The Role of Temperature and Subphase Components in Shaping Selected Physicochemical Properties of the Phosphatidylinositol Monolayer

<i>Acne vulgaris</i> is one of the most common skin diseases, and its development is closely linked to the overgrowth of the bacterium <i>Cutibacterium acnes</i>. More than half of the strains of this bacterium are resistant to antibiotics, which has prompted scientists to look for alternatives, such as antibacterial peptides, that can replace traditional drugs. Due to its antioxidant properties, ascorbic acid may be a promising ally in the treatment of acne. The aim of our study was to evaluate the effect of peptide (KWK)₂-KWWW-NH₂<b>(P5)</b> in the presence of ascorbic acid (AA) and its derivative (3-O-ethyl-L-ascorbic acid, EAA) on the stability and organization of phosphatidylinositol monolayers (PI) at temperatures of 25-35 °C. This study showed that the monolayers were in the expanded liquid state (35.28-49.95 mN/m) or in the transition between the expanded liquid and condensed phases (51.50-57.49 mN/m). Compression and decompression isotherms indicated the highest flexibility of the PI + P5 system, where the compression reversibility coefficient of isotherm values ranged from 80.59% to 97.77% and increased for each loop with increasing temperature. At 35 °C, the surface pressure of the monolayer in the PI + P5, PI + P5 + AA and PI + P5 + EAA systems changed less with time.