Characterization of lysosomal contribution to whole-cell light scattering by organelle ablation

Angularly resolved light scattering measurements made at visible wavelengths have the ability to quantify subcellular morphology, with particular sensitivity to organelles the size of mitochondria and lysosomes. We have recently reported on a lysosome-staining-based method that provides scattering contrast between stained and unstained cells, and through the use of appropriate models, we extracted a size distribution and contribution to cellular light scattering that we attributed to lysosomes. We provide an independent measurement of the lysosomal size distribution and contribution to cellular light scattering by exploiting photodynamic ablation of lysosomes and observing its effect on angularly resolved light scattering measurements. From these measurements, we conclude that lysosomes scatter approximately 14% of the light from EMT6 cells at 633 nm and that their size distribution has a mean and standard deviation of 0.8 and 0.4 microm, respectively.