Glucose-Sensitive Biohybrid Roots for Supercapacitive Bioanodes

Plants as living organisms, as well as their material-structural components and physiological processes, offer promising elements for developing more sustainable technologies. Previously, we demonstrated that plants could acquire electronic functionality, as their enzymatic activity catalyzes the in vivo polymerization of water-soluble conjugated oligomers. We then leveraged plant-integrated conductors to develop biohybrid energy storage devices and circuits. Here, we extend the concept of plant biohybrids to develop plant-based energy-harvesting devices. We demonstrate plant biohybrids with modified roots that can convert common root exudates, such as glucose, to electricity. To do so, we developed a simple one-step approach to convert living roots to glucose-sensitive electrodes by dipping the root in a solution of the conjugated trimer ETE-S and the enzyme glucose dehydrogenase flavin adenine dinucleotide. The biohybrid device responds to glucose concentrations down to 100 μM while it saturates at 100 mM. The performance of our approach was compared with a classic mediator-based glucose biosensor functionalization method. While the latter method increases the stability of the sensor, it results in less sensitivity and damages the root structure. Finally, we show that glucose oxidation can be combined with the volumetric capacitance of p(ETE-S)-forming devices that generate current in the presence of glucose and store it in the same biohybrid root electrodes. The plant biohybrid devices open a pathway to biologically integrated technology that finds application in low-power devices, for example, sensors for agriculture or the environment.