Materials Science Forum Vols. 745-746

Abstract: In recent years, electrospinning has received much attention to prepare porous tubular scaffold due to electrospun nanofibers mat, which can mimic the structure characteristics of the extracellular matrix (ECM). In the present paper, silk fibroin (SF) tubular scaffolds with small-diameter were prepared by electrospinning from regenerated silk fibroin (RSF) aqueous solutions with rotating mandrel collector. The morphology and fiber diameter distribution of SF tubular scaffolds were influenced much by the concentration of regenerated silk fibroin (RSF) solution, collecting distance and mandrel diameter. The results showed that SF tubular scaffold, which was in flat surface with smaller fiber diameter and uniform distributed, could be obtained at the concentration of 22%, collection distance of 10 cm and mandrel diameter of 4 mm. The structure of SF tubular scaffolds before and after ethanol treatment was characterized by FTIR and XRD. After ethanol treatment, the SF tubular scaffolds had a conformation transition from random-coil conformation to Silk II conformation.

Abstract: In the present study, a new antibacterial bone graft substitute has been developed for repairing bone defects and inhibiting related infections at the same time. Calcium sulphate hemihydrate (CSH) was introduced into nanohydroxyapatite/collagen (nHAC) to prepare a self-setting in situ bone repair materials. The nHAC/CSH was used as a carrier of vancomycin (VCM) for anti-infection and the treatment of osteomyelitis. The VCM/nHAC/CSH composite was a porous scaffold with porosity of 38.8% and the compressive mechanical strength was about 4.8 MPa. The final setting time was about 15~20 min. The inhibition ratio of VCM/nHAC/CSH was more than 99.8% and the distinct inhibition zone of 18 mm was formed in Staphylococcus aureus bacterium incubation dish with VCM/nHAC/CSH disc in the center of agar matrix for 16 hours of incubation. After incubating 17 days at 37 in vitro, the concentration of vancomycin in elution fluild was around 12 μg/mL. Therefore, the VCM/nHAC/CSH bone substitute presents ideal self-setting antibacterial, cytocompatibility, sustained release properties and has great potential applications for the treatment of bone defect-related infection in orthopedic surgeries.

Abstract: An ideal injectable bone cement should be able to fill fully the fractures gap and provide good mechanical support. In the present work, the mineralized collagen and calcium sulphate dehydrate (CSD) was incorporated into α-calcium sulphate hemihydrates (α-CSH) to explore an injectable composite cement. The injectability, the setting time and the biomechanics properties were investigated. A porcine thoracolumbar burst fracture model was used to evaluate the biomechanical performance of composite cements. The porcine thoracolumbar burst fracture models in vitro were prepared. A half of models was made by the vertebroplasty of the composite cements, the other half of models was used as control. Imaging analysis showed the composite cements distributed uniformly and solidified well. Biomechanical test showed the ability of the composite cements to repair spinal burst fractures was significant.

Abstract: Micro-arc oxidation (MAO) process was conducted on ZK60 Mg alloy in a basic biologic electrolyte composed of silicate by addition of (NaPO₃)₆ and NaH₂PO₄. The microstructural evolution, phase composition and in vitro corrosion resistance of the coating were investigated by means of scanning electron microscopy (SEM) coupled with an energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The results revealed that bioactive elements Mg, Ca, P and Si were remained in the bio-ceramic coating which can be prepared in suitable biologic electrolyte. For the interaction of (NaPO₃)₆ and NaH₂PO₄ , the Ca/P molar ratio of the coating in the optimized biologic electrolyte reached to 1.24 by L₉ (3⁴) orthogonal experiments. Compared with the bare ZK60 Mg alloy, the corrosion resistance of the optimized sample in 37 Ringers solution was improved by 4 orders.

Abstract: Magnesium alloys are promising candidate materials for cardiovascular stents due to their good biocompatibility and degradation property in human body. However, in vivo tests also show that improvement in mechanical property and corrosion resistance is necessary for wide application. In this study, hot extrusion and cyclic extrusion compression (CEC) were used on Mg-Zn-Y-Nd alloy, the effects of hot extrusion and CEC process on the microstructures, mechanical properties and corrosion properties of alloy were studied. The results showed that the microstructures of CEC treated Mg-Zn-Y-Nd alloy became finer and more homogenous, some nanoparticles which came from the cluster phase uniformly precipitated inside grains, alloy had good mechanical properties and corrosion resistance. The immersion test results in SBF solution at 37 for 24h showed that the alloy after CEC treatment is uniform corrosion.

Abstract: In order to improve the mechanical properties and processing performance of the Mg alloys, and to prevent magnesium alloy from non-uniform corrosion and too fast degradation in the degradation process, the biological medical Mg-Zn-Y-Nd alloy was modified by the friction stir processing (FSP) technique in this paper. The microstructural evolution and phase constitute of the stir zone of Mg-Zn-Y-Nd alloy were investigated, the microhardness and the corrosion properties of the alloy after FSP process was studied. The results showed that the FSP parameters had significant influence on the stir zone and thermo-mechanically affected zone. The stir zone experienced severe plastic deformation and complete dynamic recrystallization after FSP. The stir zone consists of fine equiaxed recystallized grains, and thermo-mechanically affected zone (TMAZ) has deformed grain structure. The second phase distributed along grain boundaries in as-cast state was broken during the FSP and transformed into fine, uniform and dispersed particles in the grains. After FSP, the size of grains was reduced from 50μm (as-cast alloy) to 1-2μm. However, the second phase constitution didnt change. The alloy obtained good comprehensive mechanical properties after FSP. The microhardness of alloy after FSP increased from 39HV (as-cast alloy) to 64HV(FSPed alloy). The results of electrochemical tests in simulated body fluid showed that the corrosion potential of FSP alloy increased and corrosion current density decreased, which confirmed the uniform corrosion of FSPed alloy.

Abstract: A novel adsorbent which is effective to adsorb Au³⁺ was prepared using immobilized persimmon tannin (PT) on collagen fiber by glutaraldehyde crosslinking. The adsorption behaviour of this new adsorbent to Au³⁺ in aqueous solution was investigated. The effects of various factors such as initial solution pH, temperature, ionic strength and initial concentration of Au³⁺ on the influence of the adsorption process were studied. The equilibrium adsorption capacity reached 2347 mg/g at 323 K and pH value 2.0 when the initial concentration of Au³⁺ in aqueous solution was 500 mg/L. The immobilized PT was characterized by FT-IR, XRD and SEM. The results indicated that Au³⁺ changed to gold by oxidation adjacent phenol hydroxyl groups of persimmon tannin. Experiments also showed that adsorption isotherms of immobilized tannin for Au³⁺ could be described by Langmuir models. Immobilized PT adsorption provided a new way for the separation of the precious metal ions

Abstract: t is of great importance to improve the hydrophilicity of Cu/LDPE composite, a material for a new type of IUDs (Intrauterine Devices). The aim of the study is not only satisfying the biocompatibility of medical devices implanted in human bodies, but also improving the releasing rate of cupric ions. In this study, various hydrophilic materials (sodium chloride, anhydrous glucose and soluble starch) were added respectively, in order to improve the hydrophilicity of Cu/LDPE composite. The microstructure of Cu/LDPE composite was characterized, moreover, the influence of the addition of these hydrophilic materials on the surface hydrophilicity and the releasing rate of cupric ions of Cu/LDPE composite was studied. The compatibility between three hydrophilic materials and the matrix of LDPE is rather different, which can affect the dispersible uniformity of these additives in Cu/LDPE composite, and the dispersible uniformity of NaCl is the worst among these three hydrophilic materials. The addition of three hydrophilic materials was all beneficial to the improvement of the hydrophilicity of Cu/LDPE composite. Connected holes were formed in Cu/LDPE composite, which provided channels for the infiltration of solution and the diffusion of cupric ions, and improved the releasing rate of cupric ions in the Cu/LDPE composite IUDs.

Abstract: In this work, Poly (methy methacrylate-styrene-divinyl benzene) (MMA-S-DVB) microspheres were prepared by suspension polymerization approach in the presence of n-dodecane as porogenic agent. Various types of measurements,such as binocular biological microscope with micrometer, fourier transform infrared (FT-IR) and N2 absorption analysis (BET) were conducted to characterize the MMA-S-DVB microspheres. The effect of the amount of surfactants (PVA and NaCl), porogenic agent and crossing agent (DVB) on the morphology of microspheres was investigated and mass ratio of oil/water and the stirring speed were also discussed. Finally, according to the experimental results,the optimum experimental condition was obtained as follow: the mass ratio of S:MMA:DVB=3:3:4, the concentration of PVA in the water phase is 2.2 wt %, the concentration of NaCl is 5 wt %, the mass ratio of oil/water is 1:11, the stirring speed is 500rpm.Via controlling the optimum reaction conditions of the suspension polymerization, the crosslinked macroporous resin polymer MMA-S-DVB microspheres with excellent sphericity and controllable diameter in a range of 200~400 μm can be gained.