Papers by Author: Kun Tian

Abstract: The formation of organized nanocrystals that resemble tooth-like hydroxyapatite is crucial for successful enamel remineralization. Based on the principles of biomineralization , spindle - shaped hydroxyapatites (HA) were synthesized through biomimetic method with chitosan as template under a controllable way in vitro. We observed that hydroxyapatite nanorods can be controlled followed by in situ crosslinking process and triggered by conditions of pH and ionic strength. The dentinal tubule were blocked by neonatal hydroxyapatite layer and this composite a continuous structure of columns crystal with size of 10-40nm. At the same time, XRD showed that the precipitation was calcium fluoride phosphate and Ca:P was 1.6. Furthermore, there were column crystal with parallel direction inside, as same as the crystal array in the top of enamel rod. The results suggest that chitosan monolayer may be useful in the modulation of mineral behavior during in situ dental tissue engineering.

Abstract: Tooth morphogenesis results from reciprocal interactions between oral epithelium and ectomesenchyme culminating in the formation of mineralized tissues, enamel, and dentin. Based on these basic theory, we design a organic molecules model to induced the crystallization of hydroxyapatite to synthesized tooth-like calcium phosphate/hydroxyapatite with 3D-structure in a controllable way in vitro. We observed that hydroxyapatite nanorods can be controlled followed by in situ phosphorylation process and triggered by conditions of pH and ionic strength. The results showed that he dentinal tubule were blocked by neonatal hydroxyapatite layer and this composite a continuous structure of columns crystal with size of 30-80nm. At the same time, XRD showed that the precipitation was calcium fluoride phosphate and Ca:P was 1.6. Furthermore, there were column crystal with parallel direction inside, as same as the crystal array in the top of enamel rod. The results suggest that collagen monolayer may be useful in the modulation of mineral behavior during in situ dental tissue engineering.

Abstract: Based on the basic theory of molecular recognition, we designed an organic molecules model that spontaneously form three-dimensional fibrillar scaffolds to induce the crystallization of hydroxyapatite to synthesized enamel-like calcium phosphate/hydroxyapatite under a controllable way in vitro. Cross-linking of collagen on the dentin surface and silk fibroin with N,N-(3-dimethylaminopropyl)-N'-ethyl-carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) was optimized by varying the NHS/EDC molar ratio at constant EDC concentration. CaCl₂ and Na₃PO₄-12H₂O solution was added with Ca: P odd as 1.67:1 after conjugated. The results showed that the dentinal tubule were blocked by neonatal hydroxyapatite layer which has a continuous structure of columns crystal with size of 10-40nm. Furthermore, there were column crystal with parallel direction inside, similar to the crystal array in the top of enamel rod. The results suggest that silk protein monolayer may be useful in the modulation of mineral behavior during in situ dental tissue engineering.

Abstract: Based on the basic theory of molecular recognition , we design a organic molecules model to induce the crystallization of hydroxyapatite to synthesized tooth-like calcium phosphate/hydroxyapatite under a controllable way in vitro. The cross-linking of collagen on the dentin surface and extraneous collagen was optimized by varying the molar ratio of N,N-(3-dimethylaminopropyl)- N'-ethyl-carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) at a constant EDC concentration. CaCl2 and Na3PO4-12H2O solutions were added after the crosslinking process. X-ray photoelectron spectroscopic (XPS) and Fourier transform infrared spectroscopy (FTIR) analysis of organic protein monolayer for samples. The obtained composite were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) as well as energy dispersive X-ray (EDX). XPS and FTIR analysis showed the surface organic compositions in experimental group is higher than that of normal dentin and decalcified dentin surface. The results showed that the dentinal tubule were blocked by neonatal hydroxyapatite layer which has a continuous structure of columns crystal with size of 10-40nm. Furthermore, there were column crystal with parallel direction inside, similar to the crystal array in the top of enamel rod. This study showed that the specific organic molecule model can be used as a potential effective crystal growth modifier.

Abstract: To study the biomimetic mineralization behaviour of piezoelectric pulp-cap films, bioelectret chitosan films were prepared by polarization in an electric field and soaked in PBS with lysozyme for piezoelectricity attenuation testing. The results showed that comparing these with samples stored in an exsiccator, the films soaked in PBS had accelerated d33 loss. Calcium phosphate crystals nucleated and grew on the surfaces of samples soaked in supersaturated calcification solution at 37
for 1, 6, 12 and 24 h. OCP and HA were found to co-precipitate on the surfaces within 24 h of immersion. This novel piezoelectric inorganic-organic pulp-cap has the potential to be applied in dental pulp capping.

Abstract: A three-dimensional biomimetic electrospun scaffold was prepared from a nanohydroxyapatite/ polymer blend in the present study. Viscosity of n-HA/PEA compound solution determined by PEA concentration and additives of n-HA was investigated while other parameters were fixed in the electrospinning process. The fiber diameter increased with the increasing viscosity of solution. 20wt% n-HA in the composite ultrafine fibrous scaffold was proved to be a preferable ratio. The n-HA/PEA scaffold was characterized by XRD, SEM and EDX. The fibrous electrospun scaffold, which is made up of ultrafine fibers with average diameter 400±50 nm and well-interconnected pores, was characterized with high surface–to-volume ratio, which is conducive to cell and tissue growth. A comparatively uniform distribution of n-HA crystals in a single fiber even in the whole scaffold was confirmed by EDX. The biocompatibility of the composite was investigated by culturing osteobalsts on the scaffold. Good cell adhesion and proliferation manner was observed on the fibrous scaffold by SEM and MTT assay. It could be expected that the electrospun HA/PEA composite scaffold would be a potential biomimetic extracellular matrix biomaterial for bone tissue engineering.

Abstract: The bioactivity of poled piezoelectric PLLA membrane was investigated by studying the calcium phosphate formation in vitro using a biomimetic method. Samples (φ10mm) were poled under DC electric field of 8~l0kV/cm at 70°C for 30 min followed by cooling under the electric field. Surface chemistry of the samples before and after poling treatment was studied by X-ray photoelectron spectroscopy (XPS). Poled/unpoled samples were immersed in supersaturated calcification solution (SCS) for periods up to 24 h (36.5°C). The surface morphology and composition of the soaked samples were evaluated by using scanning electron microscope (SEM) and X-ray diffraction analysis (XRD). Poled samples showed two different charged surfaces, negatively-charged surface (N-PLLA) and positively-charged surface (P-PLLA). On the N-PLLA surfaces, SEM together with XRD showed a gradually formed calcium phosphate (Ca-P), while no obvious Ca-P on either P-PLLA or unpoled samples was observed. This study demonstrated that poled piezoelectric PLLA substrates induce substantially higher level of Ca-P formation than electrically neutral substrates and only N-PLLA, however, can improve Ca-P formation after immersion in SCS.

Abstract: Poly 3-hydroxybutyrate (PHB) as a kind of polysaccharides has been proved promising for tissue engineering because of its biocompatibility and biodegradability. But its poor mechanical properties and hydrophilicity limit its application. In order to explore a new useful porch to improve the performance of PHB-based GTR membrane, membrane composed of nano-HA / PHB composite was manufactured through the air/jet electrospinning process which can potentially generate nanometer scale diameter fibers and enlarge surface area of materials while maintaining high porosity. Successively, the biomineralization behavior of the membrane in supersaturated calcification solution (SCS) was studied. The Results of this investigation show that the successfully manufactured porous nano-HA/PHB membrane has high activity in SCS and its ability of inducing the formation of mineral crystal in vitro than that of the unfilled PHB membrane. It can be concluded that the addition of nano-HA and the novel technology could improve the performance of the PHB-based GTR membrane.

Abstract: Based on the molecular recognition theory, an organic molecules model was designed to induce the hydroxyapatite crystallization, to build a tooth-like calcium phosphate/hydroxyapatite under a controllable way in vitro. The cross-linking of collagen on the dentin surface and gelatin was optimized by varying the molar ratio of N,N-(3-dimethylaminopropyl)- N'-ethyl-carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) at a constant EDC concentration. CaCl2 and Na3PO4-12H2O solutions were added after the crosslinking process. The whole process requires repeating the crosslinking and mineralization process for five times. The obtained composite were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) as well as energy dispersive X-ray photoelectron spectroscopy (XPS). The results showed that the dentinal tubule were blocked by neonatal hydroxyapatite layer which has a continuous structure of columns crystal with size of 10-40nm. Furthermore, there was column crystal with parallel direction inside, similar to the crystal array in the top of enamel rod. This study showed that the specific organic molecule model can be used as a potential effective crystal growth modifier.