Disposable Stainless-Steel Wire-Based Electrochemical Microsensor for In Vivo Continuous Monitoring of Hydrogen Peroxide in Vein of Tomato Leaf

As one of the pivotal signal molecules, hydrogen peroxide (H2O2) has been demonstrated to play important roles in many physiological processes of plants. Continuous monitoring of H2O2 in vivo could help understand its regulation mechanism more clearly. In this study, a disposable electrochemical microsensor for H2O2 was developed. This microsensor consists of three parts: low-cost stainless-steel wire with a diameter of 0.1 mm modified by gold nanoparticles (disposable working electrode), an untreated platinum wire with a diameter of 0.1 mm (counter electrode), and an Ag/AgCl wire with a diameter of 0.1 mm (reference electrode), respectively. The microsensor could detect H2O2 in levels from 10 to 1000 µM and exhibited excellent selectivity. On this basis, the dynamic change in H2O2 in the vein of tomato leaf under high salinity was continuously monitored in vivo. The results showed that the production of H2O2 could be induced by high salinity within two hours. This study suggests that the disposable electrochemical microsensor not only suits continuously detecting H2O2 in microscopic plant tissue in vivo but also reduces the damage to plants. Overall, our strategy will help to pave the foundation for further investigation of the generation, transportation, and elimination mechanism of H2O2 in plants.