Description of FTIR and DSC of collagen interaction - Hydroxylapatite

In the present work, we studied the effect of the mineral content (hydroxyapatite), on the thermal stability of the bone collagen matrix. The demineralization process was followed measuring the percentage of remaining mass and characterized by Fourier Transform Infra Red Spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC), using a Calcium chelant agent (EDTA). A 52 % loss of the initial weight was observed after 72 hours of treatment, associated with a decrease of the mineral content, indicated by changes in the intensity of the peaks correspondent to PO4-3 vibrations. The bone collagen's denaturalization and degradation temperatures was followed by DSC, showing an endotherm in 166 degrees C for the untreated bone and in 113 degrees C for the 72 hours treated bone, correspondent both to the bone collagen denaturalization temperature. The thermogram for the 12 hours demineralized exhibited a small endotherm in 250 degrees C, corresponding to slight degradation, for the 72 hours treated bone the endotherm decreased to 230 degrees C, correspondent to the bone collagen degradation. The above results lead us to conclude that the bone collagen triple helix losses its thermal stability when the interactions with the surrounding hydroxyapatite are eliminated.