A research team from Zhejiang University has developed an implantable and self-powered sensing system for the continuous in vivo monitoring of dynamic hydrogen peroxide (H₂O₂) levels in plants, with their findings published in Engineering. The system addresses the long-standing challenge of real-time tracking of H₂O₂, a key reactive oxygen species (ROS) and early signal molecule in plant stress responses, and offers a reliable analytical tool for studying plant abiotic stress mechanisms and crop health diagnosis.

The integrated sensing system consists of a microsensor, a data-acquisition and transmission module, and a photovoltaic (PV) module. The PV module harvests sunlight or artificial light in agricultural environments to charge a 3.0 V lithium-ion battery with a 6.0 V output voltage, providing sustainable power for the microsensor and eliminating the limitations of wired power or frequent battery replacement. Data collected by the sensor is transmitted over up to 1000 meters via a LoRa network to a multi-channel monitoring interface for visual analysis, with the system achieving a high time resolution of 0.1 seconds.

The core microsensor is based on three-dimensional porous laser-induced graphene sheets (LIGS) modified with platinum nanoparticles (PtNPs) and a Nafion anti-interference layer. Fabricated on a polyimide (PI) substrate with a protective PI mask layer, the microsensor is implanted into plant stems to reach the xylem, enabling direct detection of H₂O₂. Optimized electrochemical characterization shows the sensor exhibits a good linear response to H₂O₂ in the range of 2–200 μmol·L⁻¹, with a limit of detection of 0.35 μmol·L⁻¹. It also demonstrates strong anti-interference performance against common plant interferents such as ascorbic acid, K⁺, Na⁺, Ca²⁺, glucose and sucrose, and maintains stable performance under pH fluctuations (5.0–8.0), temperature changes (17–35°C), air flow and mild mechanical disturbance.

In vitro simulations using tomato plant bleeding sap validated the sensor’s performance, with a detectable minimum H₂O₂ concentration of 5 μmol·L⁻¹ after peroxidase inactivation. In vivo tests on tomato plants monitored H₂O₂ dynamics under osmotic, mechanical injury and UV radiation stress—three typical abiotic stresses. The system captured the time and concentration specificity of H₂O₂ signals: mechanical injury triggered rapid H₂O₂ signals within minutes (transmitting at 0.23–1.58 mm·s⁻¹) that lasted tens of seconds; UV stress induced signals lasting tens of minutes; and osmotic stress caused a delayed oxygen burst peaking at 12.5 hours post-stress, with signals persisting for tens of hours. H₂O₂ concentrations generated by all three stresses ranged from 10–100 μmol·L⁻¹, consistent with existing research. The sensor maintained effective analytical performance after 50 hours of continuous in vivo operation, detecting 88.33 μmol·L⁻¹ H₂O₂ in tomato bleeding sap post-use.

This self-powered implantable system enables label-free, real-time electrochemical detection of H₂O₂ in plants, and its findings reveal the specific H₂O₂ signal characteristics of tomato plants in response to different abiotic stresses. The research provides a new tool for plant stress-resistance breeding and early stress diagnosis in facility agriculture, with potential for extension to real-time monitoring of signaling molecules in other crop species. The team notes future research will focus on improving sensor fixation, reducing baseline drift and noise, and investigating the impact of device implantation on plant growth.

The paper “An Implantable and Self-Powered Sensing System for the In Vivo Monitoring of Dynamic H₂O₂ Level in Plants,” is authored by Chao Zhang, Xinyue Wu, Shiyun Yao, Yuzhou Shao, Chi Zhang, Shenghan Zhou, Jianfeng Ping, Yibin Ying. Full text of the open access paper: https://doi.org/10.1016/j.eng.2023.11.021. For more information about Engineering, visit the website at https://www.sciencedirect.com/journal/engineering.