Bio-Medical Materials and Engineering - Volume 15, issue 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: In an attempt to reduce complications in cases of severe open fracture, we developed a bio‐artificial periosteum composed of osteogenic cells and collagen sponge. In the present study, we evaluated the osteogenic potential of the bio‐artificial periosteum in vivo and in vitro. After 4‐week incubation in vitro, the bio‐artificial periosteum had high alkaline phosphatase activity and osteocalcin content. Moreover, energy dispersive X‐ray analysis revealed numerous crystal structures consisting of P and Ca on the surface of the bio‐artificial periosteum. Using a rat model for severe bone injury, we examined the bone formation process in defect sites covered with the bio‐artificial…periosteum. New bone formation occurred in the central part of the bone defect as well as at the bone edge. We conclude that by using the bio‐artificial periosteum, the fracture site benefited from an improved osteogenic environment. These results indicate that a clinical trial to further evaluate this technique should be conducted.
Abstract: Photooxidation is a method of tissue fixation resulting in protein crosslinking due to illumination in the presence of a dye. The aim of the study was to evaluate the impact of dyes, photooxidation time and the type of applied light on the porcine pericardial collagen crosslinking. The collagen modifications were evaluated on the basis of pericardial sensitivity to pepsin digestion. The hydrolysate components were evaluated qualitatively and quantitatively. All hydrolysates contained collagen α chains, their aggregates and degradation products. Methylene blue and methylene green‐mediated 4 h photooxidation in the presence of visible light caused similar decrease in pericardium sensitivity to…pepsin. However, both fixation types generated remarkable amounts of α chain degradation products. The prolongation of photooxidation time to 8 h did not increase the pericardial sample resistance to pepsin. Moreover, these sample hydrolysates revealed an elevated α chain content. Violet light mediated photooxidation did not alter pericardial sensitivity to pepsin when compared with fixation under visible light. Nevertheless, violet light fixed tissues displayed a decrease in collagen degradation products. The application of violet light in photooxidation of porcine pericardium will probably allow to obtain enzyme resistant bioprostheses with better mechanical properties compared with those obtained after visible light mediated process.
Abstract: In this paper, we report on the development of a three‐dimensional model of human lower lumbar spine based on actual geometry of L4–L5 motion segment. The simulation is performed on the model extracted from 2 mm slices of CT‐Scan data of a healthy subject. The finite element model includes different parts, such as, cortical shell, cancellous core, endplates, pedicle, lamina, transverse process, and spinous process. Additionally, it takes into account the intervertebral disc including the nucleus pulposus and annulus fibrosus. The seven ligamentous structures of the L4–L5 motion segment, such as, anterior longitudinal ligament, posterior longitudinal ligament, and supraspinous ligament,…were also incorporated. Various biomechanical characteristics of the computer generated model are studied under different physiological loadings. The focus of this study is on the role of posterior elements on load sharing of the lower lumbar region. The simulation yields data on the stress distribution inside the vertebrae and the amount of resulting deformation that takes place. Different simulated models of an injured lumbar spine are also being analyzed for two cases of facetectomy and degraded nucleus disorders. It is shown that the inclusion of the posterior elements along with the ligamentous tissues lead to an increase in the stiffness and stability of the L4–L5 motion segment.
Keywords: Finite element analysis, lumbar spine, stability, motion segment
Abstract: A bio‐scaffold can be broadly termed as a structure used to substitute an organ either permanently or temporarily to restore functionality. The material that can be used varies with the application intended. Tissue engineering is one such application demanding certain requirements to be met before it is applied. One of the applications in tissue engineering is the tissue scaffold, which provides either a permanent or temporary support to the damaged tissues/organ until the functionalities are restored. A biomaterial can exhibit specific interactions with cells that will lead to stereotyped responses. The use of a particular material and morphology depends on…various factors such as osteoinduction, osteoconduction, angiogenesis, growth rates of cells and degradation rate of the material in case of temporary scaffolds, etc. The current work reviews the state of art in tissue scaffolds and focuses on permanent scaffold materials and applications with a brief overview of temporary scaffold materials and their disadvantages.
Keywords: Tissue scaffolding, titanium, bioactive materials, bone reconstruction
Abstract: In this study, several provisional resin materials were investigated by dynamic mechanical analysis (DMA). The materials were autopolymerized PMMA and PEMA, light cured PMMA. Autopolymerized PMMA has the highest Tg (131°C) compared to that of the autopolymerized PEMA (102°C) and light cured PMMA (120°C). The storage moduli for autopolymerized PMMA, autopolymerized PEMA and light cured PMMA are 2.9, 1.8 and 2.3 GPa, respectively. The loss moduli of the same resins are 330, 300 and 350 MPa, respectively. Each of these resins were reinforced with 1%, 3% and 5% of each of metal oxides of MgO, ZrO2 and Al2…O3 and then studied with DMA. Small changes were observed for dynamic mechanical properties tested. However, the changes are not systematic and noticeable. This is most probably due to smaller size of metal oxides particles compared to that of polymer particle size.
Abstract: In this paper, a frequency analysis for the microcirculation model is introduced to find new microcirculation parameters in the frequency domain. By using Bode Plot of transfer function, we found two characteristic parameters of the model: damping ratio ξ and break frequency ωn . By analyzing the variation of ξ and ωn , it enables us to have better understanding of different states of microcirculation. At low damping, 0<ξ<1, the state of microcirculation will be better and better along with the increasing of the ωn . At over damping, ξ≥1, the state of microcirculation will be worse and worse along…with the descending of the ωn . The results of experiments on 120 subjects are consistent with the analytical results of the model.
Keywords: Frequency response, blood volume pulse, microcirculation, damping ratio, break frequency
Abstract: In a previous work by the author [H.S. Hedia and M. Nemat‐Alla, Design optimization of functionally graded dental implant, submitted to be published in the J. Bio‐Medical Materials and Engineering], a functionally graded material dental implant was designed without cansellous bone in the model. In this investigation the effect of presence cancellous bone as a thin layer around the dental implant was investigated. It is well known that the main inorganic component of natural bone is hydroxyapatite (HAP) and that the main organic component is collagen (Col). Hydroxyapatite HAP implants are not bioabsorbable, and because induction of bone into…and around the artificially made HAP is not always satisfactory, loosening or breakage of HAP implants may occur after implantation in the clinical application. The development of a new material which is bioabsorbable and which has osteoconductive activity is needed. Therefore, the aim of the current investigation is to design an implant, in the presence of cancellous bone as a thin layer around it, from functionally graded material. In this study, a novel biomaterial, collagen/hydroxyapatite (Col/HAP) as a functionally graded material (FGM), was developed using the finite element and optimization techniques which are available in the ANSYS package. These materials have a self‐organized character similar to that of natural bone. The investigations have shown that the maximum stress in the cortical bone and cancellous bone for the Col/HAP functionally graded implant has been reduced by about 40% and 19% respectively compared to currently used titanium dental implants.
Keywords: Dental implant, functionally graded material (FGM), finite element, optimization, von mises stress, biocompatibility
Abstract: In order to evaluate functions of a bioartificial liver (BAL), containing porcine hepatocytes in a hollow fiber cartridge, some chemical loading tests have been employed. However the kinds of functions that can be evaluated by chemical loading tests are limited. We desire versatile methods to estimate various BAL functions. The purpose of this report is to propose a method using the reverse transcription polymerase chain reaction (RT‐PCR) for functional evaluation of a BAL. In vitro perfusion culture of a BAL cartridge was carried out using 20% of human whole blood. At pre‐determined periods of perfusion culture, hepatocytes were taken from…the cartridge and mRNA was extracted from the hepatocytes. The mRNA expression levels of albumin and cytochrome P450 (CYP3A29) were determined by RT‐PCR method. In order to quasi‐quantitatively determine the time courses of mRNA expression levels during the perfusion culture, PCR of target DNA was carried out by co‐amplification with its competitor DNA that was constructed by means of the partial deletion of target DNA. The results showed that the amounts of both albumin and cytochrome P450 mRNA rapidly decreased during the initial few days' perfusion culture and remained at a constant level for the following week. This fact corresponded with the analysis of lidocaine metabolic functions via pharmacokinetics in our previous study. Additionally, the RT‐PCR is so sensitive that we can measure much more minute quantity of various proteins. Consequently, this method is useful for comprehensive evaluation of BAL functions.
Keywords: Bioartificial liver, hepatocyte, RT‐PCR, function, chemical loading test
Abstract: A bioresorbable bone repair material made from the unsaturated polyester poly(propylene glycol‐co‐fumaric acid), PPF, was investigated for its potential to act as an adjunct to alleviate the disadvantages associated with wire fixation. The PPF bone repair material is an injectable system that can be delivered to the intramedullary site and crosslinked in the presence of a hydroxylapatite filler and effervescent agents. To test the feasibility of using a bioabsorbable material as an adjunct in fracture fixation, femoral osteotomies were created in two groups of 10 Sprague‐Dawley rats. Osteotomies were fixed with a threaded Kirschner wire or stabilized with a Kirshner…wire augmented with the PPF bone repair material. The quantity of new bone across the osteotomy site was assessed at 4 weeks postoperatively. Histologic analysis of the healing process revealed enhanced osteoconduction across the osteotomy with the PPF bone repair material. These findings were corroborated by histomorphometric analysis of new bone formation. These findings imply suitability of the PPF bone repair material to act as an adjunct to wire fixation, such as techniques used in hand surgery.
Abstract: p‐Carboxyphenoxy propane (CPP) prepolymer consisting of 4 units and sebacic acid (SA) prepolymer consisting of about 10 units were synthesized by reacting CPP and SA in the presence of excess acetic anhydride, respectively. Polyanhydride, poly(CPP‐SA) copolymers were copolymerized by a melt polycondensation process with a mixture of CPP and SA prepolymer. Copolymers of average molecular weight up to 110,000 g/mol were achieved. The crystallinity of poly(CPP‐SA) copolymers was decreased by the addition of the CPP homopolymer segment to SA homopolymer. Poly(CPP‐SA) copolymers gradually degraded for period of 10 days. No large difference of weight loss observed according to molecular weight…variation of poly(CPP‐SA) copolymers. BCNU release from wafers fabricated by poly(CPP‐SA) showed a sustained release pattern with no initial burst and delay of drug release.
Keywords: Polyanhydride, polycondensation, BCNU, sustained drug release
Abstract: Local bone loss after implantation of traditional stem‐type prostheses remains an unsolved problem during the long‐term application of total hip replacement. The stress shielding effect and osteolysis were thought to be the two main factors that result in local bone loss after prosthesis implantation. A newly designed stemless cervico‐trochanteric (C‐T) prosthesis was thus developed to reduce stress shielding and osteolysis caused by the implantation of conventional stem‐type prosthesis. Eight synthetic femora were implanted with C‐T and porous coated anatomic (PCA) prostheses. Under 2,000‐Newton load, the surface strains of proximal femora were compared between the intact, PCA press‐fit femora and the…C‐T implanted femora with three different fixation modes: two‐screw fixation, three‐screw fixation, and three‐screw combined with cement fixation. The results revealed that stress shielding in the C‐T implanted femora was significantly eliminated compared to that of the PCA implanted femora (p<0.01). No statistical difference in strain magnitude was found for the C‐T implanted femora among the three different fixation modes (p>0.1). The C‐T implanted femur has more physiological strain distribution. Moreover, from the C‐T prosthetic characteristic design, the localized osteolysis would be also reduced due to the overall coverage of neck‐trochanteric area. The newly designed C‐T prosthesis may be a useful alternative to the traditional stem‐type prosthesis in the future.
Keywords: Hip arthroplasty, stemless prosthesis, strain measurement, stress shielding, osteolysis