The goal of this research project is to develop quantitative optical imaging methods for bioenergetic studies of cardiac tissue. In this proposal, methods are being developed for the optical determination of tissue and circulatory oxygen concentrations based on palladium porphyrin phosphorescence quenching by collisional interaction with molecular oxygen. During Phase I of this project palladium (IV) meso-tetra(p- sulfonatophenyl)porphin was synthesized and used to demonstrate the correlation between porphyrin phosphorescence and oxygen concentration. Phosphorescence intensity images were obtained from normal hearts and hearts with impaired circulation to demonstrate the utility of oxygen concentration images in evaluating epicardial circulation and metabolism. Phase II will involve the construction of a phosphorescence lifetime system to obtain palladium porphyrin images and convert these into images of oxygen concentration. In addition the system will produce NADH fluorescence images so that the dual function videofluorometer will allow rapid, sequential imaging of tissue metabolism and oxygen concentration. The system will be used with different phosphorochromes to determine their distribution between vascular and epicardial tissue regions. Studies will be undertaken to determine the utility of these methods to evaluate models of cardiac ischemia and hypoxia. This instrument will have much greater utility in spatially quantifying tissue metabolism and oxygen supply/demand for research and clinical purposes than current devices.
