Resveratrol

Crushed grape powder (including pericarp, seed, flesh, and grape stem) (Zero Co. Ltd., Chiba, Japan) was dissolved in 70% ethanol, macerated for 7 days, and centrifuged at 3000 rpm for 20 min. The supernatant was filtered through a 0.22 μm membrane and completely dried. The resulting grape extract was dissolved in DMSO and stored at –80 °C. Resveratrol (Wako, Osaka, Japan) was also dissolved in DMSO at 100 mM and stored at −80 °C. A UPLC system (UPLC–SYNAPT G2-S HDMS) from Waters Co. (MA, USA) was used to roughly calculate the Resveratrol content in the grape extract (Figure S3). HPLC separation was achieved on a 2.1 × 150 mm column (Waters Co., MA, USA). The mobile phases consisted of (A) water and (B) methanol. The separation was carried out at room temperature with a 0.2 mL/min flow rate, under the following conditions: 0–30 min, 0–50% B, 30–50 min, 50–95 % B, 50–55 min, 95 % B isocratic, 55–60 min, 100–0% B, followed by a 5 min re-equilibration time of the column. Calculated by comparing the peak area at the same position, the grape extract contained 7% Resveratrol, so the concentration of Resveratrol in 50 μg/mL (100 μg/ml) grape extract was determined to be about 15 μM (30 μM).

Resveratrol (Sigma-Aldrich, USA) dissolved in DMSO (1 mg/ml) was added into peptide solution (2% wt) to obtain the Resveratrol-loaded peptide-hydrogel. The samples with final Resveratrol concentrations of 8 and 32 μg/ml in 2% wt peptide (Pep/8RES and Pep/32RES) were, respectively, prepared. Hydrogels were formed by placing samples at 37°C for 30 min.
The hydrogel samples were immersed into 1 ml phosphate saline buffer (PBS) to detect the release kinetic of Resveratrol. The supernatants were collected after immersion for 1, 2, 3, 5, 7, 8, 10, 12 and 14 days, respectively. The Resveratrol concentrations in the collected samples were detected by high-performance liquid chromatography (E2695, Waters).