Spectroscopic Investigations of Solid Uranyl Compounds and of Tissue-Engineered Myocardial Scaffolds
AdvisorMonts, David L.
Singh, Jagdish P.
For this dissertation, I investigated the laser-induced fluorescence (LIF) of solid uranyl compounds to develop an optical screening technique for the presence of uranyl compounds and I applied Raman spectroscopy to tissue-engineered myocardial scaffolds. Uranyl (UO2+2) compounds yield an easily detectable, characteristic emission. The fluorescence emission is in the 450–600 nm (22200 cm-1 to 16700 cm-1) spectral region. Typically five emission bands are observable, regardless of the excitation wavelength and the emission spectrum can be used as a fingerprint for uranyl compounds. In order to develop an optical screening technique for the presence of uranyl compounds, I investigated the dependence of uranyl LIF emission intensity on laser excitation wavelength and on laser power, and compared the advantages of continuous wave lasers with pulsed lasers. Based on our studies, we successfully designed a field-deployable Fluorescence Spectral Imaging (FSI) system for in situ detection of uranyl compounds. Tissue-engineered myocardial scaffolds are used to study cell recellularization into a three-dimensional (3-D) scaffold for true multilayered 3-D cellular growth and organization. Decellularization and recellularization processes necessarily are accompanied by specific molecular composition changes in the tissues and Raman spectroscopy is highly sensitive to these molecular composition changes. Raman spectroscopy is suitable for accurate molecular-level elucidation of reconstruction mechanisms. In this study, I recorded characteristic Raman spectra of fresh native porcine myocardium, decellularized porcine myocardium, fresh native rat myocardium, and decellularized porcine myocardium recellularized with rat stem cells. The results show that for fresh porcine myocardium and fresh rat myocardium have characteristic Raman peaks at 1004, 1448 and 1661 cm-1, which reflects cell compositions such as lipids. The Raman spectra of decellularized samples exhibit seven peaks at Raman shifts of 857, 938, 1063, 1253, 1300, 1448 and 1661 cm-1, which reflects that the extracellular matrix (ECM) after removal of cells. We also found that long time exposure to continuous laser irradiation produced the Raman spectra with increased background and blackened tissue in fresh heart tissue due to thermal denaturation. Our results demonstrate the feasibility of using Raman spectroscopy to analyze the recellulization process in tissue engineering myocardium.