Thermal analysis study of human bone

We have studied the thermal stability of human bone tissue and also its bone-extracted type-I collagen. We have used differential thermal analysis (DSC), infrared spectroscopy (FTIR) and gas chromatography. For type-I Collagen, variations of an exothermic maximum peak were observed between 500 and 530°C depending on the extraction method. These variations are related to high thermal stability of extracted collagen as opposed to thermal stability found in bone tissue, which maximum exothermic peak was found at ≈350°C. Total combustion enthalpy ΔH values are similar: −8.4 ± 0.11 kJ/g for bone tissue, and between −7.9 to −8.9 kJ/g in extracted collagen (depending on the extracting method). These findings, along with the results obtained by infrared spectroscopy and chromatographic techniques, demonstrate that the loss of thermal stability in type I collagen is due to its interactions with carbonate hydroxyapatite nanocrystals. The interactions cause a change in the molecular properties of collagen during mineralization, (specifically in its cross-links and other chemical interactions) which have an effect on fiber elasticity and on strength of bone tissue as a whole. We discuss the decomposition/combustion process and also how calorimetric measurement affects specific interactions between mineral and organic phases.