Blue molecule blueprint brightens fluorescent probes for disease imaging

Chemists at the University of Bath have worked out how the smallest of molecular tweaks can transform the colour and the brightness of a family of fluorescent probes built around a strikingly blue natural compound, a finding that could sharpen the molecular tools scientists use to watch disease unfold inside living cells. The research, funded by the Engineering and Physical Sciences Research Council and published in Organic Chemistry Frontiers, delivers what the team describes as a blueprint for the rational design of future probes aimed at research and diagnostics for conditions including Alzheimer’s disease, Parkinson’s disease, cancer and asthma.

The compound at the heart of the work is azulene, a naturally occurring molecule responsible for the vivid blue colour of certain fungi and corals. Among the species that carry it is Lactarius indigo, the indigo milk cap mushroom, whose unusual pigmentation has long fascinated chemists. Azulene also appears in some skincare products, where it is used to calm irritation. But it is the molecule’s optical behaviour, rather than its soothing reputation, that has made it attractive to the Bath team: azulene absorbs light at one wavelength and emits light at a different, typically longer wavelength, which is precisely the property needed for a molecule to serve as a fluorophore.

Fluorescent probes are the workhorses of modern biological imaging. Each probe is built from two functional parts: a receptor, which is engineered to detect or bind a particular substance of interest inside or around a cell, and a fluorophore, the light-handling component that turns that binding event into a visible signal. When illuminated under a microscope, the fluorophore absorbs light of a specific wavelength and re-emits light at a longer wavelength, appearing as a characteristic colour. It is this coloured glow that allows researchers to track molecules, map cellular structures and monitor disease-related processes that would otherwise remain invisible.

Building on azulene’s unusual optical properties, the Bath group, led by Professor Simon Lewis, Professor Tony James and Dr Dan Pantos in the Department of Chemistry, had previously developed the AzuFluor platform, a family of azulene-based probes capable of visualising important biological processes. The new study, whose first author is postdoctoral researcher Dr Chiara Faverio, takes that platform a significant step further. Dr Faverio synthesised and analysed a wide range of new azulene derivatives, allowing the team to systematically explore how subtle structural changes influence the fluorescence colour and brightness of the resulting molecules.

That systematic exploration produced a headline result: the team created a molecule five times brighter than the original azulene molecule. Brightness matters enormously in fluorescence imaging, because a brighter probe can be used at lower concentrations, produces cleaner images with less background noise, and makes faint biological signals easier to detect. The five-fold improvement gives the researchers what they describe as a promising candidate for future sensing and imaging applications, and demonstrates that the structural rules they uncovered can be used to tune probe performance in predictable ways.

Crucially, the study did more than produce one brighter molecule. By comparing the behaviour of many derivatives, the researchers identified the molecular features that control both brightness and emission colour in azulene fluorophores. That structure-property relationship is the real prize of the work, because it converts what had been a largely empirical exercise into a design discipline. Chemists wanting a probe that glows in a particular colour, or at a particular intensity, can now consult a set of established principles rather than relying on trial and error, dramatically shortening the path from concept to working imaging tool.

The implications reach into some of the most challenging areas of medicine. Neurodegenerative diseases such as Alzheimer’s and Parkinson’s involve molecular changes inside cells that unfold over long periods and are difficult to observe directly, while cancer research depends on tracking signalling events and molecular interactions that drive uncontrolled growth. Probes bright enough and sensitive enough to light up these processes in real time, inside living cells, give researchers a window on disease mechanisms that static measurements cannot provide. The Bath team’s blueprint is intended to make such probes easier to design on demand.

Dr Faverio framed the significance of the advance in terms of what brighter probes make possible in the laboratory. Fluorescent probes, she noted, act like molecular beacons, lighting up in response to specific biological targets and allowing researchers to observe processes that would otherwise remain invisible. Being able to design brighter, more sensitive probes, she said, opens up exciting new opportunities for studying the cellular changes associated with neurodegenerative diseases, cancer and other serious health conditions. Her synthesis and analysis of the new azulene derivatives formed the experimental backbone of the study, providing the systematic dataset on which the design principles rest.

Professor Lewis placed the work in the context of the group’s longer engagement with the molecule. When the team began exploring azulene fluorophores in 2019, he said, they recognised the compound’s unusual and exciting potential. The new publication, he added, reveals the molecular features that control brightness and emission, providing a clear roadmap for designing increasingly powerful probes for sensing and bioimaging applications. In other words, seven years of accumulated chemistry on a single blue scaffold has now been distilled into a set of rules that other laboratories can pick up and apply.

The publication also marks a personal milestone. It is the fiftieth paper of 2026 for Professor Tony D. James, capping an exceptionally productive year spanning supramolecular chemistry, sensing technologies, fluorescence imaging and molecular diagnostics. James is widely known for his work on fluorescent probes for biologically important molecules, and the azulene programme exemplifies the blend of synthetic chemistry and molecular recognition on which that reputation rests. The authors note that the University of Bath owns the trademark on the AzuFluor name, underlining how the research has moved from curiosity-driven chemistry towards a recognised platform technology. With the structure-property relationships now mapped, the team’s blueprint points towards a next generation of fluorescent materials in which colour and brightness can be engineered to order, giving disease researchers brighter beacons with which to illuminate the molecular events that matter.

Subject of Research: Structure-property relationships in azulene-based fluorescent probes for biological imaging and disease detection

Article Title: Chemists develop blueprint for designing powerful fluorescent materials for better disease detection

Article References: Chemists develop blueprint for designing powerful fluorescent materials for better disease detection. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: azulene, fluorescent probes, fluorophores, bioimaging, chemical sensing, University of Bath, Alzheimer's disease, Parkinson's disease, cancer detection, structure-property relationships, Organic Chemistry Frontiers, EPSRC