Characterisation of elastin and collagen in aortic bioprostheses

Porcine aortic valves used as cardiac valve bioprostheses are well adapted to physiological functions in the short term, but they lack long-term durab ility. Several multi-step extractions have been performed to obtain a perfe ctly acellular matrix. A new physical methodology is proposed to evaluate t he resulting fibrous protein damage after biochemical extraction (TRI-COL a nd SDS). Thermal analysis techniques are adapted to collagen and elastin ch aracterisation in the solid state. The aortic tissue thermal transitions ar e determined by differential scanning calorimetry (DSC): elastin glass tran sition is observed around 200 degrees C, and collagen denaturation is obser ved around 230 degrees C. These parameters are characteristic of the elasti n network arrangement and of collagen triple-helix stability. The technique of thermostimulated currents (TSC) is well suited to specify the chain dyn amics of proteins. The low-temperature relaxations observed in both collage n and elastin are associated with localised motions, whereas the high-tempe rature modes are attributed to more delocalised motions of the chains. Ther efore TSC and DSC spectrometries allow physical parameters specific to coll agen and elastin to be obtained and their interaction in aortic tissues to be determined. According to the significant evolution of these parameters o n SDS samples, the destabilising effect of this detergent is highlighted.