Bio-Medical Materials and Engineering - Volume 4, issue 4
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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: A multistation (8-station) hip simulator has been designed and tested that provides a practical imitation of the motions and loads seen by the hip joint during a typical walking cycle. A biaxial rocking motion of ±23 degrees is synchronized with the respective resultant forces of the extension-flexion (heel-strike to toe-off) movements of the leg. This particular simulator provides a practical engineering in vitro implementation of the walking cycle. It also provides a realistic and practical compromise between general wear screening devices (such as pin-on-disk systems) and the intensive research accomplished through full scale simulation (full 6 degree-of-freedom systems) and modeling.…Evaluation of system performance shows that control of rpm (revolutions-per-minute) for the desired axial rotation of 1 Hz was kept to 60 cpm ± 1 cpm for axial loads (per actuator) as high as 4500 Newtons. Although loading error was 2% in the peak load areas of interest (3000 Newton), station-to-station load control variability was less than .6%. Baseline wear studies with this simulator using ultra-high-molecular-weight polyethylene and Cobalt-Chromium (UHMWPE/CoCr) hip systems indicate an average specimen-to-specimen wear variability of less than 7% range after 5 million test cycles. Testing was performed in a calf serum environment at an equilibrium temperature of 33°C.
Keywords: prosthetic hips, joint simulator wear testing, implantable biomaterials, fatigue and wear of biomaterials, wear of polyethylene
Abstract: Experimental callotasis was made in rabbit femurs. In order to compare mechanical behaviors and morphological structure of callus in callotasis, mechanical tests and histological examination were performed. Twenty Japanese white male rabbits were used. The right femurs were osteotomized at the level of the midshaft with a rotary cutter and fixed with a mini-model external fixator. After a 5-day waiting period, bone lengthening was started at the rate of 0.25 mm two times a day. Animals were divided into four groups. Group 1 and Group 2 were continual distraction group, Group 3 and Group 4 discontinued distraction group. The viscoelastic…property was demonstrated in continual distraction group irrespective of distraction period, we thought the central undifferentiated connective tissue in callus was mainly responsible for the mechanical behavior. On the other hand, in discontinued distraction group, viscoelastic property shifted to elastic property corresponding to the rest period, we thought this change of mechanical behavior was histologically owing to the replacement of undifferentiated connective tissue by cartilage and the partial union of bone in callus.
Abstract: The application of hydroxyapatite-sol as a drug carrier is being developed. Hydroxyapatite-sol which is a suspension consisting of hydroxyapatite nano-crystals, was synthesized using an ultrasonic homogenizer. The size of the crystals was 40 × 15 × 10 nm3 on average and their specific surface area was 100 m2 /g. An amount of a glycoside antibiotics adsorbed onto hydroxyapatite nano-crystals was measured. The drug adsorbed 0.2 mg per 1 mg of hydroxyapatite. The affect of the drug adsorbed onto the hydroxyapatite was investigated using cancer cells. The drug, adsorbed onto the hydroxyapatite nano-crystals, inhibited cancer cell growth.
Keywords: hydroxyapatite-sol, drug carrier, nano-crystals
Abstract: Self-setting apatite cement (apatite cement) with a phase of hydroxyapatite (HAP) was employed as a delivery system for bone morphogenetic protein (BMP). A composite of BMP and apatite cement (BMPIHAP composite) was implanted both in thigh muscle and surgically created defect of a critical size of 5 mm, which is a size that does not heal spontaneously in the femur of mice, to evaluate its osteogenetic potential as an augmentation and reconstructive material for clinical usage. The histological and immunohistochemical assessment of proteoglycans reiterated osteogenesis in the muscle tissue. On day 14 postimplantation of BMPIHAP composite, chondroid tissue was formed…in the muscle, and HAP particles were seen in newly formed chondroid tissue. On the 21st day, endo-chondral ossification had occurred, however, small HAP particles remained in the newly formed bone, i.e., HAP particles and newly formed osseous tissues coexisted in a central area. BMP/HAP composite was incorporated by newly formed osseous tissue in the experimented animals. HAP particle found in BMP/HAP composite implanted into the bone defect was resorbed and replaced by osseous tissue. The apatite cement was proved to have advantages for its shaping as well as collapsing properties, and thus, apatite cement containing BMP is suggested as a favorable augmentation material in clinical usage for delivery system of BMP.
Keywords: bone morphogenetic protein (BMP), hydroxyapatite (HAP), self-setting apatite cement (apatite cement), BMP/HAP composite, delivery system
Abstract: Bend specimens of the inorganic synthetic materials hydroxyapatite (HA) and a composite of hydroxyapatite/muscovite mica have been prepared and tested mechanically. Sintering followed by hot isostatic pressing (HIP) without encapsulation gave an increased strength for HA alone, but no significant increase in strength compared with sintering alone for HA/mica composites. The bend strength of the HA/mica composite was inferior to that of HA alone, the reason being inadequate bonding between HA and mica. HIP in glass capsules and an increased cold compaction pressure tended to improve the bend strength of the composite. Corrosion in tris for 7d did not affect…the bend strength of the investigated materials significantly.
Abstract: Recently, a dominant influence of the surface roughness parameters for the soft tissue reaction at the implant tissue interface was found in an experimental study on sheep. The purpose of the present study is to correlate the surface roughness parameters of different experimental bone plates to the results of the histomorphometric analyses of the adjacent soft tissues. Pure titanium plates (35 × 5 × 1 mm) with six different surface treatments and electropolished stainless steel plates were tested. Prior to implantation the surface roughness parameters were determined using a profilometer and a scanning electron microscope. The tibia of adult…rabbits served as test sites. At least four plates of each type were implanted. Three months postoperatively the implants were harvested with an intact tissue envelope and were left in situ for the histological preparation. The difference in the roughness parameters is statistically significant for most surface conditions and has an effect on the soft tissue reaction. The histological evaluation shows a significant higher number of blood vessels for steel plates in comparison to titanium plates with handground and blasted surface conditions. For the rough type of anodized titanium surfaces a significantly thinner soft tissue capsule is found, compared to electropolished steel plates. For the steel plates a fluid film was found between the implant and the adjacent tissue layer. The material and the surface roughness of the implant, determine the tissue reaction at the interface. The rough type of anodized titanium implants seems to be preferable.
Abstract: The objective of the present study was to find a standard substance for use as a reference in the cytotoxicity assay of biomaterials, as an alternative to animal experiments in recent years. Eight kinds of rubber were made in a plate shape to keep their surface area at 1 cm2 against 10 ml of extract volume. They were extracted by the following three extraction methods (a) dynamic extraction at 200 rpm gyration on alumina balls at 37°C for 24 h; (b) static extraction at 37°C for 24 h and (c) extraction by heating in an autoclave at 121°C for…60 min. At the end of each period each extract was examined for cell viability based on an evaluation by neutral red uptake. These methods were repeated up to seven times. Two kinds of chemicals were also tested. The extracts obtained were used to treat human gingival fibroblasts that have been cultured with DMEM supplemented with 5% fetal bovine serum into a 96 well tissue culture plate by 1 × 105 cells/ml, in an incubator aerated with 5% CO2 , and 95% humidified air at 37°C for 48 h. The extracts of ethylene-propylene, butyl, nitrile rubbers, and two kinds of chemicals yielded strong cytotoxicity in all three kinds of extraction methods, while chloroprene, fluorine-contained, isoprene, India, and silicone rubbers showed little cytotoxicity. The results obtained by the three kinds of extraction methods revealed no differences in the order of cytotoxicity of the materials tested. Repetition of extraction did not change the degree or pattern of extraction in each extraction method compared to the single extraction. Therefore, a standard substance for reference should be chosen from the viewpoint of availability, handling, consistency, and safety. These findings suggested that several kinds of rubber may be candidate substances either for positive or negative controls in the cytotoxicity assay of biomaterials by the dynamic extraction method.
Abstract: It is important to estimate the mechanical characteristics and strength of biomedical membrane. For this purpose, previously we have proposyd several mechanical test methods for biomedical membranes. To establish the safety design for biomedical membrane, such as cellophane membrane for hemodialysis, it is important to estimate the viscoelastic characteristics of these materials. On the other hand, artificial biomedical membrane such as tympanic membrane, are subjected to noncontact internal air pressure under the membranous state. To estimate mechanical characteristics of such membrane, it is necessary to develop a well-simulated test under the gaseous pressure and the other mechanical test under the…membranous state. In this paper, several test methods for these purposes were shown. Furthermore, results obtained by these methods were shown and related to clinical problems. These proposed test methods are quite different from the axial tensile test. But they are also important to estimate the mechanical property of biomedical membrane. Each result obtained by these test methods has its own significance. By selection of the most suitable test method for each purpose and revealing these mutual relations, safety design of artificial organs can be performed from the viewpoint of the strength.
Keywords: biomedical membrane, mechanical property, test method, viscoelastic characteristics, quasi creep test, internal air pressure test, contact loading test, axial tensile test
Abstract: From the viewpoint of the tatget of biomaterials, the needs for biomedical reliability as well as development of novel function is discussed. Some approaches to guidelines or standatdization of biomaterials and the related devices are pointed out.