Synthesis and characterisation of cobalt oxide nanoparticles decorated graphene oxide and its electrocatalytic behaviour

A novel and ultrasensitive electrochemical DNA biosensor for pralatrexate detection

An attempt was made to develop a new sensitive biosensor for pralatrexate, as an anticancer drug, based on its interaction with the guanine of fish sperm DNA anchored on a screen-printed electrode (SPE) modified with polypyrrole (PP)/octahedral Pd-doped Co₃O₄ composite (Oh-Pd-doped Co₃O₄ C). Electrochemical techniques like differential pulse voltammetry verified the mechanism of such an interaction on the dsDNA/PP/Oh-Pd-doped Co₃O₄ C/SPE surface. A reduction in the peak current of guanine oxidation elucidated the interaction in acetate buffer with pH = 4.8. The optimization of response was performed for the interaction method according to potential, accumulation time, reproducibility and drug content. The linear dynamic range was estimated at 1.0 nM to 150.0 μM as well as a limit of detection as low as 0.61 nM for the DNA and pralatrexate concentrations. The practical potential of the proposed sensor was verified by determining pralatrexate in its pharmaceutical matrices.

Potentiometric polyphenol oxidase biosensor for sensitive determination of phenolic micropollutant in environmental samples

The present study demonstrates the development of polyphenol oxidase (PPO) biosensor for the detection of catechol using strontium copper oxide (SrCuO₂) and polypyrrole nanotubes (PPyNT) matrix. The SrCuO₂ micro-seeds, a perovskite compound, are synthesized by co-precipitation under pH 8.0. The as-synthesized micro-seeds are characterized by scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction spectroscopy (XRD). The proposed sensor is fabricated on pencil graphite (P-Gr) by successive deposition of PPyNT, SrCuO₂, and PPO enzyme. The developed PPO/SrCuO₂/PPyNT/P-Gr sensor is characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) techniques. The PPO/SrCuO₂/PPyNT/P-Gr displayed excellent electrocatalytic activity towards the oxidation and detection of catechol. The as-developed sensor showed sensitive response ascribing to limit of detection (LOD) of 0.15 μM and sensitivity of 15.60 μA μM^-1 cm^-2. The fabricated sensor exhibited excellent repeatability and longer shelf life. The proposed biosensor finds its application within the broad linear range of 1-50 μM. Real sample analysis of mineral water, tap water, and domestic wastewater using developed sensor showed acceptable recovery. Hence, the biosensor endeavors its application in environmental monitoring and protection.

TiO2 Nanoparticles Decorated Graphene Nanoribbons for Voltammetric Determination of an Anti-HIV Drug Nevirapine

In the present study, electrochemical behavior of nevirapine on a glassy carbon electrode (GCE) modified with TiO2 nanoparticles decorated graphene nanoribbons was investigated. Characterization of different components used for modifications was achieved using Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The electrochemical behavior of nevirapine on the modified electrodes was examined using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), chronoamperometry (CA), and differential pulse voltammetry (DPV). A considerable oxidation potential decrease of +352 mV for nevirapine in 0.1 M phosphate-buffered saline (PBS), pH 11.0, was achieved due to synergy offered by graphene nanoribbons and TiO2 compared to graphene nanoribbons (+252 mV) and TiO2 (−37 mV), all with respect to the glassy carbon electrode. Under optimized conditions, DPV gave linear calibrations over the range of 0.020–0.14 µM. The detection limit was calculated as 0.043 µM. The developed sensor was used for determination of nevirapine in a pharmaceutical formulation successfully.

Synthesis and utilization of Co3O4 doped carbon nanofiber for fabrication of hemoglobin-based electrochemical sensor

In this paper cobalt oxide (Co₃O₄) nanoparticles were mixed with polyacrylonitrile to prepare Co₃O₄ doped carbon nanofiber (CNF) composite by electrospinning and carbonization, which was further used to modify on carbon ionic liquid electrode (CILE). Hemoglobin (Hb) was immobilized on Co₃O₄-CNF/CILE surface with Nafion acted as the protective film to fabricate an electrochemical biosensor (Nafion/Hb/Co₃O₄-CNF/CILE). Electrochemical behavior of Hb on the electrode was investigated with a pair of quasi-reversible redox peak appeared on cyclic voltammogram and electrochemical parameters were calculated. Moreover, this biosensor had good analytical capabilities for electrocatalytic reduction of different substrates including trichloroacetic acid, potassium bromate and sodium nitrite with wider detection range from 40.0 to 260.0 mmol L^-1, 0.1 to 48.0 mmol L^-1 and 1.0 to 12.0 mmol L^-1 by cyclic voltammetry, respectively. The proposed method showed excellent anti-interferences ability with good selectivity and was successful used for quantitative detection of real samples, which displayed the potential applications to develop into a new analytical device.