Optical techniques that measure endogenous fluorescence can provide useful information on the status of cellular metabolism, but extensions of these techniques to turbid media (such as tissue) are often complicated by a multitude of emission signals. Phasor analysis is class of analytical approaches used to monitor emission signals that has potential to simplify measurements in tissue. Because knowledge of cellular-level metabolism at the tissue scale could contribute to important medical and diagnostical advances, here we propose to extend the phasor approach from the cellular regime to tissue.
We consider a series of experiments where the fluorescence of excited Saccharomyces cerevisiae cells (baker’s yeast) is monitored in real time. A cellular suspension of yeast cells is prepared and excited via laser pulses. To mimic the multitude of emission signals present in tissue, 9-cyanoanthracene, a chemical that contributes a strong emission signal, is added to the sample prior to inducing a metabolic response. Potassium cyanide (KCN), a chemical which inhibits cellular respiration, is then added to the sample to induce a metabolic response. The concentration of 9CA is varied in each experiment, while the concentration of KCN is held constant and saturates the response of the cells (adding more KCN will not cause any change). Results are compared with and without the addition of 9CA.
Analysis of the resulting data clearly demonstrates “three-component behavior”, a property that provides an interpretation of metabolic state despite the presence of background emission. Moving forward, we consider more realistic sources of background emission, including the addition of collagen to the cellular sample as well as preliminary measurements in real tissue.
Performing this research gives me valuable experience and knowledge in the fields of biology, physics, and mathematics which are integral to obtaining a PhD in mathematical biology and related career paths.
Author: Max Kreider
Faculty Advisor: Dr. Urayama, Department of Physics
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