Preparation and characterization of two new composites: collagen-brushite and collagen octa-calcium phosphate

Recent studies have focussed on understanding the fundamental aspects of mineralization, searching for insight into the physical and chemical interactions between the organic and inorganic counterparts in bio-inorganic composites. Structural alterations in organic matrices interacting with minerals during the phase transition from un-calcified to calcified affect the mineral micro-environment, resulting in calcification. The present study deals with the fabrication of two novel bio-inorganic composites: collagen-brushite and collagen-octacalcium phosphate. The mineral counterparts are grown onto collagen by crystal growth, to produce composites adapted to the ambient environment in bone, at pH 5.8 and pH 7.0. The biophysical and material characteristics provide some interesting insights into calcifying mechanisms.

The biophysical parameters were evaluated by Fourier Transform Infra Red (FTIR) spectroscopic studies, Differential Scanning Calorimetry (DSC), and Scanning Electron Microscopic (SEM) studies, with biochemical characterization of demineralized and remineralized samples for hydroxyproline, hexosamine, uronic acid, and net protein content.

The biochemical characterization of demineralized and remineralized samples revealed protein loss on mineralization and indicated the possible role of non-collagenous proteins (osteonectin) in mineralization. The FTIR spectra showed loss of amide peaks, while DSC and SEM studies showed closer association of collagen with the mineral counterpart.

In vitro collagen mineralization systems reveal the essential role of non-collagenous proteins (osteonectin) in mineralization. The novel composites have mineral counter parts with a physical similarity to bone, and their use as a substitutive tissue is presently being evaluated in animal models.