**2. Materials and Methods**

### *2.1. Materials*

*Bombyx mori* silk sericin powder (quality level 200) and all other reagents, including sodium hydroxide (reagent grade, ≥98%, pellets, anhydrous), potassium phosphate (ACS reagent, ≥98%), hydrochloric acid (ACS reagent, 37%), doxorubicin (doxorubicin hydrochloride 98.0–102.0%, HPLC), protease XIV from *Streptomyces griseus* (≥3.5 units/mg solid), *α-Chymotrypsin* from bovine pancreas (≥40 units/mg protein), and nonsolvent acetone (ACS reagent, ≥99.5%) were provided by Sigma Aldrich (3050 SPRUCE Street, St. Louis, MO 63103, USA).
