Glutaraldehyde aqueous solution

Microcrystalline cellulose (MCC) powder was supplied by FMC BioPolymer (Avicel-PH101, Philadelphia, PA, USA), 95% Sulfuric acid (H₂SO₄) Reagent Grade was procured from VWR Chemicals (Randor, PA, USA), 25 wt.% glutaraldehyde aqueous solution was purchased from Sigma-Aldrich (St. Louis, MO, USA).

Castor oil 100%, Isophorone diisocyanate (IPDI) 98%, 2,2-Dimethylolbutanoic acid (DMBA) 98%, Triethylamine (TEA) 99%, acetone 99.5%, 50% Glutaraldehyde aqueous solution 98%, phosphate buffer saline (PBS), 4′,6-diamino-2′-phenylindole dihydrochloride (DAPI) > 98%, and formaldehyde solution (36.5~38%) were obtained from Sigma-Aldrich (Yongin, Korea). All chemicals used were of analytical grade and all solutions were prepared with double deionized water. O-carboxymethyl (80%) chitosan was purchased from Beijing Wisapple Biotech Co., Ltd. (Beijing, China). Dulbecco’s modified Eagle’s medium (DMEM), fetal bovine serum (FBS), penicillin/streptomycin, and trypsin-EDTA, and CellTracker^TM Green CMFDA (5-chloromethyl derivative of fluorescein diacetate) were supplied by Invitrogen (Carlsbad, NM, USA). Human skin fibroblasts (CCD-986K) were purchased from the American Type Culture Collection (ATCC) (Manassas, VA, USA). All aqueous solutions were made with de-ionized water.

Chitosan with low average molecular weight, glutaraldehyde aqueous solution (GA, 25.0 wt%), and sodium alginate (SA) were purchased from Sigma-Aldrich. Acetic acid, sodium bicarbonate, and calcium chloride were obtained from Sinopharm Chemical Reagent Co., Ltd. Ammonia solution (NH₃·H₂O, 25.0~28.0 wt%) was purchased from Dongjiang Chemical Reagent Co., Ltd. Ultrapure water (≥18 MΩ) was used in the experiments. Home-made devices for preparing hydrogel films with certain volumes were made of glass slides containing Teflon spacers with specific sizes (40 mm × 40 mm × 1.5 mm; 80 mm × 80 mm × 2.0 mm).