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.

One-Step Synthesized ZnO np-Based Optical Sensors for Detection of Aldicarb via a Photoinduced Electron Transfer Route.

Pesticides are used in agriculture for crop production enhancement by controlling pests, but they have acute toxicological effects on other life forms. Thus, it becomes imperative to detect their concentration in food products in a fast and accurate manner. In this study, ZnO nanoparticles (ZnO nps) have been used as optical sensors for the detection of pesticide Aldicarb via a photoinduced electron transfer (PET) route. ZnO nps were synthesized directly by calcining zinc acetate at 450, 500, and 550 °C for 2 h. ZnO nps were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and UV-vis absorption and photoluminescence (PL) spectroscopies to study the phase, crystallinity, shape, morphology, absorbance, and fluorescence of the prepared ZnO nps. XRD and Raman studies confirmed the crystalline nature of ZnO nps. The average crystallite size obtained was 13-20 nm from the XRD study. The SEM study confirmed spherical-shaped ZnO nps with average sizes in the range of 70-150 nm. The maximum absorbance was obtained in the 200-500 nm regions with a prominent peak absorbance at 372 nm from UV-vis spectra. The corresponding band gap for ZnO nps was calculated using Tauc's plots and was found to be 3.8, 3.67, and 3.45 eV for the 450, 500, and 550 °C calcined samples, respectively. The fluorescence spectra showed an increase in the intensity along with the increase in the size of ZnO nps. The ZnO nps (samples calcined at 500 and 550 °C) exhibited a response toward Aldicarb, owing to their pure phase and higher PL intensity. Both the samples showed systematic detection of Aldicarb in the range of 250 pM to 2 nM (500 °C) and 250 pM to 5 nM (550 °C). Among the various quenching mechanisms, PET was found to be the dominant process for the detection of Aldicarb. This method can be used for the detection of Aldicarb in real (food) samples using a portable fluorimeter.