摘要:

AbstractEthylene oxide (EO) is used extensively to sterilize medical supplies that are heat sensitive. EO residues in materials post sterilization can present a hazard to patients at the point of use. Protracted aeration (i. e. degassing) times are necessary post sterilization to reduce EO residues to an accepted level. The sorption of EO into polyvinylchloride was found to be an active process given that at sorption equilibrium (i. e. when the net flow of diffusant into the host material has reduced to zero) the number of molecules of EO per unit volume was greater in PVC than in its external environment. The diffusion coefficient (D) was concentration (C) dependent and the relationship which best describes this dependence was D(c) ∝︁ InC. The diffusion of EO was dramatically accelerated (as evidenced by a time saving in degassing of up to 400%) if microwave heating (2.45 GHz) was used instead of conventional heating for the same macroscopic temperature. The values of activation energy for diffusion were obtained from the respective Arrhenius plots of diffusion coefficient versus inverse temperature for each process. In general, even small reductions in activation energy can greatly increase the specific rate of reaction. The relative efficacy of microwaves in eliminating EO residues as evidenced by this data occurs as a result of microwaves reducing the activation energy for diffusion by almost a factor of two. The relative efficiency of microwave desorption compared to conventional aeration offers considerable gains in the cost‐effectiveness of gas sterilization since it will permit a much greater throughput of material, thereby obviating the need for excessively large inventories of equi

ISSN:0021-9304    

DOI:10.1002/jbm.820230202

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe adsorption of fibrinogen from both human whole blood and plasma to a number of “foreign” surfaces is reported. Adsorption was measured as a function of plasma or blood dilution using radioiodine labeling. We showed previously that adsorption of fibrinogen from plasma exhibits a maximum at a plasma dilution of about 100:1, and have attributed this behavior to competition from other plasma proteins. (The same phenomenon is manifest as a time transient in fibrinogen adsorption.) In the present work we show that exactly the same trends are observed in whole blood. For each of the four surfaces, glass, siliconized glass, collagencoated glass and polyethylene, the adsorption of fibrinogen as a function of dilution is the same in whole blood as in plasma. Each of these surfaces shows a unique dependence of fibrinogen adsorption on plasma or blood dilution. On cuprophane and a hydrophilic polyether urethane there is essentially no adsorption of fibrinogen from blood or plasma. For the hydrophilic polyurethane this result may be artifactual, but the absence of fibrinogen binding to cuprophane in blood or plasma is real since fibrinogen is found to be adsorbed in monolayer amounts from buf

ISSN:0021-9304    

DOI:10.1002/jbm.820230203

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractPolyethylene terephthalate in textile form (Dacron®) has been used extensively as a surgical implant material for applications such as vascular grafts and percutaneous access devices. It is moderately histocompatible eliciting a chronic inflammatory reaction predominnately in tissue which has grown into the pores of the fabric. Titanium implants on the other hand, induce only the slightest inflammatory response and connective tissue adhesion to the titanium oxide surface is excellent. It was, therefore, hypothesized that a titanium coating on Dacron® fabric might improve its histocompatibility while leaving its desirable mechanical properties unaffected. To test this idea, Dacron® velour specimens were coated with titanium by vacuum deposition and were implanted together with uncoated controls in rabbits subcutis. After various implantation times, the specimens were recovered and the associated tissue was examined histologically. Qualitative and semiquantitative analysis revealed that tissue ingrowth quantity and quality was highly variable, not only between test and control specimens, but also between animals and even between specimens within the same animal. This indicated that there may be a number of factors influencing tissue ingrowth that were not adequately controlled in this study. The titanium coating which was undoubtedly highly oxidized had a profound qualitative and quantitative effect on fibroblast activity (ground substance formation) and fibroblast adhesion to the Dacron® fibers. The results obtained after these short‐term implantation periods indicate that titanium coating affects the quality of the interfacing tissue and may actually improve long‐term histocompatibility. Long‐term studies will have to confirm these prelimi

ISSN:0021-9304    

DOI:10.1002/jbm.820230204

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractInteractions of platelet with novel polyetherurethaneurea and its heparinized derivative were investigated. Platelet adhesion onto the material and release of serotonin or adenosine phosphate from platelet‐rich plasma (PRP) were suppressed by an introduction of amino groups to polyetherurethaneurea, by quaternization of the polymer. When the material was precoated with one of major plasma proteins and the protein‐coated materials were taken to contact with washed platelet suspension (WP), the dependence of platelet adhesion and activation on the properties of polymers was different from that observed for PRP interaction. Platelet adhesion and activation were promoted according to the nature of coating proteins in the order albumin<γ‐globulin

ISSN:0021-9304    

DOI:10.1002/jbm.820230205

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractBioprosthetic heart valves are being used more often because of certain advantages they have over artificial valves. The bioprostheses are less thrombogenic, cause a lower incidence of hemolysis, and usually fail in a slow progressive manner. A combination of flow characterization and accelerated testing was used to assess the durability of two types of pericardial valves, the Ionescu‐Shiley Low Profile Mitral and the Carpentier‐Edwards Low Profile Aortic valve. The flow characterization work was done in an aortic chamber designed forin vivosimulation. The function of the valve was monitored between different stages of the accelerated testing using laser Doppler anemometry. Accelerated testing was performed at 1300 cardiac cycles per minute, and physiologic conditions both in closing pressures and the ambient temperature were maintained. Results indicated a change in flow characteristics owing to cyclic loading of the leaflet tissue. The flow orifice increased over time leading to a decrease in peak velocity. Future developments in Doppler ultrasound may facilitate non‐invasive assessment of these peak velocity variations. Calcification of the tissue was not considered, since this was anin vitro

ISSN:0021-9304    

DOI:10.1002/jbm.820230206

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractAttachment and growth of mouse fibroblast cells on polypeptide derivatives with different wettabilities were studied in the presence or absence of serum proteins. In the presence of serum, a peak level of cell attachment was observed for substrates with a contact angle of around 70°. However, no relationship was found between cell attachment and water contact angle of the substrate in the absence of serum. Ca2+‐dependent cell attachment was observed on hydrophobic polypeptides in the absence of serum proteins. This suggests that Ca2+‐dependent membrane proteins function as mediators for cell attachment to hydrophobic polypeptides. In the presence of serum proteins, it was found that cell attachment is affected by the metabolism, Ca2+, and the cytoskeleton of the cell. Cell growth rate on hydrophilic polypeptide substrates was higher than that on intermediate or hydrophobic polypeptide substrates. This demonstrates that the strong interaction between cells and substrates will be unfavorable for a dewebbing process during mit

ISSN:0021-9304    

DOI:10.1002/jbm.820230207

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractAt high frequencies, electrochemical impedance behavior for corroding dental amalgams cannot be interpreted in terms of a simple Randles equivalent circuit. This may often be ascribed to the imperfect cell geometry resulting in a nonuniform current distribution. However, the insertion of a constant phase element (CPE) in the nonfaradaic branch of the equivalent circuit offers a new scope for interpretation as the circuit provides anm‐parameter corresponding to the degree of distortion. The decrease ofmas a function of time was explained by a mathematical model reflecting an increasing number of pores. Moreover, that same model allows a better understanding of the passivating effect of NaHCO3and of the differences between conventional and Cu‐rich dental amalg

ISSN:0021-9304    

DOI:10.1002/jbm.820230208

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractWe report the biocompatibility in the rat brain of a controlled‐release, biodegradable polymer, the polyanhydride poly‐[bis(p‐carboxyphenoxy)propane‐sebacic acid] copolymer (PCPP‐SA) in a 20:80 formulation. The biodegradable polyanhydride can be used for drug delivery directly into the brain, circumventing the difficulties posed by the blood—brain barrier and avoiding the consequences of having to administer toxic doses systemically to reach therapeutic doses in the central nervous system. The tissue reaction in the presence of PCPP‐SA was compared to that seen with other standard neurosurgical implants. Fifty‐six adult Sprague‐Dawley rats were assigned to one of seven groups and underwent bilateral frontal lobe implantation of PCPP‐SA (42 hemispheres), Surgicel (oxidized regenerated cellulose) (35 hemispheres), or Gelfoam (absorbable gelatin sponge) (35 hemispheres). None of the animals showed any behavioral changes or neurological deficits suggestive of either systemic or localized toxicity from the biodegradable polyanhydride, all surviving to the scheduled data of sacrifice. PCPP‐SA evoked a well localized inflammatory reaction, comparable to that of Surgicel, which resolved as the PCPP‐SA polymer degraded over five weeks. The biodegradable polyanhydride has been shown in this study to be nontoxic and biocompatible in the rat brain, when compared to standard

ISSN:0021-9304    

DOI:10.1002/jbm.820230209

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractRandom copolypeptides and block copolypeptides were synthesized, and an interaction between these polypeptide membranes and the cells was studied by a cell culture method (cell line, Ca. 9.22). In random copolypeptides composed of γ‐methyl L‐glutamate and γ‐benzyl L‐glutamate, cell attachment and cell growth depended on the monomer composition, and showed a maximum at around 70 mole % of benzyl glutamate. Block copolypeptide composed of L‐methionine and oxyethylene exhibited low cell attachment and cell growth even at 10 mole % of oxyethylene content, compared to L‐methionine homopolymer. ESCA study of the membrane suggested this result to be due to concentration of the poly(oxyethylene) block chain of the polymer on the surface of the membrane. Block copolypeptide composed of N5‐(3‐hydroxypropyl) L‐glutamine and L‐leucine exhibited low cell attachment and cell growth, while the corresponding random copolypeptide exhibited high cell attachment and cell growth. This difference is attributable to the microheterophase structure with the hydrophilic domains embedded in the hydrophobic matrix in the block c

ISSN:0021-9304    

DOI:10.1002/jbm.820230210

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

ISSN:0021-9304    

DOI:10.1002/jbm.820230211

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY