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.