtOH aqueous solutions were colorless and transparent. The transparency remained unchanged for at least one month. The particle morphologies also remained unchanged. The nanoparticle structure, which was maintained even in water after EtOH was removed, was maintained even after freeze-drying. Results of SDS-PAGE show that the same molecular weight as those of native sericin was maintained in the nanoparticles. The intact or partially degraded high-molecular-weight sericin proteins constituted the nanoparticles obtained in this study.
