Advanced Materials Research Vols. 287-290

Abstract: The radiation technology has been applied extensively in the field of biological engineering, tissue engineering, medical practices and so on. It also plays an important role in the sterilization and modification of biomaterials. This work reviews recent development of several types of radiation technology which have been applied in the field of medical biomaterials.

Abstract: TiB₂/TiN composites with various content of Ni and Mo as sintering aid were hot-pressed at 1530°C. Effect of the content of sintering aid on microstructure and mechanical properties is investigated. Experimental results show that the fracture toughness of the composites increases consistently with an increase in the sintering aid content, however, the flexural strength gets to the maximum when the content of sintering aid is 10vol%. A new eutectic phase of MoNi can be found in the composites by X-ray diffraction (XRD) when the amount of sintering aid is over 7vol%. Scan electron microscope (SEM) analysis shows that the density of the composites increases consistently with the increasing of the sintering aid. But the abnormal-growth grains can be found and deteriorates the flexural strength in the composite No.4 because of the excessive sintering aid.

Abstract: Considering the influence on the downstream process of microalgae recovery by cell surface characteristics, in this paper , Microelectrophoresis and Hydrocarbon adsorption have been used for researching the surface electrical property and hydrophobicity of microalgae. The influence on surface characteristics of microalgae cell have been studied by the solution chemistry condition of pH and cationic flocculant. The results show that: The surface charge of microalgae cell is negative under the natural condition. The surface electrical property decreases with the declining pH when pH is less than 7 , but the isoelectric point is not observed until pH low to 1, while it changes little with the pH increased when pH is more than 7; Within the value of experimental pH, microalgae cells have strong hydrophobicity, which increases with the decreasing pH when pH is less than 7 and rises with the pH increased when pH is more than 9. It attains to the minimum value when the pH is about 8. The hydrophobicity of microalgae increases with anhydrous ferric chloride(FeCl₃) when cationic flocculant (FeCl₃) is added , but the trend became weaker. So the hydrophobicity can be improved by cationic flocculant, which can promote the microalgae cohesion.

Abstract: This article used glutaraldehyde to immobilize laccase and then used the immobilization laccase to treatment papermaking effluent. The study first discussed the effect of PVA crosslinking degree, epoxidation temperature and epoxidation time for the performance of PVA carrier. The research found 100g PVA ( mass fraction is 10%), 35mL glutaraldehyde, 10mL DMSO and 10mL epoxy chloropropane reacted 6h in 60 °C, pH=11-12 and surface amount of epoxidation reached the max value. its amount is 0.3073mmol . And then the laccase were fixed with the max value. The optimum conditions of immobilization laccase treated papermaking effluent were researched. The effects of treated time, temperature, pH value, the dosage of enzyme and HBT, the removal value of COD_Cr and decolorization were tested. The effects of treated time, temperature, pH value, the dosage of enzyme and HBT, concentration of Cu²⁺ on the removal value of COD_Cr and decolorization were tested. It was found that the optimum conditions for immobilization laccase treatment were Cu²⁺ 0.006μmol/L, HBT 0.008g/L, pH=4, temperature 50°C, reation time 6h (with air injected). The result showed that the COD_Cr removal rate reached 63.15%, the decolorization rate reached 61.53% in 8h. Furthermore BOD/COD of chemical pulp effluent was increased from 0.17 to 0.455. Comparing with dissociation laccase, stabilities of immobilization laccase for hot and pH increased. Through this research a new advanced treatment method can be found. This method can improve biodegradation performance of papermaking effluent. Papermaking effluent treated by aerobic, anaerobic and laccase system will achieve standard discharge.

Abstract: Two Schiff bases of chitosan (CTS) were synthesized from 4-methoxylbenzylaldehyde (CH₃O-CTS) and 4-methylbenzylaldehyde(CH₃-CTS). The Schiff bases were characterized by FTIR, DSC-TGA, solid ¹³C CP-Mas NMR, and elemental analysis. Antibacterial activities of the Schiff bases against Escherichia coli and Staphylococcus aureus were measured by the optical density method. The antibacterial activity of the Schiff bases is better than that of the original CTS. The IC₅₀ of CH₃O-CTS and CH₃-CTS against Escherichia coli is respectively 40.3 ppm and 43 ppm, which being 38.5 ppm and 39.5 ppm against Staphylococcus aureus, lower than IC₅₀ of chitosan, being 59.5 ppm and 52 ppm against Escherichia coli and Staphylococcus aureus, respectively.

Abstract: Poly (γ-glutamic acid) (γ-PGA) is a special anionic, water-soluble and high viscous polymer ^[1] which is condensed by glutamate via amide linkages between their a-amino and γ-carboxylic acid groups ^[2]. For its excellent characters, potential applications of γ-PGA have been of interest in the past few years in a broad range of industrial fields ^[3]. And the decision to application of γ-PGA will be done, depending on its’ molecular weight. So this article main expresses the influence of different carbon sources to γ-PGA’s molecular weight distribution. By SDS-PAGE, we found that the molecular weight distributions of biosynthetic γ-PGA were different in the different carbon sources. All the results showed that changing the carbon source of mediums did make the biosynthetic γ-PGA’s yield and molecular weight distribution been changed.

Abstract: Despite drug eluting stents (DESs) have revolutionized the interventional cardiology over the past decade since the first DES became commercially available nearly a decade ago, burst release of loaded drugs and late thrombosis caused by polymer coatings of the stents are high concerned. In this situation, inorganic coatings, such as silica-based hybrid materials, have aroused researcher’s interest. In this study, aspirin (ASA) was incorporated into the sol-gel derived silica matrix with polyethylene glycol (PEG) as an organic modifier to improve the flexibility and extensibility of the inorganic matrices. We also used L-3,4-dihydroxyphenylalanine (L-DOPA) as a bio-adhesive reagent to enhance interface adhesion between the coating materials and the 316L stainless steel substrate. The results show that the introduction of D-LOPA can greatly improve the coating quality by enhancement of uniformity and adhesion. The loading ASA was slowly released from the coatings and burst release was effectively inhibited owing to the encapsulation of ASA molecules in the silica-PEG matrices.

Abstract: Hyaluronic acid (HA) is an extremely ubiquitous polysaccharide of extracellular matrix in body and plays various biological roles. In this study, cell viability, insulin secretion and cytosolic free Ca²⁺ concentration were investigated in HIT-T15 cells after HA-treatment. The cell viability was determined by the MTT assay while the insulin secretion was detected by ELISA technique. The Flou-3/AM was applied to probe intracellular free calcium concentration. HA (0.25, 0.5, 1.0 mg/dish) increase insulin secretion in the 3 or 25 mM glucose-stimulation for 4 h. Cytosolic Ca²⁺ fluorescent intensity in HA-treatment groups (0.25, 0.5, 1.0 mg/dish) is significantly higher than that in control group. This study implied that the increasing of insulin secretion of HIT-T15 cells by HA-coating result from the enhancement of cytosolic Ca²⁺. And these data also provide some information on design biocompatibility when HA used as a biomaterial for bioartificial pancreas.

Abstract: We report the synthesis and characterizations of Poly(ethylene glycol) (PEG) modified P₂O₅-CaO-SiO₂ gel bioglass. Three kinds of PEG with different molecular weight (400，6 000，10 000) were used in the preparation and their influence on the nanostructure of the resultant gel bioglasses was investigated. Due to the excellent aqueous solubility and compatibility of PEG with the inorganic P₂O₅-CaO-SiO2 components, no phase separation was detected in the hybrid gel glasses under scanning electron microscopy (SEM) observation. FT-IR spectra indicate that hybridization between the organic and inorganic part was successfully achieved at the molecular level. SEM images and N₂ adsorption-desorption experiments show that, among the three samples, S6 000 is the most promising candidate for bone scaffold material, because of its hierarchical pore structure, high porosity and surface area.

Abstract: In order to improve the corrosion resistance, the samples made of Mg-Zn-Zr alloy were immersed in 20% or 40% hydrofluoric acid (HF) aqueous solutions for different intervals to prepare magnesium fluoride (MgF₂) coating on the surface. By comparing the surface morphologies, the samples immersed in 20% HF solution for 6 h on which fine particles in nanoscale covered was selected for the further study. Immersion and electrochemical tests showed that the dense MgF₂ coating would improve the corrosion resistance of Mg-Zn-Zr alloy. The corrosion current density (i_corr) decreased from 2.10 μA·cm^-2 to 0.05 μA·cm^-2. The influence of HF treatment on the cytocompatibility was evaluated in vitro. There were significant differences in the cell number between the naked and coated samples after culturing for 3 and 5 days (p<0.05). All the results demonstrate that HF treatment is a promising approach to improve the corrosion resistance and in vitro biocompatibility of Mg-Zn-Zr alloy used as intravascular stents.