Antibacterial and antibiofilm activity of silver nanoparticles stabilized with C-phycocyanin against drug-resistant Pseudomonas aeruginosa and Staphylococcus aureus

Biofilms are bacterial communities that can protect them against external factors, including antibiotics. In this study, silver nanoparticles (AgNPs) were formed by modifying AgNPs with C-phycocyanin (Ag-Pc) to inhibit the growth of carbapenem-resistant (CR ) and methicillin-resistant (MRSA) and destroy biofilm of these bacteria. The AgNPs were prepared with the green synthesis method, and Pc was used to stabilize the AgNPs. The Ag-Pc's antibacterial and antibiofilm effects were evaluated using the Microbroth dilution method and microtiter plate assay. The inhibitory effect of Ag-Pc on the expression of biofilm-related genes was evaluated by real-time PCR. Moreover, the MTT assay was used to assess the Ag-Pc toxicity. The Ag-Pc minimum inhibitory concentration (MIC) was 7.4 μg/mL for CR and MRSA. Pc did not show antibacterial effects against any of the strains. Ag-Pc suppressed biofilm formation and destroyed matured biofilm in both bacteria more efficiently than the AgNPs (P< 0.05). The expression of all genes was not significantly reduced in the presence of synthesized nanoparticles. Finally, the MTT assay results did not show toxicity against a murine fibroblast cell line (L929) at MIC concentration. The present study showed the promising potential of Pc for improving the antibacterial and antibiofilm function of AgNPs and inhibiting drug-resistant bacteria. Therefore, Ag-Pc nanoparticles can be considered a promising therapeutic approach for the managing of the bacterial biofilm.