Cellulose and collagen: from fibres to tissues

Most biological tissues are built with polymeric fibres. Two of the most abundant fibres found in Nature are cellulose and collagen. Cellulose is predominately found in plants, but is also produced by bacteria, for instance. It is one of the major constituents of the plant cell wall and confers rigidity to the plant body. Recent advances give a better insight into the relation between the arrangement of cellulose fibrils inside the cell wall and its mechanical properties. One of the most important questions in this context is the way in which the cellulose architecture is assembled and controlled by the cell. Despite some recent discoveries relating to cellulose biosynthesis, the full understanding of the self-assembly of cellulose fibrils into larger scale structures remains a challenge. Collagen is a major constituent of animal bodies and can be found in large quantities in tendon, bone, skin, cornea, cartilage. A long-standing debate on the packing of collagen molecules into fibrils has led in recent years to a consensus on the collagen fibril structure. Progress has also been made in describing the relation between structure and deformation mechanisms of collagen-rich tissues. The principles for the self-assembly of collagen fibrils into larger scale structures still remain a mystery, though the importance of liquid crystal-like arrangements have been highlighted by recent experiments. (C) 2003 Elsevier Science Ltd. All rights reserved.