A Biohydrogel-Enabled Microneedle Sensor for In Situ Monitoring of Reactive Oxygen Species in Plants.

Abstract

This study introduces a plant sensor utilizing an array of microneedles to monitor hydrogen peroxide (H 2 O 2 ) in tobacco and soybean plants under biotic stress response. The microneedle array features a biohydrogel layer composed of the natural biopolymer chitosan (Cs) and reduced graphene oxide (rGO), functionalized with horseradish peroxidase (HRP) (HRP/Cs-rGO). This HRP/Cs-rGO biohydrogel combines biocompatibility, hydrophilicity, porosity, and electron transfer ability, making it a suitable bioelectrode material for an electrochemical sensor. The sensor detects H 2 O 2 through the catalytic reaction of the enzyme, either by direct attachment to the plant leaf with the inserted microneedle or by exposure to the solution extracted from plant parts such as leaves. Utilizing chronoamperometry, the sensor demonstrates high sensitivity of 14.7 μA/μM across a concentration range of 0.1-4500 μM with a low detection limit of 0.06 μM. The sensor enables rapid detection of H 2 O 2 levels by exposing the sensor to extracted leaf solutions. For in situ measurements within the leaf, results are obtained in approximately 1 min, eliminating the need for sample preparation. H 2 O 2 levels in leaves following bacterial pathogen inoculation are evaluated alongside results from qualitative histological staining and quantitative fluorescence-based Amplex Red Assay, validating the ability of the sensor to detect changes in H 2 O 2 concentrations during plant defense responses. This sensor technology has the potential to function as a portable device for on-site measurement of reactive oxygen species in plants, providing a rapid and cost-effective solution for H 2 O 2 quantification.

Plant phenotyping relevance

植物体内の過酸化水素濃度という生理状態を測定するマイクロニードル電気化学センサーを開発し、既存アッセイ等で妥当性を検証しており、測定手法が研究の中心である。

Code and data availability

The article describes a microneedle electrochemical H2O2 sensor and plant measurements, but no public phenotype dataset, image/sensor data deposit, author analysis code, or trained model is mentioned. The only supplementary material is a PDF of methods/figures with no public URL or deposit language, and no data or code

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