Effects of Fretting Stimulation Amplitude on Bone Growth and Micro-Injury at the Interface Between Bone Tissues and TitaniuBead Coating / 医用生物力学

Objective To improve the performance of artificial joint at biological fixed interface by frettingmechanical stimulation. Methods Taking the bonding sample of active rat bone tissues and inactive titanium bead coating as the research object, by using the self-developed fretting mechanical stimulation test device, the effects of mechanical stimulation with different tangential fretting amplitudes on growth promotion and micro-injury of bone tissues at fixed interface were explored, and the mechanism of growth promotion and micro-injury of bonetissues on the surface of titanium bead coating under fretting stimulation was revealed. Results The mechanical stimulation group with 40 μm fretting amplitude showed the maximum interface bonding force between bone tissues and titanium bead coating. The tangential fraction force-displacement curves changed from elliptic shape to linear shape, and the bonding interface was in adhesion area, which was difficult to become loose. The bone tissues had the most complete structure, and the number of tissue cells adhering and growing on the surface of titanium bead coating was the largest, as well as the distribution range was the widest. With the increase of fretting amplitude, the promoting effect of fretting stimulation on bone growth weakened, the bonding strength between bone tissues and titanium bead coating interface gradually decreased, the internal cavity area increased, the number and proliferation activity of tissue cells decreased to varying degrees as well. Conclusions Fretting stimulation with different amplitudes can promote the growth of bone tissue and cause micro-injury at the same time, and the optimal fretting amplitude is 40 μm.

Biological activity evaluation of porous HA ceramics using NH4 HCO3/PVA as pore-creating agents / 生物医学工程学杂志

Porous HA ceramics were prepared by using NH4 HCO3/PVA as pore-formed material along with biological glass as intensifier, and these ceramics were immersed in Locke's Physiological Saline and Simulate Body Fluid (SBF). The changes of phase composition, grain size and crystallinity of porous HA ceramics before and after immersion were investigated by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The biological activity was evaluated. The porous HA ceramics showed various degrees of decomposition after immersion in the two solution systems, but there was no evident change in respect to crystallinity. Besides, the impact of different degrees of solution systems on the change of grain size and planar preferred orientation was observed. The TCP phase of the ceramics immersed in Locke's Physiological Saline decomposed and there was no crystal growth on the surface of ceramics; however, the grain size of ceramics immersed in SBF became refined in certain degree and the surface of ceramics took on the new crystal growth.

The appraisal of mechanical properties and friction coefficient of PVA hydro-gel / 生物医学工程学杂志

Gelatin and hydroxyapatite were introduced to polyvinyl alcohol (PVA) hydrogel with an attempt to enhance the performances of PVA hydrogel. Through a reiterative freezing-thawing methods, three kinds of PVA composite hydrogels were prepared. The mechanical performances of these composite hydrogels with the same PVA and HA content but varying gelatin content, such as tensile strength, elasticity modulus, creep curve, relaxation curve and friction coefficient were evaluated by using a computer-controlled universal electronic mechanical testing machine and a UMT-II frictional testing machine. The additional effects of hydroxylapatite and varying gelatin on the performances of composite PVA hydro-gels were analyzed. It was found that the gelatin content directly influenced the physical performances of PVA composite hydrogels; but no linear relationship was recorded. PVA composite hydrogel containing 2wt-% gelatin gave optimal results, i.e. tensile strength of 5.5MPa, compressive elastical modulus of 1.48MPa, creeping rate of 31% in 45 minutes, stress relaxing rate of 40.3%, and the starting friction coefficient of 0.332.

Construction and eukaryotic expression of recombinant plasmid encoding fusion protein of goat complement C3d and foot-and-mouth disease virus VP1 / 生物工程学报

We constructed a recombinant plasmid encoding VP1 gene of O type foot-and-mouth disease virus fused to a molecular adjuvant, goat complement C3d gene. The goat C3d gene was cloned and three copies were tandem-linked with the linker (G4S)2 sequence. VP1 gene of O type foot-and-mouth disease virus was linked to three tandem repeats of C3d through the linker sequence and cloned into pUC19 to obtain the recombinant plasmid pUC19-VP1-C3d3. The VP1-C3d3 fusion gene was then subcloned into the eukaryotic vector pcDNA3.1(+) that had been modified to contain the tissue plasminogen activator (tPA) leader sequence to obtain pcDNA3.1-tPA-VP1-C3d3. HeLa cells were transfected with pcDNA3.1-tPA-VP1-C3d3 by Lipofectamine 2000. Indirect immunofluorescent assay and Western blot assay showed that VP1-C3d3 fusion gene was successfully expressed in HeLa cells. The fusion protein with the expected size 133 kD could be secreted outside the cells. This study laid a good foundation to further research on the novel vaccine against foot-and-mouth disease virus by using goat C3d as a molecular adjuvant to enhance the immunogenicity of VP1.