Anisotropic swelling behavior of the cornea

松浦 豊明*; 池田 仁英*; 井戸田 直和*; 元川 竜平; 原 嘉昭*; 安中 雅彦*

Journal of Physical Chemistry B, 113(51), p.16314 - 16322, 2009/12

https://doi.org/10.1021/jp907232h

The phase equilibrium property and structural and dynamical properties of pig cornea were studied by macroscopic observation of swelling behavior, dynamic light scattering (DLS), and small-angle X-ray scattering (SAXS) under various conditions. The corneal gel collapses uniformly into a compact state at a temperature above 55C because of the denaturation of collagen, whereas it collapses along an axis parallel to the optic axis with increasing NaCl concentration. Anisotropic deswelling was also observed during desiccation. SAXS measurements revealed that the periodicity of the collagen fiber of the cornea does not change even at higher NaCl concentration, which indicates that hydration and dehydration resulting from changes in salt concentration simply cause swelling and deswelling of the glycosaminoglycan (GAG), which is located between the regular two-dimensional lattices of collagen fibers, which obliges the change in thickness. From observations of the dynamics of light scattered by the corneal gel, intensity autocorrelation functions that revealed two independent diffusion coefficients were obtained. Divergent behavior in the measured total scattered light intensities and diffusion coefficients with varying temperature was observed. That is, a slowing of the dynamic modes accompanied by increased static scattered intensities was observed. This is indicative of the occurrence of a phase transition as a function of temperature.