Antibacterial efficacy of silver nanoparticle–chitosan composite films against acne-associated bacteria

Background: Acne vulgaris is a common skin disorder primarily associated with Cutibacterium acnes and Staphylococcus epidermidis. Increasing antibiotic resistance among these bacteria has driven the search for alternative, safe, and effective treatments. Silver nanoparticles (AgNPs) have potent broad-spectrum antibacterial activity, but their cytotoxicity at high concentrations limits clinical use. Combining AgNPs with biocompatible polymers such as sodium alginate (SA) and chitosan (CS) offers a promising strategy to enhance antibacterial efficacy while minimizing toxicity.

Methods: Low-dosage AgNP–SA–CS nanocomposite films were synthesized via an in-situ reduction method. AgNPs were stabilized and uniformly distributed within the SA–CS matrix. Physicochemical properties were characterized by UV–Vis spectroscopy, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Antibacterial activity was evaluated using the agar diffusion method and determination of minimum inhibitory concentration (MIC) against both pure reference strains (C. acnes, S. epidermidis) and clinical isolates from acne patients. Cytotoxicity was assessed on human keratinocyte (HaCaT) cells using the MTT assay.

Results: The nanocomposite films exhibited uniform AgNP dispersion with particle sizes predominantly in the 15–25 nm range. At low silver concentrations (≤0.01 mg/mL), the films demonstrated significant inhibition zones against both C. acnes and S. epidermidis, including multidrug-resistant clinical strains, with MIC values as low as 0.003 mg/mL. Cytotoxicity tests revealed >85% cell viability at all tested concentrations, indicating favorable biocompatibility. The synergistic effect between AgNPs and the SA–CS matrix enhanced antibacterial potency compared to individual components while reducing the silver dosage needed for therapeutic effects.

Conclusion: The developed low-dosage AgNP–SA–CS nanocomposite films present a safe, effective, and sustainable antibacterial material for potential application in acne management. Their strong activity against clinical multidrug-resistant strains and minimal cytotoxicity highlight their promise for integration into topical wound dressings or acne treatment patches. Further in vivo studies are warranted to validate clinical applicability.

Nguyen Quang Thai is a 4th-year medical student at Can Tho University of Medicine and Pharmacy, Vietnam. He is the co-author of a Q1-ranked publication in RSC Advances on antibacterial nanocomposite films. Thai has been awarded multiple full scholarships, including the VAW Global Health Outreach in Uzbekistan and the Vietnam School of Biology, reflecting his commitment to integrating clinical practice with innovative biomedical research. His academic interests span immunology, oncology, and nanomedicine, aiming to advance patient care through translational research and international collaboration.