Ciprofloxacin-loaded silver and zinc oxide nanoparticles: synthesis, characterization, and antibiofilm evaluation

Abstract

Background: Biofilms formed by Staphylococcus aureus display marked tolerance to conventional antibiotic therapy, which contributes to the persistence of chronic infections and complicates their clinical management. There is therefore a pressing need to develop alternative delivery strategies capable of penetrating the biofilm matrix and reducing the antibiotic dose required for effective bacterial eradication. Methods: A composite nanocarrier was designed by combining ciprofloxacin-loaded silver nanoparticles with zinc oxide nanoparticles (Ag–ZnO). The formulation was characterised by dynamic light scattering (DLS), atomic force microscopy (AFM), and Fourier-transform infrared spectroscopy (FTIR). Drug adsorption efficiency, in vitro release behaviour at pH 5.8 and 7.4, minimum inhibitory concentration (MIC), and antibiofilm activity against S. aureus were subsequently evaluated. Results: DLS measurements indicated a mean particle size of 93.3 nm, a polydispersity index of 0.31, and a zeta potential of –31.2 mV, reflecting good colloidal stability. AFM showed spherical, uniformly dispersed nanoparticles of approximately 90 nm, while FTIR confirmed the physical adsorption of ciprofloxacin without any chemical alteration. The composite achieved an adsorption efficiency of 93.7% and a biphasic, sustained release profile slower than that of pure ciprofloxacin or ciprofloxacin–AgNPs. The MIC was 36 μg/mL, substantially lower than AgNPs (162 μg/mL) or ciprofloxacin–AgNPs (126 μg/mL), and biofilm inhibition exceeded 80% at just 1 μg/mL. Conclusion: The synergistic interplay between Ag, ZnO, and ciprofloxacin positions this nanocomposite as a promising dose-sparing platform for tackling biofilm-associated antibiotic resistance.