Materials Science Forum Vols. 610-613

Abstract: The Nano-HA powder was prepared by chemical precipitation. Magnesium powders were used to make porous ultramicron HA ceramic, and the biological properties of which were investigated by hemolysis rate and cytotoxicity tests. The experimental results shows that the hemolysis rate of the nano-HA powder and porous ultramicron HA ceramic were all less than 5% and none of them showed cytotoxicity. The results indicated that nano-HA and porous ultramicron HA ceramic were provided with good biocompatibility.

Abstract: The adsorption of two different proteins (bovine serum albumin (BSA) and collagen-I) onto poly (L-lactic acid) (PLLA) surface was investigated using quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM). It’s found that protein characteristics would greatly affect the adsorption kinetics, structure and viscoelastic properties of adsorbed protein layers. Compared with BSA, collagen-I trended to form a loose, dissipative layer with a slower adsorption rate and larger adsorption reversibility, which is consistent with AFM observation. The results provided some valuable information for controlling the structure and properties of adsorbed proteins to develop an alternative surface-modification approach for biomaterials.

Abstract: A gradient bioceramic composite coating was prepared by wide-band laser cladding technique on TC4 alloy surface. The influence of rare earths oxide CeO2 on microstructure of bioceramic coating was studied. The experimental results indicated that CeO2 plays an important role in inducing HA + β-TCP formation. There is almost no HA+β-TCP in bioceramic coating without CeO2. When CeO2 content is higher than 0.2 wt.%, the amount of HA+β-TCP catalyzed by CeO2 gradually increases. The amount of HA+β-TCP becomes largest when CeO2 content is up to 0.4wt%. However, when CeO2 content ranges from 0.6 wt.% to 0.8 wt.%, the amount of synthesizing HA+β-TCP conversely goes down. Through cell culture experiment in vitro, the effect of bioceramic coating with different CeO2 contents on the expression of characteristic protein is investigated. The results show that the largest amount of expression of hydroxyproline(Hyp) at 2d and alkaline phosphatase(ALP) at 6d on coating is complied with 0.4wt.% CeO2, The result indicates that bioactivity of bioceramic coating is dependent on the amount of HA + β-TCP catalyzed by different CeO2 contents.

Abstract: An adherent apatite coating was deposited on titanium substrate through the three steps. First, titanium substrate was modified in 10M NaOH solution at 60°C, and then immersed in acidic solution of calcium phosphate resulting in the deposition of monetite (CaHPO4) coating using induction heating technique. Finally the monetite crystals were transformed to HA by a hydrothermal process at 160°C for 2 hours. Composition、morphology and structure of the initial and final coatings were identified using X-ray diffraction (XRD), Scanning Electron Microscopy, and Energy Dispersive Spectroscopy (EDS). The final coating consisted of compact HA crystals and these HA apatite crystals stacked tightly and kept the initial morphology of the monetite crystals. The coating adhesion measured using scratch test was 25.25N. In conclusion, hydrothermal treatment and induction heating techniques are effective surface coating methods that improve bonding to titanium substrate.

Abstract: The gradient silk fibroin (SF)/ hydroxyapatite (HA) porous composite used for the scaffold of cartilage-bone tissue regeneration was prepared with SF powder and HA powder by layer-by-layer mould pressing method and granular NaCl as porogent. The characteristics were performed by Electron Microprobe and Energy Dispersive Spectometer (EDS). It indicated that the distribution of SF and HA presented linear gradient along the thickness direction in the materials. The porosity of composites increased with NaCl content increasing, while the density decreased. As the result of mechanical properties measurement, the bending strength and compressive strength decreased with NaCl content increasing. Compared the mechanical properties between gradient material and non-gradient material, it indicated that bending strength of gradient SF/HA porous material was higher than non-gradient SF/HA porous material’s.

Abstract: In this study, a novel nitric oxide (NO) endogenously releasing polyurethane (PU) material, i.e. PU-g-L-cysteine(PU-Cys), was synthesized by grafting L-cysteine on the film surface. Fluorescence analysis and a BCA method were used to characterize qualitatively and quantitatively the grafted L-cysteine. The results showed that L-cysteine was successfully immobilized on the PU film surface and the density of L-cysteine grafted was calculated to be 15.3nmol/cm2. The NO releasing behavior study of PU-Cys film demonstrated that endogenous NO could be continuously released from PU-Cys film and the accumulated releasing amount within 3h added up to 1.06nmol/cm2. The releasing rate of NO was well matchable to the self-releasing rate of resting platelets in human body. The results of dynamic blood clotting test and hemolysis ratio measurement showed that PU-Cys film had a better haemocompatibility than PU film, which might be the result of endogenously released NO inhibiting platelet adhesion and thrombus formation. Therefore, PU-Cys with the property of endogenous NO releasing is expected to be an ideal blood compatibility material in clinical application.

Abstract: This study mainly describes the synthesis of Arginine-Glycine-Aspartic (RGD) peptide modification of copolymer: poly(lactic acid-co-L-lysine) (PLA-PLL- RGD) and preparation of mitoxantrone(DHAQ)-loaded PLA-PLL-RGD nanoparticles (DHAQ-NP), and researches the effects of exercise on antitumor efficacy of DHAQ-NP in hepatocellular carcinoma. Experimental results show that compared with DHAQ-only group, the DHAQ concentration of tumor in Exercise+DHAQ-NP and DHAQ-NP groups up-regulate significantly. Tumor volume and weight of mice were significantly decreased in the DHAQ-NP and Exercise+DHAQ-NP groups as compared to with the Control group. Suggesting that DHAQ-NP can effectively inhibit the growth of hepatocellular carcinoma. Compared with DHAQ-NP group, the DHAQ concentration, tumor volume of Exercise+DHAQ-NP group have no significant changes. This suggests exercise can not significantly influence the antitumor efficacy of DHAQ-NP. These studies are essential to fully understand the safety and application of exercise as a supportive intervention in targeted therapies.

Abstract: Konjac glucomannan (KGM) were modified by deacetylation with sodium hydroxide, calcium hydroxide, sodium carbonate, sodium phosphate, respectively and mechanical properties of modified KGM films were investigated. The modification mechanism was explored by FTIR. Results show that deacetylation of KGM play an important role on the flexibility of the modified membranes, and the flexibilities vary with different modifiers. The flexibility of the films modified by sodium hydroxide is significantly higher than that of the others. The modified films with good flexibility were prepared by simple steps as follows: NaOH modifiers and KGM (1%) were added to water, stirred until the pH arrived at 9. And then the KGM swelled at the temperature of 50°C for 2 hours, the modified KGM sol was cast onto glass plates, the modified membranes were formed after dried at 50°C.

Abstract: Owing to the unique characters of the hybrid scaffold components, a novel biodegradable porous composite scaffold was prepared. The nano hydroxyapatite (HAP) (73~136 nm) was crystallized in situ on the organic polyelectrolyte complex matrix through a biomimetic method. The polyelectrolyte complex composed of chitosan and hyaluronic acid had strong impacts on the formation of the nano HAP and directed in situ crystallization of the nano HAP as template. The in situ nano HAP reduced the interfacial energy and presented nano intensifier to the nano hybrid scaffold. Meanwhile, the scaffold kept high porosity.

Abstract: Exothermal behavior is always present during the hydration of cements. The biocompatibility and curing effect of a bone cement is in close relationship with its exothermal behavior. The exothermal behavior in the hydration process of the partially crystallized calcium phosphate (PCCP)+dicalcium phosphate anhydrate (DCPA) system cement was studied in this article. The results show that with the decrease of the particle size of DCPA, the heat release rate was greatly increased; whereas, with the decrease of the particle size of PCCP, the heat release rate was not obviously altered. The heat release in the hydration process of the PCCP+DCPA system cement was only 137 J/g, which was quite smaller than that of the tetracalcium phosphate (TTCP)+dicalcium phosphate dihydrate (DPCD) system cement, and the temperature increase was very small for this cement.