Cellular viability represents whether a cell is performing normal functions, relating to intracellular energy synthesis. Accurately quantifying the cellular viability would facilitate novel studies on how pathological environments affect the functioning of cells in various diseases. Nevertheless, technologies for monitoring the cellular viability in live tissue models are currently lacking. This study aims at testing a recently developed technology, which integrates dynamic light scattering and optical coherence tomography (called DLS-OCT), to image the cellular viability with single-cell resolution. DLS analyzes fluctuations in light scattered by particles to measure diffusion or flow of the particles, and OCT uses coherence gating to collect light only scattered from a small volume for high-resolution structural imaging. Integrating the two technologies, DLS-OCT constructs high-resolution diffusion coefficient and flow velocity 3D maps. It is known that the motion of intracellular organelles, often called intracellular motility, resembles a random walk in the confined cytoplasm space, thus it can be quantified by the diffusion coefficient. Since the intracellular motility is correlated with the cell’s metabolism level, the diffusion coefficient map of DLS-OCT is expected to enable us to image the cellular viability. Here, the DLS-OCT imaging of cellular viability was validated by characterizing responses of the measured intracellular motility to the environmental conditions such as the temperature and pH, in animal retinal explant samples. First, we characterized our new OCT system and optimized scanning sequences and processing procedures for DLS-OCT data, to match the dynamic range of our DLS-OCT measurement with the typical range of intracellular motility. Both numerical simulation and phantom experiments were performed for optimization. Second, methods required for animal retinal explant experiments were established, and DLS-OCT data from retinal tissue while manipulating the cellular viability were acquired and analyzed, to test the technical hypothesis that DLS-OCT-measured intracellular motility of neurons significantly diminishes when the cellular viability levels are out of the physiological ranges. Similar operations were performed to tissue spheroids with additional morphological measurements. As a result, we measured individual cells’ healthiness for tempered conditions, which will enlighten studying cells’ healthiness during disease progress or therapeutic treatment in stroke, epilepsy, and Alzheimer’s disease among others.
Lee, Julia Seungmi,
"Cellular Viability Imaging Using Dynamic Light Scattering Optical Coherence Tomography"
Engineering Theses and Dissertations.
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