Electron beam induced water-soluble silk fibroin nanoparticles as a natural antioxidant and reducing agent for a green synthesis of gold nanocolloid

• WSSF-NPs were successfully prepared using electron beam irradiation.
• Electron beam irradiation reduces MW of SF from 250 to 37 kDa.
• WSSF-NPs are spherical with nanoscaled size as small as 40 nm.
• WSSF-NPs show effective antioxidant and reducing power than non-irradiated SF.
• WSSF-NPs display powerful reducing agent for green synthesis of gold nanocolloid.

The research proposes a novel water-soluble silk fibroin nanoparticles (WSSF-NPs) created by electron beam irradiation. In this report, we demonstrate the effects of electron beam irradiation doses ranging from 1 to 30 kGy on the molecular weight (MW), nanostructure formation, antioxidant activity and reducing power of the WSSF-NPs. Electron beam-induced degradation of SF causing MW reduction from 250 to 37 kDa. Chemical characteristic functions of SF still remained after exposing to electron beam. The WSSF-NPs with the MW of 37 kDa exhibited spherical morphology with a nanoscaled size of 40 nm. Antioxidant activities and reducing powers were investigated using 2,2-diphenyl-1-picrylhryl free radical (DPPH∙) scavenging activity and ferric reducing antioxidant power (FRAP) assays, respectively. The WSSF-NPs showed greater antioxidant activity and reducing power than non-irradiated SF. By increasing their antioxidant and reducing power efficiencies, WSSF-NPs potentially created gold nanocolloid. WSSF-NPs produced by electron beam irradiation would be a great merit for the uses as a natural antioxidant additive and a green reducing agent in biomedical, cosmetic and food applications.