Arsenic accumulation, distribution and source analysis of rice in a typical growing area in north China.

Rice (Oryza sativa) is believed to be a major source of arsenic (As) exposure in humans, especially in Asia. In this study, As accumulation, distribution and source analysis of rice are investigated in five sites (SZ, QH, XZ, WS and JX) in the Nansi Lake area, an important rice-growing region in north China. Findings show that total As average concentrations were 6.3-13.6 mg kg-1 and 5.5-9.9 µg L-1 in paddy soil and irrigation water, respectively. Inorganic arsenic As(III) and dimethylarsinic acid DMAs(V) were the major speciation in polished rice, with a small proportion of As(V) evident. Notably, the percentage of As(III) increased by 63.9-68.5%. Based on survey data, the addition of total As to farm soil due to fertilizer application was 31.5-11,580 mg per hectare per year. According to the results of Spearman's rank correlation analysis and Principal Component Analysis (PCA), As levels in soil and irrigation water may be important factors influencing As concentration in rice.

Nebivolol protects against myocardial infarction injury via stimulation of beta 3-adrenergic receptors and nitric oxide signaling.

Nebivolol, third-generation ß-blocker, may activate ß3-adrenergic receptor (AR), which has been emerged as a novel and potential therapeutic targets for cardiovascular diseases. However, it is not known whether nebivolol administration plays a cardioprotective effect against myocardial infarction (MI) injury. Therefore, the present study was designed to clarify the effects of nebivolol on MI injury and to elucidate the underlying mechanism. MI model was constructed by left anterior descending (LAD) artery ligation. Nebivolol, ß3-AR antagonist (SR59230A), Nitro-L-arginine methylester (L-NAME) or vehicle was administered for 4 weeks after MI operation. Cardiac function was monitored by echocardiography. Moreover, the fibrosis and the apoptosis of myocardium were assessed by Masson's trichrome stain and TUNEL assay respectively 4 weeks after MI. Nebivolol administration reduced scar area by 68% compared with MI group (p<0.05). Meanwhile, nebivolol also decreased the myocardial apoptosis and improved the heart function after MI (p<0.05 vs. MI). These effects were associated with increased ß3-AR expression. Moreover, nebivolol treatment significantly increased the phosphorylation of endothelial NOS (eNOS) and the expression of neuronal NOS (nNOS). Conversely, the cardiac protective effects of nebivolol were abolished by SR and L-NAME. These results indicate that nebivolol protects against MI injury. Furthermore, the cardioprotective effects of nebivolol may be mediated by ß3-AR-eNOS/nNOS pathway.

A shape memory stent of poly(ε-caprolactone-co-DL-lactide) copolymer for potential treatment of esophageal stenosis.

Biodegradable polymer stent with shape memory effect is expected to be developed in the treatment of esophageal stenosis, most likely due to traditional stents having such shortages as considerable rigidity and nondegradation. A tubular stent with the inner and outer diameters of 28 and 30 mm was manufactured from biodegradable poly(ε-caprolactone-co-DL-lactide) (PCLA) copolymer consisting of ε-caprolactone and DL-lactide at a weight ratio of 10/90. A series of tests were accomplished to investigate its properties including shape memory effects (SMEs), compression property and influence of in vitro degradation of polymer matrix on its shape recovery and dilation force. Significantly, an implantation of the stent into a dog model was performed to evaluate its function for the treatment of esophageal stenosis. The deformed stent needs about 36 s to recover its initial shape in vitro in 37°C warm water. The primary animal experiment in vivo has revealed that the implanted deformed stent could be triggered by body temperature and expectedly returned to a nearly-round shape to support esophageal wall. Therefore, the biodegradable intelligent polymer stent may be great potential to displace the conventional metallic stents for the esophageal stenosis therapy.

A biodegradable shape-memory nanocomposite with excellent magnetism sensitivity.

This paper reports a kind of biodegradable nanocomposite which can show an excellent shape-memory property in hot water or in an alternating magnetic field with f = 20 kH and H = 6.8 kA m(-1). The nanocomposite is composed of crosslinked poly(epsilon-caprolactone) (c-PCL) and Fe(3)O(4) nanoparticles. The crosslinking reaction in PCL with linear molecular structure was realized using benzoyl peroxide (BPO) as an initiator. The biocompatible Fe(3)O(4) magnetite nanoparticles with an average size of 10 nm were synthesized according to a chemical coprecipitation method. The initial results from c-PCL showed crosslinking modification had brought about a large enhancement in shape-memory effect for PCL. Then a series of composites made of Fe(3)O(4) nanoparticles and c-PCL were prepared and their morphological properties, mechanical properties, thermodynamic properties and shape-memory effect were investigated in succession. Significantly, the photos of the shape-memory process confirmed the anticipatory magnetically responsive shape-recovery effect of the nanocomposites because inductive heat from Fe(3)O(4) can be utilized to actuate the c-PCL vivification from their frozen temporary shape. All the results imply a very feasible method to fabricate shape-memory PCL-based nanocomposites since just a simple modification is required. Additionally, this modification would endow an excellent shape-memory effect to all other kinds of polymers so that they could broadly serve in various fields, especially in medicine.

In situ preparation and characterization of a novel gelatin/poly(D,L-lactide)/hydroxyapatite nanocomposite.

A novel biodegradable polymer-ceramic nanocomposite was prepared using the in situ preparation method, which consisted of gelatin (gel), poly(D,L-lactide) (PDLLA), and hydroxyapatite (HA) nanofibers. In this article, the HA nanofibers with length/diameter (L/D) ratio of 19.8 in gel/PDLLA/HA nanocomposites were synthesized and precipitated in polymeric matrix by one-step hydrothermal mineralization. The crystalline phases, structural morphology, mechanical characterization, and chemical interaction of gel/PDLLA/HA nanocomposites were investigated by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, mechanical test, and Fourier transform infrared spectroscopy. The results showed that the crystalline HA nanofibers were uniformly mineralized in gel and PDLLA matrix and the interaction between Ca(2+) in HA (nanofibers and negative-charged functional groups in gel and PDLLA molecular chains was formed. Thus, the schematic model of two polymeric chains bridged by inorganic nanofibers was designed on the basis of the experimental results. Moreover, it can clearly explain why the mechanical properties of gel/PDLLA/HA nanocomposites turned strong.

Pressure-induced crystal memory effect of spider silk proteins.

Spider silk is a novel material with high strength and toughness and is lightweight, making it attractive for high-performance fiber and biomedical applications. The amino acid sequence and molecular architecture of spider silk protein are becoming known gradually with science and technology development. However, its relationship of structure and function is a puzzle which attracts materials scientists to unveil it. In this study we investigated the changes of the crystal structure as a result of different processing techniques to spider silk protein. Although the crystallization of biomacromolecules is very difficult and complex, we did observe the crystal of electrospun spider silk protein treated by external high pressure in its solid state. This study also provides us a simple and effective method to prepare protein crystals. It is most important that this is the first time that we found spider silk protein as a result of electrospinning that had a crystallization memory property when it was stimulated by a high pressure, which will further extend the list of its particular properties. This finding will also lead us to study it deeply and widen our research on proteins of other organisms.

Shape memory effect of poly(D,L-lactide)/Fe3O4 nanocomposites by inductive heating of magnetite particles.

In this paper, the preparation of biocompatible poly(D,L-lactide) (PDLLA)/magnetite (Fe(3)O(4)) nanocomposites and their shape memory effect are reported. Fe(3)O(4) nanoparticles with an average size of 20 nm were synthesized by chemical co-precipitation and mixed uniformly with a PDLLA matrix. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and mechanical testing were carried out to determine the micro-surface morphology, glass transition temperature (T(g)), functional groups change and mechanical properties of the PDLLA/Fe(3)O(4) nanocomposites. The interesting shape memory behavior of the nanocomposites induced by an ultrasonic alternating magnetic field were also observed. SEM and DSC showed that there was a close interaction between the polymer matrix and the magnetic nanoparticles. Formation of weak hydrogen bonds between the C=O in PDLLA and Fe-OH groups of the surface of nano-crystalline Fe(3)O(4) was examined by FTIR. The PDLLA/Fe(3)O(4) nanocomposites displayed a desirable shape memory effect.

Preparation and characterization of a novel electrospun spider silk fibroin/poly(D,L-lactide) composite fiber.

In the paper, we successfully prepared spider silk fibroins (Ss)/poly( d, l-lactide) (PDLLA) composite fibrous nonwoven mats for the first time to the best of our knowledge. The morphology of the fibers was observed by a scanning electron microscope (SEM) and transmission electron microscope (TEM). The secondary structure change of the spidroin before and after electrospinning was characterized using Fourier transform infrared spectroscopy (FT-IR). Herein, a qualitative analysis of the conformational changes of the silk protein was performed by analyzing the FT-IR second-derivative spectra, from which quantitative information was obtained via the deconvolution of the amide I band. A mechanical test was carried out to investigate the tensile strength and the elongation at break. A water contact angle (CA) measurement was also performed to characterize surface properties of the fibers. The cytotoxicity of electrospun PDLLA and Ss-PDLLA nonwoven fibrous mats was evaluated based on a CCL 81(Vero) cells proliferation study. The results showed that the hydrophilic and mechanical property of the composite fiber were improved by introducing spidroin.

Effect of in vitro degradation of poly(D,L-lactide)/beta-tricalcium composite on its shape-memory properties.

The in vitro degradation characteristic and shape-memory properties of poly(D,L-lactide) (PDLLA)/beta-tricalcium phosphate (beta-TCP) composites were investigated because of their wide application in biomedical fields. In this article, PDLLA and crystalline beta-TCP were compounded and interesting shape-memory behaviors of the composite were first investigated. Then, in vitro degradation of the PDLLA/beta-TCP composites with weight ratios of 1:1, 2:1, and 3:1 was performed in phosphate buffer saline solution (PBS) (154 mM, pH 7.4) at 37 degrees C. The effect of in vitro degradation time for PDLLA/beta-TCP composites on shape-memory properties was studied by scanning electron microscopy, differential scanning calorimetry, gel permeation chromatography, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The changes of structural morphology, glass transition temperature (T(g)), molecular weight, and weight loss of composites matrix and pH change of degradation medium indicated that shape-memory effects at different degradation time were nonlinearly influenced because of the breaking down of polymer chain and the formation of degradation products. Furthermore, the results from XRD and FTIR implied that the degradation products, for example, hydroxyapatite (HA), calcium hydrogen phosphate (CaHPO(4)), and calcium pyrophosphate (Ca(2)P(2)O(7)) phases also had some effects on shape-memory properties during the degradation.