Marine
collagen has been attracting attention as a medical material in recent times due to the low risk of pathogen
infection compared to animal
collagen.
Type I collagen extracted from the swim bladder of Bester sturgeon fish has excellent characteristics such as high denaturation temperature, high solubility, low viscosity and an extremely fast rate to form large bundle of fibers under certain conditions. These specific characteristics of swim bladder
collagen (SBC) permit us to create stable, disk shaped
hydrogels with concentric orientation of
collagen fibers by the controlled diffusion of neutral
buffer through
collagen solution at room temperature. However, traditionally used animal
collagens, e.g. calf skin
collagen (CSC) and porcine skin
collagen (PSC), could not form any stable and oriented structure by this method. The mechanism of the superstructure formation of SBC by a diffusion induced gelation process has been explored. The fast fibrillogenesis rate of SBC causes a quick squeezing out of the
solvent from the gel phase to the
sol phase during gelation, which builds an internal stress at the gel-
sol interface. The tensile stress induces the
collagen molecules of the gel phase to align along the gel-
sol interface direction to give this concentric ring-shaped orientation pattern. On the other hand, the slow fibrillogenesis rate of animal
collagens due to the high viscosity of the
solution does not favor the ordered structure formation. The denaturation temperature of SBC increases significantly from 31 °C to 43 °C after gelation, whereas that of CSC and PSC were found to increase a little. Rheology experiment shows that the SBC gel has storage modulus larger than 15 kPa. The SBC
hydrogels with thermal and mechanical stability have potential as bio-materials for tissue engineering applications.