Ionic liquid and ZnO/carbon quantum dots derived from cat hair as an electrochemical sensor for ciprofloxacin in food samples: Experimental and cell-imaging studies

Ciprofloxacin (CIP) has been widely used to treat bacterial infections, generating biofluid residues and it endangers health via the food chain; thus, the determination of CIP is essential in food samples. In this work, CPE/ZnO/CQD was prepared from ZnO nanoparticles (ZnO NPs) and carbon quantum dots (CQD) derived from cat hair and modified the graphite carbon paste electrode (CPE); the above electrode sample was further modified by incorporating ionic liquid (IL) to give CPE/ZnO/CQD@IL. The above materials were employed as electrochemical sensors for the recognition of CIP in milk and eggs after the characterization by different analytical techniques (XRD, FT-IR, SEM, TEM, and EDS). The results show that the presence of nanoparticles in the CPE has improved the electrocatalytic properties, giving a greater heterogeneous electron transfer rate constant (k⁰=6.51×10⁻⁴ cm/s) for CPE/ZnO/CQD as compared to unmodified CPE (3.94×10⁻⁴ cm/s), and for CPE/ZnO/CQD/IL, with modification of sample by IL, the rate constant has been further increased to k⁰=8.34×10⁻⁴ cm/s. Thereafter, CPE/ZnO/CQD and CPE/ZnO/CQD@IL were employed for the detection of CIP in food samples such as milk and eggs, observing a maximum oxidation current for CIP at pH 3.0; the limit of detection (LOD) was 0.24, and 0.30 μM for CPE/ZnO/CQD, and CPE/ZnO/CQD@IL, respectively, and those values are much lower than those reported due to the synergistic effect generated by the combination of ZnO/CQD and IL. Furthermore, cell images were developed using ZnO/CQD and ZnO/CQD@IL in real samples like Saccharomyces cerevisiae cells in the presence of CIP.