Xinhua Xu

Controllable biodegradability, drug release behavior and hemocompatibility of PTX-eluting magnesium stents.

Cardiovascular magnesium-based stents have been already applied in patients. However, their high corrosion rate hinders their clinical application. In this study, we adopt a new approach in the design of a Mg-based stent to improve the biodegradation rate and the drug release rate. By fabricating a micro-arc oxidation/poly-l-lactic acid (MAO/PLLA) composite coating on the magnesium alloy AZ81 substrate, the corrosion resistance decreased and the biodegradation rate became controllable. The drug release coating was composed of one Poly(dl-lactide-co-glycolide)/paclitaxel (PLGA/PTX) layer and one pure PLGA blank layer without paclitaxel, and this coating also functions to provide controlled biodegradation rate of the stent. The drug release rate was controlled by controlling the ratio of the LA:GA of the PLGA without PTX. The scanning electron microscopy (SEM) images were used to demonstrate the morphology of the samples before and after this modification. The blood compatibility of the samples was demonstrated by the platelet adhesion test. The drug release was determined by ultraviolet-visible (UV-visible) spectrophotometer. The result showed that the PLLA effectively sealed the micro-cracks and micro-holes on the surface of the MAO coating to give controllable biodegradation of the AZ81. The drug release rate of PTX exhibited a nearly linear sustained-release profile with no significant burst releases that would come from the uncontrolled oxidation/corrosion of AZ81. The samples modified had better hemocompatibility than 316L stainless steel.

Anticorrosion and cytocompatibility behavior of MAO/PLLA modified magnesium alloy WE42

Recently, biodegradable magnesium alloys have been introduced in the field of cardiovascular stents to avoid the specific drawbacks of permanent metallic implants. However, the major obstacle of the clinical use of magnesium-based materials is their rapid corrosion rate. In this paper, a composite micro-arc oxidation/poly-l-lactic acid (MAO/PLLA) coating was fabricated on the surface of the magnesium alloy WE42 to improve its corrosion resistance and the cytocompatibility of the modified materials was also investigated for safety aim. In our study, the morphology of materials was analyzed by Scanning electron microscopy. Potentiodynamic polarization was used to evaluate the corrosion behavior of the samples and corrosion weight loss was used to demonstrate their degradation rate. Furthermore, we applied cytotoxicity test in testing the cytocompatibility of the modified samples. The results showed that the PLLA coating effectively sealed the microcracks and micropores on the surface of the MAO coating by physical interlocking to interfere the corrosion ions. The corrosion rate was decreased and the cyototoxicity test showed that the MAO/PLLA composite coating WE42 had good cytocompatibility.

Novel hollow Sn–Cu composite nanoparticles anodes for Li-ion batteries prepared by galvanic replacement reaction

Nanostructured hollow Sn–Cu multi-phase composite nanoparticles anode that contains Sn and Cu6Sn5 was synthesized via galvanic replacement reaction using Sn nanoparticles as a sacrificial template. The sacrificial oxidation of Sn and simultaneous reduction of Cu on the surface because of the redox potential difference is proposed to account for the formation of hollow Sn–Cu nanostructures. The structural evolution of the Sn–Cu hollow nanoparticle, in the process of galvanic replacement and structure, composition changes during charge/discharge processes were studied based on scanning electron microscope, X-ray powder diffraction, transmission electron microscopy, and energy dispersive X-ray spectroscopy investigations. The electrochemical properties of the samples were evaluated by galvanostatic discharge–charge cycling, cyclic voltammetry, and electrochemical impedance spectroscopy. Compared with solid Sn–Cu nanoparticles, hollow Sn–Cu nanoparticles showed better capacity retention. The improved electrochemical performance may be attributed to the stable hollow structure and the combination of Cu6Sn5. The facile solution-based process and excellent cycling stability show great potential of the multi-phase Sn–Cu hollow composite nanoparticles as an anode material for lithium-ion batteries.

A novel non-enzymatic amperometric glucose sensor based on a hollow Pt–Ni alloy nanotube array electrode with enhanced sensitivity

A non-enzymatic electrode is proposed as a glucose sensor based on Pt-replaced Ni nanowires which are prepared by constant current electro-deposition within the anodic alumina membrane and galvanic replacement reaction. The amperometric detection of glucose shows a wide linear range up to 13.5 mM with a high sensitivity of 124.17 μA mM−1 cm−2 and a low detection limit of 32 μM (S/N = 3). More important, another attractive feature of the Pt–Ni NATs electrode is the quite low working potential at −0.35 V (versus SCE), which is favorable to avoid the influence of possible intermediates. Furthermore, the non-enzymatic glucose sensors reveal good stability and repeatability. All these excellent properties of the Pt–Ni NATs electrodes can be attributed to the large active area supported by the unique nanotube array structure.

A coral-inspired nanoscale design of Sn–Cu/PANi/GO hybrid anode materials for high performance lithium-ion batteries

A facile and scalable synthesis approach is developed for fabrication of a three-dimensional (3D) polyaniline (PANi)/graphene oxide (GO) hybrid hydrogel evenly embed with hollow Sn–Cu nanoparticles (Sn–Cu NPs) as high performance anode for lithium-ion batteries. The hierarchical conductive hydrogel was prepared via in situ polymerization of aniline monomer on the surface of Sn–Cu NPs and GO nanosheets. The morphology and structure of the resulting hybrid materials have been characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The hierarchical conductive hydrogel framework with dendritic PANi nanofibers and 2D GO nanosheets serve as a continuous 3D electron transport network and high porosity to accommodate the volume expansion of Sn–Cu NPs. The PANi coating plays an “artificial SEI” function to preserve the structural and interfacial stabilization of Sn–Cu NPs during the cycling processes. As a consequence of this 3D hybrid anode, an extremely long stable cycling performance is achieved with reversible discharge capacity over 693 mA h g−1 after 200 cycles at current rate of 0.2 C and a reversible capacity of 371 mA h g−1 retention at a much higher current rate of 2 C, suggesting that this novel Sn–Cu/PANi/GO composite is a promising candidate for energy storage applications.

Effect of Short Carbon Fibers and Carbon Nanotubes Dispersed by Utilizing Hollow Glass Beads as Carriers on the Tensile and Curing Properties of Epoxy Resin

The effects of the combination of silane functionalized hollow glass beads (silanized HGBs), acid functionalized carbon nanotubes (oxidized CNTs), and short carbon fibers (SCFs) on the tensile properties of epoxy (EP) resin were investigated. The combined utilization of silanized HGBs, oxidized CNTs and SCFs led to a pronounced synergy in the tensile properties of the SCF/HGB/CNT/EP composites. The composites exhibited greater tensile strength and Youngs modulus than the neat EP, clearly. The mechanism of such synergetic effect was analyzed by tensile fracture studies using SEM. In addition, by analyzing the DSC curves, the curing temperatures of the composites were obtained.

Morphology, Structure, and Crystallization of LaCl Modified Hollow Glass Microspheres/ Poly(vinylidenefluoride) Composites

Poly(vinylidene fluoride)/hollow glass microspheres (PVDF/HGMs) composites were prepared by using lanthanum chloride surface modified HGMs. The morphology, structure, and crystallization of the PVDF/HGMs composites were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC), respectively. The results showed that the interaction between the HGMs and the PVDF was improved by lanthanum chloride modification. The crystal structure of the PVDF was not changed by the HGMs, but the crystallinity was decreased. In addition, the Jeziorny and the Mo methods were used to analyze the non-isothermal crystallization kinetics. The results showed that the HGMs decreased the crystallization rates and extended the crystallization time of the PVDF.

Synthesis of Sn–Co@PMMA nanowire arrays by electrodeposition and in situ polymerization as a high performance lithium-ion battery anode

Transition metals have attracted much attention due to their high energy density in lithium-ion batteries (LIBs). However, the huge volume change and the fast capacity fading still limit their application. If the microstructure of the electrode materials can be designed properly, the volume change problems encountered during lithiation and delithiation could be alleviated to some extent. Here, novel three-dimensional (3D) hybrid Sn–Co nanowire arrays coated by poly(methyl methacrylate) (Sn–Co@PMMA NWs) are synthesized via a simple electrodeposition method followed by in situ emulsion polymerization. The electrode structure is well preserved after repeated Li-ion insertion/extraction, indicating that the positive synergistic effect of the Sn–Co NWs and uniform PMMA layer could effectively accommodate the volume expansion of tin anode materials. The electrochemistry results demonstrate that the Sn–Co@PMMA NWs electrode exhibits a high reversible capacity, a high initial coulombic efficiency, a good rate capability, and an improved capacity retention compared with the bare Sn–Co NWs electrode. This proposed nanoengineering strategy is proven to be an ideal candidate for the development of high performance anode for LIBs.

Fabrication and Properties of Hollow Glass Beads Loaded Carbon Nanotubes/Epoxy Composites

Hollow glass beads loaded carbon nanotubes (HGB-CNT), prepared via an amidation reaction, were used for fabricating epoxy-matrix composites. The morphology of the as-prepared beads, and the tensile properties, electrical conductivity, and thermal behaviors of as-fabricated composites were evaluated. Field emission scanning electron microscopy and differential scanning calorimetry results showed that the dispersion of CNT in the matrix was improved as compared to control epoxy/HGB/CNT samples prepared using a conventional melt mixing method. Moreover, the tensile strength and elongation at break results illustrated that when CNT loading was 1.14 wt%, those of the epoxy/HGB-CNT composites were each ca. 25% more than the control samples. In addition, electrical conductivity results showed that when CNT loading was 1.59 wt%, the electrical conductivity of the epoxy/HGB-CNT composites increased by six orders as compared to that of the pristine epoxy and by four orders compared to that of the control samples.

Phase Structure, Thermal, and Mechanical Properties of Polypropylene/Hollow Glass Microsphere Composites Modified with Maleated Poly(ethylene-octene)

Maleated poly(ethylene-octene) (POE-g-MAH), as a compatilizer and toughener, was incorporated in polypropylene/hollow glass microspheres (PP/HGM) binary composites, and the phase structure and thermal and mechanical properties of these composites were investigated. Scanning electron microscopy analysis indicated that the phase structure of ternary composites could be controlled by POE-g-MAH and the surface treatment of HGM. Fourier transform infrared spectroscopy revealed that there was an amidation reaction between the treated HGM and POE-g-MAH during melt compounding. Differential scanning calorimetry suggested that the crystallization and melting behaviors of ternary composites were influenced by phase structure. Evaluation of mechanical properties showed that the amide linkage between the treated HGM and POE-g-MAH was favorable for improving the properties of ternary composites.