PDT-induced changes in light scattering from cells using lysosomal- vs. mitochondrial-localizing photosensitizers

Jeremy D. Wilson; Thomas H. Foster

doi:10.1117/12.644907

6 March 2006 PDT-induced changes in light scattering from cells using lysosomal vs. mitochondrial-localizing photosensitizers

Jeremy D. Wilson, Thomas H. Foster

Author Affiliations +

Proceedings Volume 6139, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XV; 613903 (2006) https://doi.org/10.1117/12.644907
Event: SPIE BiOS, 2006, San Jose, California, United States

Abstract

We have previously described changes in angle-resolved light scattering measured from intact cells in suspension subjected to photodynamic therapy using photosensitizers that localize primarily to mitochondria. These changes were analyzed with a Mie theory-based model. For the sensitizers Pc 4 and ALA-induced protoporphyrin IX, the scattering data from PDT-treated cells was consistent with a coated sphere model, in which mitochondrial morphology changes were the predominant mechanism governing the scattering changes. This interpretation was supported by electron microscopy. Here we describe quite different changes in angle-resolved light scattering from cells sensitized with the lysosomal-localizing photosensitizer LS11. Unlike the case of the mitochondrial-localizing photosensitizers, analysis of these post-treatment scattering data reveals a shift toward a larger mean organelle diameter in the larger of the two particle size distributions identified from Mie-theory analysis of scattering from control cells. Further, the post-treatment scattering angular distributions are well interpreted in terms of homogeneous rather than coated spheres. On the basis of these results and results of fluorescence microscopy of LS11-PDT treated monolayers, we propose that the initial, pre-treatment scatterer population is comprised of lysosomes and mitochondria. LS11 PDT ablates a significant fraction of the lysosomes, leaving a relatively unperturbed population of mitochondria to dominate the scattering. These findings suggest that scattering measurements are capable of reporting a variety of PDT-induced changes to cell organelles. They further suggest that photodynamic action is a useful biophysical tool for understanding basic mechanisms of light scattering from intact cells.

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Jeremy D. Wilson and Thomas H. Foster "PDT-induced changes in light scattering from cells using lysosomal vs. mitochondrial-localizing photosensitizers", Proc. SPIE 6139, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XV, 613903 (6 March 2006); https://doi.org/10.1117/12.644907

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KEYWORDS

Light scattering

Scattering

Mie scattering

Photodynamic therapy

Particles

Data modeling

Luminescence

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