Researchers from the Disruptive & Sustainable Technologies for Agricultural Precision (DiSTAP) interdisciplinary research group (IRG) of the Singapore-MIT Alliance for Research and Technology (SMART), MIT’s research enterprise in Singapore, in collaboration with Temasek Life Sciences Laboratory (TLL) and Massachusetts Institute of Technology (MIT), have developed an inventive near-infrared (NIR) fluorescent nanosensor capable of simultaneously detecting and differentiating between iron forms — Fe(II) and Fe(III) — in living plants.
Iron is crucial for plant health, supporting photosynthesis, respiration, and enzyme function. It primarily exists in two forms: Fe(II), which is readily available for plants to absorb and use, and Fe(III), which must be converted into Fe(II) before plants can utilize it effectively. Traditional methods only measure total iron, failing to distinguish between these forms — a crucial aspect of plant nutrition. Distinguishing between Fe(II) and Fe(III) offers insights into iron uptake efficiency and aids in diagnosing deficiencies or toxicities. It enables precise fertilization strategies in agriculture, reducing waste and environmental impact while enhancing crop productivity.
This first-of-its-kind nanosensor by SMART researchers enables real-time, non-destructive monitoring of iron uptake, transport, and changes between its different forms, such as Fe(II) and Fe(III) — providing precise and detailed observations of iron dynamics. Its high spatial resolution allows accurate localization of iron in plant tissues or subcellular compartments, enabling the measuring of even minute changes in iron levels within plants – these changes can inform how a plant handles stress and uses nutrients.
DiSTAP researchers develop sensors for rapid iron detection and plant monitoring, enabling precision agriculture and sustainable crop management. Credit: SMART DiSTAP
Traditional detection methods are destructive or limited to a single form of iron. This new technology enables the diagnosis of deficiencies and optimization of fertilization strategies. By identifying insufficient or excessive iron intake, adjustments can be made to enhance plant health, reduce waste, and support more sustainable agriculture. While the nanosensor was tested on spinach and bok choy, it is species-agnostic, allowing it to be applied across various plant species without genetic modification. This capability enhances our understanding of iron dynamics in various ecological settings, providing comprehensive insights into plant health and nutrient management. As a result, it serves as a valuable tool for both fundamental plant research and agricultural applications, supporting precision nutrient management, reducing fertilizer waste, and improving crop health.
“Iron is essential for plant growth and development, but monitoring its levels in plants has been a challenge. This breakthrough sensor is the first to detect Fe(II) and Fe(III) in living plants with real-time, high-resolution imaging. With this technology, we can ensure plants receive the right amount of iron, improving crop health and agricultural sustainability,” said Dr. Duc Thinh Khong, DiSTAP research scientist and co-lead author of the paper.
“In enabling non-destructive real-time tracking of plant iron speciation, this sensor opens new avenues for understanding plant iron metabolism and the implications of different iron variations for plants. Such knowledge will help guide the development of tailored management approaches to improve crop yield and more cost-effective soil fertilization strategies,” said Dr. Grace Tan, TLL Research Scientist and co-lead author of the paper.
The research, recently published in Nano Letters and titled,” builds upon SMART DiSTAP’s established expertise in plant nanobionics, leveraging the Corona Phase Molecular Recognition (CoPhMoRe) platform pioneered by the Strano Lab at SMART DiSTAP and MIT. The new nanosensor features single-walled carbon nanotubes (SWNTs) wrapped in a negatively charged fluorescent polymer, forming a helical corona phase structure that interacts differently with Fe(II) and Fe(III). Upon introduction into plant tissues and interaction with iron, the sensor emits distinct NIR fluorescence signals based on the iron type, enabling real-time tracking of iron movement and chemical changes.
The CoPhMoRe technique was used to develop highly selective fluorescent responses, allowing precise detection of iron oxidation states. The NIR fluorescence of SWNTs offers superior sensitivity, selectivity, and tissue transparency while minimizing interference, making it more effective than conventional fluorescent sensors. This capability lets researchers track iron movement and chemical changes in real time using NIR imaging.
“This sensor provides a powerful tool to study plant metabolism, nutrient transport, and stress responses. It supports optimized fertilizer use, reduces costs and environmental impact, and contributes to more nutritious crops, better food security, and sustainable farming practices,” said Professor Daisuke Urano, TLL Senior Principal Investigator, DiSTAP Principal Investigator, NUS Adjunct Assistant Professor, and co-corresponding author of the paper.
“This set of sensors gives us access to an important type of signaling in plants and a critical nutrient necessary for plants to make chlorophyll. This new tool will not just help farmers to detect nutrient deficiency but also give access to certain messages within the plant. It expands our ability to understand the plant response to its growth environment,” said Professor Michael Strano, DiSTAP Co-Lead Principal Investigator, Carbon P. Dubbs Professor of Chemical Engineering at MIT, and co-corresponding author of the paper.
Beyond agriculture, this nanosensor shows potential for environmental monitoring, food safety, and health sciences, particularly investigating iron metabolism, iron deficiency, and iron-related diseases in humans and animals. Future research will utilize this nanosensor to further fundamental plant studies on iron homeostasis, nutrient signaling, and redox dynamics. Efforts are also underway to incorporate the nanosensor into automated nutrient management systems for hydroponic and soil-based farming while expanding its capability to detect other essential micronutrients. These advancements aim to improve sustainability, precision, and efficiency in agriculture.
SMART conducts the research, which is supported by the National Research Foundation under its Campus for Research Excellence and Technological Enterprise (CREATE) program.
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