Development of ciprofloxacin-functionalized carbon dots as nanocarriers for enhanced antibiotic delivery

In this study, fluorescent CQDs was synthesized using a rapid microwave method with PEG 400 and citric acid as precursors, followed by covalent functionalization with ciprofloxacin (CIP) for possible use as antibiotic nanocarriers. The produced CQDs show strong absorption peaks and excitation-dependent fluorescence activity, narrow range of sizes, spherical shape and uniform dispersibility. The abundance of surface functional groups, including hydroxyl, carboxyl, and amine has permitted further modifications, as revealed by FTIR spectroscopy. While DLS revealed a primary hydrodynamic diameter of 4.985 nm with a PDI of 0.7032, TEM investigation showed quasi-spherical nanoparticles with particle sizes ranging from 4.0 to 11.7 nm. CIP was also conjugated with the CQDs, and the successful coupling was shown by changes in the UV-visible and FTIR spectra as well as fluorescence quenching. The optimized CQD-CIP formulation, at 0.50 μg/μl, demonstrated a significant CIP-loading efficiency, at 55% and also display time-dependent release of drug during in vitro dialysis at physiological pH. This study develops a fluorescent CQD-CIP nanocarrier offering sustained antibiotic delivery, with improved ROS mediated membrane perturbation. The evaluation of the activity reported enhanced antibacterial effect on representative bacteria when conjugated drug is compared with pristine CQD, free drug and other controls. Thus, this study demonstrates an effective strategy for enhancing the antibacterial activity of ciprofloxacin (CIP), a second-generation fluoroquinolone commonly employed in the treatment of gastrointestinal infections.