Light scattering from cells: the contribution of the nucleus and the effects of proliferative status

As part of our ongoing efforts to understand the fundamental nature of light scattering form cells and tissues, we present data on elastic light scattering from isolated mammalian tumor cells and nuclei. The contribution of scattering from internal structures and in particular from the nuclei was compared to scattering from whole cells. Roughly 55 percent of the elastic light scattering at high- angles comes from intracellular structures. An upper limit of 40 percent on the fractional contribution of scattering form cells in tissue was determined. Using cell suspensions isolated from monolayer cultures at different stages of growth, we have also found that scattering at angles greater than about 110 percent was correlated with the DNA content of the cells. Based on model calculations and the relative size difference of nuclei from cells in different stages of growth, we argue that this difference in scattering results form changes in the internal structures of the nucleus. This interpretation is consistent with our estimate of 0.2 micrometers as the mean size of the scattering centers in cells. Additionally, we find that while scattering from the nucleus accounts for a majority of internal scattering, a significant portion must result from scattering off of cytoplasmic structures such as mitochondria.