Sodium alginate

Gel strength 90–110 gelatin A (GA, average 20–25 kDa) and trifluoroacetic acid (TFA) were purchased from Sigma–Aldrich (St Louis, MO, USA). Sodium alginate (SA), acetic acid, and acetonitrile (ACN) were purchased from Dae Jung (Gyeonggi-do, South Korea). Epidermal growth factor (EGF) was provided by Daewoong Pharmaceutical Co., Ltd. Dulbecco’s phosphate buffered saline (DPBS) was purchased from Welgene (Gyeongsangbuk-do, South Korea), Dulbecco’s Modified Eagle Medium (DMEM) was obtained from Hyclone (Logan, UT, USA), 0.25% Trypsin-EDTA and fetal bovine serum (FBS) were purchased from Gibco (Paisley, UK).
HaCaT cells were purchased from Lonza (Walkersville, MD, USA). The cell counting kit-8 (CCK-8) was obtained from Dojindo (Kumamoto, Japan). Human EGF antibody as primary antibody (R&D systems, Minneapolis, MN, USA), rabbit anti-mouse horseradish peroxidase (HRP) as secondary antibody (Abcam, Cambridge, UK) were purchased.

In this experiment, the chemicals purchased from Sigma-Aldrich (St. Louis, MO, USA) were as follows: caffeic acid, keracyanin chloride, kuromanin chloride, Folin-Ciocalteau reagent, quercetin, pepsin, and pancreatin. Aluminium chloride hexahydrate and potassium acetate were obtained from Junsei Chemical (Tokyo, Japan). Citric acid, sodium alginate, sodium acetate, potassium chloride, and sodium carbonate were purchased from Daejung Chemicals & Metals (Seoul, Korea).

All the chemicals were analytical-grade reagents. Calcium chloride dihydrate (CaCl₂·2H₂O, 85%) and sodium alginate (Na-Alg) were purchased from Daejung Chemicals & Metals Co. (Kyungpook, Korea). GO and polyacrylamide (PAM) were purchased from Aldrich (Tokyo, Japan). A simulated solution was prepared using ciprofloxacin (CPX, C₁₇H₁₈FN₃O₃, 98%, Aldrich, Tokyo, Japan). All solutions were prepared with ultrapure water (18.2 MΩ·cm) from Vivagen Co., Ltd. (EXL5 Analysis 16, Daejeon, Korea).