Dynamic light scattering study of salt effect on phase behavior of pig vitreous body and its microscopic implication.

The salt effects on phase equilibrium and dynamical properties of pig vitreous body was studied by the macroscopic observation of the swelling behavior and dynamic light scattering under various conditions. It was found that the vitreous body collapses with maintaining the shape when the concentrations of salts (NaCl, CaCl2, and MgCl2) were changed. From the observations of the dynamics of light scattered by the pig vitreous body, intensity autocorrelation functions that revealed two diffusion coefficients, Dfast and Dslow were obtained. We developed the theory for describing the density fluctuation of the entities in the vitreous gel system with sodium hyaluronate filled in the meshes of the collagen fiber network. The dynamics of collagen and sodium hyaluronate explains two relaxation modes of the fluctuation. The diffusion coefficient of collagen obtained from Dfast and Dslow is very close to that in aqueous solution, which suggests the vitreous body is in the swollen state. Divergent behavior in the measured total scattered light intensities and diffusion coefficients upon varying the concentration of salt was observed. Namely, a slowing down of the dynamic modes accompanied by increased "static" scattered intensities was observed. This is indicative of the occurrence of a phase transition upon salt concentration.