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This study sought to improve the mechanical and blood-absorbing properties of collagen sponges, while keeping them compressible, by incorporating blended hydroxyapatite (HA)-starch. Results were compared with CollaPlug(®) (pure collagen). The elastic modulus increased from 1.5±0.2kPa for CollaPlug(®) to 49±8kPa for sponges with composition 1:4:10 (collagen:HA:starch, by weight). The modified microstructure and surface area provided by the starch granules on the sponges improved cell viability. Sponges with composition 1:4:10 maintained their blood-clotting capability with almost no change from 5 to 15min after contact with blood, while CollaPlug(®) diminished to about half its capacity to absorb blood and form clots. Incorporation of HA-starch into the sponges with composition of 1:4:10, increased the elastic modulus of the collagen-HA sponges, making them more structurally robust. The viability of cells and the blood-clotting capability increased with starch incorporation.

The present study proposes an interpretation of the mechanism of bone deproteinization. Cortical and trabecular bovine femur bones were deproteinized using 6% NaOCl (37, 50, 60°C). The kinetic parameters (rate constant and activation energy) were calculated, and the surface area of each type of bone was considered. A statistical analysis of the rate constants shows that cortical bone deproteinizes at a lower rate than trabecular. The activation energy is higher for trabecular than cortical bone, and no significant differences are found in the protein concentration values for both bones. Therefore, although trabecular bone deproteinizes at a higher rate than cortical, trabecular bone requires more energy for the deproteinization reaction to take place. Considering that both types of bones are constituted by mineral, protein, and water; the present work shows that the individual inner matrix architecture of trabecular and cortical bones, along with characteristics such as the mineral concentration and its bonding with collagen fibers, may be the responsible factors that control protein depletion.

The goal of this study was to contribute to the interpretation of the kinetics involved in the in vitro demineralization process of bone, which has clinical uses as bone grafts (demineralized bone matrix), as well as for materials science applications. Cortical and cancellous bovine femur bones and cortical antler were demineralized in dilute hydrochloric acid and the kinetic parameters of the demineralization reaction at different temperatures and HCl concentrations were calculated. The rate of demineralization increased with both HCl concentration and temperature. During the demineralization reaction experiments, three different stages were clearly identified: a) in the first stage, the rate constant increased as HCl advanced from the periphery to the core of the sample. b) In the second stage, the demineralization occurred at a steady state, and finally, c) in the third stage, the rate constant diminished. The activation energy for demineralization was calculated for both types of bones.