Enhanced antibacterial, antibiofilm, and antioxidant potential of ciprofloxacin-loaded SDS-capped silver nanoparticles against resistant bacterial strains

Nanotechnology is becoming critical in the treatment of antibiotic-resistant bacteria infections. Ciprofloxacin was repurposed in this research by conjugation to sodium dodecyl sulfate (SDS)-capped silver nanoparticles (Cip-SDS-AgNPs) to promote antimicrobial activity. Nano-conjugates were chemically reduced with sodium borohydride (NaBH4) and stabilized by SDS; reduction of Ag+ to elemental silver formed a deep yellow colloid, which changed to a deep orange after loading with ciprofloxacin, which demonstrated successful incorporation. The evaluation of antibacterial activity was conducted against Gram-negative (Pseudomonas aeruginosa, Escherichia coli) and Gram-positive (Staphylococcus aureus, Listeria monocytogenes) resistant bacteria. Among all the formulations, Cip-SDS-AgNPs demonstrated better inhibition zones (E. coli 28 mm; P. aeruginosa 25 mm; S. aureus 32 mm; L. monocytogenes 37 mm) than SDS-AgNPs, unmodified AgNPs and free ciprofloxacin. UV-visible spectroscopy, FTIR and SEM were used to confirm the morphology, surface characterization, and stability of nanoparticle formulations. Cip-SDS-AgNPs also displayed the highest anti-biofilm activity (tube assay and tissue-culture plate method) and a strong antioxidant potential in DPPH assay (85% scavenging at 100 ugmL-1), compared to SDS-AgNPs, and bare AgNPs. P. aeruginosa was found to be the most susceptible via MIC and MBC determination (MIC 25 ugmL-1; MBC 50 ugmL-1), demonstrating the enhanced potency of Cip-SDS-AgNPs against prominent clinical bacterial strains. The formulation demonstrates the potential as a biocompatible, non-toxic carrier of effective drug delivery and increased antimicrobial efficacy. This study provides a new approach of repurposing ciprofloxacin by conjugation with nanoparticles, which offers a dual-action system with increased anti-bacterial and anti-biofilm performance against resistant strains.