Hua Tong

Preparation and characterization of homogeneous chitosan–polylactic acid/hydroxyapatite nanocomposite for bone tissue engineering and evaluation of its mechanical properties

Homogeneous nanocomposites composed of hydroxyapatite and chitosan in the presence of polylactic acid were synthesized by a novel in situ precipitation method. The morphological and compositional properties of composites were investigated. Hydroxyapatite nanoparticles in a special rod-like shape with a diameter of about 50nm and a length of about 300nm were distributed homogeneously within the chitosan-polylactic acid matrix. The interaction between the organic matrix and the inorganic crystallite and the formation mechanism of the rod-like nanoparticles were also studied. The results suggested that the formation of the special rod-like nanoparticles could be controlled by a multiple-order template effect. High-resolution images showed that the rod-like inorganic particles were composed of randomly orientated subparticles about 10nm in diameter. The mechanical properties of the composites were evaluated by measuring their compressive strength and elastic modulus. The data indicated that the addition of polylactic acid can make homogeneous composites scaffold resist significantly higher stress. The elastic modulus of the composites was also improved by the addition of polylactic acid, which can make them more beneficial for surgical applications.

Surface Functionalization of Titanium with Chitosan/Gelatin via Electrophoretic Deposition: Characterization and Cell Behavior

The electrophoretic deposition (EPD) is a versatile and cost-effective technique for fabricating advanced coatings. In this study, chitosan/gelatin (CS/G) coatings were prepared on titanium substrates via EPD. The prepared coatings were characterized using fluorescence microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and shear bond strength testing. It was found that CS/G coatings had a similar macroporous structure. The gelatin content in the CS/G coatings gradually increased with the increase of the gelatin in the blend solutions. The shear bond strength of the CS/G coatings also increased with the increasing gelatin content. In vitro biological tests demonstrated that human MG63 osteoblast-like cells achieved better affinity on the coatings with higher gelatin content. Therefore, it was concluded that EPD was an effective and efficient technique to prepare CS/G coatings on the titanium surface and that CS/G coatings with higher gelatin content were promising candidates for further loading of functional agents.

Investigation of the effects of 30% hydrogen peroxide on human tooth enamel by Raman scattering and laser-induced fluorescence.

The safety of tooth bleaching, which is based upon hydrogen peroxide (HP) as the active agent, has been questioned. Our aim was to investigate the effects of 30% HP on human tooth enamel. The specimens were divided randomly into three groups and treated with distilled water, HCl, and HP, respectively. Raman scattering and laser-induced fluorescence of enamel were determined before and after treatment. Microhardness testing and scanning electron microscopy were also used. The results of Raman scattering showed that the Raman relative intensity of enamel changed significantly after HP and HCl treatment. These findings were consistent with the results of microhardness testing and morphological observations. In addition, a small band at 876 cm(-1) due to O-O stretching of HP became pronounced during HP treatment, which provided direct evidence that HP has the ability to penetrate enamel. Meanwhile, the results of laser-induced fluorescence revealed that HP caused the greatest fluorescence reduction. This suggested that the organic matter in enamel might be greatly affected by HP, which was also supported by the results of microhardness. It can be concluded, therefore, that the 30% HP may have adverse effects on the mineral and the organic matter of human tooth enamel.

Effects of Hydrogen Peroxide on Human Dentin Structure

It has been hypothesized that hydrogen peroxide (H2O2) bleaching may cause destruction of dentin by a mechanism of protein oxidation. However, to our knowledge, there has been no direct chemical evidence to validate this viewpoint. To investigate the effects of H2O2 on the structure of human dentin, we used Fourier transform infrared spectroscopy (FTIR) and attenuated total reflection (ATR) spectroscopy. Human intact dentin specimens were treated either with 30% H2O2 or Hanks’ balanced salt solution (HBSS). Significant differences were observed in ATR spectra parameters. Additionally, demineralized dentin specimens were also tested. They were completely dissolved in the H2O2, but remained intact in the 0.1 N HCl and HBSS. The results suggested that H2O2 attacked both the organic and mineral components of dentin. Destruction of the organic components was mainly because of the oxidizing ability of H2O2, while changes in the mineral components were probably due to its acidity.

Perivascular space: possible anatomical substrate for the meridian.

BACKGROUND Despite the meridian system being an important concept in Traditional Chinese Medicine (TCM), modern biology and Western medical systems have failed to find an anatomic substrate. Since the 1960s, a variety of phenomena along meridians have been reported, among which quite a few suggest that along meridians there is a fluid pathway (but not blood vessels or lymphatics). On the other hand, perivascular space (PVS) has been demonstrated to be a body fluid pathway in addition to blood vessels and lymphatics in some mammalian tissues, such as brain, thymus, and lung. OBJECTIVES The present study was designed to examine the relationship between PVS and the meridian. We studied characteristics of the tissues around the blood vessels along the Stomach Meridian of Foot-Yangming and the Gallbladder Meridian of Foot-shaoyang, with the goal of identifying anatomical structure corresponding to the meridian described in TCM. DESIGN AND RESULTS Through perivascular dye injection and frozen section histology, we found that there is PVS around the blood vessels along the meridians, and it is a fluid pathway. Subsequent physiologic studies revealed that the PVS shows significantly greater electrical conductivity and significantly higher partial oxygen pressure (pO(2)) compared to medial and lateral tissues. CONCLUSIONS The PVS along the meridians has properties offering good explanation for the meridian phenomena. The work sheds new light on the studies of meridians and may contribute to research on the mechanism of Chinese acupuncture.

In situ analysis of the organic framework in the prismatic layer of mollusc shell

A novel in situ analytic approach was constructed by means of ion sputtering, decalcification and deprotein techniques combining with scanning electron microscopy (SEM) and transmission electron microscope (TEM) ultrastructural analysis. The method was employed to determine the spatial distribution of the organic framework outside and the inner crystal and organic/inorganic interface spatial geometrical relationship in the prismatic layer of cristaris plicate (leach). The results show that there is a substructure of organic matrix in the intracrystalline region. The prismatic layer forms according to strict hierarchical configuration of regular pattern. Each unit of organic template of prismatic layer can uniquely determine the column crystal growth direction, spatial orientation and size. Cavity templates are responsible for supporting. limiting size and shape and determining the crystal growth spatial orientation, while the intracrystal organic matrix is responsible for providing nucleation point and inducing the nucleation process of calcite. The stereo hierarchical fabrication of prismatic layer was elucidated for the first time.

Preparation and evaluation of collagen-silk fibroin/hydroxyapatite nanocomposites for bone tissue engineering.

A new in situ precipitation technique was developed to synthesize collagen-silk fibroin/hydroxyapatite nanocomposites. The componential properties and morphological of nanocomposites were investigated. It was revealed that the inorganic phase in the nanocomposite was carbonate-substituted hydroxyapatite with low crystallinity. Morphology studies showed that hydroxyapatite particles with size ranging from 30 to 100 nm were distributed uniformly in the polymer matrix. According to the TEM micrographs, inorganic particles were composed of more fine sub-particles whose diameters were between 2 and 5 nm in size without regular crystallographic orientation. The mechanical properties of the composites were evaluated by measuring their elastic modulus. The data indicated that the elastic modulus of nanocomposites was improved by the addition of silk fibroin. Finally, the cell biocompatibility of the composites was tested in vitro, which showed that they have good biocompatibility. These results suggest that the collagen-silk fibroin/hydroxyapatite nanocomposites are promising biomaterials for bone tissue engineering.

Beneficial effects of hydroxyapatite on enamel subjected to 30% hydrogen peroxide.

OBJECTIVES To evaluate the effect of combination of hydroxyapatite (HA) and hydrogen peroxide (HP) on color, microhardness and morphology of human tooth enamel. METHODS Forty-eight human dental blocks were obtained from 12 pairs of premolars and were randomly divided into four groups. Group DW was treated with distilled water, group HP with 30% HP, group HA+DW with HA mixed with distilled water and group HA+HP with HA mixed with 30% HP. Baseline and final color measurements and microhardness test were carried out before and after bleaching experiments. Two specimens from each group were selected for morphological investigation after final tests. RESULTS The DeltaE of group HP and HA+HP were significantly higher than those of group DW (p=0.000 and p=0.000) and group HA+DW (p=0.000 and p=0.000). The percentage microhardness loss of group HA+HP was significantly lower than that of group HP (p=0.047), but significantly higher than those of group DW (p=0.000) and group HA+DW (p=0.000). The obvious variation of morphology was only observed on enamel surfaces in group HP. CONCLUSIONS This study suggested that combination of HA and HP was effective in tooth whitening. HA could significantly reduce the microhardness loss of enamel caused by 30% HP and keep enamel surface morphology almost unchanged.

Application of a new hybrid organic-inorganic monolithic column for efficient deoxyribonucleic acid purification

A new hybrid organic-inorganic monolithic column for efficient deoxyribonucleic acid (DNA) extraction was prepared in situ by polymerization of N-(beta-aminoethyl)-gamma-aminopropyltriethoxysilane (AEAPTES) and tetraethoxysilane (TEOS). The main extraction mechanism was based on the Coulombic force between DNA and the amino silica hybrid monolithic column. DNA extraction conditions, such as pH, ion concentration and type, and loading capacity, were optimized online by capillary electrophoresis with laser-induced fluorescence detection. Under optimal condition, a 6.0-cm monolithic column provided a capacity of 48 ng DNA with an extraction efficiency of 74+/-6.3% (X+/-RSD). The DNA extraction process on this monolithic column was carried out in a totally aqueous system for the successful purification of DNA and removal of proteins. The PBE2 plasmid could be extracted from Bacillus subtilis (B. subtilis) crude lysate within 25 min, and the purified DNA was suitable for the amplification of a target fragment by polymerase chain reaction. This study demonstrates a new attractive solid-phase support for DNA extraction to meet the increasingly miniaturized and automated trends of genetic analyses.

Incorporation of homogeneous Co3O4 into a nitrogen-doped carbon aerogel via a facile in situ synthesis method: implications for high performance asymmetric supercapacitors

A novel high-performance electrode material, nitrogen-doped carbon aerogel/cobalt oxide (NCA/Co3O4) material, was prepared by a facile, one step and in situ coating method, followed by a freeze-drying process. The effects of different amounts of Co3O4 on the structural properties, specific surface areas, elemental compositions and electrochemical performance of the composite electrodes were investigated. Consequently, the electrode with 75% mass content of Co3O4 exhibited excellent electrochemical performance, in particular, a high specific capacitance of 616 F g−1 at a current density of 1 A g−1, excellent rate capability (445 F g−1 at 20 A g−1) and outstanding cycle performance. In addition, the asymmetric supercapacitor assembled with NCA/Co3O4-3 and NCA electrodes could be cycled in a high voltage range of 1.5 V and deliver a maximum energy density of 33.43 W h kg−1 at a power density of 375 W kg−1. The enhanced electrochemical performance is attributed to the complementary contributions of the 3D interconnected porous structure and the efficient pseudocapacitance of the uniformly dispersed Co3O4 nanoparticles. The preparation method offers a new fabrication strategy to in situ fabricate carbon-supported metal oxide electrodes for high-performance energy storage applications.