Silver Nanoparticles Engineered with Tetracycline: A Synergistic Nanoplatform Against Multidrug-Resistant Gram-Negative Bacteria

Abstract

The global escalation of multidrug-resistant (MDR) Gram-negative bacterial infections has intensified the demand for novel and sustainable antimicrobial strategies. Silver-nanoparticles Ag⁰NPs were manufactured via chemical reduction process utilizing tetracycline as both a reducing agent for the conversion of Ag^⁺ to Ag⁰ and a capping agent to stabilize the resulting nanostructures. The successful synthesis of Ag⁰NPs was verified through Ultraviolet–Visible (UV–Vis) Spectroscopy, exhibiting a distinct Surface Plasmon Resonance (SPR) peak at 407 nm. X-ray Powder Diffraction (XRD) analysis further verified the crystalline nature of the synthesized nanoparticles. The antimicrobial efficacy of tetracycline-capped Ag⁰NPs was assessed against Escherichia coli & Salmonella typhimurium, both representing clinically significant Gram-negative MDR strains. A qualitative agar well diffusion assay was employed using Tryptic Soy Agar medium seeded with standardized bacterial suspensions (10⁸ CFU/mL). Wells of 5 mm diameter were loaded with 10 µg/mL of either Ag⁰NPs or Tetracycline used as a standard antibiotic control. After incubation at 37 °C for 18–24 hours, the Ag⁰NPs demonstrated substantial Antibacterial activity, as evidenced by inhibition zones comparable to or exceeding those of the control antibiotic. These findings underscore the therapeutic potential of Tetracycline-capped silver nanoparticles as a dual-action antimicrobial agent offering both chemical antibiotic effects and nanoscale-mediated bactericidal mechanisms. The synthesis approach integrates drug functionality with nanomaterial engineering, presents a promising platform for the development of next-generation therapeutics to combat Gram-negative antimicrobial resistance.