Jiming Hu

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.

Hydrogen peroxide biosensor based on the direct electrochemistry of myoglobin immobilized on silver nanoparticles doped carbon nanotubes film

A novel H(2)O(2) biosensor has been fabricated based on the direct electrochemistry and electrocatalysis of myoglobin (Mb) immobilized on silver nanoparticles doped carbon nanotubes film with hybrid sol-gel techniques. A pair of redox peaks with peak separation of 160 mV and formal potential of -0.295V was observed at this composite film, corresponding to the direct electrochemistry of Mb. The heterogeneous rate constant was estimated to be 0.41s(-1). Under optimum conditions, the amperometric determination of H(2)O(2) was performed with a linear range of 2.0 x 10(-6)-1.2 x 10(-3)molL(-1) and a detection limit of 3.6 x 10(-7)mol/L (S/N=3). The Michealis-Menten constant was also estimated to be 1.62mmolL(-1). The proposed biosensor showed favorable reproducibility, stability, selectivity and accuracy, and has been used to determine H(2)O(2) in real samples with favorable recoveries.

Nuclear targeted nanoprobe for single living cell detection by surface-enhanced Raman scattering.

We present a novel nuclear targeting nanoprobe based on peptide functionalized gold nanoparticles and its surface-enhanced Raman scattering (SERS) in living cells. For the first time, we probe an original SERS signal from the living cell nucleus by using high-selectivity functionalized gold nanoparticles. The gold nanoparticles conjugated with SV-40 large T nuclear localization signal (NLS) peptide successfully enter the cell nucleus after the incubation with Hela cells and deliver the spatially localized chemical information of the nucleus, as well as the signature of chemicals that intruded subsequently. This new targeted nanoprobe is a nontoxic, biocompatible method for biological research, provided with multiple functions comprising subcellular targeting, intracellular imaging, and real-time SERS detection.

Detection of hepatitis B virus by piezoelectric biosensor.

A highly sensitive piezoelectric HBV DNA biosensor has been developed based on the sensitive mass-transducing function of the quartz crystal microbalance and the speciality of nucleic acid hybridization reaction. HBV nucleic acid probe was immobilized onto the gold electrodes of a 9 MHz AT-cut piezoelectric quartz crystal with the polyethyleneimine adhesion, glutaraldehyde cross-linking (PEI-Glu) method or the physical adsorption method. The coated crystal with the PEI-Glu method to immobilized HBV nucleic acid probe showed the better results than the physical adsorption method with respect to sensitivity reproducibility and stability. The frequency shifts of hybridization have better linear relationship with the amount of HBV DNA, when the amount was in range 0.02-0.14 microg/ml. The crystal could be regenerated nearly five times without perceptible decrease of sensitivity.

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.

A Method for Removing Self-Assembled Monolayers on Gold

Self-assembled monolayers (SAMs) have been widely used in studying interfacial phenomena, biological processes, electrochemistry, photoelectrochemistry, photoactivity and molecular interaction. Much research has been carried out in fabricating and removing SAMs on different substrates. In this work, we report for the first time, to our knowledge, that SAMs of thiolates on gold can be removed by immersing SAMs in 0.5 M NaBH 4 solution for 10 min. The procedure of removing thiolates was very convenient. Cyclic voltammetry, surface-enhanced Raman spectroscopy, and X-ray photoelectron spectroscopy were used to characterize this process. The results indicated that the SAMs of thiolates on gold can be removed efficiently by NaBH 4.

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.

Additive-Free Synthesis of In2O3 Cubes Embedded into Graphene Sheets and Their Enhanced NO2 Sensing Performance at Room Temperature

In this report, we developed an additive-free synthesis of In2O3 cubes embedded into graphene networks with InN nanowires (InN-NWs) and graphene oxide (GO) as precursors by a facile one-step microwave-assisted hydrothermal method. In absence of GO, the InN-NWs maintained their chemical composition and original morphology upon the same treatment. At varying mass ratios of InN-NWs and GO, the different morphologies and distributions of In2O3 could be obtained on graphene sheets. The uniform distribution, which is usually considered favorable for enhanced sensing performance, was observed in In2O3 cubes/reduced graphene oxide (rGO) composites. The room-temperature NO2 sensing properties of the In2O3 cubes/rGO composites-based sensor were systematically investigated. The results revealed that the sensor exhibited a significant response to NO2 gas with a concentration lower to 1 ppm, and an excellent selectivity, even though the concentrations of interferential gases were 1000 times that of NO2. The enhanced NO2 sensing performances were attributed to the synergistic effect of uniformly distributed In2O3 cubes and graphene sheets in the unique hybrid architectures without the interfering of extra additives.

Effects of electroacupuncture on gastric myoelectric activity and substance P in the dorsal vagal complex of rats

Acupuncture has been widely applied to treat gastrointestinal diseases in the clinic. However, its precise mechanism remains unknown. In the present study, effects of electroacupuncture (EA) at Zusanli acupoints (ST36) on gastric myoelectric activity and substance P (SP) in the dorsal vagal complex (DVC) were observed. EA at ST36 significantly increased the frequency of slow waves and the frequency of the spike potentials superimposed on the slow waves, which persisted for 90 min after cessation of EA and was completely abolished after bilateral vagotomy. Meanwhile, the mean optical density of SP immunoreactive fibers in the DVC increased following EA. The results suggested that EA at ST36 promoted the gastric myoelectric activity, which was regulated by the vagus, and SP in the DVC may be involved in the excitatory effects. Furthermore, EA had a relative long-term post-effect. We presumed that DVC may be a supraspinal center in the effect of EA on gastric function.

A novel biosensor based on single-layer MoS2 nanosheets for detection of Ag+

In this work, we use for the first time single layer MoS2 as the fluorescence quencher to design a detection method for Ag(+) with excellent robustness, selectivity and sensitivity. To maintain the ultrathin MoS2, bulk MoS2 materials have been exfoliated by intercalation with lithium followed by reaction with water. As-prepared two-dimensional MoS2 not only has good water-solubility but also obtains high fluorescence quenching efficiency within 5 min. Importantly, the detection limit of this assay for Ag(+) (1 nM) was lower than the maximum limitation guided by the United States Environmental Protection Agency (EPA) and the World Health Organization (WHO). Further, this new Ag(+) probe was demonstrated in monitoring Ag(+) in lake water samples with satisfactory results.