Biophotonics and scanning probe microscopy
Advances in our understanding of structure, and its role in homeostatic and disease processes, require techniques which can probe that structure. We are particularly interested in the molecular constituents of tissues and their arrangement on the nanometre to millimetre scales.
Second harmonic generation (SHG) has emerged as a label-free and non-destructive method for imaging collagen architecture. By combining polarised imaging with a vectorial Green's function model of SHG from collagen, we can quantitatively relate images to the underlying, tens of nanometre scale, structure within the focal volume. Through this model we can probe the early structural changes in osteoarthritis and tendonopathy. Further, our development of interferometric SHG allows the orientation of χ(2) / piezoelectric domains to be determined, providing insights into cell signalling and mechanical behaviour.
Spectroscopy provides a means to study the concentration and arrangement of the major components of musculoskeletal tissues. Scattering and absorbance of NIR and UV-Vis light are being studied in healthy and diseased tissue configurations, and analysis techniques developed to relate optical profiles to tissue state. Raman spectroscopy is being applied to characterise the extracellular matrix in lab-based studies of stem cell differentiation and to increase our understanding of early osteoarthritis in excised tissue.
Scanning probe techniques such as piezoresponse force microscopy, Kelvin probe microscopy and AMFM mechanical imaging provide insight into the relationships between structural and functional properties on the nanometre to micron scales. This is complemented by techniques such as dynamic force spectroscopy with functionalised tips to estimate patterns of kinetic and energetic parameters of adhesion and bonding. By applying multiple techniques to the sample, structural interactions can be determined on the fundamental scale of biological materials, and related to cell response.