Synthesis and Characterization of Polyamidoamine Dendrimers/Nano-hydroxyapatite and Its Role in Dentin Tubule Occlusion.

Objective To synthesis and characterization nano-composite biomaterials-polyamidoamine dendrimers/nano-hydroxyapatite (PAMAM/n-HAP),which has the properties of both organic and inorganic materials,and then evaluate its role in dentin tubule occlusion. Methods PAMAM/n-HAP was characterized and validated by Fourier transform infrared spectrometry and transmission electron microscopy after its preparation via the Pramanik aqueous-based chemical method. Scanning electron microscope was used to evaluate its role in dentin tublule occlusion. Results The peak absorption bands were found at 1244 cm-1 and 1650 cm-1 in Fourier transform infrared spectroscopy. A relatively low-density coating (about 10 nm) appeared on the n-HAP. The results of Fourier transform infrared spectrometry and transmission electron microscopy confirmed the successful synthesis of PAMAM/n-HAP. The scanning electron microscope showed that PAMAM/n-HAP could effectively reduce the diameter of the dentin tubule and close dentin tubule. Conclusion PAMAM/n-HAP,as a newly synthesized biomaterial,has a good binding capacity with collagen fibers with the help of superficial carboxyl. It can induce effective dentinal tubule occlusion,indicating that PAMAM/n-HAP have great potential in clinical practice for dentin hypersensitivity.

Preparation and characterization of 3D hydroxyapatite/collagen scaffolds and its application in bone regeneration with bone morphogenetic protein-2.

Desirable bone engineering materials should have a conducive three-dimensional (3D) structure and bioactive mediators for guided bone regeneration. In the present study, hydroxyapatite (HA)/collagen (Col) scaffolds were prepared by an optimized freeze-drying process. The porosity, moisture content, and mechanical properties of the composite have been investigated. The micro-morphology and structure were analyzed with scanning electron microscopy (SEM) and transmission electron microscopy (TEM), confirmed that self-cross-linked HA/Col was evenly distributed and formed a 3D porous scaffold. The physicochemical/mechanical characterization was carried out by Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). Morphological observation and CCK-8 assay of co-culture cells indicated that HA/Col scaffolds were biocompatible. Then HA/Col scaffolds coupled with recombinant human bone morphogenetic proteins 2 (rhBMP-2) were implanted in the mandibular critical size defect in rats, and histological staining was used to evaluate the bone reconstruction. The result showed that HA/Col coupled with rhBMP-2 could significantly improve the formation of new bone and angiogenesis within the scaffolds as well as the proliferation and differentiation of osteoblasts. Thanks to the encouraging osteogenesis effects, the well-defined 3D scaffolds (HA/Col) cooperating with bioactive agents (rhBMP-2) are expected to be a promising candidate for bone tissue engineering applied to regenerative medicine.

Effect of a new modified polyamidoamine dendrimer biomimetic system on the mineralization of type I collagen fibrils: an in vitro study.

We evaluate the effects of the new Dentine matrix protein 1 (DMP-1) biomimetic system composed of phosphorylated polyamidoamine dendrimer (PAMAM-PO3H2) and carboxylated polyamidoamine dendrimer (PAMAM-COOH) on the mineralization of type I collagen fibrils. PAMAM-PO3H2 and PAMAM-COOH were observed to have the ability to induce internal and external mineralization of type I collagen fibrils in vitro through non-classical mineralization crystallization pathway, which has become a hopeful biomimetic system of biomimetic remineralization and demineralization of dentin type I collagen fibrils and has great potential in inducing biomimetic remineralization of demineralized dentin.

Remineralization of human dentin type I collagen fibrils induced by carboxylated polyamidoamine dendrimer/amorphous calcium phosphate nanocomposite: an in vitro study.

Intrafibrillar mineralization of type I collagen fibrils is of great significance in dental remineralization, which is the key of caries prevention and treatment. Herein, two substances that have the remineralization ability, carboxylated polyamidoamine dendrimer (PAMAM-COOH) and nano-sized amorphous calcium phosphate (n-ACP) were combined to synthesize a novel nanomaterial, carboxylated polyamidoamine dendrimer/amorphous calcium phosphate nanocomposite (PAMAM-COOH/ACP). This article aims to evaluate the remineralization effect of PAMAM-COOH/ACP of dentin type I collagen fibrils in vitro. Fluorescence labeling technique was innovatively used to observe and evaluate the remineralization effect. PAMAM-COOH/ACP showed superior remineralization ability of human dentin type I collagen fibrils, especially the intrafibrillar remineralization. Therefore, the novel nanomaterial PAMAM-COOH/ACP is promising to prevent and treat various diseases caused by dentin demineralization and to improve various dental materials.

Use of phosphorylated PAMAM and carboxyled PAMAM to induce dentin biomimetic remineralization and dentinal tubule occlusion.

It is crucial to emphasize the biomineralization therapeutic method to repair etched dentin in clinic. Non-collagenous proteins (NCPs) play critical role in the biomineralization of dentine. In this paper, we synthesized the phosphate-terminated polyamidoamine dendrimer (PAMAM-PO3H2) by one-step modification successfully and examined by Fourier-transform infrared spectroscopy (FTIR) and 1H-nuclear Magnetic Resonance (1H-NMR) to characterize the structure of PAMAM-PO3H2. PAMAM-PO3H2 and carboxylterminated dendrimers (PAMAM-COOH) were applied as the dual biomimetic analogs of NCPs. Through the characterization of FT-IR, field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD), the surfaces of human dentin were covered with regenerated crystals and the dentinal tubules were occluded by PAMAM-PO3H2 and PAMAM-COOH. In summary, the combination of PAMAM-PO3H2 and PAMAM-COOH may be another feasible therapeutic method for the treatment of dentin caries and dentin hypersensitivity.

Fabrication and characterization of dendrimer-functionalized nano-hydroxyapatite and its application in dentin tubule occlusion.

The occlusion of dentinal tubules is an effective method to alleviate the symptoms of dentin hypersensitivity. In this paper, we successfully modified nano-hydroxyapatite (n-HAP) with carboxyl-terminated polyamidoamine dendrimers by an aqueous-based chemical method and verified by fourier transform infrared spectroscopy (FTIR) and transmission electron microscope (TEM). Then the demineralization dentin discs were randomly divided into 4 groups, corresponding to subsequent brushing experiments: deionized water and kept in artificial saliva (AS), dendrimer-functionalized n-HAP and stored in AS, n-HAP and saved in AS, dendrimer-functionalized n-HAP and stored in deionized water. After 7 days of simulated brushing, dentin discs followed the in vitro characterization using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy and microhardness test. These data suggested that dendrimer-functionalized n-HAP could crosslink with collagen fibers and resulted in effective dentinal tubule occlusion. Moreover, the new material can induce the HAP formation with the help of superficial carboxyl and fill the spaces in dentinal tubules furtherly. The microhardness of dendrimer-functionalized n-HAP-treated specimens was significantly higher than others. In summary, dendrimer-functionalized n-HAP can be a new therapeutic material for the treatment of dentin hypersensitivity.