Scattering

Scattering Image Caption

(A) Area scan Raman and fluorescence imaging data at 488 nm. Cluster analysis reveals the following assignments: Black (cluster 1) = area without the cells (background); Grey (cluster 2) = cell border; Green (cluster 3) = cytoplasm; Blue (cluster 4) = nucleus; Red (cluster 5) = endoplasmic reticulum/mitochondria; Orange (cluster 6) = lipid droplets. For comparison, the lipid distribution at 2888 cm-1 (sum filter: 2838–2938 cm-1) is shown relative to fluorescence Nile Red staining in A549, while the nucleus area represented by 2970 cm-1 (sum filter: 2920–3020 cm-1) is compared to NucBlue. Raman area scans of A549: scale bar is 10 μm (148 × 100 points, 0.1 s per pixel, ~25 min per image); MRC5: scale bar is 9 μm (100 × 110 points, 0.1 s per pixel, ~20 min per image). J M Surmacki, B J Woodhams, A Haslehurst, B A J Ponder, S E Bohndiek, Scientific Reports, 8(1), 12604 (2018).

The application of continuous laser (coherent) light onto cells or tissue without the addition of any reporter molecules results in a high level of contrast from amplitude, phase and polarisation scattering events.

An interesting technique arising from inelastic scattering is Raman spectroscopy, which is sensitive to vibrational excitations of molecular bonds. Since the energy of the vibrational interaction is specific to the type of bond being excited, Raman spectra provide a chemical “fingerprint” of the material being studied. For biomedical imaging, Raman spectra provide insight into the composition of cells and tissues, including their lipid, protein and DNA content, as well as chemical modifications of these molecules occurring in response to oxidative stress and chemotherapy. Studies of living cells are enabled by imaging chambers that maintain temperature, humidity and atmosphere compatible with cell culture.

Exciting opportunities for imaging early cancer, or dysplasia, also arise from quantitative phase imaging and polarisation-resolved properties of tissue. The potential of phase and polarisation dependent contrast is currently being explored in tissue mimicking phantoms and also in ex vivo tissue, with a view to future clinical application through endoscopy in the oesophagus and lung.

Lab members:

Raman: Ben Woodhams, Dr Rajesh Shahapure

Optical phase and polarisation: Travis SawyerDr James Joseph, Dr Catherine Fitzpatrick, Dr George Gordon, Dr Abby Wilson.

Collaborators:
Prof. Tim Wilkinson, Prof. Ian White (Department of Engineering, University of Cambridge); Dr Lexi Haslehurst, Prof. Bruce Ponder (CRUK CI/ Department of Oncology, University of Cambridge).