Materials Science Forum Vols. 475-479

Abstract: Wollastonite and dicalcium silicate coatings have been prepared on Ti-6Al-4V substrate via plasma spraying. Bond strength test, simulated body fluid (SBF) immersion, in vitro cell culturing, and in vivo implantation were carried out to evaluate their mechanical and biological characteristics. The results obtained showed that both coatings possess higher bond strength as compared with hydroxyapatite (HA) coating. In the meanwhile, the good bioactivity and biocompatibility were confirmed in this study.

Abstract: The influence of calcium (Ca) at titanium surface on co-precipitation of Ca-P and bovine serum albumin (BSA) has been investigated by scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The titanium surface containing Ca was prepared by immersing titanium plates into a saturated calcium hydroxyl (Ca(OH)2) solution. A solution containing BSA, calcium and phosphate ions was used for the co-precipitation test. Both BSA and calcium phosphate co-precipitated onto titanium surfaces with and without Ca. For the former, however, a thicker carbonate apatite coating, which consisted of finer crystal grains, formed and more protein precipitated compared to the surface without Ca. These results indicated that Ca at the titanium surface was favorable to the co-precipitation of BSA and Ca-P. Moreover, chemical interactions probably occurred during the co-precipitation of BSA and Ca-P.

Abstract: In recent years, electrospinning process is gradually applied in producing tissue-engineering scaffold. In this study, we chose polylacticacid(PLA) and β-tertiary calcium phosphate(β-TCP) as raw materials to fabricate PLA/β-TCP biodegradable composite scaffold by electrospinning process. The characteristics of the scaffold and effect of the scaffolds to cell proliferation and cell adhesion was studied. Compare with pure PLA scaffold, blendingβ-TCP in the spinning process of the scaffold could improve the properties of the scaffold, especially the hydrophilicity and the proliferation and adhesion of cells, this means that the material is more potential to be used as tissue engineering scaffolds.

Abstract: A composite of needle-like nano-hydroxyapatite (n-HA)/poly (D,L) lactide (PDLLA) was prepared. The n-HA crystals were poorly crystallized and uniformly distributed in the composite with a crystal size of 10–20 nm in diameter by 40–60nm in length，which was smaller than that of pure nano-HA. Molecular interactions and chemical bonds might present between n-HA and PDLLA in the composite, which were revealed by IR and XPS. The synthetic n-HA/PDLLA composite had a good homogeneity and could be a bioactive material for bone defect especially for load-bearing bone repair, which is more potential than pure HA or pure PDLLA.

Abstract: In this study, a novel bioabsorbable porous bone scaffold reinforced by chitin fibres was prepared, the porosity of which is about 90 % and the pore size is approximately 200µm. The Advanced Rheological Enlarged System (ARES) was used to study the dynamic rheological behaviors of the ropy materials which would be made into the reinforced scaffold. The increase of the fibres’ volume content (Cf) enhanced the complex modulus (G*) and complex viscosity (h*) of the materials, the reason of which is that the fibres formed networks in the materials. When Cf increased from 35 % to 45 %, the storage modulus (G’) and loss modulus (G’’) curve showed obvious yielding behavior, which indicates that G’ and G’’ of the materials are hardly variable in a wide range. When Cf was more than 35 %, the loss factor (tand) was obviously lower than 1 and the materials exhibited viscoelastic properties, which result in a disadvantage for materials’ processing.

Abstract: To design the scaffold with suitable properties for the development of tissue engineered livers, materials design, selection and scaffold construct are three dispensable steps to be followed consequently. Firstly, some natural materials such as collagen, chitosan and alignate as well as some prevailing aliphatic polyester such as poly(lactic acid) (PLA), polyglycolide (PGA) and their copolymers poly(lactide-co-glycolide) (PLGA) are selected and characterized by hepatocyte culture. The experimental results reveal that the natural materials with excellent biocompatibility are not suitable as the scaffold alone because of the poor mechanical properties. At same time, aliphatic polyesters with good mechanical properties and biodegrade abilities are also proved inapplicable for hepatocytes for the lack of right cell recognition sites. Among our study scope, the hybrid materials such as collagen/chitosan or collagen/chitosan/heparin are the very promising candidates for hepatic tissue engineering scaffold. Secondly, two novel designs composed of collagen and PLGA, namely, the spindle porous scaffold with separated channels for transportation of nutrient, plasma and the one made by dewaxen-casting method are initiated respectively.

Abstract: Implantation of drug releasing coronary stents has been developed as an useful method for prevention of the restenosis in blood vessels. Copolymers of methyl methacrylate (MMA), butyl methacrylate (BMA) and methacrylic acid (MAA) were prepared as the coating polymer for drug releasing stent. The adhesion of the polymer with metal substrate and the biocompatibility were studied. Effect of the polymer composition on the adhesion between polymer coatings and metal substrate, as well as the effect of the polymer purification method on biocompatibility of the polymer, was studied. The results showed that the copolymer coating has good dry and wet adhesion properties, which can be improved by control of the polymer compositions. Biocompatibility of the prepared copolymer comes within the permission limit.

Abstract: Poly(L-lactide) (PLLA) was synthesized by the ring-opening polymerization of L-lactide and the shape memory behavior was studied using DSC and bending test experiments. The results indicate that the specimen shows the shape memory effect (SME), the small crystalline phase of PLLA and the mobility of amorphous phase may be responsible for the SME. The shape recovery of samples decreases and approaches to steady with the testing number increases.

Abstract: Reducing the particle size of drug materials down to submicron is an important matter in pharmaceutical industry. Cryogenic milling technology is one of the mechanical milling processes, which is mostly utilized in refining grain size of metal and ceramics at extremely low temperature environment. This technique has not been readily studied in application to medical and biotechnology. This paper, therefore, describes the application of cryogenic milling process to reduce particle size of Ibuprofen. The shape and size of the Ibuprofen particle before and after the cryogenic ball milling process were analyzed. XRD analysis was performed to examine a change in crystallinity of Ibuprofen by the cryogenic ball milling process. The results showed that the size of Ibuprofen particles was reduced to 1/10 or less of its initial size. The results also showed that the degree of crystallinity of Ibuprofen was slightly reduced after cryogenic ball milling with nitrogen.

Abstract: Recently, more attention has been focused on the research and development of biomaterials such as an artificial bone because of the rapid-increasing demand for biomaterials from the aging society in the world. However, the study on the bone itself is not enough. In particular, there is little information about the fracture toughness, and fatigue property of bones, and effect of the microstructure on the fracture characteristic. In this study, the fracture toughness of the bovine and swine humerus and femur as well as the fatigue property of the bovine humerus and femur was investigated with relating microstructures. The fracture toughness of plexiform bone is greater than that of haversian bone, and the fatigue strength of the plexiform bone taken from the humerus and femur is a little greater than that of the haversian bone taken from the humerus and femur in particular in high cycle fatigue life regions.