ISSN:0920-5063    

DOI:10.1163/156856293X00078

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Fibrinogen adsorptions to surface modified polyurethanes (PU, PU-PEO, and PU-PEO-SO3) were studied from plasma in vitro. PU and PU-PEO surfaces demonstrated that initial adsorption increases with increasing plasma concentration in kinetic profiles and adsorption time in adsorption profiles as a function of plasma concentration, but after the plateau is reached, its adsorption amount decreases as plasma concentration (0.2-2.0%) and adsorption time (1-120 min) increase, respectively. In contrast, PU-PEO-SO3showed that initial adsorption is almost same regardless of plasma concentration and adsorption time, which is due to the high affinity of surface sulfonate group to fibrinogen. All the surfaces indicated the Vroman effect at about 0.6% plasma concentration; however, the displacement was relatively low. Adsorbed amount of fibrinogen at steady state decreased in the order: PU > PU-PEO-SO3> PU-PEO, regardless of adsorption time and plasma concentration. The adsorption behavior of PU-PEO-SO3is attributed to both effect of low binding affinity of PEO chain and high affinity of pendant sulfonate group toward fibrinogen.

ISSN:0920-5063    

DOI:10.1163/156856293X00087

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Macrophage activation by implanted bood-contacting biomaterials modulates smooth muscle cell and endothelial cell ingrowth. The present study evaluates the in vitro interactions between Dacron or polyglactin 910 with macrophages derived from rabbits fed either normal or atherogenic diets. Peritoneal macrophages were cultured in the presence or absence (negative controls) of either biomaterial for 7 weeks. Conditioned media was evaluated for mitogenic activity using a rabbit aortic smooth muscle cell bioassay with or without preincubation with neutralizing anti-basic-FGF antibody. Results demonstrated increased mitogen release from macrophages harvested from the atherosclerotic rabbits. Only macrophages harvested from normal diet fed rabbits increased their mitogen release following exposure to either polyglactin 910 (p < 0.05) or to Dacron (p < 0.005) over controls. The stimulation of mitogen release by polyglactin 910 did not significantly exceed that in response to Dacron. In rabbits fed normal diets neutralization with the anti-basic-FGF antibody inhibited 100% of the Dacron induced mitogen release as compared to 36% of the polyglactin 910 induced mitogen release (p < 0.01). These results demonstrate significant induced mitogen release from macrophages exposed to biomaterials in vitro, much of the smooth muscle cell mitogen represented by basic-FGF.

ISSN:0920-5063    

DOI:10.1163/156856293X00096

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Proliferation of vascular smooth muscle cells (SMC) is postulated to be a key step in the pathogenesis of atherosclerosis or restenosis after vascular interventions such as angioplasty. Natural glycosaminoglycans, such as heparin and heparan sulfate, are known for their ability to inhibit SMC proliferation in vivo and in vitro. The antiproliferative activity of synthetic derivatized dextrans exhibiting heparin-like anticoagulant and anticomplement capacities have been investigated with rat aorta smooth muscle cells in culture. We report here that some derivatized dextrans grafted with benzylamide sulfonate moieties are potent antiproliferative agents for rat smooth muscle cell (SMC) in vitro. These synthetic polymers inhibit the SMC proliferation as well as heparin. The SMC growth inhibition is dose dependent, reversible and non-toxic. Highly anionic carboxylic dextrans are not capable of inhibiting the SMC growth, excluding a simple charge effect mechanism. Using fluorescent (DTAF) probes, we demonstrated that the synthetic antiproliferative polymers and heparin are internalized into the SMC. No binding or internalization was observed with native dextran devoid of antiproliferative capacity. We conclude that a suitable distribution of functional groups on the dextran backbone can simulate heparin activity in terms of antiproliferative capacity on SMC growth.

ISSN:0920-5063    

DOI:10.1163/156856293X00104

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A series of novel polyisobutylene (PIB)-toughened poly(methyl methacrylate) (PMMA) networks consist of rubbery PIB domains covalently bonded to a glassy PMMA matrix. Materials containing 8.5-17 wt. % PIB (Mn= 18 000 g/mol) in a PMMA matrix (PIB/PMMA) were evaluated to assess their feasibility as the powder component along with methyl methacrylate (MMA) as the liquid component in a standard powder/liquid bone cement formulation. A standard ISO four-point bend test, commonly used for testing bone cements, was employed to investigate flexural properties. The mixing time and powder/liquid (P/L) ratio were studied to formulate novel PIB/PMMA cements for optimum toughness. Appropriate formulations led to improved toughness while adequate flexural strength and modulus were maintained. An experimental PIB/PMMA-system exhibited ∼57 MPa flexural strength and ∼2000 MPa flexural modulus.

ISSN:0920-5063    

DOI:10.1163/156856293X00113

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A model was developed to describe the kinetics of protein and platelet deposition and embolization on biomaterials. The model assumes that proteins can be adequately represented by fibrinogen, albumin, and Factor XII, that protein adsorption is Langmuir-type, that surfaces are homogeneous, and that all adsorption and deposition steps are first order. Eleven model parameters were determined from literature experimental data from ex vivo experiments utilizing canine and baboon blood on Silastic, one parameter came from adsorption of Factor XII on glass, and three parameters were obtained by minimizing differences between experimental and predicted fibrinogen adsorption, and platelet deposition and embolization behavior. The model well predicted observed behavior for fibrinogen adsorption, platelet deposition, and platelet embolization on Silastic, and platelet embolization from both polyacrylamide and HEMA-MAAC.

ISSN:0920-5063    

DOI:10.1163/156856293X00122

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A new method for preparing a wettability gradient on polymer surfaces was developed. Low density polyethylene sheets were treated in air with corona from a knife-type electrode whose power gradually increases along the sample length. The polymer surfaces oxidized gradually with the increasing power and the wettability gradient was created on the surfaces as evidenced by the measurement of water contact angles, Fourier-transform infrared spectroscopy in the attenuated total reflectance mode, and electron spectroscopy for chemical analysis. The wettability gradient surfaces prepared were used to investigate the interactions of model protein and cells in terms of the surface hydrophilicity/ hydrophobicity of polymeric materials.

ISSN:0920-5063    

DOI:10.1163/156856293X00131

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Gastric emptying of a polyanionic hydrogel, polycarbophil (PC), from the canine stomach was studied using a duodenal cannulation technique. The basis of the study is to employ a certain quantity of swelling hydrogel that, by virtue of its swollen size and viscosity, converts a fasted stomach to a fed state and resists discharge from the stomach for an extended period of time. Different amounts of PC, in 200 ml water plus buffering agents, were administered orally to fasted canines. The gastric emptying lag time was found to increase with the viscosity of the administered dose. Addition of a base, sodium bicarbonate, to PC increased gastric retention via an increase in its apparent viscosity. The polymer mass is retained in the canine stomach until a sufficient quantity of stomach acid secretion reduces the viscosity of the viscous mass, through protonation of polycarbophil, and, at that point, discharge of the hydrogel will commence. Thus, gastric retention of PC hydrogel in the canine stomach can be prolonged by increasing the apparent viscosity of the hydrogel administered.

ISSN:0920-5063    

DOI:10.1163/156856293X00140

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The enzyme, alkaline phosphatase, has been conjugated to a temperature-sensitive polymer which exhibits a lower critical solution temperature (LCST). A series of copolymers containing different molar ratios of N-isopropylacrylamide(NIPAAm) and N-acryloxysuccinimide(NAS) were synthesized and then conjugated to the enzyme. These polymer-enzyme conjugates precipitate and flocculate in aqueous solution above the LCST, and redissolve when cooled below that temperature. The kinetics of the conjugated enzymes have been characterized as a function of temperature and compared to free enzyme. The effect of the conjugation degree between polymer and enzyme on the activity of the conjugated enzymes was also investigated.

ISSN:0920-5063    

DOI:10.1163/156856293X00159

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Since the late 1970s, three families of poly(ortho esters) (POE) were synthesized to provide bioerodible carriers for drug delivery devices. The most recent POE is a semi-solid polymer with a viscous behavior at room temperature. Polymer synthesis by a transesterification reaction between a triol and a trialkyl orthoester is described. The structure of the polymer was confirmed by conventional methods such as1H-NMR,13C-NMR and FT-IR. Information concerning average molecular weight and intrinsic viscosity was obtained respectively by GPC and viscosimetry. Residual solvents in the polymer were determined using gas chromatography. The chromatographic conditions were optimized to enable the quantification of the solvents in concentrations of a few percent. The mechanical behavior of the semi-solid POE was determined by rheometric measurements. Hydrolysis of the polymer leads to the formation of the original triol and the carboxylic acid derived from the trialkyl orthoester used in the transesterification step. No toxicological problems associated with these compounds are anticipated.

ISSN:0920-5063    

DOI:10.1163/156856293X00168

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor