Advanced Biomaterials VI

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Authors: Kazuo Isama, Toshie Tsuchiya
Abstract: The effects of the γ-irradiatted PLLA on the osteoblasts and apatite formation were investigated in vitro. The PLLA sheet was γ-ray irradiated at the dose of 10, 25 or 50 kGy. The mouse osteoblast-like MC3T3-E1 cells and normal human osteoblast NHOst cells were micromass cultured on the PLLA sheet for 2 weeks, and then the proliferation and differentiation of the cells were determined. The proliferations of MC3T3-E1 and NHOst cells hardly changed with increasing irradiation dose. However, the differentiations of MC3T3-E1 and NHOst cells increased with irradiation dose. On the other hand, the surface of the PLLA sheet after soaking in the medium without the cells was characterized by SEM, EDX, FT-IR and XPS. The hydroxyapatite was formed on the surface of the PLLA sheet after soaking, and the amount of hydroxyapatite increased with irradiation dose. In summary, the γ-irradiated PLLA increased the differentiation of osteoblasts and also increased apatite-forming ability even without the osteoblasts. The osteoblast differentiation was enhanced well in the apatite formation on the surface of PLLA after the γ-irradiation.
Authors: Jing Hua Li, Chuan Bao Cao, Xilan Ma, Yin Tang, He Sun Zhu
Abstract: The citric acid (CA) was added to the silk fibroin and Polyvinyl Alcohol (PVA) copolymer system. The blending 4% PVA was for improving the mechanical properties of the silk fibroin films. Citric acid amount varies from 0.5% to 2% of weight. The antithrombogenecity was characterized by in vitro clot time of prothrombin time (PT), the Activated partial thromboplastin time (APTT) and thrombin time (TT). The mechanical properties of the blending films were measured and the tensile strength and breaking elongation of films reached to 25.3MPa and 102%. The anticoagulant property results indicated that APTT and TT prolonged significantly, but PT has no effective change. We discussed the relationship between the structure and properties and proposed an anticoagulant mechanism.
Authors: F. Li, Jin Wang, H. Sun, Nan Huang
Abstract: Poly(ethylene terephthalate) films were exposed under argon plasma glow discharge and induced polymerization of acrylic acid (AA) in order to introduce carboxylic acid group onto PET (PET-AA) assisting by ultroviolet radiation. Hirudin-immobilized PETs were prepared by the grafting of PET-AA, followed by chemical reaction with hirudin. The surface structure of the treated PET is determined by X-ray photoelectron spectroscopy (XPS). The wettability and surface free energy, interface free energy of the films is investigated by contact angle measurement. Platelet adhesion evaluatiion is conducted to examine the blood compatibility in vitro. Scanning electron microscopy (SEM) and optical microscopy reveal that the amounts of adhered, aggregated and morphologically changed platelets are reduced on hirudin-immobilized PET films.
Authors: In Ho Han, Jai Hyuk Choi, Hong Koo Baik, Jong Chul Park, Jeong Koo Kim, Kwon Yong Lee, S.-M. Chung, In Seop Lee
Abstract: The surface properties of scaffolds are important since cell affinity is the most crucial factor to be concerned when the biodegradable polymeric material is utilized as a scaffold in tissue engineering. The surface of biodegradable non-porous poly (lactic-co-glycolic acid) (PLGA) scaffolds were treated by atmospheric pressure dielectric barrier discharge (APDBD). The wetting angle of APDBD treated PLGA were decreased from the untreated PLGA of 73° to 42°. FTIR-ATR analyses showed hydroxyl groups were not detected regardless of treated condition, but the intensities of both ether groups and carbonyl groups were increased with treatment time and oxygen flow rate. Treatment time and oxygen flux are equally effective to make the PLGA surface more hydrophilic.
Authors: Zhi Qing Chen, Quan Li Li, Quan Zen, Gang Li, Hao Bin Jiang, Laikui Liu, Brian W. Darvell
Abstract: Phosphorylated chitosans were synthesized as templates to manipulate hydroxyapatite (HA) crystal nucleation, growth and microstructure. Two kinds of insoluble phosphorylated chitosan were soaked in saturated Ca(OH)2 solution for 4 d and in 1.5× SBF (simulated body fluid) solutions for 14 d at 37 °C for biomimetic mineralization. A lower [P]-content of phosphorylated chitosan promoted greater mineralization than higher [P]-content. Phosphorylated chitosan inhibited osteoblast proliferation and differentiation in vitro, while calcium phosphate phosphorylated chitosan composites did not.
Authors: Bin Chen, Xiang He Peng, Jing Hong Fan
Abstract: Insect cuticle possesses excellent mechanical properties, such as strength, stiffness and fracture toughness, which are closely related to its elaborate microstructures optimized through centuries’ evolution. SEM observation on Hydrophilidae cuticle shows a kind of biocomposite consisting of chitin-fiber plies and protein matrix, and the chitin-fiber plies are composed of several special arrangements. The observation also shows that there are many holes in the cuticle and the fibers passing along the brims of the holes round the holes continuously. Making use of such microstructure, a kind of biomimetic composite laminate with round-hole-fiber distribution is fabricated with preformed-hole method. The ultimate strength of the composite laminate is investigated and compared with that of the composite laminate with a hole drilled. It shows that the ultimate strength of the former is distinctly higher than that of the latter.
Authors: Guo Qiang Chen, Qiong Wu, Ya Wu Wang, Zhong Zheng
Abstract: Poly(hydroxybutyrate-co-hydroxyhexanoate) (PHBHHx) has improved mechanical properties over the existing PHA and our results have shown that PHBHHx has better biocompatibility over polyhydroxybutyrate (PHB) and polylactic acid (PLA). Surface treatment with lipases dramatically changed the material surface properties and increased the biocompatibility of the PHBHHx. PHBHHx and its PHB blends had been used to make three dimensional structures and it has been found that cartilage, osteoblast, and fibroblasts all showed strong growth on the PHBHHx scaffolds. The growth was much better compared with PLA. The molecular studies also showed that mRNA encoding cartilages were strongly expressed when cartilage cells were grown on the PHBHHx. As PHBHHx has strong mechanical properties, easily processible and biodegradable, this material can be used to develop a new class of tissue engineering materials.
Authors: Kazuhiro Takahashi, Tomoaki Takamoto, Yasuhiko Tabata
Abstract: The objective of this study is to synthesize gelatins grafted with lactic acid oligomer (LAo) and lactic acid oligomer-poly(ethylene glycol)-lactic acid oligomer (LAo-PEG-LAo) triblock copolymers and to examine their gelation behavior. The grafting ratio of LAo-grafted gelatins could be changed by the feed ratio of LAo to the amino groups of gelatin for grafting reaction, while triblock copolymers with different molecular weights of LAo were prepared. The turbidity of LAo-grafted gelatin solution increased with the increased grafting ratio, although the turbidity increase was suppressed by adding guanidine hydrochloride in a dose-dependent manner. The turbidity of LAo-grafted gelatin solution further enhanced by mixing with the solution of triblock copolymers, while the enhanced extent increased with an increase in the LAo molecular weight. A mechanically firm hydrogel was formed by mixing the LAo-grafted gelatin and triblock copolymer at the higher solution concentrations, while the compression strength of the hydrogel became higher as the grafting ratio increased. No hydrogel formation was observed in the presence of guanidine hydrochloride.
Authors: Yin Tang, Chuan Bao Cao, Xilan Ma, Jing Hua Li, He Sun Zhu
Abstract: The silk fibroin blend membranes were prepared by adding a small amount of poly (vinyl alcohol) (PVA) and heparin. By controlling the preparation conditions, the tensile strength and elongation at break reached to 8.86 MPa and 231.8%, respectively. Meanwhile the in vitro antithrombogenecity significant increased. The clot times (APTT, TT and PT) all exceeded the measurement limit of clot detection instrument. It is expectable using these natural materials to prepare small caliber vessel.

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