Tip-enhanced Raman spectroscopy: a preliminary study and force spectroscopy of collagen matrices

Brown, Katie (2022) Tip-enhanced Raman spectroscopy: a preliminary study and force spectroscopy of collagen matrices. Masters thesis, Memorial University of Newfoundland.

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Abstract

This thesis contains preliminary work on tip-enhanced Raman spectroscopy (TERS). TERS is a spectroscopy technique that uses AFM and Surface-enhanced Raman spectroscopy (SERS) to achieve nanoscale images accompanied by chemical maps. TERS can be used to identify compounds that cannot be detected with conventional Raman, such as those masked by fluorescence. Raman of retinal tissues, specifically, Raman of vitamin A (retinol) within the tissues, has been of interest within the Merschrod group, and steps have been taken within this thesis to work toward this goal. Computational Raman spectra of vitamin A and its derivatives have been completed to assist in identifying these compounds within the tissues. Biological tissues have many different components that can be detected, and vitamin A has many different products as it is degraded by light and air. These spectra can help distinguish peaks of these compounds, making analysis easier. The second part of the thesis covers force spectroscopy of collagen. Collagen is one of the main components of cell culture matrices. Previous studies indicate that changing the collagen overlay within the matrices can affect cell behaviour. The mechanical properties of these overlays may cause a change in the behaviour. It is also known that biological tissues have a change in mechanical properties when probed at different length scales. Using atomic force microscopy (AFM), I investigate the effect of tip radius on Young’s modulus (stiffness) of three different collagen matrices: fibrils, PBS collagen and HANKS collagen. The indentation studies indicate that increasing the radius of the indenter decreases the measured Young’s modulus of the sample. This suggests that the fibrils in the matrices are stiffer while the network of the matrices is softer and allows more stretching. These results tell us about the multi-scale properties of tissues.

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