Bio-Medical Materials and Engineering - Volume 27, issue 2-3
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Bio-Medical Materials and Engineering is to promote the welfare of humans and to help them keep healthy. This international journal is an interdisciplinary journal that publishes original research papers, review articles and brief notes on materials and engineering for biological and medical systems.
Articles in this peer-reviewed journal cover a wide range of topics, including, but not limited to: Engineering as applied to improving diagnosis, therapy, and prevention of disease and injury, and better substitutes for damaged or disabled human organs; Studies of biomaterial interactions with the human body, bio-compatibility, interfacial and interaction problems; Biomechanical behavior under biological and/or medical conditions; Mechanical and biological properties of membrane biomaterials; Cellular and tissue engineering, physiological, biophysical, biochemical bioengineering aspects; Implant failure fields and degradation of implants. Biomimetics engineering and materials including system analysis as supporter for aged people and as rehabilitation; Bioengineering and materials technology as applied to the decontamination against environmental problems; Biosensors, bioreactors, bioprocess instrumentation and control system; Application to food engineering; Standardization problems on biomaterials and related products; Assessment of reliability and safety of biomedical materials and man-machine systems; and Product liability of biomaterials and related products.
Abstract: Laminar, turbulent, transitional, or combine areas of all three types of viscous flow can occur downstream of a stenosis depending upon the Reynolds number and constriction shape parameter. Neither laminar flow solver nor turbulent models for instance the k –ω (k –omega), k –ε (k –epsilon), RANS or LES are opportune for this type of flow. In the present study attention has been focused vigorously on the effect of the constriction in the flow field with a unique way. It means that the laminar solver was employed from entry up to the beginning of the turbulent shear flow.…The turbulent model (k –ω SST Transitional Flows ) was utilized from starting of turbulence to relaminarization zone while the laminar model was applied again with onset of the relaminarization district. Stenotic flows, with 50 and 75% cross-sectional area, were simulated at Reynolds numbers range from 500 to 2000 employing FLUENT (v6.3.17). The flow was considered to be steady, axisymmetric, and incompressible. Achieving results were reported as axial velocity, disturbance velocity, wall shear stress and the outcomes were compared with previously experimental and CFD computations. The analogy of axial velocity profiles shows that they are in acceptable compliance with the empirical data. As well as disturbance velocity and wall shear stresses anticipated by this new approach, part by part simulation, are reasonably valid with the acceptable experimental studies.
Keywords: Laminar-turbulent-relaminarization regimes, stenosis, part by part simulation, numerical analysis, new approach
Abstract: Background: The simulated Doppler blood flow signals are widely used to assess the performance of the clutter filters for removing wall components while reserving low-velocity signals scattered from physiological blood flow approaching the inner vessel-wall injured by a stenosed lesion. Objective: By simultaneously taking into account the natural attributes of the Doppler equipment, blood flow as well as vessel wall of pulsatile carotid arteries with a stenosis, a computer simulation method is presented to produce the compound Doppler ultrasound blood flow signals. Methods: The in-phase and quadrature (I/Q) axial as well as radial blood flow signals…are simulated by superposing a series of cosine functions regulated by the spectrograms estimated from the axial and radial velocity profiles firstly obtained through the solution of the incompressible Navier–Stokes equations, respectively. Meanwhile, the I/Q Doppler signals echoed from pulsatile near (anterior) and far (posterior) walls are reproduced based on their radial movements during a cardiac cycle. Ultimately, those confirmed quadrature signals are summed to generate the compound Doppler signals including the contribution from both blood flow and stenosed vessel-wall. Results: The compound Doppler ultrasound signals echoed from both axial and radial blood flows as well as vessel walls with obstruction grades of 0% (normal arteries), 10% and 25% are simulated respectively. The real signals from the left carotid artery with an approximately 10% stenosis degree are also collected for further assessing the believability of simulated versions. Conclusions: The simulated and clinical tests demonstrate that the proposed computer simulation method can produce compound Doppler signals with confirmed qualitative and quantitative characteristics resembled with the clinical versions, which could be used as an theoretical data source for evaluating the performance of the signal separation between pulsatile blood flows and vessel walls with mild stenosed-lesions.
Keywords: Compound Doppler signal simulation, physiological pulsation, carotid artery with a stenosis, axial and radial velocity profiles
Abstract: Background: For most topical hemostatic agents the mechanism of hemostatic action is not fully understood. Objective: This work aimed to investigate the hemostatic mechanism of action and viscoelastic properties of polyurethane foam (PU) in comparison to the widely used collagen and gelatin. Methods: The hemostatic mechanism of action of the materials was tested using human whole blood and platelet-poor plasma (PPP). The ability of the hemostatic agent to exert pressure on the wound was quantified in terms of its viscoelastic properties both under dry and wet conditions using a low load compression tester (LLCT).…Results: It has been shown that collagen and PU initiate hemostasis through both thrombocyte aggregation and contact activation of the coagulation cascade. Gelatin did not show improved thrombocyte aggregation or initiation of the coagulation cascade compared to the negative control group. PU is more firm under wet conditions and shows more springback than collagen and gelatin. Conclusions: We conclude that PU is promising as a topical hemostatic agent because it initiates both the coagulation cascade and thrombocyte aggregation. Furthermore, it has favorable viscoelastic properties compared to collagen and gelatin which leads to increased pressure on a wound.
Abstract: Background: The incidence of iatrogenic pseudoaneurysms has recently increased due to the more frequent use of high doses of anticoagulants in apheresis therapy. The reason why the decision for an appropriate dose of the anticoagulant is difficult is that such information about the material properties of adsorbers is not provided. Objective: To investigate the calculations to determine the optimal dose of heparin sodium to administer during apheresis. Methods: The calculations were based on experimental data obtained during an in vivo test using dogs and theoretical pharmacokinetics data obtained using a one compartment model. Results:…When information regarding the adsorption isotherm of the adsorbent material that takes competitive adsorption into consideration was provided, the required anticoagulant dose for apheresis could be determined. Conclusions: It is important to decide the optimal dose of anticoagulant that Information about the material’s characteristics including data about its adsorption isotherm that takes competitive adsorption into consideration are provided before therapy. Then, if so, the calculation for required dose must be possible.
Abstract: The deadman theory is composed of two angles: θ 1 and θ 2 , and it is recommended that both be less than or equal to 45°. Based on this theory, surgeons insert the anchor at 45°. However, the biomechanical studies show controversial data. We reviewed the original article and the biomechanical studies in the literature. We further performed three additional studies: 1) a finite element analysis to calculate the pullout strength of thread-less anchors inserted at 45°, 90°, and 135° to the polyurethane foam; 2) the same pullout test using…thread-less anchors and the polyurethane foam; and 3) the same pullout test using metal threaded suture anchors and the simulated cortical bone. From the review and the additional studies, we came to the following explanations for the controversy: #1, the trigonometric calculation is not always applicable because of bone deformation; #2, insertion angle of 45° is the best for a thread-less anchor, but not for a threaded anchor; #3, θ 1 ⩽ 45 ° is true, but it is not equivalent to inserting an anchor at 45°. In conclusion, insertion angle of 45° is the strongest for a thread-less anchor, but 90° is the strongest for a threaded anchor. The pullout strength depends on the inclination of the anchor, friction of the anchor–bone interface, and quality of the bone.
Keywords: Deadman theory, pullout strength, suture anchor, finite element model analysis, pullout test
Abstract: Intravascular ultrasound (IVUS)-based tissue characterization is invaluable for the computer-aided diagnosis and interventional treatment of cardiac vessel diseases. Although the analysis of raw backscattered signals allows more accurate plaque characterization than gray-scale images, its applications are limited due to its nature of electrocardiogram-gated acquisition. Images acquired by IVUS devices that do not allow the acquisition of raw signals cannot be characterized. To address these limitations, we developed a method for fast frame-by-frame retrieval and location of calcification according to the jump features of radial gray-level variation curves from sequential IVUS gray-scale images. The proposed method consists of three main steps:…(1) radial gray-level variation curves are extracted from each filtered polar view, (2) sequential images are preliminarily queried according to the maximal slopes of radial gray-level variation curves, and finally, (3) key frames that include calcification are selected through checking the gray-level features of successive pixel columns in the preliminary results. Experimental results with clinically acquired in vivo data sets indicate key frames that include calcification can be retrieved with the advantages of simplicity, high efficiency, and accuracy. Recognition results correlate well with manual characterization results obtained by experienced physicians and through virtual histology.
Abstract: Total deformation and stability of straight and helical compression plates were studied by means of the finite element method (FEM) and in vitro biomechanical experiments. Fixations of transverse (TF) and oblique (45°) bone (OF) fractures have been analyzed on sheep tibias by designing the straight compression (SP) and Helical Compression Plate (HP) models. The effects of axial compression, bending and torsion loads on both plating systems were analyzed in terms of total displacements. Numerical models and experimental models suggested that under compression loadings, bone fracture gap closures for both fracture types were found to be in the favor of helical…plate designs. The helical plate (HP) fixations provided maximum torsional resistance compared to the (SP) fixations. The fracture gap closure and stability of helical plate fixation for transverse fractures was determined to be higher than that found for the oblique fractures. The comparison of average compression stress, bending and torsion moments showed that the FEM and experimental results are in good agreement and such designs are likely to have a positive impact in future bone fracture fixation designs.
Keywords: Straight and helical plates, transverse and oblique bone fractures, fixation
Abstract: Background: P. aeruginosa considered as a notoriously difficult organism to be controlled by antibiotics or disinfectants. The potential use of alternative means as an aid to avoid the wide use of antibiotics against bacteria pathogen has been recently arisen remarkably. Objective: Effect of extremely low frequency positive electric pulse with different duty cycles on Pseudomonas aeruginosa (ATCC: 27853) growth by constructed and implemented exposure device was investigated in this study. Methods: The exposure device was applied to give extremely low frequency in the range of 0.1 up to 20 Hz with the capability to control…the duty cycle of each pulse with variation from 10% up to 100%. Growth curves of Pseudomonas aeruginosa were investigated before and after exposure to different frequencies (0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 Hz) through measuring the optical density and cell count. Exposures to selected frequencies in the whole ranges of duty cycles were done. These studies were followed by DNA fragmentation, transmission electron microscope (TEM), antibiotic susceptibility tests, and dielectric measurements. Results: Findings revealed inhibition effect by 48.56% and 47.4% together with change in the DNA structural properties for samples exposed to 0.5 Hz and 0.7 Hz respectively. Moreover the data indicated important role of duty cycle on the inhibition mechanism. Conclusion: It is concluded that there are two different mechanisms of interaction between positive electric pulse and microorganism occurred; 0.5 Hz caused rupture in cell wall while 0.7 Hz caused denaturation of the inner consistent of the cell.
Keywords: Extremely low frequency, Pseudomonas aeruginosa, duty cycle, positive electric pulse, DNA, TEM
Abstract: Removal of radioactive substances, such as cesium (Cs) and strontium (Sr), has become an emerging issue after the Fukushima Daiichi Nuclear Power Plant Disaster. To assess the possibility that hydroxyapatite (HA) and zeolites can be used for removal of radioactive substances, the adsorption capacities of Cs and Sr on the HA and a zeolite were investigated. The influence of Fe ions on Cs and Sr adsorption on the HA and the zeolite was also evaluated, because Fe ions are the most effective inhibitor of Cs adsorption on the zeolite. In the Cs adsorption process on the HA and the…zeolite, the zeolite showed a higher adsorption ratio than the HA, and the maximum sorption capacity of the zeolite was calculated as 196 mg/g, whereas the HA showed a higher Sr adsorption ratio than the zeolite. The maximum sorption capacity of Sr on the HA was 123 mg/g. Under coexistence with Fe, Cs adsorption on the zeolite decreased with increasing Fe concentration, reaching 2.0 ± 0.8% at 0.1 M Fe concentration. In contrast, Cs adsorption on the zeolite was improved by adding the HA. In the case of coexistence of the HA, the Cs adsorption on the mixture of the HA and the zeolite was 52.4% ± 3.6 % at 0.1 M Fe concentration, although Cs adsorption on the HA alone was quite low. In the Fe adsorption processes of the HA and the zeolite, the HA exhibited a maximum sorption capacity of 256 mg/g, which was much higher than that of the zeolite (111 mg/g). The high affinity of Fe on the HA contributes to the improvement of the deteriorated Cs adsorption on the zeolite due to Fe ions.
Abstract: Background: Key factors for successful porous polyethylene (PPE) implantation are rapid vascularization and low inflammatory response. Dermal fibroblasts produce a variety of pro-angiogenic and immunmodulatory factors. Objective: The aim of this tissue engineering study was to investigate whether coating PPE implants with dermal fibroblasts in vitro is sustainable in vivo and whether the kinetics of blood vessel ingrowth and immunological responses are hereby affected. Methods: PPE implants were cultured with syngeneic GFP-transfected dermal fibroblasts. Cells on the biomaterial were quantified before implantation into dorsal skinfold chamber preparations of C57Bl/6 mice. Uncoated implants served as…controls. Angiogenic activity and leukocyte-endothelial cell interactions were repeatedly analyzed. After 10 days, mechanical integration was measured and surviving fluorescently labeled fibroblasts were quantified. Expression of inflammatory cytokines was assessed by quantitative real time-reverse transcription PCR. Results: PPE implants were successfully coated with dermal fibroblasts in vitro and 69% of the cells were still detectable at the end of observation. Angiogenic parameters increased during the observation period in both groups. IL-2, IL17A and IL-10 tended to be increased in coated implants, but did not affect leukocyte-endothelial cell interactions. Conclusions: Dermal fibroblast-coating of porous polyethylene implants is feasible and sustainable in vivo . Alone it does not improve biocompatibility but may be beneficial in combination with specific growth factor supplements.
Keywords: Tissue engineering, porous polyethylene, Medpor, dermal fibroblasts, angiogenesis, in vivo fluorescence microscopy