摘要:

AbstractPhysical characteristics of a Ti‐6Al‐4V implant were evaluated following fabrication using a new electrodischarge compaction technique. Ti‐6Al‐4V atomized powders were loaded into Pyrex tubes (3.3 mm ID) and subjected to a highvoltage, high‐current‐density pulse in air for a period of less than 300 μs. Single pulses (1.0, 1.5, 2.0 and 2.5 KJ/grampowder) were applied from a capacitor bank (240, 480 or 720 μF) to produce solid core implants with porous surface layers. Implants were evaluated microscopically for core size, neck size, pore size, grain structure, and incorporated oxide film. Hardness was also evaluated. Implants were compared with Ti‐6Al‐4V commercial powders. Core size increased and pore size decreased with increases in energy and capacitance. The cores were composed of equiaxed grains which were free of oxide at the grain boundary. Porous layers, consisting of particles connected in three dimensions by necks, were free of oxide films at the connecting interfaces. Neck size increased with increases in input energy and capacitance. Hardness readings of the core, necks, and porous particles resulted in readings higher than or similar to control materials. Electrodischarge compaction did not alter the physical characteristics

ISSN:0021-9304    

DOI:10.1002/jbm.820251202

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractA cage implantation technique has been adopted in a rabbit animal model to investigate the biocompatibility of an aliphatic crosslinked polyurethane based on hexamethylene diisocyanate (HDI). In this study, four cages are represented; the cage containing the candidate polyurethane material, biomedical grade polyurethane (Tecoflex), the commercial grade polyvinylchloride (PVC), and an empty cage which were implanted subcutaneously in rabbits. Exudates were aspirated from these cages at 4, 7, 14, and 21 days postimplantation. Exudates were analyzed for variations in proteins, cell counts, and extracellular enzymes. Results with the four types of cage implants showed that the candidate polyurethane caused an inflammatory response comparable to that caused by medical‐grade Tecoflex and the empty cage contro

ISSN:0021-9304    

DOI:10.1002/jbm.820251203

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractLittle is known of the release of trace elementsin vivofrom dental implant materials. Conflicting data have been reported in the literature as to the levels of trace elements released and their potential consequences, mainly because of sampling and analytical methodological errors. In this study methods for average concentration levels of Al, Cr, Co, Mo, Ni, Ti, and V in organs were developed using rabbit tissue from anin vivoimplantation study. At least 50% of the brain, liver, lung, kidney, and spleen were taken minimizing contamination. The tissue was homogenized by cryogenic milling at LN2temperature and then freeze‐dried. Samples were digested in nitric acid and hydrogen peroxide using microwave energy. Standard reference materials were utilized for quality control. One liver sample was analyzed 10 times to assess the method precision. Absorbance values in blanks, standards, and test samples were measured using a Varian GTA 95 graphite furnace and 875 spectrophotometer. Very satisfactory method precision and quality control were recorded. Low or very low levels of the trace elements were found in the various organ

ISSN:0021-9304    

DOI:10.1002/jbm.820251204

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractAs part of a study on the mechanisms of leukocyte filtration, the influence of pore size distribution on filter efficiency was investigated. Conventional leukocyte filters are not suitable for model studies, as these filters are composed of tightly packed synthetic fibers, with a poorly defined porous structure. Therefore, open cellular polyurethane membranes with pore size distributions varying from approximately 15 to 65 μm were prepared. Filtration experiments with stacked packages of these membranes showed that leukocytes are best removed (>99%) by filters with a pore size distribution of 11–19 μm. These pore sizes approach the size of leukocytes (6–12 μm). However, due to fast clogging, blood flow through these filters is rapidly reduced, which results in a low filter capacity. With an asymmetric membrane filter, in which the pore size decreases from about 65 to 15 μm in the direction of blood flow, both moderate removal of leukocytes (>80%) and maintenance of flow (∼0.2 mL/s) are obtained. This results in efficient leukocyte removal. From cell analysis of both filtrate and filter, it is concluded that adhesion rather than sieving is the major filtration mechanism. Thus, further optimization of the filter may be achieved by surface mod

ISSN:0021-9304    

DOI:10.1002/jbm.820251205

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractIn an attempt to develop biodegradable polymers which can be shapedin situand adhere to living tissues, we synthesized esterurethane prepolymers which can be cured upon contact with water in living tissues. First,D,L‐lactide polymerization orD,L‐lactide‐ϵ‐caprolactone (50:50) co‐polymerization was carried out using ethylene glycol or poly(ethylene glycol) as initiator to obtain hydroxyl‐terminated biodegradable polyesters. They were then reacted with an excess of diisocyanate such as hexamethylene diisocyanate, toluylene diisocyanate, and diphenylmethane diisocyanate to introduce a reactive isocyanate group to both of the end groups of the polyesters. The isocyanate‐terminated prepolymers could be cured in the presence of water and the cured polymers were degraded by hydrolysis bothin vitroandin vivo. It was found that the presence of appropriate amounts of hydrophilic units in the main chain was essential for giving a high curing rate and a high degradation rate for the biodegradable urethane prepolymers. The tissue responses to the cured polymers w

ISSN:0021-9304    

DOI:10.1002/jbm.820251206

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractCrosslinking of collagenous biomaterials currently employs the use of glutaraldehyde. The putative enhancement of glutaraldehyde crosslinking by lysine was investigated in three model systems: bovine pericardium, collagen membranes, and bovine serum albumin. Repetitive sequential treatment of bovine pericardium with glutaraldehyde and lysine and finally with formaldehyde produced a matrix which, by the two criteria used (shrinkage temperature and urea/SDS soluble collagen), was shown to be more highly crosslinked than pericardium fixed in glutaraldehyde alone. Essentially the same results were obtained when membranes prepared from pepsin‐soluble pericardial collagen were subjected to sequential glutaraldehyde and lysine treatments, reaching shrinkage temperatures of more than 90°C. Heart valves prepared from lysineenhanced glutaraldehyde crosslinke bovine pericardium were testedin vitroin an accelerated fatigue tester and have been shown to behave satisfactorily after 300 million cycles. These additional crosslinks proved to be stable in saline at 37°C. Studies on bovine serum albumin attempted to get an insight into the mechanisms of lysine enhancement of glutaraldehyde crosslinking by treating sequentially albumin with glutaraldehyde and lysine and analysis of the products by gel filtration and SDS‐PAGE. These studies suggest that free amino groups exposed by proteins are initially reacted with glutaraldehyde and the bridged by the diamino compound (lysine) producing more extensive intermolecular crosslinking than glutaraldehyde

ISSN:0021-9304    

DOI:10.1002/jbm.820251207

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe biocompatibility of nine different materials, including positive and negative references, 4 polyurethane based and 3 latex based materials was investigated by (1) cytotoxic assay using V79 Chinese hamster cells, (2) the thickness of inflammatory layer at 3 and 7 days after intramuscular implantation test, and (3) the course of the blood flow in tissue reaction around subcutaneously implanted materials using Laser Doppler Flowmetry (LDF) over 14 days following implantation. In addition, for some materials, different modes of sterilization were compared. Although the three methods explore different reactive systems, the material ranking obtained was highly similar for the three methods, suggesting a relative accuracy between them. For one latex however, an absence of cytotoxic effect in culture and a highly intense response by LDF investigation of the same order of magnitude as for the positive reference implant suggest that bioincompatibility may result from the material itself and cannot be exclusively investigated by the leaching of toxic components.

ISSN:0021-9304    

DOI:10.1002/jbm.820251208

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractTetrapeptides, Arg‐Gly‐Asp‐Ser (RGDS), Arg‐Gly‐Asp‐Val (RGDV), and Arg‐Gly‐Asp‐Thr (RGDT), present in the cell‐attachment domain of fibronectin, vitronectin, and collagen, respectively, were synthesized by using an improved liquid‐phase procedure. Bioactivities of RGD and RGDX (X = S, V, and T) as cell recognition determinants were investigated by two methods to evaluate interactions of these oligopeptides with L‐929 fibroblast cells originating in mouse epithelia. In the first method, these oligopeptides were immobilized to ethylene‐acrylic acid copolymer (EAA) film, and the cell‐attachment activity of the immobilized film was measured. In the second method, interaction of oligopeptides with the cells was evaluated by measuring the cell inhibition caused by oligopeptides. It was found that RGD and RGDX exhibit remarkable cellattachment activity, and the activity of

ISSN:0021-9304    

DOI:10.1002/jbm.820251209

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe objective of this study was to evaluate a new type of percutaneous device (PD) designed to be implanted in soft tissues. The new PD consisted out of: (1) a flange‐shaped subcutaneous component, made from sintered titanium fiber‐web, and (2) a percutaneous component, made from dense sintered hydroxyapatite. The PDs were inserted in the back of 15 rabbits. The surgical procedure was performed in two steps. In the first session the subcutaneous component was placed. In the second session, after 3–4 months the percutaneous component was fixed in the subcutaneous component. The implants were leftin situfor 1 and 4 months after the second implantation session. Clinical and histological investigations were performed. It is found, that there was only a limited epidermal downgrowth in the percutaneous area. No inflammatory reaction was observed in the dermal connective tissue. Histological analysis also demonstrated that titanium fiber mesh evokes minor adverse effects of the surrounding tissues. In conclusion, these experiments have shown that stabilization of the PD in the hypodermal area by using a sintered titanium fiber‐web structure favors the longevity of PDs implanted in soft

ISSN:0021-9304    

DOI:10.1002/jbm.820251210

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractSurfaces containing poly(ethylene oxide) (PEO) are interesting biomaterials because they exhibit low degrees of protein adsorption and cell adhesion. In this study different molecular weight PEO molecules were covalently attached to poly(ethylene terephthalate) (PET) films using cyanuric chloride chemistry. Prior to the PEO immobilization, amino groups were introduced onto the PET films by exposing them to an allylamine plasma glow discharge. The amino groups on the PET film were next activated with cyanuric chloride and then reacted withbis‐ amino PEO. The samples were characterized by scanning electron microscopy, water contact angle measurements, gravimetric analysis, and electron spectroscopy for chemical analysis (ESCA). The adsorption of125I‐labeled baboon fibrinogen and bovine serum albumin was studied from buffer solutions. Gravimetric analysis indicated that the films grafted with the low‐molecularweight PEO contained many more PEO molecules than the surfaces grafted with higher‐molecular‐weight PEO. The highmolecular‐weight PEO surfaces, however, exhibited greater wettability (lower water contact angles) and less protein adsorption than the low‐molecular‐weight PEO surfaces. Adsorption of albumin and fibrinogen to the PEO surfaces decreased with increasing PEO molecular weight up to 3500. A further increase in molecular weight resulted in only slight decreases in protein adsorption. Protein adsorption studies as a function of buffer ionic strength suggest that there may be an ionic interaction between the protein and the allylamine surface. The trends in protein adsorption together with the water contact angle results and the gravimetric analysis suggest that a kind of “cooperative” water structuring around the larger PEO molecules may create an “excluded volume” of the hydrated polymer coils. This may be an important factor contributing to the observed low prot

ISSN:0021-9304    

DOI:10.1002/jbm.820251211

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY