Plant biotic or abiotic stresses, such as pathogens, mechanical damage, or high temperature, can increase intracellular H2O2 concentration, damaging proteins, lipids, and DNA. Most current H2O2 detection methods require the separation or grinding of plant samples, inducing plant stresses, and the process is complicated and time-consuming. This paper constructed a metal-organic framework (MOF)-based biosensor for real-time, remote, and in situ detection of exogenous/endogenous H2O2 in plant organs through color-to-thermal signal conversion. By simply spraying horseradish peroxidase, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and the precursor of zeolite imidazolate frameworks-8 (ZIF-8), ZIF-8 biosensors were formed in situ on a plant root, petiole, or leaf. This biosensor could report sub-micromolar H2O2 in plants since the oxidation products, ABTS• +, emitted heat when they absorbed energy from near-infrared (NIR) light. Due to the plant's low absorption in the NIR region, the ZIF-8 biosensor allowed for remote thermal sensing of H2O2 transport or biotic/abiotic stresses in plants with a high signal-to-noise ratio combining NIR laser and thermometer. Our biosensor can be used for the future development of plant sensors for monitoring plant signaling pathways and metabolism that are nondestructive, minimally invasive, and capable of real-time, in situ analysis.
Keywords: biosensor; hydrogen peroxide; metal−organic framework; plant stress; thermal signal.