The physiological relevance of wet versus dry differential scanning calorimetry for biomaterial evaluation: A technical note

Collagen and its denatured form, gelatin, have been extensively used as scaffolds for tissue engineering and tissue repair applications. Denaturation temperature, commonly measured using differential scanning calorimetry (DSC), for biomaterial applications is a significant physical property that will determine the stability of a potential implant at body temperature. In order to imitate a clinical setting, DSC should be run under fully hydrated conditions. We show here that for hydrophobic polymers such as poly(ε-caprolactone) and chitosan there is no significant difference between dry and wet DSC operation (p > 0.05). In contrast, for hydrophilic polymers such as collagen, gelatin, poly(ethylene glycol) (40 kDa) and poly(ethylene oxide) (900 kDa) significant differences occur between measurements in the dry and the wet state (p < 0.0011). Moreover, we demonstrate that only when wet DSC is carried out are we able to separate the unique crystalline structure of collagen from its randomly coiled heat-denatured by-product gelatin (p < 0.0005). We therefore recommend running DSC under fully hydrated conditions when the function and properties of a biomaterial are under investigation.