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

Hydrogen peroxide (HO) 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 HO 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 HO concentrations from 10 to 1000 µM with high accuracy. In situ monitoring of HO dynamics in tomato stems under the wounding stimulation reveals that HO concentration increases as the sensor approaches the wound site, indicating localized production and transport of HO. This approach not only improves HO monitoring in plant systems but also paves the way for exploring its generation, transport, and elimination mechanisms.