The fabrication of enamel-inspired 3D FA biomaterial

Abstract

Objectives: The technique to absolutely and precisely mimic the process of amelogenesis has not been available. Recreating the distinctive apatite composition, hierarchical architecture, and corresponding properties of enamel is challenging. We thus develop a novel non-cell approach to synthesize an enamel-inspired 3D fluorapatite (FA) biomaterial with a distinctive hierarchical architecture. Methods: A customized polyethylene membrane was prepared as a mineralization template to synthesize FA crystals under a hydrothermal condition. The synthesized FA crystals aggregated to form a FA crystal film through the evaporation-based bottom-up self-assembly. The FA bulk was then constructed by the starting with hydrothermal growth of the FA crystal film followed by highly conformal adsorption to the FA crystal surface of a polyelectrolyte matrix film using layer-by-layer (LBL) deposition technique. The thickness of fabricated FA bulk was decided by the number of repeated cycles of FA crystal film and polyelectrolyte matrix film. Results: The synthesized FA nanorods were morphologically similar to the crystals in native enamel [Figure 1 A]. Through the evaporation-based bottom-up self-assembly, those FA nanorods aggregated to form a continuously prismatic-typed crystal film. The formed crystal film was composed of bundles of FA nanorods with highly organized orientation preferentially along the c-axis, almost perpendicularly growing from the surface of underlying mineralization template [Figure 1 B]. After four repeated cycles of FA crystal film and polyelectrolyte matrix film, sequentially growing FA crystal films were stacked up to form a FA bulk with a thickness of 23.5 μm [Figure 1 C]. The synthesized FA bulk possessed a distinctive hierarchical architecture of enamel across from the crystallographic scale, to nano- and microscale, and up to macroscale. Conclusions: The enamel-inspired 3D FA biomaterial with a distinctive hierarchical architecture of enamel at multiscale was successfully fabricated in this study.