Fabrication and Assessment of Quorum Sensing Inhibitor Enhanced Ciprofloxacin <scp>HCl</scp> Nanoparticles for Anti‐Biofilm Ocular Drug Delivery

ABSTRACT The escalation in the prevalence of antibiotic‐resistant microbial strains, especially in Pseudomonas aeruginosa ocular infections, necessitates innovative therapeutic strategies. The contemporary investigation emphasizes the evolution and evaluation of a novel ophthalmic formulation comprising ciprofloxacin HCl‐loaded chitosan nanoparticles coadministered with the quorum sensing inhibitor (QSI) quercetin to enhance antimicrobial efficacy and disrupt bacterial biofilms in keratitis. Chitosan nanoparticles were optimized using a Box–Behnken design to investigate the influence of chitosan concentration ( X 1 ), STPP concentration ( X 2 ), and stirring speed ( X 3 ) on particle size, entrapment efficiency, and drug release and subjected to characterization for size distribution, surface potential, encapsulation rate, and morphology. Optimized nanoparticles exhibited a size of 53.24 ± 1.26 nm, a positive charge of 34.9 ± 0.96 mV, high EE% of 88.02% ± 1.20% for ciprofloxacin HCl, along with sustained release profiles. The co‐loaded system demonstrated a biphasic drug release pattern, ensuring sustained ocular delivery through diffusion‐ and erosion‐mediated mechanisms, with ciprofloxacin HCl following Higuchi kinetics and quercetin fitting the Korsmeyer–Peppas model. In vitro assays, including biofilm inhibition (crystal violet assay), quorum sensing interference (violacein and pyocyanin assays), motility reduction, and minimum inhibitory concentration (MIC), confirmed the superior performance of the nanoparticle‐based formulation over free drugs. Fluorescence microscopy revealed significant disruption of biofilm architecture, indicating enhanced antimicrobial penetration. The combined system offers promising potential in overcoming ocular biofilm‐related resistance by integrating antimicrobial and anti‐virulence strategies, thereby improving therapeutic outcomes and compliance.