Collagen is the principal composition of human tissue and the predominant biomolecule found in blood vessels, dermis, tendons, ligaments, cartilage, and the organic phase of bone. Collagen contains 21 kinds of amino acids, mainly including glycine, proline and hydroxyproline. The amino acids can be embed in three polypeptide chains to form a triple helix structure, and then the collagen fibers formate.