4.9. Evaluation of Therapeutic Effect of Hydrogel Using Full-Thickness Wound Model

All the animal studies were performed in accordance with the Korea Institute of Science and Technology Animal Care and Use Committee Guidelines (KIST-2019-017). The BALB/c nude mice (male, 6 weeks old) (Orient Bio, Gapyeong, Korea) were randomly divided into three groups: PH, PH/FDM, and PH/sFDM (n = 3 per group/2 wounds per mouse). They were anesthetized by gas inhalation using isoflurane in oxygen prior to surgery and the dorsal skin was then scrubbed using alcohol gauze. Full-thickness wounds were created using a biopsy punch (6 mm) under sterile surgical condition. Those hydrogels were kept at 37 °C for gelation before transplantation. They were subsequently injected through a syringe needle and pasted over the wounded area, then Tegaderm™ Film and coban bandage were wrapped around the wounds to protect the treatments. The wound closure was grossly observed on day 0, 3, 7, 10, and 14 post surgery while the hydrogels were replaced every 3–4 days. The wound area at specific time points (four random images, each group) was quantitatively calculated using ImageJ software as a percentage of the skin wound area normalized to that of day 0. Three different concentrations (0.01, 0.1, and 1%) of sFDM hydrogel groups (n = 2 per group/2 wounds per mouse) was used for optimizing sFDM concentration. This preliminary test was also performed similarly with the same process above.