Studies on the Formation Mechanism and the Structure of the Anisotropic Collagen Gel Prepared by Dialysis-Induced Anisotropic Gelation

We have found that dialysis of 5 mg/mL collagen solution
into the
phosphate solution with a pH of 7.1 and an ionic strength of 256 mM
at 25 °C results in a collagen gel with a birefringence and tubular
pores aligned parallel to the growth direction of the gel. The time
course of averaged diameter of tubular pores during the anisotropic
gelation was expressed by a power law with an exponent of 1/3, suggesting
that the formation of tubular pores is attributed to a spinodal decomposition-like
phase separation. Small angle light scattering patterns and high resolution
confocal laser scanning microscope images of the anisotropic collagen
gel suggested that the collagen fibrils are aligned perpendicular
to the growth direction of the gel. The positional dependence of the
order parameter of the collagen fibrils showed that the anisotropic
collagen gel has an orientation gradient.