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Multiscale Analysis of Biomaterials
Published in Young W. Kwon, Multiphysics and Multiscale Modeling, 2015
The regular fibrils are organized during a process called fibrillogenesis, which involves the expansion and regrowth of fibrils. A collagen molecule has a C terminal and an N terminal, so named for the peptides cleaved during the transition from procollagen to collagen [19,25]. As each end of a tropocollagen exhibits different cross-linking tendencies, the amino acid sequence at each terminal of the tropocollagen defines a polar reference for each molecule. When the collagen molecules are aligned near each other, the C and N ends join to produce an organized structure. Not only do the ends of the tropocollagen molecules have preferential alignment, but also the entire length of the tropocollagen molecule contains segments of amino acids preferential to cross-linking with adjacent tropocollagen molecules [26]. These preferential segments form a collagen network with a 40-nm gap and a regular periodicity of 67 nm [22,25,26,40–44]. Hydroxyapatites grow preferentially in these gap regions, allowing for the inclusion of the reinforcing particles within the fibril composite. Figure 9.2 shows the staggered alignment of hydroxyapatite in the fibril composite. This figure is not to scale.
Collagen of porcine auricle has unique biochemical and biophysical characteristics
Published in Soft Materials, 2019
Kenji Ishi, Hiroko Hoshi, Mina Takahashi, Koji Kitagawa, Masataka Hoshi, Norihiro Kawaguchi
An important factor in mechanical strength in biomacromolecules is fibrillogenesis by self-association under physiological conditions. To examine the biophysical properties of auricular type I collagen, we measured the viscoelastic properties of PAC-A under physiological conditions. As shown in Figure 6a, PAC-A showed higher dynamic viscoelasticity than dermal type I collagen. The microrheology measurements taken during fibril assembly indicate a dynamic system in which mechanical heterogeneity is apparent even in the early stages of the growth phase. Auricular type I collagen, PAC-A, reached a high Gʹ value (60 Pa) after 5 min, and at different locations this value was increased to about 90 Pa. The variation in moduli increased with time, reaching a near plateau after 30 min. On the other hand, the Gʹ values observed for dermal type I collagen were 5 Pa after 10 min and 13 Pa after 30 min. These results were coincident with measurement of turbidity under physiological conditions.