Remineralizing Potential of Natural Nano-Hydroxyapatite Obtained from Epinephelus chlorostigma in Artificially Induced Early Enamel Lesion: An In Vitro Study

Natural, biphasic calcium phosphate from fish bones for enamel remineralization and dentin tubules occlusion

OBJECTIVES

A calcium phosphate extracted from fish bones (CaP-N) was evaluated for enamel remineralization and dentinal tubules occlusion.

METHODS

CaP-N was characterized by assessing morphology by SEM, crystallinity by PXRD, and composition by ICP-OES. CaP-N morphology, crystallinity, ion release, and pH changes over time in neutral and acidic solutions were studied. CaP-N was then tested to assess remineralization and dentinal tubules occlusion on demineralized human enamel and dentin specimens (n = 6). Synthetic calcium phosphate in form of stoichiometric hydroxyapatite nanoparticles (CaP-S) and tap water were positive and negative controls, respectively. After treatment (brush every 12 h for 5d and storage in Dulbecco's modified PBS), specimens' morphology and surface composition were assessed (by SEM-EDS), while the viscoelastic behavior was evaluated with microindentation and DMA.

RESULTS

CaP-N consisted of rounded microparticles (200 nm - 1 µm) composed of 33 wt% hydroxyapatite and 67 wt% β-tricalcium phosphate. In acidic solution, CaP-N released calcium and phosphate ions thanks to the preferential β-tricalcium phosphate phase dissolution. Enamel remineralization was induced by CaP-N comparably to CaP-S, while CaP-N exhibited a superior dentinal tubule occlusion than CaP-S, forming mineral plugs and depositing new nanoparticles onto demineralized collagen. This behavior was attributed to its bigger particle size and increased solubility. DMA depth profiling and SEM showed an excellent interaction between the newly formed mineralized structures and the pristine tissue, particularly at the exposed collagen fibrils.

SIGNIFICANCE

CaP-N demonstrated very good remineralizing and occlusive activity in vitro, comparable to CaP-S, thus could be a promising circular economy alternative therapeutic agent for dentistry.

Spontaneous Osteogenic Differentiation of Human Mesenchymal Stem Cells by Tuna-Bone-Derived Hydroxyapatite Composites with Green Tea Polyphenol-Reduced Graphene Oxide

In recent years, bone tissue engineering (BTE) has made significant progress in promoting the direct and functional connection between bone and graft, including osseointegration and osteoconduction, to facilitate the healing of damaged bone tissues. Herein, we introduce a new, environmentally friendly, and cost-effective method for synthesizing reduced graphene oxide (rGO) and hydroxyapatite (HAp). The method uses epigallocatechin-3-O-gallate (EGCG) as a reducing agent to synthesize rGO (E-rGO), and HAp powder is obtained from Atlantic bluefin tuna (Thunnus thynnus). The physicochemical analysis indicated that the E-rGO/HAp composites had exceptional properties for use as BTE scaffolds, as well as high purity. Moreover, we discovered that E-rGO/HAp composites facilitated not only the proliferation, but also early and late osteogenic differentiation of human mesenchymal stem cells (hMSCs). Our work suggests that E-rGO/HAp composites may play a significant role in promoting the spontaneous osteogenic differentiation of hMSCs, and we envision that E-rGO/HAp composites could serve as promising candidates for BTE scaffolds, stem-cell differentiation stimulators, and implantable device components because of their biocompatible and bioactive properties. Overall, we suggest a new approach for developing cost-effective and environmentally friendly E-rGO/HAp composite materials for BTE application.