Research Papers

Index-of-refraction-dependent subcellular light scattering observed with organelle-specific dyes

[+] Author Affiliations
Jeremy D. Wilson

University of Rochester, Department of Physics and Astronomy, Rochester, New York 14627

William J. Cottrell

University of Rochester, Institute of Optics, Rochester, New York 14627

Thomas H. Foster

University of Rochester, Department of Physics and Institute of Optics and Department of Imaging Sciences, 601 Elmwood Avenue, Box 648, Rochester, New York 14642

J. Biomed. Opt. 12(1), 014010 (February 02, 2007). doi:10.1117/1.2437765
History: Received July 10, 2006; Revised September 26, 2006; Accepted September 27, 2006; Published February 02, 2007
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Angularly resolved light scattering and wavelength-resolved darkfield scattering spectroscopy measurements were performed on intact, control EMT6 cells and cells stained with high-extinction lysosomal- or mitochondrial-localizing dyes. In the presence of the lysosomal-localizing dye NPe6, we observe changes in the details of light scattering from stained and unstained cells, which have both wavelength- and angular-dependent features. Analysis of measurements performed at several wavelengths reveals a reduced scattering cross section near the absorption maximum of the lysosomal-localizing dye. When identical measurements are made with cells loaded with a similar mitochondrial-localizing dye, HPPH, we find no evidence that staining mitochondria had any effect on the light scattering. Changes in the scattering properties of candidate populations of organelles induced by the addition of an absorber are modeled with Mie theory, and we find that any absorber-induced scattering response is very sensitive to the inherent refractive index of the organelle population. Our measurements and modeling are consistent with EMT6-cell-mitochondria having refractive indices close to those reported in the literature for organelles, approximately 1.4. The reduction in scattering cross section induced by NPe6 constrains the refractive index of lysosomes to be significantly higher. We estimate the refractive index of lysosomes in EMT6 cells to be approximately 1.6.

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© 2007 Society of Photo-Optical Instrumentation Engineers

Citation

Jeremy D. Wilson ; William J. Cottrell and Thomas H. Foster
"Index-of-refraction-dependent subcellular light scattering observed with organelle-specific dyes", J. Biomed. Opt. 12(1), 014010 (February 02, 2007). ; http://dx.doi.org/10.1117/1.2437765


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