Minimally invasive microneedle sensor for in vivo monitoring of indole-3-acetic acid in plant leaves.

Abstract

Indole-3-acetic acid (IAA), one of the most important phytohormones, plays critical roles in plant growth, development, and stress response. However, minimally invasive and in-situ monitoring of IAA in living plants remains challenging due to the complex biological matrix and the lack of suitable in vivo sensing platforms. Herein, we report a minimally invasive microneedle electrochemical sensor for in vivo monitoring of IAA in plant leaves. A polymer microneedle array was fabricated and coated with a conductive Au layer, followed by electropolymerization of a molecularly imprinted poly(o-phenylenediamine) (poly-OPD) recognition film using IAA as the template molecule. The resulting microneedle sensor exhibited a selective electrochemical response toward IAA with good anti-interference capability against common electroactive plant metabolites. The sensor showed a linear response toward IAA over a wide concentration range with a low detection limit (0.44 μM). The microscale structure of the microneedles enabled minimally invasive insertion into plant tissues while maintaining structural integrity and stable electrochemical performance of the sensing platform. The developed sensor was further applied for in vivo monitoring of IAA fluctuations in tomato leaves under different physiological conditions. Distinct dynamic electrochemical response patterns were observed between normal and drought-stressed leaves, demonstrating the potential of the microneedle platform for plant physiological analysis and precision agriculture applications. This work provides a promising strategy for minimally invasive phytohormone sensing in living plants and expands the application of microneedle electrochemical devices in plant bioanalysis.

Plant phenotyping relevance

植物葉内のIAAを非侵襲的に測定するマイクロニードル電気化学センサーを開発・性能評価し、乾燥ストレス下の生理状態を実植物で検証しており、表現型取得法が中心である。

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