Bio-Medical Materials and Engineering - Volume 15, issue 1-2
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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: Bridging of nerve gaps is still a major problem in peripheral nerve surgery. Alternatively to autologous nerve grafts tissue engineering of peripheral nerves focuses on biocompatible conduits to reconstruct nerves. Such non‐neural conduits fail to support regeneration over larger gaps due to lacking viable Schwann cells that promote regeneration by producing growth factors and cell guiding molecules. This problem may be overcome by implantation of cultivated Schwann cells into suitable scaffolds. In the present experiments we tested a collagen type I/III tube as a potential nerve guiding matrix. Revascularization, tolerance and Schwann cell settlement were evaluated by light, fluorescence and…scanning electron microscopy after different implantation times. The conduits were completely revascularized between day 5 and 7 post‐operatively and well integrated into the host tissue. Implanted Schwann cells adhered, survived and proliferated on the inner surface of the conduits. Nevertheless, bridging a 2 cm gap of the sciatic nerve of adult Wistar rats with these collagen/Schwann cell conduits led to a disappointing regeneration compared to controls with autologous grafts. From these results, we conclude that a sufficient biocompatibility of bioartificial nerve conduits is a necessary prerequisite, however, it remains only one of several parameters important for peripheral nerve regeneration.
Abstract: Neutrophil interaction with wound dressing materials was studied. A meshed non‐woven cellulose was chosen as model dressing. Neutrophils isolated from human blood was added to the cellulose, and the production of reactive oxygen species was measured by luminol‐amplified chemiluminescence. The respiratory burst response of the neutrophils was found to be activated upon contact with cellulose. The contact activation of the cells increased when the cellulose was oxidised with periodate, and decreased when the cellulose was reduced with cyanoborohydride, indicating that the activation of the respiratory burst response was due to carbonyl‐induced stress. The contact activation of the respiratory burst response…resulted in an inability of the neutrophils to respond to a secondary stimulation with zymosan. When radical scavenger enzymes were covalently bound to the cellulose, the contact activation was decreased and the ability to respond to stimuli was increased. Addition of the molecular scavenger glutathione (GSH) did not decrease the cell activation upon cellulose contact, but the cell showed an intact ability to respond to secondary stimuli after cellulose contact. In conclusion, the results show that the environmental redox potential effects neutrophils in a situations of clinical interest and that the addition of radical scavengers protects the neutrophils against material‐induced damage resulting in preserved cell function.
Abstract: The materials which are currently used to make maxillofacial prostheses are far from ideal and require considerable improvement with respect to their ability to mimic the properties of skin. To this aim, a novel three‐layered maxillofacial prosthesis has been designed consisting of a silicone rubber base layer, an inner gel layer and an outer polymeric coating (to simulate the elastic properties of skin). The aim of the work in this study was to develop the inner silicone gel layer which displays similar properties to facial skin. Through the use of unique linear extensometry testing, in vivo measurements for the Area…under the Curve (AUC), Hysteresis (viscoelastic behaviour), Fmax (maximum force), F30 and F60 (force after 30 and 60 seconds) were obtained from the facial skin of 15 volunteers. The results were used as a basis for developing silicone gel formulations for the inner layer, to closely resemble those of facial skin. Gels were made by the addition of both low and high molecular weight unreactive silicone fluids and were further tested for compression, water absorption and dehydration. Testing showed that a gel has been produced that closely simulates the elastic properties of skin when bonded to a base silicone rubber layer. Further testing will need to deduce whether these properties will be affected by the addition of the outer polymeric layer.
Keywords: Maxillofacial, prosthesis, silicone, linear extensometry
Abstract: A hydroxyapatite/type I collagen (HAp/Col) composite, aligning hydroxyapatite nano‐crystals along collagen molecules, has been synthesized. The biocompatibility, osteoconductivity and efficacy as an rhBMP‐2 carrier of this novel biomaterial implanted in the weight‐bearing site have been examined. The HAp/Col implants adsorbing 0 or 400 μg/ml of rhBMP‐2 were implanted into bone defects of tibiae in 3 beagle dogs and fixed according to the Ilizarov method. As a control, bone defects of 20 mm remaining in 2 beagle dogs and the dogs were allowed to walk using a Ilizarov external skeletal fixator. The radiological and histological findings suggest that the implants induce…bone remodeling units and are a superior carrier of rhBMP‐2 due to the stimulation of early callus and new bone formation. As a next step, anterior fusion was carried out on 6 beagle dogs with the implants adsorbing 400 μg/ml of rhBMP‐2, and 9 dogs with the implants without rhBMP‐2. In 3 dogs of the rhBMP‐treated group, as well as 6 dogs of the non‐rhBMP‐treated group, the implant was fixed with a poly‐L‐lactide plate. Histological and radiographical analysis suggest that enhancement of callus formation and bone bridging by rhBMP‐treatment is effective to prevent collapse of the implant.
Keywords: Hydroxyapatite/type I collagen (HAp/Col) composite, bone remodeling unit, artificial vertebra system, anterior fusion of the cervical spine, recombinant human bone morphogenetic protein‐2 (rhBMP‐2), poly‐L‐lactide (PLLA) plate
Abstract: Collagen–silica hybrid materials have been considered for potential biomedical applications. Understanding of the collagen–silica interactions is the key to control hybrids structure and properties. For this purpose, the effect of sodium silicate and sodium chloride addition at two concentrations, 0.83 and 10 mM, on the kinetic of the type I collagen fibrillogenesis at 20°C, and pH 7.4 were studied. Absorbance profiles of fibrillogenesis experiments were collected together with measures of silicic acid concentration and transmission electron microscopy analysis. The specific effect of silica addition on the collagen fibrils self‐assembly mechanisms was demonstrated by comparison with the sodium chloride. Sodium silicate…at 10 mM inhibited the collagen fibrillogenesis. At the same concentration, the sodium chloride decreased the rate of the collagen fibril assembly. Collagen fibrillogenesis kinetic was not significantly disturbed by the presence of 0.83 mM of sodium chloride. However, the same concentration of sodium silicate modified the collagen fibrillogenesis kinetic. Transmission electron microscopy indicated for experiment with 0.83 mM of sodium silicate, the formation of longer and wider fibrils than for the equivalent collagen fibrillogenesis experiment with sodium chloride. The effect of sodium chloride is explained in terms of osmotic exclusion and influence on electrostatic interactions between collagen fibrils. The specific involvement of silicic acid in collagen helices hydrogen‐bond interactions is suggested. Finally, the results of this study are discussed regarding the preparation of composites by co‐gelation of type I collagen and sodium silicate, for potential application as bone repair device.
Keywords: Sodium silicate, type I collagen, fibrils
Abstract: In the organism epithelia perform perfect barrier functions. Strong rheological and mechanical influences constitute the normal environment of this tissue throughout life. Most epithelia are exposed to different fluids at the luminal and basal sides. To obtain realistic information about tissue development in modern biomaterial testing and tissue engineering it is necessary to mimik the natural environment of epithelia. Cultured cells are brought in contact with an artificial extracellular matrix to determine whether proper development into a functional epithelium occurs. As under natural conditions the cultures have to withstand mechanical and fluid stress over a prolonged period of time in…close contact to a selected biomaterial. However, development of tissue‐specific features such as polarization, tightness and transport under in vitro conditions will only occur, if the biomaterial and the culture conditions support tissue development. Leakage, edge damage and pressure differences during culture have to be avoided so that the natural functions of the growing epithelium can develop. Our aim is to generate functional epithelia derived from renal explants containing stem cells, which are microsurgically isolated and placed into specific O‐ring carriers for optimal handling. The cells develop in combination with a collagenous matrix from an embryonic into a functional collecting duct (rCD) epithelium. To achieve optimal culture conditions the tissue is placed in a gradient culture container. A typical environment can be simulated by superfusing different culture media at the luminal and basal sides. Within days epithelia growing inside the gradient container build up a physiological barrier, which is maintained during the whole culture period. The described method allows to investigate the influence of new biomaterials over prolonged periods of time.
Abstract: SIS (small intestinal submucosa) is a 3D extracellular matrix (ECM) material of porcine origin. It has a complex composition predominantly composed of collagen type I. SIS is rapidly absorbed, supports early and abundant new vessel growth, and serves as a template for the reconstructive remodelling of several body tissues. Currently SIS products are sterilised using ethylene oxide, gamma irradiation and e‐beam irradiation. It is not known how they affect the materials properties such as structure, mechanical strength and biocompatibility. This study investigated the influence of each sterilisation method on the biocompatibility and biodegradation of SIS using L929 mouse fibroblasts. SIS…samples were sterilised by each of the above methods under standard conditions. The samples were subjected to hydrolytic degradation conditions for specific periods of time. All sterilisation methods resulted in an increase in the rate of sample degradation. The study indicated that over time e‐beam irradiation caused the greatest % weight loss. Applying sample extracts to L929 mouse fibroblasts assessed the biocompatibility of the degradation products. The % cellular protein and % metabolic activity were then assessed using the BCA assay and MTT assay, respectively. All SIS samples caused an increase in both cellular protein production and metabolic activity. Initially samples sterilised by ETO had the greatest effect but this decreased after 28 days. Unsterile samples were found to have a slower more prolonged influence. It is thought that the components released may include extractable growth factors and further studies are required to confirm this.
Keywords: Small intestinal submucosa, tissue engineering, sterilisation, biocompatibility, biodegradability
Abstract: Novel difunctional oligolactone macromers have been synthesized by ring‐opening oligomerization of various lactones (L‐lactide, glycolide, p‐dioxanone) in the presence of suitable diols (propane‐1,2‐diol, dianhydro‐D‐glucitol) and subsequent endcapping of the formed oligolactones with methacrylate moieties. Based on these macromers, two fabrication procedures were developed to fabricate highly porous scaffolds and the material properties including in vitro biodegradation behaviour of the resulting polymeric scaffolds were investigated. Preliminary in vitro studies on the cytocompatibility of the fabricated scaffolds and on osteoblast cultivation on the optimized polymeric materials demonstrated that the oligolactide based polymer networks possess an excellent biocompatibility and that they are promising…candidates as scaffolds in bone tissue engineering.
Abstract: The adsorption behavior of H–Arg–Gly–Asp–OH (RGD) oligopeptide on ion‐irradiated polymer surfaces has been studied. The RGD‐incubated surfaces of poly(ethylene terephtalate) (PET) and poly(hydroxymethylsiloxane) (PHMS) thin films, before and after irradiation with 50 keV Ar+ to 1×1015 ions/cm2 , were investigated by X‐Ray Photoelectron Spectroscopy and Atomic Force Microscopy. It was found that no significant adsorption occurs on PET, while a measurable amount of RGD is preferentially adsorbed onto irradiated PHMS surfaces. The evaluated surface coverage was found to range between 5 and 12%. In situ adsorption measurements performed by using the Quartz Crystal Microbalance with Dissipation monitoring technique…showed that the irradiation induced remarkable changes of mass uptake with respect to the unirradiated surfaces, mostly attributed to the change in the water adsorption capability of the irradiated surfaces. The adsorption results are discussed in terms of the ion‐induced changes on the morphology, chemical structure and composition, surface free energy and surface charge.
Keywords: Peptide adsorption, ion beams, polymer modification, QCM‐D, surface free energy
Abstract: Amorphous carbon (a‐C), carbon nitride (a‐CN) and titanium films were deposited on stainless steel substrates (SS) using a dc magnetron sputtering system attached to a high vacuum chamber. Films were deposited using a base pressure of 1.3×10−4 Pa. For the carbon films a pure graphite target was eroded in an Argon plasma. For the case of the a‐CN films, the Ar flux was substituted by 100% N2 gas. Titanium films were deposited in a different chamber, using a pure Ti target and an argon plasma. In vitro studies were carried out on the coated samples using human osteoblasts…cells. Cytotoxicity of carbon films was assessed by cellular adhesion and proliferation, as determined by direct cellular counting using a spectroscopic technique and a well‐defined standard curve. Osteoblasts cells were also grown on uncoated steel and prepared Petri dishes for comparison. The percentage of osteoblasts adhesion measured at 24 hrs attained maximum values for the a‐C films. Similarly, cellular proliferation evaluated at three, five and seven days showed an outstanding increase of osteoblasts cells for the a‐C and Ti coatings in contrast to the uncoated steel. The cell functionality was evaluated by the MTT test after incubation periods of 3, 5 and 7 days. The absorbance values obtained for a‐C, a‐CN and Ti surfaces resulted significantly higher with respect to the positive control, indicating that the surface did not induce any toxic effect. Preliminary bio‐mineralization was evaluated by measuring the elemental composition of the mineral grown on the substrates after periods up to 14 days.
Abstract: The ability to use biological substitutes to repair or replace damaged tissues lead to the development of Tissue Engineering (TE), a field that is growing in scope and importance within biomedical engineering. Anchorage dependent cell types often rely on the use of temporary three‐dimensional scaffolds to guide cell proliferation. Computer‐controlled fabrication techniques such as Rapid Prototyping (RP) processes have been recognised to have an edge over conventional manual‐based scaffold fabrication techniques due to their ability to create structures with complex macro‐ and micro‐architectures. Despite the immense capabilities of RP fabrication for scaffold production, commercial available RP modelling materials are not…biocompatible and are not suitable for direct use in the fabrication of scaffolds. Work is carried out with several biocompatible polymers such as Polyetheretherketone (PEEK), Poly(vinyl alcohol) (PVA), Polycaprolactone (PCL) and Poly(L‐lactic acid) (PLLA) and a bioceramic namely, Hydroxyapatite (HA). The parameters of the selective laser sintering (SLS) process are optimised to cater to the processing of these materials. SLS‐fabricated scaffold specimens are examined using a Scanning Electron Microscope (SEM). Results observed from the micrographs indicate the viability of them being used for building TE scaffolds and ascertain the capabilities of the SLS process for creating highly porous scaffolds for Tissue Engineering applications.