Conjugation of enrofloxacin with amine functionalized zinc oxide nanoparticle enhances antibacterial activity in vitro

Increased resistance to a large number of antibacterial drugs poses a serious challenge in chemotheraphy of infectious diseases. Here, we have made and attempt to redesign the existing chemotherapeutic agent enrofloxacin (EN) to treat resistant bacteria. Precisely, we synthezied EN conjugated zinc oxide nanoparticles (EN-ZNP) and explored enhancing the antibacterial activity of enrofloxacin. Zinc oxide nanoparticles (ZNP) were synthesized by microwave irradiation and amine functionalization by co-condensation with APTES and then by utilizing EPC/NHS chemistry, enrofoxacin was conjugated. Conjugation and their stability were confirmed by FT-IR spectra and Zeta potential. EN fraction in EN-ZNP was determined indirectly using UV-Vis spectroscopy. The MIC values obtained for EN-ZNP against MTCC cultures and clinical isolates of Escherichia coli, Salmonella typhimurium, Staphylococcus aureus were significantly (P <0.05) lower than ZNP and, when compared to native EN it is significantly higher. However, the concentration of conjugated EN in EN-ZNP was significantly lower than the MIC of native EN. The results suggest that enrofloxacin can be successfully conjugated with amine functionalized zinc oxide nanoparticles. The antibacterial efficacy was significantly improved when ZNP conjugated with EN against standard MTCC cultures and clinical isolates.