Structure and Strength of Bovine and Equine Amniotic Membrane.

Thin, strong scaffold materials are needed for surgical applications. New materials are required, particularly those readily available, such as from non-human sources. Bovine amniotic membrane (antepartum) and equine amniotic membrane (postpartum) were characterized with tear and tensile tests. The structural arrangement of the collagen fibrils was determined by small-angle X-ray scattering, scanning electron microscopy, and ultrasonic imaging. Bovine amnion had a thickness-normalized tear strength of 12.6 (3.8) N/mm, while equine amnion was 14.8 (5.3) N/mm. SAXS analysis of the collagen fibril arrangement yielded an orientation index of 0.587 (0.06) and 0.681 (0.05) for bovine and equine, respectively. This may indicate a relationship between more highly aligned collagen fibrils and greater strength, as seen in other materials. Amnion from bovine or equine sources are strong, thin, elastic materials, although weaker than other collagen tissue materials commonly used, that may find application in surgery as an alternative to material from human donors.Published onlin

Collagen dehydration.

Type I collagen is a ubiquitous structural protein in animal tissues. It is normally present in a hydrated form. However, collagen is very dependent on associated water for its mechanical properties. In skin, where type I collagen is dominant, there is a longstanding concern that the skin and therefore collagen may partially dry out and result in structural degradation. Here we show that dehydration of type I collagen fibrils, using 2-propanol, results in a two-stage dehydration process. Initially, the fibrils do not change length, i.e. the D-period remains constant, but shrinkage occurs within the fibrils by an increase in the gap region and a decrease in the overlap region within a D-band and a shortening of the helical turn distance and fibril diameter. Only with further dehydration does the length of the collagen fibril decrease (a decrease in D-period). This mechanism explains why collagen materials are resistant to gross structural change in the early stages of dehydration and shows why they may then suffer from sudden external shrinkage with further dehydration.Publishe

The influence of water, lanolin, urea, proline, paraffin and fatliquor on collagen D-spacing in leather

Water interacts with collagen to alter the structure at the fibrillar scale and therefore the mechanical properties of collagen. Humectants or moisturizers also alter the mechanical properties and fibril structure. The nature of these interactions and relationship between the different additives is not well understood. Changes in collagen D-spacing in leather were measured by synchrotron based small angle X-ray scattering in samples stored at various relative humidities and treated with lanolin, fatliquor, urea, proline or paraffin. The D-spacing increased with rising humidity and with increasing lanolin or fatliquor content, but not with treatment with urea, proline or paraffin. Strength increased with the addition of lanolin. Lanolin and fatliquor were shown to act as humectants whereas the other components did not act in this way. The Hofmeister effect is shown not to be a factor in the change in D-spacing, since samples treated with either proline or urea exhibited the same behavior. Different agents used in leather treatment and skin care function by different mechanisms, with collagen water retention being important for some additives but not others.fals