Scientists from the Disruptive and Sustainable Technologies for Agricultural Precision (DiSTAP) interdisciplinary research collective within the Singapore-MIT Alliance for Research and Technology (SMART), MIT’s research initiative in Singapore, in partnership with Temasek Life Sciences Laboratory (TLL) and MIT, have invented a pioneering near-infrared (NIR) fluorescent nanosensor that can both identify and differentiate between forms of iron — Fe(II) and Fe(III) — in live plants.
Iron is vital for the wellbeing of plants, facilitating photosynthesis, respiration, and enzyme activities. It is primarily present in two states: Fe(II), which is readily absorbed and utilized by plants, and Fe(III), which must be converted to Fe(II) prior to effective utilization by plants. Conventional techniques only quantify total iron, overlooking the distinction between these forms — a crucial aspect of plant nutrition. Differentiating Fe(II) from Fe(III) allows for insights into the efficiency of iron uptake, aids in diagnosing deficiencies or toxic levels, and supports refined fertilization techniques in agriculture, curtailing waste and environmental ramifications while enhancing crop productivity.
The unprecedented nanosensor crafted by SMART investigators permits real-time, non-invasive observation of iron uptake, transport, and transitions between its various forms — delivering accurate and comprehensive insights into iron dynamics. With its high spatial resolution, it precisely locates iron within plant tissues or subcellular structures, enabling the detection of slight fluctuations in iron concentrations within plants — alterations that can inform on how a plant copes with stress and utilizes nutrients.
Classic detection methodologies are often destructive or restricted to identifying a single form of iron. This innovative technology paves the way for diagnosing deficiencies and refining fertilization techniques. By pinpointing inadequate or excessive iron absorption, adjustments can be implemented to bolster plant vitality, minimize waste, and promote more sustainable agricultural practices. Although the nanosensor was evaluated on spinach and bok choy, it is oblivious to species, allowing it to be utilized across a wide array of plant types without genetic alterations. This capability deepens our understanding of iron dynamics across various ecological contexts, offering extensive insights into plant vitality and nutrient stewardship. Consequently, it emerges as a vital instrument for both fundamental plant investigation and agricultural applications, facilitating precision nutrient oversight, minimizing fertilizer waste, and enhancing plant health.
“Iron is integral for plant nourishment and development, yet monitoring its levels in plants has proved challenging. This groundbreaking sensor is the first of its kind to detect both Fe(II) and Fe(III) in living vegetation with real-time, high-resolution imaging. With this advancement, we can ensure plants are provided with the appropriate amounts of iron, enhancing crop health and agricultural sustainability,” comments Duc Thinh Khong, DiSTAP research scientist and co-lead author of the study.
“By facilitating non-destructive, real-time monitoring of iron speciation in plants, this sensor creates new possibilities for comprehending plant iron metabolism and the implications of distinct iron forms for plants. Such understanding will assist in shaping customized management strategies to boost crop yield and develop more economically viable soil fertilization approaches,” states Grace Tan, TLL research scientist and co-lead author of the manuscript.
The findings, recently published in Nano Letters and entitled, “Nanosensor for Fe(II) and Fe(III) Allowing Spatiotemporal Sensing in Planta,” builds upon the established proficiency of SMART DiSTAP in the field of plant nanobionics, utilizing the Corona Phase Molecular Recognition (CoPhMoRe) framework developed by the Strano Lab at SMART DiSTAP and MIT. The newly developed nanosensor incorporates single-walled carbon nanotubes (SWNTs) encased in a negatively charged fluorescent polymer, creating a helical corona phase architecture that interacts distinctly with Fe(II) and Fe(III). Upon introduction into plant tissues and interaction with iron, the sensor emits unique NIR fluorescence signals contingent on the type of iron, enabling real-time observation of iron movement and chemical alterations.
The CoPhMoRe methodology was integral in achieving highly specific fluorescent reactions, enabling accurate identification of iron oxidation states. The NIR fluorescence of SWNTs provides remarkable sensitivity, selectivity, and transparency in tissues while reducing interference, making it superior to traditional fluorescent sensors. This feature permits scientists to monitor iron dynamics and chemical variations in real time using NIR imaging.
“This sensor equips us with a powerful instrument to explore plant metabolism, nutrient transport, and responses to stress. It promotes enhanced fertilizer application, diminishes costs and environmental impact, and contributes to the creation of more nutritious crops, thereby enhancing food security and sustainable farming methodologies,” remarks Professor Daisuke Urano, TLL senior principal investigator, DiSTAP principal investigator, National University of Singapore adjunct assistant professor, and co-corresponding author of the publication.
“This collection of sensors grants us insights into a significant type of signaling in plants, along with a vital nutrient necessary for chlorophyll synthesis. This novel tool will assist farmers not only in detecting nutrient deficiencies but also in obtaining certain signals from within the plant. It expands our capacity to understand plant responses to their growth environments,” shares 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 the realm of agriculture, this nanosensor holds potential for environmental monitoring, food safety, and health sciences, particularly in the examination of iron metabolism, iron deficiency, and iron-associated diseases in humans and animals. Future investigations will concentrate on employing this nanosensor to advance foundational studies about plant iron homeostasis, nutrient signaling, and redox dynamics. Furthermore, efforts are in progress to incorporate the nanosensor into automated nutrient management systems for hydroponic and soil-based agriculture and enhance its capabilities to identify other essential micronutrients. These developments aim to boost sustainability, precision, and efficiency in agricultural practices.
The research is conducted by SMART and funded by the National Research Foundation as part of its Campus for Research Excellence And Technological Enterprise initiative.