The challenge the researchers set out to solve is one that anyone who has tried to measure glucose in tissue will recognise. Carbohydrates, and glucose above all, are the fuel of cellular life, and their flux through cells underpins everything from insulin signalling to tumour growth. Yet glucose itself is a small, colourless, non-reactive molecule that carries no natural handle for imaging. Conventional approaches typically require destroying tissue, taking blood samples at discrete time points, or relying on indirect readouts that average activity across large regions. What has been missing is a way to watch sugar dynamics unfold inside intact, living systems, cell by cell, as they happen. That is precisely the gap the Bath-led team set out to close with synthetic chemistry.

The heart of the new technology lies in a class of compounds called boronic acids. These chemicals have long been known to bind selectively to sugars: the boron atom forms reversible bonds with the diol groups that decorate carbohydrate molecules such as glucose. Chemists have exploited this property for years in sensors, but turning it into a tool that works inside a living vertebrate is far harder. The probe must be bright enough to detect, stable enough to survive in biological tissue, non-toxic to the organism, and designed so that its fluorescence changes measurably when it captures glucose. The interdisciplinary team combined sugar-binding boronic acids with advanced imaging technologies capable of visualising molecular behaviour inside living systems, creating probes that report on glucose-related processes rather than simply staining cells.

Crucially, the researchers did not rely on brightness alone. They paired their probes with multiphoton fluorescence lifetime imaging microscopy, or MP-FLIM, an advanced technique that measures how long a fluorescence signal lasts after excitation rather than simply how strong it is. This distinction matters enormously in practice. Fluorescence intensity can be distorted by probe concentration, tissue depth, light scattering and uneven illumination, all of which are unavoidable complications in a living animal. Fluorescence lifetime, by contrast, is an intrinsic property of the excited molecule and is far more robust to those confounders. When the probe binds glucose, the local chemical environment of the fluorophore shifts, and with it the lifetime of its emitted light. By mapping those subtle lifetime changes across tissue, MP-FLIM allowed the team to visually identify which cells were absorbing and using sugars in real time within a living system.

To test whether the approach could truly work in vivo, the team turned to the zebrafish, a small freshwater fish that has become one of the most widely used model organisms in metabolic research. Zebrafish larvae are optically transparent, develop rapidly, and share core aspects of glucose regulation with humans, making them an ideal platform for live imaging. In the experiments, several of the probes accumulated strongly in the digestive system of zebrafish larvae, and their fluorescence changed in response to an external glucose challenge delivered to the animals. In other words, when the larvae were exposed to more sugar, the probes reported it, providing direct visual evidence that the sensors could follow glucose fluctuations in a living vertebrate.

The most striking demonstration came when the researchers applied the same approach to zebrafish carrying a diabetes-like mutation. These insulin-deficient fish, which model aspects of the disease in a genetically controlled way, were successfully distinguished from their healthy siblings using the probe-and-FLIM combination. The diabetic fish showed significantly reduced fluorescence, a consequence of their elevated glucose levels altering the binding state of the probes in their tissues. That result is significant because it shows the technology detecting not just an artificial sugar bolus but a genuine disease state, caused by a broken hormonal regulatory loop, within an intact living organism. It suggests the platform could one day be used to monitor metabolic dysfunction as it develops, rather than inferring it from endpoint measurements.

The researchers themselves frame the work as a step change in how metabolic processes can be studied. Professor Sofia I. Pascu, from the University of Bath’s Department of Chemistry and one of the study’s corresponding authors, said the work demonstrates that synthetic carbohydrate-recognising probes can monitor glucose-related processes in living organisms in real time, representing an important step towards next-generation tools for investigating metabolic disorders and developing precision diagnostic technologies. Dr David Gurevich, corresponding author and Sir Henry Dale Wellcome Trust Research Fellow in the University’s Department of Life Sciences, noted that the results show synthetic boronic acid-based fluorescent probes can report on glucose fluctuations caused by both external sugar exposure and an insulin-deficient living organism, potentially giving researchers a new way to connect changes in glucose with the biological effects of metabolic and other diseases.

The implications extend well beyond glucose monitoring. Abnormal carbohydrate metabolism is a hallmark not only of diabetes but also of many cancers, where rapidly dividing cells dramatically rewire their sugar uptake in a phenomenon long exploited by PET imaging. Because the probe platform is built on modular chemistry, the researchers believe it could be adapted to detect other biologically important carbohydrates and metabolic markers, opening the door to earlier diagnosis, drug discovery and personalised treatment strategies. Professor Tony D. James, co-corresponding author, said that by bringing together supramolecular chemistry, advanced photonics and biological models, the team has created a versatile platform for imaging metabolic processes in real time, adding that the work demonstrates the power of combining chemistry, biology and advanced imaging to gain new insights into living systems. The group is now exploring how the technologies might be developed further for theranostic applications, which combine therapy and diagnostics, and for future drug-screening tools.

The research also stands as a testament to international, interdisciplinary collaboration, involving biologists, physicists and chemists from the University of Bath, the University of Birmingham, the Universidad Autónoma de Madrid, the Spanish National Research Council (CSIC) and the STFC Rutherford Appleton Laboratory. Among the contributors was the late Professor John S. Fossey of the University of Birmingham, a leading figure in boronic acid chemistry and molecular recognition whose insight and collaboration helped shape this project and many related studies. The publication in Advanced Science, carrying the DOI 10.1002/advs.77481, is presented by the team as a tribute to his scientific legacy and enduring impact on colleagues, students and collaborators across the field. For a field that has long had to infer what sugar is doing inside living bodies from snapshots and averages, the ability to watch glucose dynamics unfold in real time, in a whole organism, marks a genuinely new way of seeing metabolism in action.

Subject of Research: Fluorescent boronic acid probes for real-time in vivo imaging of glucose metabolism in zebrafish

Article Title: Fluorescent sensors could help researchers see diabetes in action

Article References: Fluorescent sensors could help researchers see diabetes in action. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: fluorescent probes, boronic acids, glucose imaging, diabetes, zebrafish, multiphoton FLIM, metabolism, supramolecular chemistry, cancer metabolism, live imaging, University of Bath, Advanced Science