Journal of Biomimetics, Biomaterials and Tissue Engineering Vol. 13

Abstract: The quest for new biomaterials to serve as cell scaffolds for applications in tissue engineering is of prime importance. In this work, we investigated microfiber assemblies of Ellagic Acid (EA), a plant polyphenol to serve as scaffolds for attachment and proliferation of osteoblasts. The advantage of Ellagic Acid self-assembling system is its intrinsic ability to order into multiple layers due to its capability to form liquid crystalline assemblies. We prepared ellagic acid-microfiber composites by the layer-by-layer (LBL) assembly method, where collagen (COL), poly-Arginine (poly-R), and calcium phosphate nanocrystals were coated on the surface of ellagic acid microfibers. The attachment of the various layers was confirmed by various spectroscopic and microscopic methods. The samples were found to be porous with an average pore size of 600 nm. The formed microconjugates were biodegradable and supported the growth of human fetal osteoblast (hFOB) cells in vitro. Our findings suggest that this system not only promotes initial cell adhesion but also can be utilized to deliver the vital biological molecule ellagic acid to cells at the scaffold interface and displays a new strategy for the design of biomaterials.

Abstract: Austenitic stainless steel 316L is widely used in implantology due to its biocompatibility, a lower price than titanium and because can be easily mechanically machined. The drawback is due to the fact that toxic nickel and chromium ions are released into human body fluids. Our proposal is to coat 316L austenitic stainless steel with biovitroceramic layers made of oxide system SiO₂, B₂O₃, Na₂O, CaO, TiO₂, P₂O₅, K₂O, Li₂O and MgO by means of an enamelling procedure in order to hinder the release of Ni and Cr ions from the metallic implant surface toward the tissue around the implant. In order to achieve a firm adherence of biovitroceramic layer onto the metal, with an optimal composition for biocompatibility and bioactivity, we have modified the steel surface by a titanizing thermochemical treatment. The adherence of the biovitroceramic layer to the 316L stainless steel with modified surface is very good. The biovitroceramic coating - metallic substrate couple was studied by optical microscopy, electron microscopy (SEM and EDAX), X-ray diffraction analysis and microhardness trials.

Abstract: This paper concerns a venation-like design method of rib layout and its application on some plates subjected to bending loads. Main topological characters of dicotyledonous venation and two determinative mechanical parameters in leaf venation morphogenesis theories are extracted, on the basis of those elicitations, a venation growing algorithm is proposed as an attempt at the proper layout of ribs in plate. Energy criterion and shear stress is specified as the factor orienting mainvein and subveins respectively. Vectorial equation equilibrium is used in reorganization to calculate widths and adjust vein cells slightly. Finite element method functions as background technique, under which several simple-shaped plates under bending loads are designed by venation growing algorithm. The resultant venation-like ribs offer multi-balanced improvements.

Abstract: Zirconia-alumina ceramic foam scaffolds with a nanocrystalline HAP coating were used for the preparation of integrated motile orbital implants. This study demonstrated that open-cell ceramic foams with enhanced strength-to-density ratio are quite suitable as biocompatible materials for the manufacture of orbital implants for post-enucleation syndrome treatment. In-vivo studies demonstrated that the application of a nanocrystallyne (not sintered) HAP coating facilitated the formation of dense fibrous capsule around the implant as well as the fast tissue ingrowth into the implant’s internal space. Orbital implants with the optimized pore size and HAP content were implanted to the animal’s eye cavity with their fixation to the extraocular muscles, and their motility was ensured.

Abstract: Anterior cruciate ligament injuries commonly in traffic accident, sports activities and extreme sports. Anterior cruciate ligament reconstruction is a common practice to help the patients restore the knee stability. However, there is no previous comparison study of single bundle reconstruction, double-femoral double-tibial tunnel reconstruction, single-femoral double-tibial tunnel reconstruction, and double-femoral single-tibial tunnel reconstruction with respect to biomechanical characteristics such as rotational stability, force and stress inside the ligament and grafts, stresses inside the soft tissues. In this study, we developed a pair of three-dimensional finite element models of a lower extremity including femur, tibia, fibula, cartilage, meniscus, and four major ligaments at 0°，25°，60° and 80°of knee flexion. Based on the intact models, single bundle reconstruction, double-femoral double-tibial tunnel reconstruction, single-femoral double-tibial tunnel reconstruction, and double-femoral single-tibial tunnel reconstruction models were also developed. Then, the anterior tibial translations, the forces and stresses inside the ACL and ACL replacements, as well as the stresses inside the menisci, femoral and tibial cartilage were predicted under a combined rotatory load of 10Nm valgus moment and 5 Nm internal torque, respectively using finite element analysis. The rotational stability, ligament forces and stresses in the menisci, femoral and tibial cartilage following double bundle augmentation were superior to the other reconstruction techniques, while there is little advantage in ligament stress compared to that of the single bundle reconstruction. We conclude that double-femoral double-tibial tunnel reconstruction may have advantages with regard to biomechanical characteristics such as rotational stability, force inside the ligament and grafts, stresses inside the soft tissues.

Abstract: The only grouting material used for anchoring cemented arthroplasties to contiguous bones is PMMA (Polymethyl methacrylate) bone cement. In this study the flow of bone cement through porous cancellous bone is modelled to determine the degree of penetration in total hip replacement using FIDAP simulation software. Power law viscosity model is used with constant consistency index and power law index less than 1 for pseudoplastic behaviour of Simplex P® and Zimmer bone cement. The effect of bone cement amount has been investigated under four different prosthesis insertion velocity 5, 10, 15 and 20 mm/s. The result shows that the depth of penetration increases with decreasing bone cement amount. In the case of Zimmer bone cement more penetration through cancellous bone was observed than Simplex P® bone cement.

Abstract: Problems that occur in the mitral valve are now worrying an increasing number of patients each day. In the mitral valve, regional variations in structure and material properties combine to affect the biomechanics of the entire valve. Previous studies have shown that the mitral valve leaflet tissue is highly extensible. The objective of this study was to investigate the relationship between the rigidity of mitral valves leaflet and backflow problems. Two stages of mitral valves analysis systolic and diastolic condition and also with and without ventricle were investigated. 2D models of the mitral valve leaflet (MVL) were created in ADINA-FSI for computational fluid dynamic analysis. The results show a linear relationship between rigidity of the mitral valves leaflet and volume of backflow. In conclusion, these computational techniques are very useful in the study of both mitral valve leaflet disease and failure of prostheses.

Abstract: Blood-viscosity reducing drugs like “Pentoxifylline” improve blood flow by making the blood less viscous. The resistance to flow of blood in diabetic patients is higher than in non-diabetic patients. Thus diabetic patients with higher resistance to flow are more prone to high blood pressure. Therefore the resistance to blood flow in case of diabetic patients may be reduced by reducing viscosity of the plasma. Viscosity of plasma can be reducing by giving Pentoxifylline. In this paper an attempt has been made to investigate the blood flow behaviour and significance of non-Newtonian viscosity through a stenosed artery using Bingham Plastic fluid model. Numerical illustrations presented at the end of the paper provide the results for the resistance to flow, apparent viscosity and the wall shear stress through their graphical representations. It has been shown that the resistance to flow, apparent viscosity and wall shear stress increases with the size of the stenosis but these increases are comparatively small due to non-Newtonian behaviour of the blood indicating the usefulness of its rheological character in the functioning of the diseased arterial circulation.

Abstract: Al₂O₃ Fiber-reinforced HAp was sintered using microwave and conventional heating. Microwave heating cycles were ~50 times faster than conventional sintering cycles and enabled the use of reduced densification temperatures and soak times by as much as ~100°C and 55 min, respectively. However, although there was a significant improvement in densification levels attainable before decomposition, the improvements were insufficient to produce near-fully or fully dense samples.