Bio-Medical Materials and Engineering - Volume 13, issue 2

Authors: Otsuka, Makoto | Marunaka, Sunao | Matsuda, Yoshihia | Ito, Atsuo | Naito, Hiroshi | Ichinose, Noboru | Kokubo, Tadashi | Nakamura, Takashi | Higuchi, William I.

Article Type: Research Article

Abstract: The effect of particle size on in vivo and in vitro Zn release of ZnTCP was investigated for the purpose of understanding Zn release behavior from a sustained‐release device. The tricalcium phosphate powders (Ca2.7 Zn0.3 (PO4 )2 ), with particle size of 7.5 and 553 μm (S‐ZnTCP and L‐ZnTCP), including a 10 mol% of Zn (6.17 w/w%), as new sustained‐release preparations, were synthesized by heating, after then ground and sieved using 38 and 300 μm screens. The different powder samples were characterized by the X‐ray powder diffractometry and scanning electron microscopy. The release rates from Zn‐TCP powders (10 mg) were …measured in 10 ml of simulated body fluid (SBF) containing 10 mg/100 ml Ca2+ (SBF/H), SBF containing 5 mg/100 ml Ca2+ (SBF/L) or SBF without Ca2+ (SBF/‐) at 37.0°C. The in vitro Zn release profiles for the smallest and the largest particles size of ZnTCP powders (L‐ZnTCP and S‐ZnTCP) at various Ca concentrations in SBF were significantly higher in SBF/‐ and SBF/L than in SBF/H. The Zn release rate from ZnTCP with different particle sizes were found to be inversely proportional to the concentration of calcium in SBF. After injection of a ZnTCP suspension containing 30 mg of S‐ZnTCP powder on the backs of the rats, the plasma Zn level increased rapidly, reaching a concentration range of around 2 μg/ml. The area under the curve values of the plasma Zn concentration (Zn‐AUC) over 6 days post injection of S‐ZnTCP and L‐ZnTCP were significantly higher than that of the control experiment. After the injection of S‐ZnTCP and L‐ZnTCP suspension, the plasma alkaline phosphatase activity (AIP) levels increased to more than 300 IU/l. In contrast, the AIP for the control decreased after 2 days. The area under the curve of the AIP (AIP‐AUC) for 6 days of S‐ZnTCP was significantly higher than that of other groups. Show more

Keywords: Biomaterial, zinc, drug delivery system, tricalcium phosphate, in vitro release, in vivo release, calcium level‐responsive drug release

Citation: Bio-Medical Materials and Engineering, vol. 13, no. 2, pp. 103-113, 2003

Authors: Lewandrowski, Kai‐Uwe | Bondre, Shrikar P. | Wise, Donald L. | Trantolo, Debra J.

Article Type: Research Article

Abstract: The bioactivity of a nano‐hydroxyapatite‐augmented, bioresorbable bone graft substitute made from the unsaturated polyester, poly(propylene fumarate), was analyzed by evaluating biocompatibility and osteointegration of implants placed into a rat tibial defect. Three groups of eight animals each were evaluated by grouting bone graft substitutes into 3‐mm holes that were made into the anteromedial tibial metaphysis of rats. Thus, a total of 24 animals was included in this study. Two different formulations varying as to the type of hydroxyapatite were used: Group 1 – nano‐hydroxyapatite, Group 2 – micron‐hydroxyapatite, with a Group 3 control defect remaining unfilled. Animals of each of …the three groups were sacrificed in groups of eight at postoperative week three. Histologic analysis revealed best superior biocompatibility and osteointegration of bone graft substitutes when nanohydroxyapatite was employed. At three weeks, there was more reactive new bone formation in this group when compared to the micron‐hydroxyapatite group. The control group showed incomplete closure of the defect. This study suggested that nano‐hydroxyapatite may improve upon the bioactivity of bone implant and repair materials. The model scaffold used in this study, poly(propylene fumarate), appeared to provide an osteoconductive pathway by which bone will grow in faster. Clinical implications of the use potential advantages of nano‐hydroxyapatite on bone repair and orthopaedic implant design are discussed. Show more

Keywords: Bioactivity, nanohydroxyapatite, bioresorbable, bone graft substitute

Citation: Bio-Medical Materials and Engineering, vol. 13, no. 2, pp. 115-124, 2003

Authors: Ichinose, Shizuko | Muneta, Takeshi | Aoki, Hideki | Tagami, Motoki

Article Type: Research Article

Abstract: We demonstrate that a myriad of fine particles produced by the abrasion of both cobalt‐chromium‐molybdenum (Co‐Cr‐Mo) and titanium‐aluminum‐vanadium (Ti‐Al‐V) alloys accumulate in the synovial cells next to surgical implants made from these alloys. The metallic particles were of various sizes, and were observed within the lysosomes. Energy dispersive X‐ray spectroscopy studies revealed that the fine spherical particles consisted solely of Cr, and that other larger particles were composed of the Co‐Cr‐Mo alloy. We measured the size of the metallic particles using the public domain NIH image program, and found that most of the fine spherical particles were 10–15 nm in …diameter (n=1000). Eighty percent of the large particles were 30–35 nm in length and 20–25 nm in width (n=300). In addition, EDS examination clarified that all of the fine particles of the Ti‐Al‐V alloy were composed of that alloy. For this alloy, when discounting the larger particles, the fine metal deposits were 20–25 nm in length and 10–15 nm in width (n=1000). From these findings, we conclude that the Co‐Cr‐Mo alloy is easily corroded and that Co is released from the cells. In contrast, the Ti‐Al‐V alloy is very stable and does not corrode, although the Ti‐Al‐V alloy does produce particles that are smaller than those produced by the Co‐Cr‐Mo alloy. Show more

Keywords: Knee prosthesis, Co‐Cr‐Mo alloy, Ti‐Al‐V alloy, transmission electron microscopy, energy dispersive X‐ray spectroscopy

Citation: Bio-Medical Materials and Engineering, vol. 13, no. 2, pp. 125-134, 2003

Authors: Mishra, Sanjay | Viano, Ann | Fore, Neil | Lewis, Gladius | Ray, Asit

Article Type: Research Article

Abstract: The changes in the tensile toughness (U), degree of crystallinity (%C), melting temperature (Tm ), lamella thickness, and lamella alignment of uncrosslinked and unaged GUR 1150HP ultra‐high‐molecular‐weight polyethylene specimens, following different sterilization treatments (none, γ‐irradiation in air, γ‐irradiation in a nitrogen‐rich atmosphere, ethylene oxide gas, and gas plasma) were determined. For each of the properties – U, %C, and Tm – the only significant difference in the mean value was found between the set of specimens γ‐irradiated in air, on the one hand, and each of the other sets, on the other hand. It was found that lamella thickness …showed little change between the groups of specimens but there was a significant difference in the lamella orientation between the set of specimens that had been γ‐irradiated in air, on the one hand, and each of the other sets, on the other. It thus appears that the changes seen in the physical and mechanical properties determined may be a reflection of the change in the polymer's lamella alignment. Show more

Keywords: Ultra‐high‐molecular‐weight polyethylene (UHMWPE), sterilization, tensile toughness, degree of crystallinity, melting temperature, lamella thickness, lamella alignment

Citation: Bio-Medical Materials and Engineering, vol. 13, no. 2, pp. 135-146, 2003

Authors: Sánchez‐Muñoz, Orlando L. | Nordström, Egon G. | Prérez‐Hernández, Ever

Article Type: Research Article

Abstract: The main purpose of our investigation is to achieve better insight into the electrophoretic and thermodynamic properties of protein‐coated biomaterial particles. Many academic studies have been performed to understand the complex phenomena of microscopic biomaterial particles as a function of ionic strength, pH and temperature. By electrophoretic measurements of biomaterial particles, the surface structures of it can be analysed with a suitable model. Therefore, the zeta potential measurements are useful to know the effects of adsorbed BSA concentration upon the electrophoretic properties of bioceramics and bioglasses. Unexpectedly, the zeta potential of the BSA‐coated biomaterials exhibits a local minimum as the …concentrations of adsorbed BSA increases. Apparently, the structures of the attached BSA layer on the biomaterial particles play a significant role. In an attempt to elaborate the phenomenon observed, a model for proteins, which composes two BSA sublayers with different structures and properties, is proposed. Also, the association or equilibrium constant were determined and represented the isotherm curves in function of the zeta potential measurements. Show more

Keywords: Zeta potential, bioceramic, bioglass and association constant

Citation: Bio-Medical Materials and Engineering, vol. 13, no. 2, pp. 147-158, 2003

Authors: Gülmezoğlu, M. Bilginer | Barkana, Atalay

Article Type: Research Article

Abstract: In this work, the cross‐sectional areas of the vocal tract are determined for the lossy and lossless cases by using the pole‐zero models obtained from the electrical equivalent circuit model of the vocal tract and the system identification method. The cross‐sectional areas are used to compare the lossy and lossless cases. In the lossy case, the internal losses due to wall vibration, heat conduction, air friction and viscosity are considered, that is, the complex poles and zeros obtained from the models are used directly. Whereas, in the lossless case, only the imaginary parts of these poles and zeros are used. …The vocal tract shapes obtained for the lossy case are close to the actual ones. Show more

Keywords: Vocal tract losses, vocal tract area function, vocal tract shape

Citation: Bio-Medical Materials and Engineering, vol. 13, no. 2, pp. 159-166, 2003

Authors: Qassem, W.

Article Type: Research Article

Abstract: The human body is a dynamic system with dynamic behaviour. Linear and nonlinear models of a standing human are investigated. The models simulated the body by 15‐lumped masses connected by springs and dampers. A square wave impulse input is applied at the shoes and the lumbar spine response is presented as an example. The results show that the mechanical response is affected by the kind of representation (linear or nonlinear model) and the shoes stiffness and damping coefficients.

Citation: Bio-Medical Materials and Engineering, vol. 13, no. 2, pp. 167-180, 2003

Authors: Geng, Jianhua | Chen, Yingmao | Yin, Dayi | Tian, Jiahe | Chen, Shengzu

Article Type: Research Article

Abstract: Noise components on PET images were studied. The results showed that the square of synthetic noise Δ2 and the square of signal‐to‐noise ratio (N/Δ)2 varied with the signal intensity N and the relationships were respectively expressed with: Δ2 =0.0395N2 +0.1427N+0.0025 (R2 =0.9358) and (N/Δ)2 =−1.13932N2 +7.0185N−0.0746 (R2 =0.9377). The synthetic noise on PET image may be categorized into three components. The first one varies directly as signal intensity, which depend on random coincidence; the second one varies directly as the square root of signal intensity, which depend on Poisson fluctuation; and the third one is independent of signal …intensity. Show more

Keywords: Positron emission tomography, PET, image, noise

Citation: Bio-Medical Materials and Engineering, vol. 13, no. 2, pp. 181-186, 2003