Formulation and Evaluation of a Chitooligosaccharide Peel-Off Gel Mask for Anti-Acne Activity Against Propionibacterium acnes

Acne vulgaris is an inflammatory skin condition primarily caused by Propionibacterium acnes (P. acnes), which can lead to physical and psychological effects. Chitooligosaccharide (COS), a chitosan-derived oligosaccharide, possesses antibacterial and film-forming properties, making it a promising candidate for topical anti-acne formulations. This study aimed to formulate and evaluate the physical characteristics and antibacterial activity of a COS-based peel-off gel mask against P. acnes. Three formulas were prepared using COS concentrations of 0.25% (F1), 0.5% (F2), and 0.75% (F3). Evaluation parameters included organoleptic properties, homogeneity, pH, viscosity, spreadability, adhesiveness, drying time, and stability. Antibacterial activity was assessed using diffusion and dilution methods to determine the inhibition zone diameter, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC). Among the three formulas, F3 demonstrated the most optimal physical properties—clear, homogeneous, pH 6.50 ± 0.10, viscosity 3,595.43 ± 136.55 cps, spreadability 5.00 ± 0.10 cm, adhesiveness 6.60 ± 0.10 s, and drying time 18.30 ± 0.10 min—without any phase separation. F3 also exhibited strong antibacterial activity with a 21.67 ± 1.65 mm inhibition zone, comparable to the positive control (p 0.05). MIC and MBC values for F3 were determined to be 1250 ppm and 2500 ppm, respectively. These findings suggest that COS at 0.75% concentration is effective in a peel-off gel mask formulation with favorable physical stability and strong antibacterial efficacy against P. acnes, supporting its potential as a natural-based anti-acne treatment.