Chemists at the University of Bath have discovered how tiny molecular changes can transform the colour and brightness of fluorescent probes based on the blue molecule azulene, paving the way for more powerful imaging tools for detecting diseases such as Alzheimer's, Parkinson's and cancer.
The team, led by Professor Simon Lewis, Professor Tony James and Dr Dan Pantos in the University's Department of Chemistry, have transformed azulene, a naturally occurring blue compound found in certain mushrooms and corals, into a versatile tool for biological imaging and chemical sensing.
Scientists use chemical probes that bind to a specific molecule in the cell and glow different colours under a microscope to observe biological processes and monitor disease.
Fluorescent probes consist of two parts: a 'receptor' (which detects a particular substance) and a 'fluorophore' (a molecule with fluorescent properties). Fluorophores absorb light of a specific wavelength and emit light of a different, typically longer, wavelength, which appears as a colour.
It is this coloured light makes them stand out when viewed under a microscope.
Their research, funded by the EPSRC and published in Organic Chemistry Frontiers , has discovered how tweaking the molecular structure of azulene-based fluorescent probes can change the colour and brightness of the material, providing a blueprint for the rational design of future probes for disease research and diagnostics.
Inspired by nature
Azulene is the chemical responsible for the striking blue colour of species such as the mushroom Lactarius indigo and certain corals and is used in some skincare products to calm irritation. Azulene can be used as a fluorophore because it absorbs light at one wavelength and emits at a different wavelength.
The researchers took advantage of this unusual property to develop the AzuFluor® platform, creating a whole family of azulene-based probes capable of visualising important biological processes.
The programme, funded by the EPSRC, aimed to create new tools that could help researchers study diseases including Alzheimer's disease, Parkinson's disease, cancer and asthma by enabling molecular events inside living cells to be observed in real time.
The first author on the study, postdoctoral researcher Dr Chiara Faverio, successfully synthesised and analysed a wide range of new azulene derivatives, allowing the research team to systematically explore how subtle structural changes influence fluorescence colour and brightness.
Major milestone towards better disease imaging
The team developed a molecule that was five times brighter than the original azulene molecule, giving a promising candidate for future sensing and imaging applications.
Dr Faverio said: "Fluorescent probes 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 opens up exciting new opportunities for studying cellular changes associated with neurodegenerative diseases, cancer and other serious health conditions."
Professor Lewis said: "When we began exploring azulene fluorophores in 2019, we recognised their unusual and exciting potential.
"This work reveals the molecular features that control brightness and emission, providing a clear roadmap for designing increasingly powerful probes for sensing and bioimaging applications."
In addition to marking a major outcome of the EPSRC-funded azulene programme, the publication is also the 50th paper of 2026 by Professor Tony D. James, highlighting an exceptionally productive year spanning supramolecular chemistry, sensing technologies, fluorescence imaging and molecular diagnostics.
