*2.2. Preparation of Silk Sericin Nanoparticles*

Firstly, silk sericin solutions were obtained by direct dissolution of protein in distilled water considering the hydrophilic character and good water solubility. Briefly, solutions with 0.1, 0.25, 0.5, and 1% (*w*/*v*) were prepared under moderate stirring at room temperature.

Silk sericin nanoparticles were prepared via nanoprecipitation in which silk sericin solutions (0.1, 0.25, 0.5, and 1% *w*/*v*) were added into an organic phase of a nonsolvent, acetone. The nanoprecipitation technique involved the drop-wise addition of protein aqueous solution into acetone under vigorous stirring. The resulted nanoparticles were recovered by water and acetone vaporization. The workflow of nanoparticle preparation is shown in Scheme 1. The nanoparticle formulations were called SER 0.1%–SER 1% following the sericin concentration.
