Antiseptic Potential of Lactiplantibacillus plantarum-Derived Postbiotic-Loaded Polymeric Gels: Comparative Evaluation of Chitosan and Carbopol Matrices

The development of multifunctional topical antiseptic formulations incorporating microbial-derived bioactive compounds represents a promising strategy for improving antimicrobial and antibiofilm performance. This study aimed to develop and comparatively evaluate chitosan- and Carbopol® 940-based antiseptic polymeric gels containing a Lactiplantibacillus plantarum-derived postbiotic. The postbiotic preparation was obtained through fermentation, cell removal, membrane filtration, and lyophilization and subsequently incorporated into polymeric gel formulations. The developed systems were characterized in terms of physicochemical and rheological properties, antimicrobial activity using agar well diffusion and minimum inhibitory concentration (MIC) assays, inhibitory effects on biofilm formation against Staphylococcus aureus and Pseudomonas aeruginosa, and antioxidant activity using the DPPH radical scavenging assay. Both formulations exhibited homogeneous appearances and shear-thinning behavior, supporting their potential suitability for topical application. The chitosan-based postbiotic formulation generally demonstrated superior antimicrobial performance, producing inhibition zones of up to 22.4 mm and achieving a two-fold reduction in MIC values compared with the non-formulated postbiotic. Concentration-dependent antibiofilm activity was observed, with the chitosan-based formulation achieving maximum biofilm inhibition of 62.5% against S. aureus and 59.3% against P. aeruginosa. Antioxidant evaluation further demonstrated enhanced radical scavenging activity following postbiotic incorporation, with the chitosan-based formulation reaching 72.0% DPPH inhibition and exhibiting the most favorable IC50 among the postbiotic-containing systems. The findings highlight the influence of polymeric matrix composition on the biological performance of postbiotic-containing polymeric gels and identify chitosan as a promising carrier for multifunctional topical antiseptic formulations. Further standardized antiseptic efficacy and safety studies are required to establish their practical applicability.