Cross-Linking of Apatite-Gelatin Nanocomposites as the Basis for Dentine Replacement Materials.

A novel approach for the production of a bioinspired dentine replacement material is introduced. An apatite-gelatin nanocomposite material was cross-linked with various cross-linkers. These nanocomposites have a high resemblance to mammalian dentine regarding its composition and properties. A precipitation reaction was used to produce apatite-gelatin nanocomposites as starting materials. Cross-linking of the gelatin has to be performed to produce dentine-like and thus tough and robust apatite-gelatin nanocomposites. Therefore, the efficacy of various protein cross-linkers was tested, and the resulting materials were characterized by scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, and EXAFS as well as CHNS analysis and tested for their mechanical performance using Vickers hardness measurements as well as for their dissolution stability in EDTA. Especially glutaraldehyde, proanthocyanidins, and transglutaminase gave promising results with hardness values of up to 63 HV0.2. To further improve the material properties, we combined the effective cross-linker transglutaminase with casein, which led to an improved interconnection between the single nanocomposite platelets. By doing so, a cross-linked composite was obtained, which shows even higher hardness values than does human dentine, at 76 HV. The combination of apatite-gelatin nanocomposites with an effective cross-linker resulted in a bioinspired material with composition and properties close to those of human dentine.