Mr. Behnam Arzhang

Monochromatic light scattering can be used as a label-free, non-invasive biological cell detection and analysis method. Scattered light diffraction images can be used to extract information about the density, size, shape, as well as internal organelles of the cell. One cell death pathway is apoptosis and its study in a cell’s response to stress or disease such as cancer is important. Mitochondria play a key role in activating apoptosis and the phenomena of aggregation of mitochondria has been linked to apoptosis (X. Su, Y. Qiu, L. Marquez-Curtis, M. Gupta, C. E. Capjack, W. Rozmus, A. Janowska-Wieczorek, and Y. Y. Tsui, “Label-free and noninvasive optical detection of the distribution of nanometer-size mitochondria in single cells,” Journal of biomedical optics, 16(6), 2011). In this paper we show that forward angle scattered light patterns can be used to infer changes in interior cell components like mitochondria and nucleus, as well as cell size. 

We employ a Multi-shell MIE theory approach, which provides an analytical solution for light scattering from a heterogeneous shelled sphere interacting with a planar electromagnetic wave. We use this to model a biological cell, where changes in the cell's properties, such as changes to cytoplasm or nucleoplasm density, the size of the cell or its nucleus, or the distribution of internal organelles, are reflected in changes in the refractive index of the shells. The developed model is used to simulate the effect of these variations on a Chinese hamster ovary (CHO) cell. The results are related to light scattering measurements obtained using a lens-less microfluidics-based cytometry device (A. Fazelkhah, S. Afshar, N. Durham, M. Butler, E. Salimi, G. Bridges, and D. Thomson, “Parallel single-cell optical transit dielectrophoresis cytometer.” Electrophoresis, 41, 720-728, 2020). In the simulations, we consider scenarios where the mitochondria are concentrated within various regions of the cytoplasm and demonstrate it is possible to discern these changes using the forward scattering patterns.