Biomimetic mineralization of dentin induced by agarose gel loaded with calcium phosphate.

A novel biomimetic mineralization system was designed to induce a layer of hydroxyapatite on a demineralized dentin surface. This system was constructed as follows. A layer of 0.5% agarose gel containing 0.26M Na(2) HPO(4) was used to cover acid-etched dentin slices, followed by a layer of agarose gel without phosphate ions. Then a neutral 0.13M CaCl(2) solution was added onto the ion-free gel surface. The mineralization system (dentin-agarose gel containing phosphate ions-CaCl(2) solution) was kept in a water bath at 37°C, and the gel and CaCl(2) solution were replaced at various intervals. The results showed that the deposited hydroxyapatite crystals densely packed to each other, completely covered the dentin surface, and occluded the dentinal tubules after 10 days of biomimetic mineralization in vitro. Therefore, this method may provide the experimental basis for dentin remineralization and for a new method to treat dentin hypersensitivity and dental caries.

Minocycline-released hydroxyapatite-gelatin nanocomposite and its cytocompatibility in vitro.

The incorporation of antibacterial agents into biomaterials is extremely desirable for repairing bone defects. Minocycline, a semi-synthetic tetracycline antibiotic, is active against aerobic, anaerobic, Gram-positive and Gram-negative bacteria, and can enhance bone formation, decrease connective tissue breakdown and diminish bone resorption. In this study, a novel minocycline-releasing biomaterial was synthesized using a biomimetic method. A measured amount of an acidic hydroxyapatite and minocycline solution was respectively added to a gelatin solution and kept at 40 °C and pH 7-8 for 2 h. The mixture was aged overnight, lyophilized and a hydroxyapatite-gelatin-minocycline composite was obtained. The composite was co-cultured with rat bone marrow stromal cells (BMSCs) in vitro. Our results show that nanohydroxyapatite was distributed evenly in the fibrils of the gelatin. Minocycline was incorporated into the composite and could be released from the composite particles slowly over 2 weeks in vitro. The composite promoted BMSC adhesion, proliferation and differentiation in vitro. The approach described here may provide a basis for the preparation of an antibacterial biomaterial for bone regeneration.