Biophysics / Internet Invited Lecture

OPTICAL PROPERTIES OF MUTANT VS WILDTYPE MOUSE SKIN MEASURED BY REFLECTANCE-MODE CONFOCAL SCANNING LASER MICROSCOPY.

Steven L Jacques, Ravikant Samantham, Oregon Health & Science University, Portland, Oregon, USA; Paul Campanola, Univ. of Connecticut Health Center, Farmington, CT, USA

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ABSTRACT

Separation of the two optical scattering properties, the <em>scattering coefficient (µ<sub>s</sub>)</em> and the <em>anisotropy of scattering (g)</em>, has been experimentally difficult in tissues. A new method for measuring these properties in tissues uses reflectance-mode confocal scanning laser microscopy (rCSLM). The method was applied to 3 mouse tissues, one wild type (wt/wt), one heterozygous mutant (mut/wt), and one homozygous mutant (mut/mut), where the mutation is for <em>osteogenesis imperfecta</em>, a bone disease that affects collagen I structure. The mutation also affected the collagen fibrils of the skin. The measurements showed that the average scattering coefficient (<em>µ<sub>s</sub></em>) decreased with the presence of the mutant allele, varying as mut/mut < mut/wt < wt/wt. The anisotropy of scattering (<em>g</em>) increased with added mutant allele, varying as mut/mut > mut/wt > wt/wt. <font color="#0000ff">Such behavior may suggest that the tropocollagen molecules are failing to organize into fibrils with the 70-nm periodicity that is putatively responsible for the Rayleigh scattering that dominates blue light reflectivity. Without the periodicity of refractive index fluctuation, the fibril structure becomes more optically homogeneous and scattering decreases. Without this Rayleigh scattering that yields nearly isotropic scattering (g ≈ 0), the Mie scattering from the large 2-3 µm-dia. collagen fiber bundles that yield forward scattered light (g --> 0.90+) would become more optically dominant, and a trend toward higher g values would be expected.</font>

Representing Author:

Steven L Jacques, Oregon Health & Science University, Prof., Dermatology and Biomedical Engineering (Portland, Oregon, USA)

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DEDICATION:

SFM 2006 is dedicated to the memory of Professor Mark L. Katz on the 100 anniversary of his birth and the 60th anniversary of the Chair of Optics and Biomedical Physics founded by him in 1946 in Saratov State University.