Poly-glutamic acid-modified green-synthesized ZnO nanoparticles and carbon composite paste electrode for the electrochemical detection of adenosine

Abstract

This study presents the synthesis of zinc oxide nanoparticles (ZnO-NPs) using Acalypha wilkesiana leaves for electrochemical applications, specifically for “adenosine” (ADS) detection. “Adenosine”, a key molecule in cellular signalling and physiological homeostasis, is widely studied in biomedical research and diagnostics. The study investigates the simultaneous detection of ADS, “adenine” (AD), with L-tyrosine (TS) using a novel electro-polymerized glutamic acid (PGA)-modified “ZnO-NPs” composite carbon paste electrode (PGA/ZnO-NPs/CPE) and unmodified “ZnO-NPs/CPE” in 0.2 M phosphate buffer saline (PBS) at a scan rate of 0.1 V/s. The synthesized “ZnO NPs” were characterized by X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX), and electrochemical impedance spectroscopy (EIS) techniques. The surface morphologies of the CPE, MCPE, “ZnO-NPs”, “ZnO-NPs/CPE”, and “PGA/ZnO-NPs/CPE” were examined using scanning electron microscopy (SEM). Different voltammetric techniques were used, including cyclic voltammetry (CV), differential pulse voltammetry (DPV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (ESI), to assess the electrochemical performance of the electrode. The “PGA/ZnO-NPs/CPE” sensor introduces a novel hybrid platform that combines poly-glutamic acid (PGA) with zinc oxide nanoparticles (ZnO-NPs) on carbon paste electrode (CPE) for enhanced electrochemical sensing. These unique composite exhibits improved electron transfer, increased surface area, and excellent biocompatibility, enabling high sensitivity and selective detection of ADS. The proposed sensor exhibits a significant improved concentration variation range for ADS of 20–500 µM (CV), 50–650 µM (DPV), and 20–500 µM (LSV), with a limit of detection (LOD) of 0.21 µM CV, 0.40 µM DPV, and 0.25 µM LSV and a limit of quantification (LOQ) 0.87 µM, 0.93 µM, and 0.84 µM, and sensitivity of ADS is 0.975 A/M/cm². The scan rate varied from 0.025 to 0.400 V/s, it indicating an adsorption-controlled process. Moreover, the modified sensor demonstrated good reproducibility, repeatability, and stability, making it sensitive and selective method for ADS detection and suitable for pharmaceutical applications.

Graphical abstract