In Planta Nitrate Sensor Using a Photosensitive Epoxy Bioresin

Abstract

Nitrogen management through monitoring of crop nitrate status can improve agricultural productivity, profitability, and environmental performance. Current plant nitrate test methods require expensive instruments, time-intensive labor, and trained personnel. Frequent monitoring of in planta nitrate levels of the stalks in living plants can help to better understand the nitrogen cycle and the physiological responses to environmental variations. Although existing enzymatic electrochemical sensors provide high selectivity, they suffer from short shelf life, high cost, low-temperature storage requirement, and potential degradation over time. To overcome these issues, an artificial enzyme (vitamin B12 or VB12) and a two-dimensional material (graphene oxide or GO) are introduced into a conventional photoresist (SU8) to form a bioresin SU8-GO-VB12 that can be patterned with photolithography and laser-pyrolyzed into a carbon-based nanocomposite C-GO-VB12. The electrocatalytic activity of the cobalt factor in VB12, the surface enhancement properties of GO, and the porous feature of pyrolytic carbon are synergized through design to provide C-GO-VB12 with a superior ability to detect nitrate ions through redox reactions. In addition, laser writing-based selective pyrolysis allows applying thermal energy to target only SU8-GO-VB12 for selective pyrolysis of the bioresin into C-GO-VB12, thus reducing the total energy input and avoiding the thermal influence on the materials and structures in other areas of the substrate. The C-GO-VB12 nitrate sensor demonstrates a year-long shelf lifetime, high selectivity, and a wide dynamic range that enables a direct nitrate test for the extracted sap of maize stalk. For in situ monitoring of the nitrate level and dynamic changes in living maize plants, a microelectromechanical system-based needle sensor is formed with C-GO-VB12. The needle sensor allows direct insertion into the plant for in situ measurement of nitrate ions under different growth environments over time. The needle sensor represents a new method for monitoring in planta nitrate dynamics with no need for sample preparation, thus making a significant impact in plant sciences.

Modern analytical and bioanalytical technologies and concepts for smart and precision farming

“…A nitrate photosensitive bioristor composed of an artificial enzyme (VB12), 2D graphene oxide, and a photoresist capable of in vivo and in vitro nitrate determination was introduced. 44 The bioristor demonstrated good repeatability and stability without compromising selectivity and sensitivity. It shows the potential of a biomimetic enzyme to address the shelf-life issue of enzyme-based biosensors.…”

“…Biosensors can also be designed into needles with the help of microelectromechanical (MEMS) system technology. 44 This allows for miniaturization and a reduction in material consumption. Moreover, the detection mechanism of a biosensor is not solely electrically driven but depends on the molecular binding events of proteins, DNA, and aptamers.…”

Internet of Things‐Enabled Food and Plant Sensors to Empower Sustainability

“…[83,98] Researchers have shown that needle-based plant sensors can be used to monitor plant nitrates to improve agricultural productivity, profitability, and environmental performance (Figure 5c). [99] To maintain a biocompatible sensor interface during the long-term monitoring of plant nitrate dynamics, this sensor uses an artificial enzyme (vitamin B 12 ) combined with a carbon-based nanocomposite (which converts nitrate to nitrite and produces electrons for measurement). [99] This needle-based sensor provides a novel approach for monitoring nitrate dynamics in plants without precalibration or preprocessing, thus potentially impacting plant sciences.…”

“…Spathiphyllum wallisii [95] Photosensitive epoxy bioresin Agriculture sector Nitrate [99] Implantable organic electrochemical transistor sensor Agriculture and plants Glucose and sucrose [100] Smart plant-wearable biosensor…”

“…c) Biomimetic implantable in-planta sensor for long-term, continuous, and in situ monitoring of plant nitrate. Adapted with permission [99]. Copyright 2022, American Chemical Society.…”