Fluence- and time-dependant lysosomal and mitochondrial damage induced by LS11 PDT characterized with light scattering

Jeremy D. Wilson; Thomas H. Foster

doi:10.1117/12.697458

16 February 2007 Fluence- and time-dependant lysosomal and mitochondrial damage induced by LS11 PDT characterized with light scattering

Jeremy D. Wilson, Thomas H. Foster

Author Affiliations +

Proceedings Volume 6446, Biomedical Applications of Light Scattering; 64460F (2007) https://doi.org/10.1117/12.697458
Event: SPIE BiOS, 2007, San Jose, California, United States

Abstract

Light scattering from cells originates from sub-cellular organelles. Our measurements of angularly resolved light scattering have demonstrated that at 633 nm, the dominant scattering centers within EMT6 cells are mitochondria and lysosomes. To assess their specific contributions, we have used photodynamic therapy (PDT) to induce organelle-specific perturbations within intact cells. We have developed a coated sphere scattering model for mitochondrial swelling in response to ALA- and Pc 4-PDT, and in the case of Pc 4-PDT we have used this model to map the scattering responses into clonogenic cell survival. More recently, we demonstrated the ability to measure the size, scattering contribution, and refractive index of lysosomes within cells by exploiting the localization and high extinction of the photosensitizer LS11 and an absorbing sphere scattering model. Here we report on time- and fluence-dependant scattering measurements from cells treated with LS11-PDT. LS11-PDT causes rapid lysosomal disruption, as quantified by uptake of acridine orange, and can induce downstream effects including release of mitochondrial cytochrome c preceding the loss of mitochondrial membrane potential (Reiners et al., Cell Death Differ. 9:934, 2002). Using scattering and these various methods of analysis, we observed that the induction of lysosomal morphology changes requires a fluence significantly higher than that reported for cell killing. At lower fluences, we observe that at 1 h after irradiation there is significant mitochondrial swelling, consistent with the onset of cytochrome c-induced cell death, while the morphology of lysosomes remains unchanged. We also expand on the ideas of lysosomal staining to demonstrate the sensitivity of scattering measurements at different wavelengths to different organelle populations.

Citation Download Citation

Jeremy D. Wilson and Thomas H. Foster "Fluence- and time-dependant lysosomal and mitochondrial damage induced by LS11 PDT characterized with light scattering", Proc. SPIE 6446, Biomedical Applications of Light Scattering, 64460F (16 February 2007); https://doi.org/10.1117/12.697458

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