Innovative COF-Silk Sensors for Early Detection of Plant Drought Stress

Have you ever questioned whether your plants are adequately hydrated or if you’re providing enough water? Farmers and gardening enthusiasts now have a promising solution to monitor plant hydration in real-time.

Innovative Sensors for Real-Time Plant Monitoring

In recent years, researchers have made strides in developing sensors capable of detecting a variety of chemical compounds. A significant challenge has been creating sensors suitable for use within living biological systems. This landscape is changing with innovative sensors from the Singapore-MIT Alliance for Research and Technology (SMART) that can monitor pH variations in living plants. These changes can indicate drought stress, allowing for timely management to prevent significant yield losses.

A team from the Disruptive and Sustainable Technologies for Agricultural Precision (DiSTAP) group at SMART, in partnership with the Temasek Life Sciences Laboratory and MIT, has introduced the world’s first covalent organic framework (COF) sensors embedded within silk fibroin (SF) microneedles. These sensors allow for in-plant detection of physiological pH changes, providing an advanced method to identify reductions in acidity within plant xylem tissues, alerting farmers to potential drought stress up to 48 hours ahead of traditional methods.

Addressing Agricultural Challenges Amid Climate Change

Drought is a critical factor that diminishes crop yields by disrupting essential metabolic pathways in plants. It can lead to reduced leaf size, stunted stem growth, and limited root expansion. Prolonged drought conditions may result in discoloration, wilting, and ultimately plant death. With agricultural challenges such as climate change, increasing costs, and land scarcity on the rise, farmers often struggle to take proactive measures or diagnose issues before they escalate. This highlights the urgent need for enhanced sensor integration to facilitate real-time assessments and interventions in agricultural practices.

“This sensor can be easily attached to plants and queried with straightforward instrumentation, empowering farmers and researchers with powerful analytical tools,” remarks Professor Michael Strano, a key investigator at DiSTAP.

Breakthroughs in Covalent Organic Framework Sensors

SMART’s innovation addresses a long-standing obstacle faced by COF-based sensors that previously could not interact with biological tissues. COFs are structured networks of organic molecules or polymers composed of carbon atoms bonded to elements like hydrogen, oxygen, or nitrogen. These structures change color in response to varying pH levels. Given that drought stress can be detected through pH fluctuations in plant tissues, this novel COF-based sensor enables real-time monitoring of pH levels in xylem tissues, assisting farmers in optimizing crop production amidst changing climate conditions.

“The COF-silk sensors exemplify new tools necessary for precision agriculture in a world increasingly challenged by climate change, resource limitations, and the need for reduced carbon footprints,” states Professor Benedetto Marelli, another principal investigator at DiSTAP. “This seamless integration of nanosensors and biomaterials allows for the effortless measurement of vital plant fluid parameters such as pH, facilitating effective monitoring of plant health.”

“This seamless integration of nanosensors and biomaterials allows for the effortless measurement of vital plant fluid parameters such as pH, facilitating effective monitoring of plant health.”

Advanced Techniques for In-Vivo Chemical Tomography

The groundbreaking research documented in an open-access paper titled “Chromatic Covalent Organic Frameworks Enabling In-Vivo Chemical Tomography” published in Nature Communications showcases real-time pH detection in plant tissues. Notably, this technique allows for 3D mapping of pH levels using just a smartphone camera, offering a minimally invasive alternative to traditional optical methods.

The researchers developed four COF compounds that demonstrate tunable acid chromism—color shifts associated with pH variations—utilizing SF microneedles coated with COF films. The transparency of these microneedles facilitates in-vivo observation of pH distributions through color changes.

“Building on our previous work with biodegradable COF-SF films for food spoilage detection, we have now created a method to monitor pH changes in plant tissues. In practical use, these COF compounds transition from dark red to red as pH levels rise in xylem tissues, signaling drought stress and the need for early intervention to avoid yield loss,” explains Song Wang, a research scientist at SMART DiSTAP.

“The robustness of SF microneedles ensures stability when interfacing with biological tissues. Their transparency allows for multidimensional mapping in a minimally invasive manner. Combined with COF films, these tools empower farmers to monitor plant health in real-time and effectively tackle challenges such as drought while enhancing crop resilience,” adds Yangyang Han, senior postdoc at SMART DiSTAP.

Future Prospects and Support

This research lays the groundwork for future advancements in COF-SF microneedle-based chemical imaging technologies. Moving forward, the team aims to expand this innovative approach beyond pH detection to include a wide range of biologically relevant analytes such as plant hormones and metabolites.

This project is supported by the National Research Foundation of Singapore under its Campus for Research Excellence And Technological Enterprise program.