Glucose is a crucial biomarker reflecting plant metabolism and growth. While glucose sensing is well-established in human healthcare, continuous in situ measurement in living plants remains challenging. In this study, we developed a non-enzymatic microneedle (MN) electrochemical sensor for the direct, real-time monitoring of glucose in plant leaves. To achieve this, we utilized a highly customizable and cost-effective fabrication strategy. A three-electrode MN system was fabricated by combining SU-8 micromolding with 3D printing of a carbon paste circuit, significantly reducing the reliance on complex cleanroom processes. The working electrode was then functionalized via a single-step co-electrodeposition of Co3O4 catalysts and multiwall carbon nanotubes in a chitosan matrix. This co-deposition effectively compensated for the inherently low electrical conductivity of Co3O4. The optimized sensor exhibited reliable in vitro analytical performance. Furthermore, the MN sensor was inserted into living leaves to monitor glucose levels under varying light and dark conditions. The sensor successfully recorded dynamic real-time current signals, showing an average of 71.5 ± 11.0 nA in the dark and 9.6 ± 2.8 nA in the light. This customizable MN platform provides a practical diagnostic tool for continuous plant health monitoring.
Kim et al. (Thu,) studied this question.