Silver Nanoparticles Functionalized with Polymeric Substances to Reduce the Growth of Planktonic and Biofilm Opportunistic Pathogens

The global rise in antimicrobial resistance, particularly among ESKAPE pathogens, has intensified the demand for alternative therapeutic strategies. Silver nanoparticles (AgNPs) have exhibited broad-spectrum antimicrobial activity and represent a promising approach to combat multidrug-resistant infections. This study aimed to synthesize and functionalize AgNPs using various polymeric agents-ethylene glycol (EG), polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), and their combinations-and to evaluate their antimicrobial and antibiofilm efficacy against clinically relevant bacterial strains. AgNPs were synthesized via chemical reduction and functionalized as Ag@EG, Ag@PEG, Ag@EG/PVP, and Ag@PEG/PVP. A total of 68 clinical isolates-including <i>Staphylococcus aureus</i>, <i>Staphylococcus epidermidis</i>, <i>Staphylococcus lugdunensis</i>, <i>Escherichia coli</i>, <i>Klebsiella pneumoniae</i>, and <i>Pseudomonas aeruginosa</i>-were tested. Antimicrobial susceptibility was assessed using disc diffusion and broth microdilution assays, while antibiofilm activity was evaluated via the crystal violet method. Among all tested formulations, Ag@EG/PVP exhibited the highest antimicrobial and antibiofilm activity, with notably low minimum inhibitory concentrations (MIC₅₀) and minimum biofilm eradication concentrations (MBEC₅₀) for <i>Ps. aeruginosa</i> and <i>K. pneumoniae</i>. In contrast, AgNPs functionalized with PEG or EG alone showed limited efficacy. Biofilm-forming isolates, particularly <i>Staphylococcus</i> spp., required higher concentrations for inhibition. These results highlight the critical role of functionalization in modulating the antimicrobial properties of AgNPs, with Ag@EG/PVP demonstrating potent activity against both planktonic and biofilm-associated multidrug-resistant bacteria. Overall, this study supports further developing AgNPs-based formulations as adjuncts or alternatives to conventional antibiotics, particularly for managing biofilm-related infections. Future research should focus on formulation optimization, safety assessment, and translational potential.