To modify the existing liquid dressing with pH dependence, verify its effectiveness through animal experiments.

Measured the pH of normal skin, clean wounds, and infected wounds as the theoretical basis for pH dependent film formation. On the basis of existing commercialized liquid dressings, a new type of pH dependent film-forming liquid dressing was prepared by adding different concentrations of carbopol. The moldability was tested in vitro under different pH conditions. Based on the pH of the wound, a carbopol concentration that could form a film on the wound but couldn′t form a film on normal skin was selected to prepare a pH dependent film-forming liquid dressing. Detectd the biocompatibility (cytotoxicity, sensitization, intradermal stimulation) and physical barrier effect (moisturizing properties, antibacterial properties) of the liquid dressing. The effectiveness of the liquid dressing in vivo was detected though the full thickness skin defect wound model in SD rats.

The pH of normal skin was 5.90±0.25, which was significantly lower than 6.54±0.36 of clean wounds and 7.54±0.35 of infected wounds (t=-3.32, P=0.011; t=8.61, P<0.001). The pH of clean wounds was also significantly lower than that of infected wounds (t=-4.44, P=0.002). Configured agar plates with pH values of 6, 7, and 8, applied liquid dressings. Complete film formation could be achieved at pH values of 7 and 8, but sheet-like film couldn′t be formed at pH values of 6. The cytotoxicity of the liquid dressings was level 1, with no potential cytotoxicity. No sensitization and irritation during intradermal implantation was found in the liquid dressings. Adjusted the pH of the liquid dressing to 6, 7, and 8. When the pH was 6, it didn′t have moisturizing and antibacterial properties. When the pH was 7 and 8, the moisture retaining rate was (4.76±2.04)% and (7.58±1.62)%, respectively, and the antibacterial rate was (33.17±5.59)% and (45.36±7.57)%, respectively. Animal experiments showed that compared to liquid dressings without film forming properties, the wound healing rate on the 10th day after modeling significantly increased[(69.02±3.39)% vs (75.34±3.64)%, t=2.84, P=0.022], and the wound healing time significantly reducted [(23.60±0.89)d vs (20.40±2.61)d, t=2.60, P=0.032] .

By adjusting the concentration of carbopol, pH dependent film-forming liquid dressings can be made, which form a film on the wound surface without affecting normal skin, promote wound healing, and improve comfort level.