Bio-Medical Materials and Engineering - Volume 25, issue 1
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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: The paper discusses several theoretical and practical aspects of the application of currents flowing through the body of a radiotelephone operator and Specific Absorption Rate (SAR). SAR is known as the physical quantity which is a perfect solution for biological experiments. Unfortunately, SAR cannot be measured directly. Contrary to SAR, which is limited to the penetration depth, a current induced in a point of a body is measurable in any other point of the body. The main objective of this paper is to show that the current induced in a human body when using a radiotelephone or mobile phone…is significant and should be analyzed as widely as SAR is. Computer simulations of a human's hand with a radiotelephone were made. Experiments were also conducted. The results of the experiments show that induced current is also as important as SAR and it cannot be omitted in bioelectromagnetic experiments. In biomedical studies both parameters: induced current and SAR play a major role.
Keywords: Specific absorption rate, induced current, bioelectromagentics
Abstract: A clear understanding of the dependence of mechanical properties of bone remains a task not fully achieved. In order to estimate the mechanical properties in bones for implants, pore cross-section area, calcium content, and apparent density were measured in trabecular bone samples for human implants. Samples of fresh and defatted bone tissue, extracted from one year old bovines, were cut in longitudinal and transversal orientation of the trabeculae. Pore cross-section area was measured with an image analyzer. Compression tests were conducted into rectangular prisms. Elastic modulus presents a linear tendency as a function of pore cross-section area, calcium content and…apparent density regardless of the trabecular orientation. The best variable to estimate elastic modulus of trabecular bone for implants was pore cross-section area, and affirmations to consider Nukbone process appropriated for marrow extraction in trabecular bone for implantation purposes are proposed, according to bone mechanical properties. Considering stress–strain curves, defatted bone is stiffer than fresh bone. Number of pores against pore cross-section area present an exponential decay, consistent for all the samples. These graphs also are useful to predict elastic properties of trabecular samples of young bovines for implants.
Keywords: Elastic modulus, bone implants, trabecular bone, bone fragility
Abstract: This study investigated the biologic properties of nano-hydroxyapatite (nHAp) using the rat calvarial defect, ectopic bone formation, and rabbit tibia implant installation models. Animals were divided into two groups: those implanted with nHAp, and negative controls (Collagen). Eight weeks after creating an 8 mm calvarial defect, bone regeneration was evaluated radiographically and histologically. To investigate ectopic bone formation, materials were injected into the right thigh muscle and were evaluated after 8 weeks. nHAp coated implant and conventional titanium implant were placed bilaterally in rabbit tibias. After 4 weeks, bone–implant contact (BIC), new bone area inside the thread, and removal torque…were measured. In the calvarial defect model, radiographic and histologic analysis showed more bone formation in the nHAp Group; particularly, histologically assessed bone area (p=0.034) and microcomputed tomography assessed bone mineral density (p=0.034). In the ectopic bone formation model, calcification and expression of osteogenic biomarkers were seen in the nHAp-injected samples but in none of the controls. nHAp coated implant resulted in increased BIC, new bone area, and increased removal torque, with statistical significance for BIC (p=0.034). This study suggests that nHAp has potential as a coating material for dental implant surfaces and as a bone graft material.
Keywords: Nano-hydroxyapatite, calvarial defect, ectopic bone formation, implant surface coating
Abstract: Macroporous bacterial nanocellulose (BNC) scaffolds with calcium phosphate coated surfaces is a candidate for future bone tissue engineering applications. The mineralization of the macroporous BNC scaffolds was achieved by a biomimetic process, resulting in an environment resembling native bone tissues' mineralized extra cellular matrix both topographically and chemically. The deposited crystals were analyzed with electron spectroscopy for chemical analysis (ESCA), energy-dispersive X-ray spectroscopy (EDX) and X-ray crystallography (XRD). MSCs were cultured in osteogeneic medium for 21 days on the scaffolds. The results of this study show that macroporous BNC can be mineralized with hydroxyapatite and that MSCs retain their ability…to proliferate and differentiate towards an osteoblastic phenotype within the mineralized BNC, showing the promise of this material in bone tissue engineering applications.
Abstract: The stability of the Co–Cr–Mo dental alloy immersed in artificial salivas (pH 6.7) was investigated over 24 h. Three artificial salivas have been studied: saline saliva (saliva I); saline saliva buffered with phosphate ions (saliva II) and saliva II plus mucin molecules (saliva III). For all the systems, open circuit potential shift positively over 24 hours of immersion. Data extracted from the steady-state polarization curves demonstrated that the Co–Cr–Mo alloy has higher corrosion potential in saliva III, lower corrosion potential in saliva I and lower initial corrosion resistance in saliva III. After 24 hours of immersion in the artificial salivas,…the Co–Cr–Mo alloy presents high corrosion stability, due to the protective action created by the presence of corrosion products. From the analysis of the breakdown potential it was concluded that, the presence of the phosphate ions and mucin promote the oxidation process, inducing the formation of etch pits. Regarding the effect of the mucin concentration in the corrosion behaviour of the Co–Cr–Mo dental alloy, it was observed a negative shift in the corrosion potential, pointing to a cathodic inhibitor role for the mucin molecules. Nevertheless, no correlation between the mucin concentration and corrosion rate was possible to establish.
Abstract: In this paper, we investigated the effect of laser polishing at different treatment times on the surface roughness and corrosion resistance of a biliary nickel–titanium (NiTi or Nitinol) stent. A specific area of the stent wire surface was checked for changes in roughness by scanning electron microscopy (SEM) and a noncontact profilometer. The corrosion resistance was assessed by potentiodynamic polarization test and electrochemical impedance spectroscopy. The surface characterization revealed that laser polishing reduced the surface roughness of stent by 34–64% compared to that of the as-received stent surface condition depending on the treatment time (i.e., 700–1600 μm). Measurements using potentiodynamic…polarization in simulated body fluid solution showed better anti-corrosion performance of laser-polished stent compared to magnetically-polished stent and has comparable corrosion resistance with the as-received stent condition. In this paper, we have shown a preliminary study on the potential of laser polishing for the improvement of surface roughness of stent without affecting much its corrosion resistance.
Abstract: BACKGROUND: Degradation periods of biodegradable medical devices strongly affect their clinical performance and therefore special attention has been drawn to modulate their degradation rate. OBJECTIVE: This paper presents an experimental study on the effect of hydrophobic coating on the degradation behavior of PLLA samples. METHODS: PLLA films were coated with a thin layer of PCL, and a combination of scanning electron microscopy (SEM), Ubbelohde Viscometer Capillary, and chromatograph of gel permeation (GPC) was used to evaluate the morphology and molecular weight changes of samples during degradation. In addition, the mass loss of samples was also measured during the…experiment. RESULTS: PLLA samples with PCL coatings showed a slower degradation rate than those without PCL coatings, which indicated that PCL coatings could protect inside PLLA samples and slow down the degradation rate of PLLA samples. CONCLUSIONS: The results of the study suggest that hydrophobic coating on polymer materials is a useful approach to control the degradation of polymer medical device.
Abstract: BACKGROUND: Immobilization of phosphoproteins on type-I collagen via covalent binding may induce extra- and intrafibrillar mineralization. OBJECTIVE: This study tested the hypothesis that methacrylate phosphate esters immobilized on reconstituted type-I collagen can mimic the nucleating role of phosphoproteins. METHODS: Three functional monomers (MDP, GPDM and Phenyl-P) that differed in chemical structure and steric hindrances around the phosphate moiety were evaluated. Reconstituted type-I collagen was either left untouched (control) or treated by 5% monomer/ethanol for 20 s. All samples were incubated in simulated dentinal fluid as mineralizing medium at 37°C for 7 or 14 days. The extra- and intrafibrillar…mineralization were examined by SEM and TEM/SAED crystallography, respectively. RESULTS: FT-IR spectroscopy showed that the phosphate groups were incorporated on reconstituted collagen, irrespective of their chemical structure. MDP immobilization induced dense growth of extrafibrillar mineral over time, while with GPDM- and Phenyl-P-immobilized collagen, mineralization was moderate and sparse, respectively. TEM/SAED evidence disclosed that intrafibrillar minerals exclusively occurred in MDP-immobilized collagen. CONCLUSIONS: Immobilization of MDP, which had the lowest steric hindrance, could induce significant biomimetic extra- and intrafibrillar mineralization; resembling the lowest level of hierarchy organization of dentin.
Abstract: Gastric bleeding is one of the irritant problems in ulcer patients. In this study, we evaluated hemostatic action of ulcer-coating powder (EGF-endospray) on gastric ulcer animal models. EGF-endospray, containing epidermal growth factor, is designed to be applied through an endoscope. Hemostatic action of the EGF-endospray was evaluated on gastric hemorrhage models of rabbits and micro-pigs. The EGF-endospray was directly applied onto a mucosal resection (MR)-induced gastric bleeding focus in a rabbit model. In a porcine model, the EGF-endospray was applied once via an endoscopy to a bleeding lesion created by endoscopic submucosal dissection. The bleeding focus was then observed via…an endoscope. In the rabbit model, EGF-endospray treatment significantly shortened mean bleeding time in comparison with other treatments (104.3 vs 548.0 vs 393.2 s for the EGF-endospray, the non-treated control and the epinephrine injection, respectively). In the micro-pig model, EGF-endospray showed immediate hemostatic action and prolonged covering of the bleeding focus for over 72 h. Histology proved mucosal thickness was more efficiently recovered in all EGF-endospray treated animals. The results of the present study suggest that the EGF-endospray is a promising hemostatic agent for GI bleeding.
Abstract: The biodegradability of oxidized microporous, mesoporous and macroporous silicon films in a simulated body fluid with ion concentrations similar to those found in human blood plasma were studied using gravimetry. Film dissolution rates were determined by periodically weighing the samples after removal from the fluid. The dissolution rates for microporous silicon were found to be higher than those for mesoporous silicon of comparable porosity. The dissolution rate of macroporous silicon was much lower than that for either microporous or mesoporous silicon. This is attributed to the fact that its specific surface area is much lower than that of microporous and…mesoporous silicon. Using an equation adapted from [Surf. Sci. Lett. 306 (1994), L550–L554], the dissolution rate of porous silicon in simulated body fluid can be estimated if the film thickness and specific surface area are known.
Keywords: Porous silicon, biodegradability, bioactivity, simulated body fluid, gravimetry