How aerogel substrates affect the biomechanical and biochemical properties of collagen I: An in vitro study

Collagen, the most abundant protein in mammals, is often used as a layer between biomaterials and cells/tissues to enhance cell attachment. Without proper cell attachment, key cellular functions such as proliferation will not occur, therefore the collagen layer plays an important role in tissue construction. Our earlier studies demonstrated that rat tail collagen I provided optimum cell attachment conditions for PC12 cells on aerogels at a concentration of 4µg/cm² and was the preferred dilution ratio for aerogels with pore diameters from 50nm to 10um. A strong dependency of the collagen microstructure on the substrate topography was however observed and thus demanded further investigation. Here, the authors present a comprehensive analysis of how the collagen microstructure is affected by its concentration, as a function of key aerogel substrate properties. These include surface roughness, Young’s modulus, and pore diameter. Concentrations that were tested ranged from X1(4µg/ cm²) to X5(20µg/cm²) and results indicate a gradual transformation from a fibrous layer to a continuous thin film where the individual collagen fibers are no longer distinguishable. Results suggest that the onset of this transformation is mostly dictated by the aerogel surface roughness. Furthermore, the tension in individual collagen fibers, which was affected by the substrate pore diameter, determined the formation of a collagen film and as a result played a key role in the continuity or discontinuity of the collagen film.