Effect of temperature on surface tension and surface dilational rheology of type I collagen

The dynamic surface tension and surface dilational rheology of native collagen (type I, from bovine calf skin) were analyzed in the temperature range from 21 to 34.5 °C. In addition, the effect of heating the collagen solutions up to 90 °C followed by cooling down to room temperature, on surface tension and rheological parameters of the adsorbed layers was studied. As a water-soluble fibrous protein with little exposed hydrophobicity, native collagen is weakly surface active. However, its layers formed by spontaneous adsorption on the water/air surface display exceptional dilational rheology parameters, comparable with those of globular proteins: at high frequency limit (0.1 Hz) the layers are predominantly elastic, with the storage modulus, E′ = 58 mN/m for collagen concentration of 1.3 × 10−5 M (4 g/L). Increasing temperature during adsorption helps to reduce the surface tension, but the resulting layers show diminished surface elastic response. On the other hand, the samples heated at elevated temperatures and measured after cooling down to the room temperature maintain their high surface elasticity. The results suggest that collagen, even in its native form (not processed to gelatin) has a potential to stabilize biocompatible foams/emulsions by forming mechanically strong adsorbed layers.