Biomimetic Remineralization Of Demineralized Enamel Induced By A Self-assembly Amelogenin-inspired Oligopeptide

Objective To biomimetic the process of enamel mineralization, we construct aspecific biomineralization template of enamel, remineralizing the demineralizedenamel.Methods Construction of a specific biomineralization template of enamel:Inspired by amelogenin that self-assembles into nanospherical supermolecularstructures and controls mineral nucleation and growth during enamel formation, anovel oligopeptide amphiphile was designed. Two features were taken into account inthe design of the peptide molecule. First, we choose the amino sequence-Thr-Lys-Arg-Glu-Glu-Val-Asp for the amphiphile head. Second, the hydrophobic tailis an alkyl tail with18carbons. The fatty acid C18H35COOH was coupled to theN-terminal amino acid of the-Thr of the ionic peptide. The oligopeptide amphiphilewas synthesized by standard solid-phase peptide synthesis, purified and characterizedby high performance liquid chromatography (HPLC) and mass spectrometry (MS).Peptide self-assembly was induced with HCl vapor and CaCl2solution andcharacterized with scanning electron microscope (SEM) and transmission electronmicroscope (TEM). Biomimetic mineralization was performed by alternatelyimmersing the peptide in CaCl2and Na2HPO4solution and was characterized bySEM, TEM and energy dispersive spectrometer (EDS).Finally, when the peptide was assembled on the enamel surface and was exposedto the calcification solution containing fluorine, or the peptide was added into thecalcification solution containing fluorine,the deposits on enamel was characterizedby FTIR, XRD and SEM. Results The sequence of the amelogenin-inspired oligopeptide amphiphile wasC18H35O-Thr-Lys-Arg-Glu-Glu-Val-Asp. The oligopeptide was purified by HPLC.Peptide molecule weight (MV) and purity were1142.41and98.29%accordingly,identified with MS and HPLC respectively. The oligopeptide amphiphile couldself-assemble into a gel in the presence of acid or by Ca2+induction. TEM showedthat the self-assembly hydrogel consisted a β-sheet conformation nanofiber networks;the peptide fiber can adsorb calcium and phosphate ions from the solution. Then,minerals crystals nucleated, grew on the surface of the peptide fiber, and orientatedalong the fiber. Electron diffraction pattern showed that very low crystallized HAprecipitated at room temperature, however, nano-crystals corresponded well tohigh-crystallinity HA precipitated and oriented along the peptide fibers at40°C.The FTIR and the XRD spectra showed that the deposition corresponded well tohigh-crystallinity HA. The oligopeptide amphiphile can assemble on the enamelsurface. When the enamel slices assembled with peptide were exposed to thecalcification containing fluorine, well-developed needle-like fluorapatites verticallygrew on the enamel surface, bundled together and resembled enamel prism.Conclusions A novel amelogenin-inspired oligopeptide amphiphile wasdesigned and synthesized. The peptide was able to self-assemble on demineralizedenamel surface and to induce enamel-like structure in the calcification solutioncontaining fluorine, remineralizing the demineralized enamel. It provides a potentialmolecular tool for biomimetic mineralization of enamel. This study provides a newtheoretical and experimental basis for the construction of biomimetic dentalrestorative materials and self-healing restoration of dental hard tissue defects.