Effect of gravity and diffusion interface proximity on the morphology of collagen gels

Collagen solutions (0.25% w/v) were polymerized in microgravity (STS-77, 10 days) along with simultaneous ground controls. Assembly conditions were achieved by the passage of buffer ions across a dialysis membrane into a reaction chamber containing the dissolved collagen. The gels were analyzed macroscopically and microscopically to assess the influence of gravity and the oriented diffusion of buffer ions on the resulting product. Double-blind rankings based on visual observation of the gels established that all of the flight gels (n = 8) were more uniform in appearance than all of the ground gels (n = 6). Photography using side illumination of the gels revealed the more granular appearance of the ground gels relative to the highly uniform appearance of the flight gels. Scanning electron microscopy established this difference at the microscopic level. Proximity to the dialysis interface and the presence or absence of gravity were both found to control the porosity and uniformity of the matrix.