Postbiotic_Loaded Hyalurosome: Investigating Their Potential as Antimicrobial and Antioxidant Agents

The skin microbiota supports skin health by defending against pathogens and regulating immunity, while its imbalance can lead to disorders. With rising interest in natural ingredients, postbiotics (bioactive metabolites from probiotic fermentation) are emerging as natural antimicrobial and antioxidant agents.

This study evaluates the antibacterial and antioxidant properties of cell-free supernatants (CFS) from four lactic acid bacteria (LAB) (Lacticaseibacillus rhamnosus [LGG], Limosilactobacillus reuteri [LR], Limosilactobacillus fermentum [LF], and Weizmannia coagulans [WCO]) and encapsulates the two most potent samples (one with the highest antibacterial and the other with the strongest antioxidant activity) into hyaluronic acid-based nanoparticles (hyalurosome) for enhanced topical delivery.

Growth curve analysis, supernatant preparation, antibacterial assays (determination of minimum inhibitory concentration [MIC], minimum bactericidal concentration [MBC], and inhibition zone), antioxidant assay (measuring the scavenging activities of 2,2-diphenyl-1-picrylhydrazyl [DPPH assay]), nanoparticle synthesis and characterization, and cytotoxicity testing were performed.

LGG demonstrated potent, broad-spectrum antibacterial activity, showing the highest efficacy against Micrococcus luteus (M. luteus) (30 mm inhibition zone, MIC/MBC of 5/7.5% v/v). In contrast, WCO exhibited superior antioxidant capacity, with an IC₅₀ of 17.48 μg/mL in the DPPH assay, outperforming ascorbic acid (IC₅₀ = 32.50 μg/mL). The optimized hyalurosomes were spherical, monodisperse (80-200 nm, PDI < 0.7), and retained the bioactivity of the postbiotics. LGG-hyalurosomes achieved complete eradication of M. luteus and Staphylococcus aureus (S. aureus) within 48 h, demonstrating sustained release, while WCO-hyalurosomes maintained strong antioxidant activity (IC₅₀ = 37.63 μg/mL). Crucially, encapsulation significantly reduced cytotoxicity, increasing human dermal fibroblast viability from 60% (free CFS) to over 90% at a 6.25% (v/v) concentration.

These results position LAB-derived postbiotics delivered via hyalurosomes as a potent and safe dual-function strategy, addressing both microbial dysbiosis and oxidative stress in advanced skincare.