Novel biomimetic peptide-loaded chitosan nanoparticles improve dentin bonding via promoting dentin remineralization and inhibiting endogenous matrix metalloproteinases.

OBJECTIVE: This study aims to synthesize novel chitosan nanoparticles loaded with an amelogenin-derived peptide QP5 (TMC-QP5/NPs), investigate their remineralization capability and inhibitory effects on endogenous matrix metalloproteinases (MMPs), and evaluate the dentin bonding properties of remineralized dentin regulated by TMC-QP5/NPs. METHODS: TMC-QP5/NPs were prepared by ionic crosslinking method and characterized by dynamic light scattering method, scanning electron microscopy, transmission electron microscope, atomic force microscope, Fourier transform infrared spectroscopy, and differential scanning calorimetry. The encapsulation and loading efficiency of TMC-QP5/NPs and the release of QP5 were examined. To evaluate the remineralization capability of TMC-QP5/NPs, the mechanical properties, and the changes in structure and composition of differently conditioned dentin were characterized. The MMPs inhibitory effects of TMC-QP5/NPs were explored by MMP Activity Assay and in-situ zymography. The dentin bonding performance was detected by interfacial microleakage and microshear bond strength (µSBS). RESULTS: TMC-QP5/NPs were successfully synthesized, with uniform size, good stability and biosafety. The encapsulation and loading efficiency of TMC-QP5/NPs was respectively 69.63 ± 2.22% and 13.21 ± 0.73%, with a sustained release of QP5. TMC-QP5/NPs could induce mineral deposits on demineralized collagen fibers and partial occlusion of dentin tubules, and recover the surface microhardness of dentin, showing better remineralization effects than QP5. Besides, TMC-QP5/NPs significantly inhibited the endogenous MMPs activity. The remineralized dentin induced by TMC-QP5/NPs exhibited less interfacial microleakage and higher µSBS, greatly improved dentin bonding. SIGNIFICANCE: This novel peptide-loaded chitosan nanoparticles improved resin-dentin bonding by promoting dentin remineralization and inactivating MMPs, suggesting a promising strategy for optimizing dentin adhesive restorations.

Unveiling the mechanism of an amelogenin-derived peptide in promoting enamel biomimetic remineralization.

Amelogenin and its derived peptides have exhibited excellent efficacy in promoting enamel biomimetic remineralization. However, little is known about their specific action mechanisms. Herein, by combining experiments and computer simulation, the mechanism of an amelogenin-derived peptide QP5 in regulating enamel biomimetic remineralization is unveiled for the first time. In experiments, peptide QP5 was separated into (QPX)5 and C-tail domains, the interactions of peptide-minerals in nucleation solution and the regulation of peptide on enamel biomimetic remineralization were explored. QP5 exhibited an unordered conformation when mineral ions existed, and it could adsorb on minerals through its two domains, thereby inhibiting spontaneous nucleation. The remineralized enamel regulated by C-tail showed better mechanical properties and formed more biomimetic crystals than that of (QPX)5, indicating the C-tail domain of QP5 played an important role in forming enamel-like crystals. The simulation results showed that the conformation of QP5 changed greatly, mainly exhibiting ß-bend, ß-turn, and coil structures, and it eventually adsorbed on enamel through negatively charged residues of the C-tail domain, then captured Ca2+ from solution to promote enamel remineralization. This study improved the evaluation methods of the mechanism of biomimetic peptides, and laid a theoretical basis for the amelioration and clinical transformation of peptide QP5.

Mineralization promotion and protection effect of carboxymethyl chitosan biomodification in biomimetic mineralization.

Biomimetic mineralization emphasizes reversing the process of dental caries through bio-inspired strategies, in which mineralization promotion and collagen protection are equally important. In this study, carboxymethyl chitosan (CMC) was deemed as an analog of glycosaminoglycan for biomimetic modification of collagen, both of the mineralization facilitation and collagen protection effect were evaluated. Experiments were carried out simultaneously on two-dimensional monolayer reconstituted collagen model, three-dimensional reconstituted collagen model and demineralized dentin model. In three models, CMC was successfully cross-linked onto collagen utilizing biocompatible 1-Ethyl-3(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxy sulfosuccinimide sodium salt to achieve biomodification. Results showed that CMC biomodification increased collagen's hydrophilicity, calcium absorption capacity and thermal degradation resistance. In demineralized dentin model, the activity of endogenous matrix metalloproteinases was significantly inhibited by CMC biomodification. Furthermore, CMC biomodification significantly improved cross-linking and intrafibrillar mineralization of collagen, especially in the two-dimensional monolayer reconstituted collagen model. This study provided a biomimetic mineralization strategy with comprehensive consideration of collagen protection, and enriched the application of chitosan-based materials in dentistry.

Promoting effect of a calcium-responsive self-assembly ß-sheet peptide on collagen intrafibrillar mineralization.

Recently, a de novo synthetic calcium-responsive self-assembly ß-sheet peptide ID8 (Ile-Asp-Ile-Asp-Ile-Asp-Ile-Asp) has been developed to serve as the template inducing hydroxyapatite nucleation. The aim of this study was to evaluate the effect of ID8 on intrafibrillar mineralization of collagen making full use of its self-assembly ability. The mineralization experiments were carried out in vitro on both bare Type I collagen and fully demineralized dentin samples. The calcium-responsive self-assembly of ID8 was revealed by circular dichroism spectrum, 8-anilino-1-naphthalenesulfonic acid ammonium salt hydrate assay, attenuated total reflection Fourier transform infrared spectrum (ATR-FTIR) and transmission electron microscope (TEM). Polyacrylic acid (450 kDa) with a concentration of 100 µg ml-1 was selected as the nucleation inhibitor based on the determination of turbidimetry and TEM with selected area electron diffraction (TEM-SAED). The results showed that collagen intrafibrillar mineralization was significantly promoted with the pretreatment of self-assembly ID8 detected by TEM-SAED, SEM, X-ray diffraction and ATR-FTIR. The pretreatment of collagen utilizing self-assembly ID8 not only enhanced intermolecular hydrogen bonding but also contributed to calcium retention inside collagen and significantly increased the hydrophilicity of collagen. These results indicated that peptides with self-assembly properties like ID8 are expected to be potential tools for biomimetic mineralization of collagen.