Bio-Medical Materials and Engineering - Volume 15, issue 6

Authors: Gorschewsky, Ottmar | Puetz, Andrej | Riechert, Katrin | Klakow, Andreas | Becker, Roland

Article Type: Research Article

Abstract: Allografts were used in the 80s and 90s to replace ruptured anterior cruciate ligaments (ACL) in the reduction of donor site morbidity. It was evident that in comparison with the autologous cruciate ligament grafts (ligamentum patellae) using Allografts (Tutoplast® ), a noticeably higher rupture rate appeared. The results from the work submitted serve as a detailed, highly structured description of human bone-patellar, tendon-bone (BPTB) and allografts (Tutoplast® ), which were used to replace ruptured anterior cruciate ligaments. The biochemical parameters: hydroxyproline or, as the case may be, total collagen content and non-reducible crosslinks were quantified. The examined material consisted of …allografts, which had been taken from human ligamentum patellae and implanted five years ago as cruciate ligament reconstructions. The total collagen content in the analysis material amounted to 52.74%. The pyridinoline concentrations indicated in the test material amounted to 0.2135 mol PYR/mol collagen. The tissues examined contained 0.009245 mol DPD/mol collagen. The results show that in comparison with the values given for these tissues in the literature, there was a clear reduction in the total collagen content and the concentration of non-reducible correlations. On the basis of the analysis it may be supposed that the changed biochemical parameters are a cause of the increased rupture rate in allografts. Show more

Keywords: Ligament, tendon, hydroxyproline, non-reducible crosslinks, allograft

Citation: Bio-Medical Materials and Engineering, vol. 15, no. 6, pp. 403-411, 2005

Authors: Liu, Mine-Yine | Yeh, Ming-Long | Luo, Zong-Ping

Article Type: Research Article

Abstract: An understanding of collagen ultrastructure is very important for designing biopolymers mimicking collagen functions in tissue engineering, or for diagnosing abnormal collagen structure in clinical study. The present study examined formation of a large population of type I collagen single fibrils under different buffer compositions and temperatures. Fibril structures were investigated by dark-field microscopy and atomic force microscopy (AFM). In the phosphate buffered saline (PBS) buffer, the average lengths of single fibrils were 4.8±2.2, 5.0±1.9 and 9.2±5.0 μm for 37°C, 33°C and 29°C, respectively. The differences were significant (P<0.05) between 37°C and 29°C and between 33°C and 29°C. In the …sodium phosphate (SP) buffer, the average lengths of single fibrils were 10.6±5.4, 11.1±4.5 and 19.6±11.7 μm for 37°C, 33°C and 29°C, respectively. Similarly, the differences were significant (P<0.05) between 37°C and 29°C and between 33°C and 29°C. While at the same temperature, the average lengths of single fibrils differed significantly (P<0.05) between PBS and SP buffers. Single fibrils formed in SP buffer were found to have greater average length than those formed in PBS buffer. Show more

Keywords: Type I collagen single fibril, dark-field microscopy, atomic force microscopy, buffer compositions, temperature

Citation: Bio-Medical Materials and Engineering, vol. 15, no. 6, pp. 413-420, 2005

Authors: Connolly, Joan | St. Pierre, Timothy G. | Dobson, Jon

Article Type: Research Article

Abstract: The magnetic properties of 5 commercially available magnetic microsphere samples are tested and compared with those stated by their manufacturers. A suspension of magnetic, iron oxide nanoparticles is studied for comparison. Two of the microsphere samples have magnetic properties which do not support the manufacturer's claims of superparamagnetism. The remaining 3 microsphere samples as well as the nanoparticle suspension are superparamagnetic or ferromagnetic as claimed by the manufacturers. Field cooled and zero field cooled magnetisations indicate that the non-superparamagnetic microsphere samples contain blocked magnetic particles at room temperature. This observation is supported by the open hysteresis loops of the room …temperature, field dependent magnetisation measurement. There is a significant paramagnetic component in the superparamagnetic microspheres. This is also present to a lesser extent in a nanoparticle suspension. Show more

Keywords: Microspheres, magnetic, iron oxide nanoparticles, physical properties

Citation: Bio-Medical Materials and Engineering, vol. 15, no. 6, pp. 421-431, 2005

Authors: Koo, T.K.K. | Chao, E.Y.S. | Mak, A.F.T.

Article Type: Research Article

Abstract: A primary function of external fixator is to stabilize the fracture site after fracture reduction. Conventional fracture reduction method would result in fixator configurations deviated from its neutral configuration. How the non-neutral configurations would affect the biomechanical performance of unilateral external fixators is still not well-documented. We developed a finite element model to predict the fixation stiffness of the Dynafix unilateral external fixator at arbitrary configurations under compression, torsion, three-point, and four-point bending. Experimental testing was done to validate the model using six Dynafix unilateral external fixators in neutral and particular non-neutral configurations. Effects of loading directions on bending stiffness …were also studied. It appeared that the model succeeded in revealing the relative stiffness of the neutral and non-neutral configuration in all the loading conditions. Our results also demonstrated that bending stiffness could vary substantially for different loading directions and the principle loading directions could be very different for different fixator configurations. Therefore, a more logical way to compare the bending stiffness is to identify the principle loading directions of each fixator configuration and used their maximum and minimum bending stiffness as comparison criteria. Given that fixator configurations could substantially change the stiffness properties of the bone–fixator system, computer simulation with finite element modeling of this kind will provide useful clinical information on the rigidity of certain configurations in stabilizing the fracture site for bone healing. Show more

Keywords: Finite element analysis, external fixator, fixation stiffness, bone fracture fixation

Citation: Bio-Medical Materials and Engineering, vol. 15, no. 6, pp. 433-444, 2005

Authors: Zehbe, R. | Libera, J. | Gross, U. | Schubert, H.

Article Type: Research Article

Abstract: The biological, biochemical, mechanical, and structural properties of artificial scaffolds for tissue engineering are known to be of great importance. Therefore, in this study a hydrogel derived scaffold with biomechanical and structural properties similar to native articular cartilage was synthesized. The gelatine-based hydrogel was processed by freeze-structuring, structuring by electrochemical water-decomposition, freeze-drying and chemical fixation resulting in a defined scaffold-structure. By electron microscopy a perpendicular pore-channel structure was verified with channel diameters between 30 μm and 70 μm. Mechanical testing showed mechanical properties similar to native cartilage. Human chondrocytes from biopsy samples were cultivated on these hydrogel scaffolds for three …days. Two different cell densities (1.2×106 cells/cm3 and 12.0×106 cells/cm3 ) were used for cultivation. Histology of the cell seeded artificial scaffolds demonstrated vital cells that are widely distributed within the scaffold and mimic a columnar arrangement. Show more

Keywords: Cartilage tissue engineering, chondrocyte, cross-linking, hydrogel, scaffold

Citation: Bio-Medical Materials and Engineering, vol. 15, no. 6, pp. 445-454, 2005

Authors: Rodrigues, J.M. | Luís, A.L. | Lobato, J.V. | Pinto, M.V. | Lopes, M.A. | Freitas, M. | Geuna, S. | Santos, J.D. | Maurício, A.C.

Article Type: Research Article

Abstract: Entubulation repair of peripheral nerve injuries has a lengthy history. Several experimental and clinical studies have explored the effectiveness of many biodegradable and non-degradable tubes with or without addition of molecules and cells. The main objective of the present study was to develop an economical and also an easy way for culturing a neural cell line which was capable of growing, differentiating and producing locally nerve growth factors that are otherwise extremely expensive, inside 90 PLA/10 PLG nerve guides. For this purpose the authors have chosen the N1E-115 cell line, a clone of cells derived from mouse neuroblastoma C-1300 with …the perspective of using this differentiated cellular system to cover the inside of 90 PLA/10 PLG nerve guides placed to bridge a gap in the rat sciatic nerve experimental model. The N1E-115 cells proliferate in normal culture medium but undergo neuronal differentiation in response to DMSO. Upon induction of differentiation, proliferation of N1E-115 cells ceases, extensive neurite outgrowth is observed and the membranes become highly excitable. While it is known that Ca2+ serves as an important intracellular signal for various cellular processes, such as growth and differentiation. It is also known that can be toxic to cells and is involved in the triggering of events leading to excitotoxic cell death in neurons. The [Ca\[$^{2+}]\tsub{i}$ in non-differentiated N1E-115 cells and after distinct periods of differentiation, have been determined by the epifluorescence technique using the Fura-2-AM probe. The results of this quantitative assessment revealed that N1E-115 cells which undergo neuronal differentiation for 48 hours in the presence of 1.5% DMSO are best qualified to be used to cover the interior of the nerve guides since the [Ca\[$^{2+}]\tsub{i}$ was not found to be elevated indicating thus that the onset the cell death processes was not occurred. Show more

Keywords: N1E-115 cells, nerve regeneration, PLGA, intracellular calcium concentration, epifluorescence technique

Citation: Bio-Medical Materials and Engineering, vol. 15, no. 6, pp. 455-465, 2005

Authors: Sokhanvar, Saeed | Dargahi, Javad | Packirisamy, Muthukumaran | Esmailzadeh, Ebrahim

Article Type: Research Article

Abstract: This paper addresses the fundamental understanding of the chemical control of respiratory system that would be needed to improve the efficiency of artificial ventilators and implement appropriate controllers. Hence, non-linear model for simulation of chemical control of human respiratory system under different physiological conditions is presented. The paper also presents the non-linear dissociation behaviors for oxygen and carbon dioxide solutions in the blood and the Bohr–Haldane effects as well as a new controller model. Tests were conducted on the model under different conditions such as hypoxia, hypercapnia, hypoventilation, and hyperventilation with some combination tests, in order to verify the validity …of the assumptions that were made. Results indicate a very close agreement between the responses obtained from the present model and other published experimental and theoretical results. This model can be used to design a novel artificial respirator controller meeting the bodily requirements of the patient under mechanical ventilation. Show more

Keywords: Respiratory system, non-linear modeling, chemical regulation, Bohr–Haldane effect, hypercapnia, hypoxia, hyperventilation, microdevices, MEMS

Citation: Bio-Medical Materials and Engineering, vol. 15, no. 6, pp. 467-481, 2005

Authors: Kaprielian, N. | Lagneau, C. | Zydowicz, N. | Lissac, M. | Grosgogeat, B.

Article Type: Research Article

Abstract: The aim of this study is to assess the influence of plasma lamps on the properties of the composites compared to the influence of conventional polymerization. Vickers hardness tests, three-point bending tests, and measurement of the shrinkage marginal gap by scanning electron microscopy were carried out on three resin composites (Tetric® Ceram, Z-100™ and Inten-S® ) irradiated with to lamps (Flipo® plasma and Astralis® 7 halogen lamps). With a 3-second exposure, the results of Vickers hardness and resistance to flexion (excepting values for Z-100™) were lower for the composites cured by the Flipo® plasma lamp, than …after 40-second curing by the conventional halogen lamp (Astralis® 7), notably at a depth of 3 mm. With a 5-second exposure the results of Vickers hardness and resistance to flexion obtained using the plasma lamp approached those obtained by using the halogen lamp. Whatever the polymerization protocol used, the measurements of the gap between the tooth and the filling are very similar except for Z-100™/Astralis® 7, for which shrinkage results are more important. For any one resin composite and lamp used, the shrinkage values obtained at a depth of 4 mm are twice higher than those obtained at the surface. In conclusion, for a 3-second exposure the level of polymerization obtained by plasma curing is lower than the one obtained by halogen curing, particularly in depth. On the other hand, 5-second plasma curing results recommends the use of this kind of lamp. Show more

Keywords: Halogen curing, plasma curing, resin composite, micro-hardness, flexural strength, marginal gap

Citation: Bio-Medical Materials and Engineering, vol. 15, no. 6, pp. 483-493, 2005