Towards disease diagnosis through terahertz spectroscopy of biological components and tissue

• Main Author: Jones, Peri
• Published: Cardiff University 2017
• Subjects: QC Physics
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.732260

Using a Martin-Puplett interferometer and high sensitivity cryogenic detectors, a Fourier Transform Spectrometer (FTS) was used to investigate a range of biological samples in the Terahertz frequency region. Large biological molecules such as deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) and their constituent nucleobases and nucelosides: guanine, cytosine, adenine, thymine and uracil; guanosine, cytidine, adenosine, thymidine and uridine, have shown clear resonances within the region between 0.6 THz and 18 THz. Interest must be paid to the difference in the spectra of cytosine when the samples were prepared using different solvents, showing the potential and sensitivity of this tool for identifying small differences in the crystalline structure of biological samples. Modelling the nucleobases using Density Functional Theory (DFT) provided confirmation with experimental data of the frequency location of the resonances, and identifies the nature of the resonances. Further experimental work is undertaken on samples of animal tissue and liquid solution (H2O and D2O) which renders difficulties in the analysis of the results due to the complexity of sample. This thesis provides a better understanding of the electromagnetic interaction of large biological molecules with THz radiation which will compliment and strengthen the future application of THz spectroscopy for detecting mutations that lead to cancer.