Small Angle Light Scattering Analysis of Tissue

Dahlgren, Eric D

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Small Angle Light Scattering Analysis of Tissue

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Tissue, in particular its mechanical properties, is of interest from a material science point of view. The collagen fiber framework found in nearly all tissue forms the basis for the tissueâ€™s behavior. Connective tissue provides more interesting behavior, designed to bear significant load in one direction, while retaining the ability to stretch in other directions. Contributing factors to such behavior are fiber diameter and orientation. Small angle scattering analysis has been developed over the past century. Particular attention has been paid to x-ray and neutron scattering, both of which characterize features on a nanometer scale. Small angle light scattering (SALS) has the ability to characterize features on a micron scale, and is thus suitable for the analysis of collage fibers. Scattering data from several tendons were analyzed using the Generalized Indirect Fourier Transform (GIFT) program developed by Dr. Otto Glatter. The data is fit using cubic B-splines, and transformed into a probability density distribution function (abbreviated PDDF or p(r)). The PDDF can then be interpreted to give an average fiber diameter, as well as other structural information. Since this type of analysis has never been performed on collagen fibers, emphasis was placed on validating small angle light scattering as an appropriate technique to characterize collagen fiber diameter. This was accomplished by comparing the results with optical microscopy. Results from SALS analysis agree with features observed by optical microscopy. Small angle light scattering analysis is able to provide an analysis of structures superior to that of optical microscopy. Small angle scatter theory provides a three dimensional analysis of the structure. On the other hand, optical microscopy provides only a two dimensional view of the sample. The structure of collagen fibers in tissue is certainly three dimensional, making small angle light scattering a more suitable technique for characterization.

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