Development and Incorporation of a Multifunctional Essential Oil Blend into a Pullulan-Based Film for Enhanced Acne Management.

Objective: Acne vulgaris is a widespread chronic inflammatory condition of the pilosebaceous unit that is often accompanied by post-inflammatory hyperpigmentation (PIH). In this sebum-rich microenvironment, factors such as altered keratinization and inflammation contribute to follicular obstruction, creating favorable conditions for the proliferation of Cutibacterium acnes, a key microbial factor in acne pathogenesis. In this context, natural substances such as essential oils (EOs) are gaining increasing attention in the treatment of acne due to their combined antimicrobial and anti-pigmentation properties. The present study focused on a blend of EOs—including Litsea cubeba (Lour.) Pers., Pinus mugo Turra, and Cymbopogon winterianus Jowitt ex Bor—developed in a previous study, which demonstrated promising tyrosinase inhibitory activity. This combination was specifically designed to reduce the concentration of citral—an important active component with known anti-pigmentation activity but also listed as a potential allergen—in order to minimize the risk of skin sensitižation while maintaining its functional activity. Building on this, the study further investigates the antimicrobial efficacy of the EO blend, develops a pullulan-based topical delivery system, and evaluates its physicochemical properties and retention of antimicrobial activity. Methods: The EOs and their blend were chemically characterižed by GC-MS/FID. Tyrosinase inhibition was evaluated using an in vitro colorimetric assay optimižed by the authors. Antimicrobial activity was evaluated in vitro against Cutibacterium acnes, Staphylococcus aureus, and Staphylococcus epidermidis using Clinical and Laboratory Standards Institute microdilution methods to determine the minimum inhibitory concentration (MIC). Minimum bactericidal activity (MBC) was also determined. Bioactive films were prepared by solution casting with 3% (w/v) pullulan, 15% (w/w) glycerol, and the EO blend at the highest MIC observed among the three tested microorganisms. Film characterižation included measurements of grammage, thickness, mechanical, and optical properties. EO incorporation was confirmed by FTIR and DSC analyses. The wettability and surface free energy were evaluated through contact angle measurements. The antimicrobial activity of the final films was assessed via a solid diffusion assay on inoculated agar plates. Results: The EO blend showed significant tyrosinase inhibition and antimicrobial activity against all tested strains, exhibiting a bactericidal effect against C. acnes and S. aureus, and a bacteriostatic effect on S. epidermidis, determined by the MBC/MIC ratio. S. epidermidis is a commensal species increasingly recognized for its role in modulating C. acnes growth and maintaining skin microbiome balance. The pullulan-based film functionaližed with the EO blend exhibited favorable physicochemical properties suitable for topical application and a good aesthetic appearance, supporting potential consumer acceptance. Antimicrobial assays confirmed that the EO blend’s activity was maintained after incorporation into the film. Conclusions: This study highlights the potential of a multifunctional essential oil blend—applied in this work for both antimicrobial and tyrosinase inhibitory activity—and its successful incorporation into a biodegradable pullulan-based delivery system. The results suggest that it is a sustainable and user-friendly skin care approach targeting both the microbial and pigmentation aspects of acne. Future studies will focus on evaluating the formulation's ecotoxicity and further exploring its pigment-modulating effects using advanced in vitro skin tissue models.