ISSN:0920-5063    

DOI:10.1163/156856289X00019

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

—The interactions of human serum albumin (HSA) with a poly(vinyl alcohol) gel packing (Asahipak GS-520) for high-performance liquid chromatography of proteins were investigated. Under certain conditions, the elution of HSA from the GS-520 column was retarded and its chromatogram was split into two peaks, indicating weak adsorption of HSA onto the gels and also the existence of two subfractions, i.e. human mercapto-albumin (HMA) and human non-mercapto-albumin (HNA). The chromatograms were confirmed to be greatly influenced by the salt composition, the pH, and the temperature of the isocratic mobile phase. It is characteristic for the adsorption of HSA onto the gels to be suppressed at a pH near its isoelectric point. The HSA-gel interaction parameters calculated using an adsorption chromatography theory demonstrate that the adsorption of HSA is caused by enthalpy-driven interactions, which are depressed by lowering the pH, in addition to hydrophobic interactions. Under the recommended chromatographic conditions for high resolution of HMA/HNA, it was found that the HSA samples possessed some subfractions besides HMA and HNA fractions.

ISSN:0920-5063    

DOI:10.1163/156856289X00028

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

—Segmented poly(etherurethaneureas) (SPUUs) with hydrophilic and hydrophobic polyether components were prepared. The surface chemical composition of SPUUs in various environments was investigated by means of X-ray photoelectron spectroscopic and dynamic contact angle measurements. These measurements revealed that in a hydrated state, the higher surface free energy component is enriched on the surface of the SPUU in order to minimize the interfacial free energy between water and the solid surface. The surface molecular mobility showed a strong correlation with bulk molecular motion. Platelet adhesion tests and dynamic contact angle measurements after adsorption of bovine serum albumin revealed that the surface of SPUUs with hydrophilic soft segments has a non-adhesive nature. The platelet reactivity of hydrophobic SPUUs is influenced by microphase separation at the surface.

ISSN:0920-5063    

DOI:10.1163/156856289X00037

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

—Heparin, immobilized to polyvinyl alcohol by reaction with glutaraldehyde (heparin-PVA), retained its ability to accelerate the antithrombin III inactivation of thrombin, in a recirculating flow loop using heparin-PVA coated polyethylene tubes. The extent of inactivation, for a constant flow time, was approximately constant over ten cycles of exposure to thrombin and antithrombin III, suggesting that the immobilized heparin was reusable, as expected from the catalytic nature of non-immobilized heparin. Assessment of the chromogenic substrate activity of adsorbed thrombin and the extent of displacement were less conclusive with the implication that thrombin is adsorbed to heparin-PVA or PVA without heparin in multiple states.

ISSN:0920-5063    

DOI:10.1163/156856289X00046

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

—The bulk, surface, and blood-contacting properties of a series of polyether polyurethanes based on polyethylene oxide (PEO) (MW = 1450), polytetramethylene oxide (PTMO) (MW = 1000), and mixed PEO/PTMO soft segments were evaluated. The effect of varying the weight percentage of PEO, and thus the overall polarity of the mixed soft segment phase, was investigated. Two polymer blends prepared from a PTMO-based and a PEO-based polyurethane were also studied. Differential scanning calorimetry (DSC) and dynamic mechanical analysis indicated that the polyurethanes based on either the PEO or the PTMO soft segments are relatively phase mixed. The degree of phase mixing in the polymers increased with increasing weight fraction of PEO. As expected, water absorption and the hydrophilicity of the polymer increased with increasing PEO soft segment content. In vacuum, the PEO-rich polymers have a lower concentration of soft segment at the surface, possibly due to the migration of the polar PEO segments away from the polymer/vacuum interface. The blood-contacting results indicated that the higher PEOcontaining polymers were more thrombogenic than the pure PTMO-based polyurethane. A threshold concentration of PEO in the polyurethane appeared to be required before the blood-contacting properties were significantly affected.

ISSN:0920-5063    

DOI:10.1163/156856289X00055

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

—Heparin has been shown to interact with acidic fibroblast growth factor (aFGF) and to potentiate the biological activity of aFGF on fibroblastic cells. Water-soluble dextran substituted with methyl carboxylic benzylamine and sulfonate groups has been shown to mimic the effect of heparin in its anticoagulant and anticomplement activity. We have studied the effect of a dextran derivative named E (DDE), which had an anticoagulant activity equivalent to 0.5 IU heparin/mg, on the mitogenic activity of aFGF on Chinese hamster fibroblasts (CCL39). DDE interacts with aFGF in a comparable manner to heparin. We have shown that 20μg of heparin or 400μg of DDE added to 1 ml of culture medium has no effect on cell proliferation alone but potentiates the mitogenic activity of aFGF ten fold if aFGF is added at doses corresponding to half maximum stimulation (ED50). We have also studied the effect of various concentrations of heparin and DDE on the binding of125I-aFGF on bovine brain membranes. Interestingly, the binding of125I-aFGF increased three-fold as the concentration of heparin was increased up to 0.2μg/ml. At 1μg/ml of heparin, the amount of bound125I-aFGF is comparable to that obtained in the absence of heparin. At higher concentrations, heparin displaces bound125I-aFGF, and a 50% displacement is seen with 20μg/ml of heparin. In the presence of DDE, no increase in125I-aFGF binding is seen and a displacement is obtained with increasing doses. A possible explanation of these results may be the existence of specific receptors to heparin on the cellular membrane. These receptors to heparin apparently do not have an affinity for DDE. Our data show that DDE can replace heparin in its interaction with aFGF and that it has the capacity to potentiate the biological activity of these growth factors. Furthermore, our binding studies suggest that this potentiation is not mediated through the cellular receptor of125Ι-aFGF. The interaction of heparin with aFGF stabilizes and protects aFGF from chemical and proteolytic degradation. DDE may also be a useful aFGF stabilizer with much weaker hemostatic properties than heparin for in vivo application of FGF.

ISSN:0920-5063    

DOI:10.1163/156856289X00064

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor