Bio-Medical Materials and Engineering - Volume 16, issue 6

Authors: Comlekci, Selcuk

Article Type: Research Article

Abstract: The main objective of this paper is to study on the fields, resultant forces, and the dielectric substances in biologic tissues. Additionally, to unveil the possible mechanism which affects on major biological activities were examined. In the scientific literature, there are many studies conducted with low frequency Electromagnetic Fields (MFs), Static Magnetic Fields (SMFs), and Pulsed Electromagnetic Fields (PEMFs). However, we face in some cases; merely electric fields may be effective on biological functions (around 10 kV/m). Parallel plate exposure system was chosen as a model in this paper. In order to overcome the difficulty of generating virtual homogenous low …frequency ac (power frequencies) or dc fields, a pair of appropriately designed parallel plates exposure model may be mighty tool. In this study, an important assumption, with deriving an equation that possible explanation for heat rise in a living tissue, has been made. Consequently it has been assumed that the field Eloc may be responsible both for the induced and oriented polarization. Show more

Keywords: Electric fields, dielectric forces, low frequency EF, parallel plate exposure system

Citation: Bio-Medical Materials and Engineering, vol. 16, no. 6, pp. 363-367, 2006

Authors: Geronilla, Kenneth | Wu, John Z. | Baker, B.A. | Cutlip, Robert G.

Article Type: Research Article

Abstract: Many work related injuries stem from the exertion of skeletal muscle forces over an extended period of time. Musculoskeletal injury can be caused by muscle's inability to maintain force during occupational exposure. The goal of the present study is to test how various rest times (duty cycles) between long isometric contractions will affect decrements in force, and develop a model that characterizes force decrements due to skeletal muscle fatigue. All tests were performed in vivo on the tibialis anterior muscle of anesthetized Sprague–Dawley rats. Animals were randomly assigned to either a 10 second (N=8), 1 minute (N=8), or 5 minute …(N=8) duty cycle group. All animals were then subjected to 7 isometric contractions (duration of 2.8 seconds). A model was constructed to characterize forces changes over the duration of a contraction and over multiple contractions. The model consisted of a power law and an exponential component; these two components were combined by using an exponential weighting function. Overall, the combination of a power law and exponential model with a weighting function satisfactorily characterized the changes in isometric force for the 10 second duty cycle, but a simpler exponential model could be used where longer duty cycles are performed. Show more

Keywords: Skeletal muscle, modeling, injuries, isometric contractions, cyclic

Citation: Bio-Medical Materials and Engineering, vol. 16, no. 6, pp. 369-380, 2006

Authors: Verma, Arpana | Choubey, Animesh | Raval, Ankur | Kothwala, Devesh

Article Type: Research Article

Abstract: In the current investigation, annealing was employed as a means to improve the mechanical performance of 316LVM coronary stents. Two different temperatures (1000°C and 1150°C) were explored for the thermal processing of the device. Acid pickling was done as a pre-annealing step to remove the debris and slag material attached to the stent after laser cutting. Post annealing operation involved the electrochemical polishing of the device which was also a parameter for assessment of the feasibility of the annealing process. Microstructural characterization, balloon expandability and tensile testing of the stents were performed to characterize the properties after thermal treatment. A …fine grained austenitic structure with marked improvement in the % elongation (>40%) could be achieved after annealing the stents at 1000°C. Balloon expandability tests of the stents annealed at 1000°C indicated that the device was implantable. Show more

Keywords: Cardiovascular stent, acid pickling, annealing, electrochemical polishing

Citation: Bio-Medical Materials and Engineering, vol. 16, no. 6, pp. 381-395, 2006

Authors: Hsu, Shan-hui | Chuang, Shang-Chi | Chen, Chung-Hsin | Chen, David C.

Article Type: Research Article

Abstract: Previously we have fabricated the small diameter polyurethane (Pellethane 2363-80A, abbreviated PU) vascular grafts that were modified by epoxy-crosslinked gelatin (abbreviated gelatin) and an RGD-containing protein (abbreviated CBD-RGD) to facilitate the endothelial cell (EC) seeding on the surface. In this study, the biocompatibility of such surface after freeze-drying and gamma irradiation was evaluated. The contact angle of the irradiated PU dropped a little and the ESCA spectra revealed oxygen bonding. The increases in the amount of extractables as well as in the molecular weight distribution were observed. The mechanical properties decreased only slightly. The irradiated PU surface showed enhanced EC …affinity that persisted after several months of storage. Gelatin, CBD-RGD (used with either gelatin or PU), and PU modified by gelatin and CBD-RGD all demonstrated higher EC affinity after freeze-drying and gamma irradiation (2.5 Mrad). The positive cellular effect remained after storage. Based on these results, freeze-drying followed by gamma irradiation at 2.5 Mrad is a proper way to process and store these vascular grafts. Show more

Keywords: Polyurethane, gelatin, RGD-containing protein, gamma irradiation, endothelial cells

Citation: Bio-Medical Materials and Engineering, vol. 16, no. 6, pp. 397-404, 2006

Authors: Tadokoro, Mika | Hattori, Koji | Takakura, Yoshinori | Ohgushi, Hajime

Article Type: Research Article

Abstract: Fresh frozen sections are the best materials to assess tissue-engineered bone using cells/ceramic complexes. However, there are a lot of technical difficulties in obtaining serial sections suitable for microscopic examinations. Kawamoto et al. developed a method for the production of fresh frozen sections using new adhesive tape, and showed that sections were very useful for histological and histochemical studies. However, no study reported that the method was useful for tissue-engineered bone from histochemical and histomorphological points of view. This study aimed to determine the efficacy of fresh frozen sectioning for evaluating tissue-engineered bone. We revealed that fresh frozen sections retained …the original morphology of tissue-engineered bone, and their biochemical characteristics. Therefore, rapid preparation of fresh frozen sections using adhesive tape is extremely useful for research of tissue-engineered bone, and serial sections can be assessed from both histomorphological and biochemical point of views. It is expected that this method will become a powerful tool in tissue-engineering of hard tissues. Show more

Keywords: Bone tissue engineering, ceramic structure, fluorescence, histomorphometry, immunochemistry, mesenchymal stem cell

Citation: Bio-Medical Materials and Engineering, vol. 16, no. 6, pp. 405-413, 2006

Authors: Fernández-Fairén, M. | Sala, P. | Gil, F.J.

Article Type: Research Article

Abstract: Fifty two ceramic femoral heads have been investigated after implantation. All heads had articulated against ultra high molecular weight polyethylene (UHMWPE) cups. Examination of the heads shows changes in sphericity and surface roughness due to the wear. The behaviour of these retrieved heads after clinical use confirms the problems derived from the use of yttria-stabilised tetragonal zirconia heads. In this paper, a failure mechanism for this type of ceramic is proposed. The slow yttria dissolution produces the transformation from tetragonal to monoclinic phase with a volume change. This fact provokes an important decrease in mechanical properties favouring wear. The yttria …dissolution and the zirconia solid transformation were confirmed by X-ray diffraction. Show more

Keywords: Fracture toughness, femoral heads, wear

Citation: Bio-Medical Materials and Engineering, vol. 16, no. 6, pp. 415-422, 2006

Authors: Lei, Dang | Wardlaw, D. | Hukins, D.W.L.

Article Type: Research Article

Abstract: Setting times, volume after setting, injectability and hardness (at 37°C in contact with Ringer's solution) were determined for cements made of mixtures of calcium sulphate hemihydrate (CS) and hydroxyapatite (HA) with a range of compositions. The purpose of these experiments was to determine the behaviour of a mixture that could be used as an injectable cement for orthopaedic applications, including spinal fusion. A suitable mixture consisted of 60% CS and 40% HA by mass; a slurry was made by mixing solid (36 g) with water (15 cm3 ). The slurry had initial and final setting times of 5.7±1.3 min and …19.6±0.7 min (mean ± standard deviation), respectively. The hardness of the cement did not systematically increase or decrease in the 72 h following the final setting time. The volume of the cement was 99.8±0.4% of the volume of the initial slurry, i.e. there was negligible shrinkage on setting. It was able to withstand a pressure of 7.3±1.2 MPa, applied by a hemispherical indenter before the onset of permanent damage, indicating adequate strength for spinal fusion. Show more

Keywords: Bone repair, calcium sulphate, hydroxyapatite, injectable cement, spinal fusion

Citation: Bio-Medical Materials and Engineering, vol. 16, no. 6, pp. 423-428, 2006

Article Type: Other

Citation: Bio-Medical Materials and Engineering, vol. 16, no. 6, pp. 429-437, 2006

Article Type: Other

Citation: Bio-Medical Materials and Engineering, vol. 16, no. 6, pp. 439-441, 2006