A highly sensitive label-free amperometric biosensor for norfloxacin detection based on chitosan-yttria nanocomposite

Here, non-invasive and label-free detection of trace-level of norfloxacin (NF) in human urine samples has been reported using the electrochemical technique. Nanostructured yttrium oxide (nY₂O₃) was synthesized at low-temperature using a one-step hydrothermal process. These nY₂O₃ were characterized by various methods including XRD, FT-IR, Raman spectroscopy, and TEM. A biosensing platform based on nY₂O₃ modified with chitosan (CH) was fabricated for the detection of NF. The nanocomposite film (CH-Y₂O₃/ITO) was characterized by FE-SEM, contact angle measurements, and electrochemical techniques. Further, fluoroquinolones antibodies (anti-FQ) were used to modify the CH-Y₂O₃/ITO electrode via covalent interaction. Non-specific sites were blocked by bovine serum albumin (BSA), those present on the anti-FQ/CH-Y₂O₃/ITO electrode surface. The response study of BSA/anti-FQ/CH-Y₂O₃/ITO bioelectrode towards NF detection revealed a wide range (1 pM-10 μM) with a lower detection limit of 3.87 pM using differential pulse voltammetry (DPV). The sensitivity obtained is as high as 10.14 μA μM^-1 cm² with a fast response time of ~10 min. Moreover, the diagnostic performance of the fabricated sensor was evaluated to detect NF in urine spiked sample. The recovery of NF from the spiked sample was observed from 90.5 to 101.1%, with a maximum relative standard deviation of 7.04. The obtained results of the fabricated bioelectrode (BSA/anti-FQ/CH-Y₂O₃/ITO) was validated with ELISA. The results were found better when compared with earlier described biosensors and commercially existing ELISA in terms of sensitivity and lower detection limit.