Synergistic antimicrobial nanocomposite: Protamine-loaded PVP-capped silver nanoparticles for combating multidrug-resistant infections

The emergence of multidrug-resistant (MDR) bacterial infections has become a critical global health concern, driving the urgent need for innovative therapeutic strategies beyond conventional antibiotics. In this study, we developed a novel nanotherapeutic platform comprising protamine-loaded poly(N-vinyl-2-pyrrolidone)-stabilized silver nanoparticles (PVP-AgNPs) designed to enhance antimicrobial efficacy while improving biocompatibility. AgNPs were synthesized via chemical reduction using silver nitrate and sodium borohydride, with PVP serving as a stabilizing and capping agent. Protamine sulfate, a cationic antimicrobial peptide, was subsequently incorporated to exploit its strong affinity for bacterial membranes and synergistic bactericidal effects. The resulting nanoparticles exhibited spherical morphology with an average diameter of 70.96 ± 0.27 nm, a PDI of 0.25 ± 0.002, a zeta potential of +10.4 ± 0.15 mV, and a protamine loading efficiency of 66.2% ± 3.2%, indicating excellent colloidal stability and drug incorporation. In vitro antimicrobial testing demonstrated a two- to four-fold reduction in minimum inhibitory concentration values compared to blank PVP–AgNPs and free protamine, with disk diffusion assays confirming significantly enhanced activity against both Gram-positive ( Staphylococcus aureus ) and Gram-negative ( Escherichia coli, Pseudomonas aeruginosa ) bacteria. Furthermore, in vivo evaluation using a murine wound infection model showed effective bacterial clearance, accelerated wound closure, and improved tissue regeneration. These findings demonstrate that protamine-loaded PVP-AgNPs offer multimodal antibacterial activity, enhanced cytocompatibility, and the potential to overcome resistance mechanisms. Collectively, this work introduces a promising nanotherapeutic strategy for managing MDR infections and promoting wound healing, with significant implications for future biomedical applications.