Abstract:Tissue engineering is one of the most promising subjects,which has broad application prospects in the fields of regenerative medicine and human health care. According to the papers published in this current issue about scaffold material preparation and mechanical environment affection to cells during the construction process of tissue engineering, this paper describes the current status and progress of tissue engineering research at home and abroad, indicating that tissue engineering research is developing to a deeper and wider field.

Abstract:Objective The influencing parameters of solid and fluid computing fields for the scaffolds models with regular square holes were discussed by nonlinear fluid-solid-coupling approaches, the numerical computational results of which the models were regarded as both rigid body and non-linear elasticity were compared as well. Method one direct fluid-solid-coupling approach and two indirect fluid-solid-coupling approaches were adopted, and the calculating reliability of three kinds of fluid-solid coupling methods were verified. Results The solid-fluid-coupling computational results are obtained in light of 12 kinds of scaffolds which were constructed by 3 groups of square side length (50,100 and 150μm) and 4 groups of porosity (61%,65%,77% and 84%). The field parameters of those solid models including stress, strain and displacement and those fluid models including static pressure, velocity, wall shear stress and strain rate are achieved and compared.Conclusions A quiet difference between the results of porous scaffold models as a rigid body and that of non-linear elasticity. The different porosity with the same pore radius or the different pore radius with the same porosity effected the field parameters of solid models and fluid models in varying degrees.

Abstract:Objective: To observe the adhesion of MC3T3-El osteoblastic progenitor cells to the three-dimensional chitosan-decellularised-derma scaffolds, and evaluate the cytocompatibility of the scaffolds. Methods: The three-dimensional chitosan-decellularised-derma scaffolds were prepared by the freeze-drying method, the porosity, density and water absorption of which were measured. The microscopic morphology of the composite scaffolds was analyzed by the scanning electron microscopy (SEM). The MC3T3-E1 cells cultivated in vitro were seeded onto the composite scaffolds, and then co-cultured for 2, 3, 4 and 5 hours. At each time point, three specimens from each matrix were taken to determine the cell-adhesion rate, in order to ascertain the best time of the cell-adhesion. The cells were seeded onto the composite scaffolds, and then co-cultured for 1, 3, 5, 7, 9, 11 and 13 days. The MC3T3-E1 cells inside were evaluated with MTS test. The cell morphology was observed by the histological staining. The compression tests were performed using a Universal Testing Machine, at room temperature, as compared with no-cell-scaffolds.Results: The three-dimensional chitosan-decellularised-derma scaffolds had high interval porosity with the porosity (92.8%), the density (0.09796g/ml) and the water absorption (2169±100)%. The cytocompatibility test showed that the seeded MC3T3-E1 cells could adhere to the scaffolds and proliferate.Conclusion：The three-dimensional chitosan-decellularised-derma scaffolds had high interval porosity with the well-distributed diameter. The MC3T3-E1 cells were easy to adhere the scaffolds and proliferate which showed that the scaffolds had a good cytocompatibility.

Abstract:Objective To investigate the mechanical prosperity and degradation rate of the scaffolds by compounding collagen and the nano sol-gel derived bioactive glass were studied in this paper，and that would provide the theoretical basis for the further application of collagen based scaffold. Method The scaffold by compounding collagen and the nano sol-gel derived bioactive glass (58S) were prepared using the freeze-drying techniques with the bioactive glass as phase addition. To affect the aggregation state of the collagen fibers with adjusting the supplementation of bioactive glass, then the microstructures of the compound scaffold would be different. At last, the compound scaffolds with different mechanical properties were prepared. Results (1) As the aggregation state of the collagen fibers changed, the scaffold with the coarser collagen fibers with the diameters 400-600nm approximately is prepared. The coarser collagen fibers would play an important role in improving the mechanical property and slowing down the degradation rate of the collagen based scaffolds. (2) The interactions between bioactive glass and collagen are studied by FTIR and Raman technologies. When the quality of content of collagen in the compound scaffold is lower than 20%, the secondary structure of collagen is damaged severely. Conclusions The composite scaffold with the mass ratio of collagen to bioactive glass to 40:60 has the best performance in mechanical property and degradation, which would be helpful for further applications

Abstract:Objective To improve the long-term biocompatibility and mechanical stability of Titanium alloy implants. Method micro-nano patterned TiO2 thin films have been prepared on TC4 substrates via a sol-gel dip-coating method with Ti(OC4H9)4 (TEOT) as precursor and polyethylene glycol (PEG) as organic template. The influence of PEG concentration upon the morphology of the target films has been studied by using AFM. The wettability and tribological properties of the target films have been studied by means of optical contact angle measuring instrument and UMT-2. Results When increasing the PEG concentration to 3.5g/100mL, a parallel arranged groove structure can be obtained on the surface of the sample; compare with TiO2 sol-gel film without adding organic template, the wear resistance of the patterned film is better. Conclusions The feature of the patterned TiO2 films can be controlled by adding different amount of organic template; and it has been proved that a certain kind of patterned structure can improve the wear resistance of the film.

Abstract:Objective Prepare biomimetic multilayered scaffold which has similar structure of natural cartilage. Methods By lyophilizing the scaffolds which were prefrozen at -20℃ and in liquid nitrogen successively, we prepared double-layered spongy scaffolds. By partially thawing the prefrozen samples and refreezing them in liquid nitrogen before the final liyophilization, we prepared biomimetic multilayered scaffolds. XRD and FT-IR were used to confirm the interaction between collagen and chitosan. SEM was used to observe the morphologies of the scaffolds. The mechanical properties of pure chitosan scaffolds, pure collagen scaffolds, composite single-layered scaffolds and biomimetic multilayered scaffolds were compared. Results There is chemical interaction between collagen and chitosan. Composite materials eill form better pore structure. The biomimetic multilayered scaffolds had upright pores, round pores and a dense layer from bottom to top of the scaffolds. The scaffolds had quite different mechanical properties between dry and wet state. Under wet state, the different layers of the biomimetic multilayered scaffolds have different mechanical properties. Conclusions The biomimetic structure of the multilayered scaffold is very close to that of the natural articular cartilage, and the different layers of the biomimetic multilayered scaffolds had different mechanical properties under wet state. These are hopefully beneficial to help maintain the phenotypes of chondrocytes and promote the repairing effect of cartilage defects .

Abstract:Objective To evaluate the cellular toxic and release of pharmaceutical dressing. Methods Following the State standard GB/T14233.2-2005, the L929 cellular morphology was observed by inverted microscopy after 72h and proliferation of the cells was examined using mitochondrial function (MTT) assay. Relative growth rate (RGR) was calculated and cytotoxicity grade was evaluated. With PBS7.4 as dissolution media, and (32±0.5)℃ as dissolution temperature, the release rate was determined with UV method with the determination wavelength of 288nm and the dissolved liquid in1/6, 1/2, 1, 3, 16, 24, 36 and48h. Results The average cell RGR of the pharmaceutical dressing was 91.25% and reached 1 grade. L929 cellular morphology was normal. Pharmaceutical dressing release accord to Higuchi equation，and the simulated equation is Mt/M∞＝0.3271t0.239. Conclusion Biologic compatibility of the pharmaceutical dressing is good, and the release of levofloxacin from the pharmaceutical dressing is sustained in vitro.

Abstract:Objective Clutching internal fixtor (CIF) loose and the fixed part weakly heal up are often found in orthopedic clinic.In the present paper, biomechanics methods were used to try to explain and analyze these issues, provide a helpful suggestion for the application of CIF in clinic. Method Commercial finite element method(FEM) Program ANSYS was applied to set up the Finite Element Models of orthopedic CIF and bone tissue to analyze and evaluate the biomechanical performances of the Ni Ti shape memory alloy CIF. Results There is an interaction force between embracing force of CIF and resistant force of bone tissue during the orthopedic clinical treatment. The embracing force along two semi-circular arms of CIF is increasing from the open position and reached the maximum value at the open symmetry position where the deformation of the bone occurre. Conclusion It is the key to choose the force loading position during the practical treatment, as the concentration force is the main force when there is an interactive force between the bone and the CIF.

Abstract:Objective In order to avoid potential injuries imposed to human body, it can be feasible to use the musculoskeletal models which can be reconstructed from the cadaver color cryosection (CCC) images, computerized tomography (CT) images, magnetic resonance (MR) images or other images to analyze the dynamic properties of muscles in vivo during human movement. Methods We reconstruct the lower limb musculoskeletal model and define the uniform joint coordinate system (JCS) on the model and the subject. The coordinate transformation of the muscle attachment points both on the model and the subject is described in detail. Results The length and the moment arm of the biceps femoris (short head) during knee flexion are calculated and analyzed. Conclusion This method plays an important role in improving the kinematics and dynamic simulation and the muscle force estimation.

Abstract:Objectives To construct three-dimensional finite element model of lumbar spondylolysis, then to verify its validity by comparison of biomechanics in vitro. Methods According to the radiological data of a patient with lumbar spondylolysis, the bone and intervertebral disc of L4-S1 were reconstructed by Simpleware software. The lumbar attaching ligaments and articular capsule were added into simulating model by Ansys software. Finally, the three-dimensional finite element model of lumbar spondylolysis was simulated successfully, and validated by lumbar spondylolysis biomechanical experiment in vitro. Results The reconstruction of digital model is contained of the bones of lumbar spine which includes of vertebral cortical bone, cancellous bone, facet joint, pedicle, lamina, transverse process and spinous process,as well as annulus fibrosus, nucleus pulposus,superior and inferior end-plates. Besides, anterior and posterior longitudinal ligaments, flavum ligament, supraspinal and interspinal ligaments and articular capsule of facet joint are also attached. The model consisted of 281,261 nodes and 661,150 elements. Imitation of spondylolysis is well done in this model. The validity of the model is verify by comparison of the results of biomechanics in vitro which involved in the trends under loading of stress/strain of L4 inferior facet process, L5 superior and inferior facet process, S1 superior facet process and the trend of stress/strain of lateral and medial L4 inferior facet process. Conclusions Lumbar spondylolysis is reconstructed to three-dimensional model using finite element analysis, and can be further used in the research of biomechanics of lumbar spondylolysis.

Abstract:Objective Objective To evaluate the biomechanical effects of using a new injectable calcium phosphate cement to consolidate the fixation of osteoporotic intertrochanteric fracture. Method Five matched pairs of human cadaver femora were used to produce the model of intertrochanteric fracture. All fractures were fixed with dynamic hip screws(DHS),and divided into two groups. In the CPC consolidation group of each pair, CPC was used to grout the hip screw and to fill the posteromedial defect. All femora were subjected to biomechanical test. Result Under the loading of 500 N, in the CPC consolidation group, the mean axial stiffness was (691.93±18.90) N/mm and the horizontal shear stiffness was (5553.84±27.47) N/mm. The mean lateral and medial strength was 5.15±0.35 MPa and (4.13±0.24) MPa. The torsion stiffness was 0.41 and the ultimate loading was (3580±286)N. In the control group, the mean axial stiffness was (453.45±19.75) N/mm, the horizontal shear stiffness was (3848.87±22.63) N/mm, the mean lateral and medial strength was (3.12±0.37) MPa and (1.80±0.21) MPa, and, the torsion stiffness was 0.35 and the ultimate loading was (2512±189)N. Consolidation fixation with CPC increased each of the biomechanical efficiency（P<0.05）. Conclusion CPC consolidation of osteoprotic femoral head and the medial defect of intertrochanteric fracture could significantly improve the overall stability and decrease the rate of postoperative complication.

Abstract:Objective The objective of this study is to investigate the effects of the thickness of the adhesives (3M ESPE RelyX ARC) on the internal stress distribution of the IPS Empress II full-ceramic crowns using Finite Element Analysis (FEA). Methods A dummy Empress II ceramic crown restoration of the mandible right first molar was prepared according to standard dental process. Followed by micro-CT scanning, four 3D numerical models with cement thickness 60, 90, 120 and 150μm were established. The models were subjected to four loading conditions and stresses in veneer and core layers were presented. Results Numerical results indicate that when adhesive thickness increases from 60μm to 90μm, the maximum principal stress either in veneer or core decreases. However, when thickness increases to 150μm, stress variation trends differ from adhesives. Conclusion The normal stresses in adhesives remain a low level when the thickness varies from 90μm to 120μm, while the shear stress is less sensitive to the thickness when it exceeds 90μm. There is an optimal thickness which can reduce the tensile stress in the core and veneer. Attention should be paid to the shear strength of the adhesives since the shear stress could cause failure in the adhesive layer.

Abstract:Objective The mechanical model of nonlinear blood flow in large blood vessels is developed and the propagation of nonlinear pressure wave is studied. Methods Taking the effect of large deformation, nonlinear equation of motion is established in the current configuration in terms of the constitutive equations proposed by demiray for soft biological tissues. Results Employing the reductive perturbation method the KdV equation is derived from the nonlinear partial equations governing the motion of coupled system. Conclusion It is shown from this that the system admits an accurate periodic wave solution or solitary wave solution under certain conditions.

Abstract:Abstract Objective After the implantation, coronary stent was expected at least to keep integrity and maintain the predicated function for over 10 years or 4e8 cycles under the pulsatile loading conditions, and the fatigue property of the stent should be evaluated. Method The finite method was used to analyze the stress distribution of different phases and evaluate the fatigue life according to Goodman criteria, meanwhile, the accelerated fatigue experiment was also performed . Results It could be concluded that the dangerous points were located in the lateral inner surface of stent curvature. Conclusion The results proved that the fatigue property could be simulated through the finite element analysis, which can provide the theoretical guidance for the stent design.

Abstract:Objective To evaluate the diagnosis value of urodynamics in patients with benign prostate hypertrophy(BPH).Methods With urodynamic device,the full set of urodynamic exam was administrated in 427 patients with BPH,and the externalsphincter urethral myogram was monitored simultaneously in pressure-flow studies(PFS).The umdynamic finding such as Qmax 、Pdet-Qmax、Popen、DS(descending slope) and post-voiding residual(PVR)were recorded,as well as the situation of bladder detrusor constraction and bladder compliance and urethral sphincter coordination. The bladder outflow obstruction was diagnosed by A-G nomogram，P-Q plot and DS.The IPSS score and prostate volume were also acquired. Results The diagnostic rate of BOO is 81.5％,among them concomitantly detrusor muscle impair in 117 cases(27.4％), decreased bladder compliance in 162 case (37.9％)，urethral sphincter dyssynergia in 148 cases(34.7％)，and unstable bladder in l64 cases (38.4％). The increase degree of BOO show an increasing tendency with urodynamic findings such as Qmax ,Pdet-Qmax,Popen,DS and IPSS score and prostatic volume respectively，however a decreasing tendency with Qmax and bladder compliance. Conclusions The urodynamic exam plays an important role in diagnosis of BOO.There is a positive relation among degree of BOO with urodynamic finding such as Pdet-Qmax,Popen,DS and IPSS score and prostatic volume,however，negative relation with Qmax and bladder compliance respectively.