The effects of various purification conditions on the characteristics of telopepeptide-poor collagen fiber were compared. It was first confirmed that a 1:50 ratio of pepsin to skin was favorable for the digestion of porcine skin. The morphological characteristics observed by scanning electron microscopy (SEM) showed that fibril collagen, porous fibril membrane or dense membrane were all possibly formed depending on the digestion and freeze-drying media. Analysis by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and size-exclusion HPLC revealed that the collagen sample produced by digestion with pepsin in a pH 2.5 HCl solution to obtain telopeptide-poor collagen, and freeze-drying in 0.5 M acetic acid for the final step, resulted in less oligomers. Not only were its fibril characteristics qualitatively identical to those of standard collagen but also were easily hydrated suggesting that this procedure is an appropriate choice for both isolation and purification. Furthermore, it was demonstrated that gel formulations prepared by gelling the vehicle mixture of citric acid solution, ethanol and propylene glycol with 1% w/w of such a collagen sample was suitable for transdermal delivery.
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