Dual-Electrode Wearable Biosensors for In-Field MicroRNA Analysis in Living Plants

MicroRNAs (miRNAs) are pivotal regulators of plant growth and stress response. The development of plant wearable miRNA-specific sensors holds significant potential to unveil new insights into plant physiology and to advance precision agriculture. However, monitoring miRNA expression in living plants remains a formidable challenge due to their low abundance, short sequence length, and complex matrix of real plant tissues. Herein, a plant wearable dual-electrode ratiometric chip (DER-Chip) was designed and fabricated for the direct, in-field sensitive determination of miRNA without the requirement of target enrichment or any pretreatment. The DER-Chip consists of two flexible electrodes: a hydrogel electrode for housing the DNA probes and extracting targets from the complex plant extrudate and a specially designed gold nanoparticle-modified laser-induced graphene (LIG/Au) electrode for reliable electrochemical signal readout. Through being equipped with target-triggered hybridization chain reaction amplification, ratiometric electrochemical signal output, and a magnetic-driven directional transfer strategy, the DER-Chip exhibited excellent analytical performance for plant miRNA with a detection limit down to 3.2 fM. Given the advancements in scalable manufacturing techniques and the miniaturization of biological assays, the proposed wearable chip can be engineered with a portable analyzer for in situ assessment of miRNA expression levels in tomatoes under drought and salt stress conditions.