Selective Antimicrobial Chitosan Films Incorporating Green-Synthesized Silver and Copper Oxide Nanoparticles for Acne Treatment

<b>Background/Objectives:</b> Chitosan-based films incorporating green-synthesized silver nanoparticles AgNPs) or copper oxide nanoparticles (CuONPs) were developed to compare their selective antimicrobial action for topical applications. While AgNPs are known for broad-spectrum activity, this study hypothesized that CuONPs would exhibit superior, targeted efficacy against the acne-associated bacterium <i>Cutibacterium acnes</i>. <b>Methods:</b> Nanoparticles were synthesized using Camellia sinensis extract and characterized. Antimicrobial activity was evaluated using Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) assays. Chitosan films containing AgNPs or CuONPs were further tested for selective antimicrobial activity and fibroblast cytocompatibility. <b>Results:</b> AgNPs showed strong activity against <i>Escherichia coli</i> and <i>Staphylococcus aureus</i> (MIC = 15 µg/mL) but were less effective against <i>C. acnes</i> (MIC = 125 µg/mL). In contrast, CuONPs demonstrated selective efficacy against <i>C. acnes</i> (MIC = 62 µg/mL; MBC = 125 µg/mL). When incorporated into chitosan films, AgNPs@CHI inhibited <i>E. coli</i> (35 mm halo) and <i>S. aureus</i> (30 mm), whereas CuONPs@CHI were selectively effective against <i>C. acnes</i> (45 mm). All films preserved fibroblast viability above the 70% ISO 10993-5 threshold. <b>Conclusions:</b> CuONPs@CHI films validated selective anti-C. acnes performance, highlighting their promise for targeted anti-acne therapies, while AgNPs@CHI films served as effective broad-spectrum antimicrobial barriers.revealed that AgNPs were potent against <i>Escherichia coli</i> and <i>Staphylococcus aureus</i> (MIC = 15 µg/mL) but less effective against <i>C. acnes</i> (MIC = 125 µg/mL). Conversely, CuONPs demonstrated a marked selective advantage against <i>C. acnes</i> (MIC = 62 µg/mL; MBC = 125 µg/mL). When incorporated into chitosan films, AgNPs@CHI films inhibited <i>E. coli</i> (35 mm halo) and <i>S. aureus</i> (30 mm), whereas CuONPs@CHI films were selectively effective only against <i>C. acnes</i> (45 mm), confirming the targeted performance. All films maintained fibroblast viability above the 70% ISO 10993-5 cytotoxicity threshold. These findings validate the selective action of CuONPs@CHI films, positioning them as a promising biomaterial for targeted anti-acne therapies, while AgNPs@CHI films serve as effective broad-spectrum antimicrobial barriers.