Enhanced bioavailability and improved antimicrobial, antibiofilm, and antivirulence activities of fish gelatin-based nanoformulations prepared by coating of maltol-gold nanoparticles

Biofilm formation by a single and multiple microbial species poses a significant challenge to healthcare due to biofilm-related antibiotic resistance. This study aimed to develop a nanoformulation (Mal-AuNP-Gel) by synthesizing gold nanoparticles (AuNPs) with maltol (Mal), and coating them with fish gelatin (Gel) to reduce biofilm formation and virulence characteristics of microbial pathogens. Mal-AuNP-Gel showed increased antibacterial activity against all pathogens studied, including bacterial (Pseudomonas aeruginosa, Staphylococcus aureus, Klebsiella pneumoniae, Listeria monocytogenes, Escherichia coli, and methicillin-resistant S. aureus) and fungal pathogens (e.g., Candida albicans), with MICs up to 2-fold lower than those of Mal-AuNPs. At the sub-MIC level, Mal-AuNPs-Gel, compared to Mal-AuNPs, improved the inhibition of initial-stage biofilm development by a single species of P. aeruginosa, S. aureus, and C. albicans as well as the mixed-species biofilm of S. aureus and C. albicans. Additionally, these nanoparticles significantly inhibited several virulence characteristics such as hemolysis, pyoverdine and pyocyanin production, protease activity, and motility of P. aeruginosa. Furthermore, the expression of genes associated with biofilm formation, quorum sensing, motility, and virulence factors in P. aeruginosa was found to be suppressed by Mal-AuNPs-Gel at a higher level than that of Mal-AuNPs, corroborating the phenotypic effects. The non-cytotoxic effects of Mal-AuNPs and Mal-AuNPs-Gel at sub-MIC levels, as evidenced by results of in vitro cell cytotoxicity and in vivo phytotoxicity tests, further indicated biocompatibility of the synthesized nanoparticles.