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 the Temasek Life Sciences Laboratory (TLL) and the Massachusetts Institute of Technology (MIT), have developed the world's first near-infrared (NIR) fluorescent nanosensor. This sensor is capable of real-time, non-destructive, and species-agnostic detection of indole-3-acetic acid (IAA)—the primary bioactive auxin hormone that controls how plants develop, grow, and respond to stress.
Auxins, especially IAA, are crucial in regulating key plant processes such as cell division, elongation, root and shoot development, and responses to environmental cues like light, heat, and drought. External factors like light affect how auxin moves within the plant, temperature influences how much is produced, and a lack of water can disrupt hormone balance. When plants cannot effectively regulate auxins, they may struggle to grow well, adapt to changing conditions, or produce as much food.
Existing methods for detecting IAA, such as liquid chromatography, require taking samples from the plant, which harms or removes part of it. Traditional methods also measure the effects of IAA rather than detecting it directly and cannot be universally applied across different plant types. Additionally, because IAA molecules are small and difficult to track in real-time, biosensors with fluorescent proteins need to be inserted into the plant's genome to measure auxin, causing the plant to emit a fluorescent signal for live imaging.
SMART's newly developed nanosensor allows for direct, real-time tracking of auxin levels in living plants with high precision. This sensor uses NIR imaging to non-invasively monitor IAA fluctuations across tissues like leaves, roots, and cotyledons. It can bypass chlorophyll interference to provide highly reliable readings even in densely pigmented tissues. The technology does not require genetic modification and can be integrated with existing agricultural systems, offering a scalable precision tool to advance both crop optimization and fundamental plant physiology research.
By providing real-time, precise measurements of auxin—a hormone central to plant growth and stress response—the sensor gives farmers earlier and more accurate insights into plant health. With these insights and comprehensive data, farmers can make smarter, data-driven decisions on irrigation, nutrient delivery, and pruning, tailored to the plant's actual needs, ultimately improving crop growth, boosting stress resilience, and increasing yields.
"We need new technologies to address the problems of food insecurity and climate change worldwide. Auxin is a central growth signal within living plants, and this work provides a way to tap into it to give new information to farmers and researchers. The applications are numerous, including early detection of plant stress, allowing for timely interventions to safeguard crops. For urban and indoor farms, where light, water, and nutrients are already tightly controlled, this sensor can be a valuable tool in fine-tuning growth conditions with even greater precision to optimize yield and sustainability," said Prof. Michael Strano, Co-Lead Principal Investigator at DiSTAP and Carbon P. Dubbs Professor of Chemical Engineering at MIT, and co-corresponding author of the paper.
The research team documented the nanosensor's development in a paper titled "A Near-Infrared Fluorescent Nanosensor for Direct and Real-Time Measurement of Indole-3-Acetic Acid in Plants," published in the journal ACS Nano. The sensor comprises single-walled carbon nanotubes (SWNTs) wrapped in a specially designed polymer, which enables it to detect IAA through changes in NIR fluorescence intensity. It has been successfully tested across multiple species, including Arabidopsis, Nicotiana benthamiana, choy sum, and spinach. The nanosensor can map IAA responses under various environmental conditions such as shade, low light, and heat stress.
"This sensor builds on DiSTAP's ongoing work in nanotechnology and the CoPhMoRe technique, which has already been used to develop other sensors that can detect important plant compounds such as gibberellins and hydrogen peroxide. By adapting this approach for IAA, we're adding to our inventory of novel, precise, and non-destructive tools for monitoring plant health. Eventually, these sensors can be multiplexed, or combined, to monitor a spectrum of plant growth markers for more complete insights into plant physiology," said Dr. Duc Thinh Khong, Principal Research Scientist at DiSTAP and co-first author of the paper.
"This small but mighty nanosensor tackles a long-standing challenge in agriculture: the need for a universal, real-time, and non-invasive tool to monitor plant health across various species. Our collaborative achievement not only empowers researchers and farmers to optimize growth conditions and improve crop yield and resilience but also advances our scientific understanding of hormone pathways and plant-environment interactions," said Dr. In-Cheol Jang, Senior Principal Investigator at TLL and Principal Investigator at DiSTAP, and co-corresponding author of the paper.
Looking ahead, the research team aims to combine multiple sensing platforms to simultaneously detect IAA and its related metabolites to create a comprehensive hormone signaling profile, offering deeper insights into plant stress responses and enhancing precision agriculture. They are also working on using microneedles for highly localized, tissue-specific sensing and collaborating with industrial urban farming partners to translate the technology into practical, field-ready solutions.
The research is carried out by SMART and supported by the National Research Foundation under its Campus for Research Excellence and Technological Enterprise (CREATE) programme.
For more information:
Singapore-MIT Alliance for Research and Technology (SMART)
www.smart.mit.edu
