Advanced Materials Research Vols. 399-401

Abstract: Enzymatic hydrolysis of silk fibroin is studied in detail by both single factor experiments and orthogonal experiments. The results of single factor experiments show that enzyme concentration, temperature and pH value have significant effects on the hydrolysis. With the changes of them, the structures of enzyme molecules will also change, which will cause different hydrolysis rates. According to the results of orthogonal experiments, the degree of influence of these three factors can be sorted in descending order: temperature, concentration and then pH value. The optimized conditions of hydrolysis achieved in this paper are enzyme concentration 0.5g/L, temperature 60°C and pH value 8.60.

Abstract: This paper introduced several conventional stainless steels for piercing jewelry, and discussed their corrosion resistance, nickel allergy problem and risk of piercing infection. The authors proposed that several requirements should be taken into consideration in developing stainless steel materials for piercing jewelry, including corrosion resistance, safety, anti-bacterial, castability, workability, weldability, surface treatment property, and etc. High nitrogen and nickel free or low nickel stainless steels with anti-bacterial performance, which had many unique characteristics such as excellent corrosion resistance, no nickel allergy and less risk of piercing infection, would become a new development trend of stainless steels for piercing jewelry.

Abstract: Microporous membranes were prepared by immersion precipitation phase inversion method from the semi-interpenetrating polymer network (semi-IPN) of shape memory polyurethane (SMPU) and poly (N-isopropylacrylamide) (PNIPAM). The influence of material compostion and preparation procedure on the morphology of membranes such as pore structure and porosity was investigated by methods including Fourier-transform infrared (FT-IR) spectroscopy and scanning electronic microscopy (SEM). Both sponge-like structure and large-pore structure were found in the membranes. The introduction of PNIPAM content in the semi-IPN promotes the formation of large-pore structures and increases the porosity of membranes, due to the improvement of water diffusion into the casting solution. We also found that by increasing the temperature of coagulation bath and the concentration of DMF in the coagulation solution, the formation of large pores could be impeded, and membranes with more sponge-like structure could be prepared.

Abstract: Abstract: Purpose To screen out the optimal conditions of cross-linking reaction of preparing for an injectable cross-linked sodium hyaluronate gel(CHA-gel) with higher resistance to hyaluronidase and research for its viscoelasticity and anti-enzyme degradation properties. Methods The CHA hydrogels were prepared with different molecular weights of PEG as cross-linking agent, such as PEG400, PEG1000, PEG6000, PEG10000, PEG20000. The optimal preparing conditions were determined by single factor test and orthogonal experiment. The Enzyme-resistant degradation properties in vitro of CHA-gels were analysed by carbazole and spectrophotometry. Its viscoelasticity was also compared with natural HA-gel by Stabinger method. Results the results of range analysis and variance analysis show that the pH of CHA solution and the ratio of cross-linking agent to HA were significant factors. The optimal preparing conditions of the parameters are 1.5% of HA, 0.001mol/L NaOH, at 37°C, reacting 4hr and 1:15 PEG20000/HA (g/g). Under these conditions, the CHA-gel has excellent Enzyme-resistant properties, R=85.1%, an high percentage of enzyme-resistant property. Its viscoelasticity can reach 61.3×10⁴mPa.s, three times as much as natural HA-gel. Conclusion The CHA-gel with excellent physicochemical properties can be prepared under the optimal conditions, which can set foundation for developing better mechanical and Enzyme-resistant properties products of CHA-gel.

Abstract: With the development of functional and structural materials, increasing interests have been shown in the field of biomaterials with a negative Poisson’s ratio (auxetic), which exhibit the unusual property of becoming thinner when compressed. This unusual property makes it potentially a synthetic replacement biomaterial with adequate mechanical property and wear resistance. In this study, the potential of applying the auxetic ultra-high molecular weight polyethylene (UHMWPE) for the artificial hip joint was discussed. The contact mechanics characteristics in artificial hip joint replacement under different Poisson's ratios of -1<μ≤0.5 were investigated and compared using the finite element method. The results show that Poisson’s ratio had great effect on the contact mechanics in artificial hip joint replacement. Therefore, the future work should focus on tailoring an auxetic UHMWPE with a suitable Poisson’s ratio for artificial hip joint replacements.

Abstract: Wear on Co-Cr-Mo biomedical implants is still a major issue especially for applications in articulation joints like in total ankle, knee and hip arthroplasty. Generation of excessive wear particles can coagulate in body tissues which later cause inflammation, bone loss and necrosis. Modification of implant surfaces is a common technique for increasing the hardness and thus minimizing these effects. In this study, thermal oxidation method was carried out on the Co-Cr-Mo to investigate the effects of different pretreatment processes and surface roughness on the hardness of oxide layer formed. Prior to oxidation process, all samples were annealed and pickled to remove residual stress and oxide scales respectively. The oxidation process was done inside furnace under atmospheric condition for 3 hours at 1160 °C. The metallic compositions, surface morphology and hardness of the oxide layer formed on the substrate were verified using X-ray diffraction (XRD), scanning electron microscope and micro-Vickers hardness analysis respectively. It is found that mechanical pretreatment provides oxide/carbide layer with higher hardness than chemical pretreatment method. It is believed that remnants of polishing diamond pastes trapped in roughness valleys react with metal matrix and later transform into carbides during oxidation process. In contrast, initial surface roughness of the substrate has no significant effect on the hardness of oxide/carbide layer.

Abstract: Chitosan is a new kind of material in life-science, it can be used in lipid-lowering. Chitosan microspheres (CTS-MP) were prepared by spray-drying, chitosan nanoparticles (CTS-NP) and chitosan-capsaicin microspheres (CTS-CAP-MP) were prepared by ionic gelation process. The effect of these samples on lowering lipids was evaluated by measuring its’ binding capacities with lipids under the conditions mimicking the gastrointestinal tract in vitro. Also, the particle sizes of chitosan preparations were examined by scanning electron microscopy (SEM) and particle size analyzer. The results showed that the lipids-binding capacities of CTS-MP and CTS-NP were far more higher than that of CTS and CTS-CAP-MP. In conclusion, CTS-MP and CTS-NP will be better fat-lowing food additives to replace chitosan. The mechanism of lipids-binding in vitro is not only physical adsorption. Particle size is not the determinant factor, electrostatic action is maybe another factor of lipids-binding.

Abstract: The pickled goat skins were crosslinked by chromium, aluminum, wattle extract and chestnut extract, respectively. The samples were thermal treated in a container held at different temperature for 5 h for different cycles. The xerothermic stability, water vapor permeability and dimensional stability of the samples were characterized before and after thermal treatment. The effect of thermocycling on the properties of tanned samples was discussed. It was found that the thermocycling at moderate temperature (50 °C) exerted little influence on the xerothermic shrinkage temperature (T_xs) of the tanned collagen fibers. The treatment at higher upper limit temperature (100 °C and 150 °C) decreases the Txs and results in an impaired thermal stability. The water vapor transmission rate was decreased after the thermal treatment, likely due to the reduction of the amount of hydrophilic groups of collagen macromolecules as well as the decrease of the pore ratio of leather. Treatment at high temperature damaged the dimensional stability of the specimens.

Abstract: Porous Ti alloys are novel biomedical candidates for surgical implant application. The corrosion resistance of porous Ti-24Nb-4Zr alloy with 41.54% porosity prepared from conventional sintering was investigated by means of open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy techniques in 0.9% NaCl physiological and Hank’s solutions with different pH values (2.4, 5.4, 7.4) at 310 K, respectively. Meaning solid Ti-24Nb-4Zr alloy was chosen as a reference. Porous Ti-24Nb-4Zr alloy shows wide passive regions based on anodic polarization curves. These observations suggest that porous Ti-24Nb-4Zr alloy owns excellent corrosion resistance. Therefore, they are potential for biomedical applications.

Abstract: In this paper, the terbium -doped nano-HA powders with strong fluorescence was prepared by hydrothermal synthesis and its crystal structure，morphology and fluorescent properties are characterized by XRD, TEM, XPS, ICP and PL spectroscopy. Results showed that with the doping concentration of Tb³⁺ increasing, the aspect ratio of Tb³⁺-doped HA particles decreased, while the fluorescence intensity excited by ultraviolet ray at 272 nm is significantly enhanced. With pH values increased from 6.5 to 10.0, the aspect ratio of Tb³⁺-doped HA decreased greatly, and the morphology of nano-Tb:HA particles changes from rod particles to equiaxed particles and the actual doping content and the fluorescence intensity tends to increase correspondingly, which can be explained that under alkaline solution, Tb³⁺ was more easier entering the HA crystal, and the Tb³⁺ would substitute the Ca2+ in both hydroxyapatite Ca(Ⅰ) and Ca(Ⅱ) site, which may block the active growth sites of the seed crystals and resulted in the growth rate and the ratio of length to radius decreasing.