Andy Downes: Label-free Optical Spectroscopy and Imaging

Cancer Research Programme

Our research uses label-free optical methods to characterize cancer cells and tissue.

Raman spectroscopy is a label-free optical spectroscopy which characterizes the chemical composition by exciting vibrations in molecular bonds with laser light. These vibrations (C-C, C-H, etc) occur at different frequencies, and are measured at different wavelengths in a spectrometer. This spectrum reveals the chemical composition of the region in which the laser spot is focussed – i.e. down to the sub-cellular level. We have revealed subtle differences between cell phenotypes – for example, primary vs. secondary cancer cells, and can use this method to characterize an unknown cell (as primary or secondary).

A high-speed Raman microscope acquires images of chemical composition in seconds without requiring labels. As this technique requires picosecond lasers we also acquire images of two-photon excited fluorescence or autofluorescence [green, elastin], as well as second harmonic generation [blue, collagen]. The corresponding Raman image shows proteins in red [left], for comparison with a Haematoxylin & Eosin stained tissue [centre] and a transmitted light image [right].

As well as these optical techniques we also perform atomic force microscopy on individual cells and tissue to measure their mechanical properties, which change between healthy and diseased cells. We have also detected significant changes between primary (stiffer) and secondary (softer) tumour cells.

Details of our Bio-imaging facility in the School of Engineering are available at the Bioimaging Facility