AuNPs/GO/Pt microneedle electrochemical sensor for in situ monitoring of hydrogen peroxide in tomato stems in response to wounding stimulation

Abstract

Hydrogen peroxide (H₂O₂) is a critical signaling molecule with significant roles in various physiological processes in plants. Understanding its regulation through in situ monitoring could offer deeper insights into plant responses and stress mechanisms. In this study, we developed a microneedle electrochemical sensor to monitor H₂O₂ in situ, offering deeper insights into plant stress responses. The sensor features a platinum wire (100 µm diameter) modified with graphene oxide (GO) and gold nanoparticles (AuNPs) as the working electrode, an Ag/AgCl wire (100 µm diameter) as the reference electrode, and an untreated platinum wire (100 µm diameter) as the counter electrode. This innovative design enhances sensitivity and selectivity through the high catalytic activity of AuNPs, increased surface area from GO, and the superior conductivity of platinum. Operating at a low potential of -0.2 V to minimize interference, the sensor detects H₂O₂ concentrations from 10 to 1000 µM with high accuracy. In situ monitoring of H₂O₂ dynamics in tomato stems under the wounding stimulation reveals that H₂O₂ concentration increases as the sensor approaches the wound site, indicating localized production and transport of H₂O₂. This approach not only improves H₂O₂ monitoring in plant systems but also paves the way for exploring its generation, transport, and elimination mechanisms.

Keywords: Hydrogen peroxide; Microneedle electrochemical sensor; Real-time and in situ electrochemical monitoring; Wounding stimulation.