摘要:

Fluorinated polyimide derived from 2,2'-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and bis[4-(4-aminophenoxy) phenyl]sulfone (APPS) was synthesized to develop a novel membrane oxygenator combining excellent gas transfer and blood compatibility. The asymmetric gas exchange membranes of 6FDA-APPS made by a dry/wet process consisted of an ultrathin and defect-free skin layer supported by a porous substructure. O2transfer through the 6FDA-APPS membrane was extremely augmented as compared with that of the presently available membrane, poly(dimethylsiloxane), and the previously reported 6FDA-DDS membrane. Since CO2transfer through the 6FDA-APPS membrane increased with a decrease in CO2pressure according to dual-mode transport theory, CO2from the membrane was selectively removed at low CO2pressure. For the evaluation of in vitro blood compatibility, the platelet adhesion and the plasma protein adsorption on the surface of the 6FDA-APPS membrane were observed by using scanning electron microscopy and the amounts of platelet and plasma protein were determined by an amino acid analyzer. The results indicated that the fluorinated polyimide membranes showed excellent blood compatibility.

ISSN:0920-5063    

DOI:10.1163/156856296X00525

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A new procedure has been developed in order to obtain heterogeneous polymer surfaces for the promotion of cell adhesion. For this purpose, a microelectronic photosensitive resin was spin coated on polystyrene (PS) substrates. The resin was then submitted to UV light irradiation through a mask and partially developed. The sample was further submitted to a plasma oxygen discharge prior to dissolution of the remaining resin. The characterization by time of flight secondary ion mass spectrometry (ToF SIMS), X-ray photoelectron spectroscopy (XPS), and dynamic contact angle (DCA) allowed us to conclude that hydrophilic paths were created on the more hydrophobic PS substrate together with the complete removal of the resin. In order to optimize cell adhesion contrast, the modified surfaces were then conditioned with a solution containing both a surfactant (pluronic F68) and a protein. Two different proteins were tested (collagen I and fibronectin). PC12 cell cultures on those conditioned surfaces showed that cell adhesion occurs only on the hydrophilic tracks. ToF SIMS spectra and images recorded on those substrates revealed the presence of the proteins only in the hydrophilic tracks. In the same time, the surfactant is suspected to adsorb mainly on the hydrophobic areas of the samples.

ISSN:0920-5063    

DOI:10.1163/156856296X00534

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Ultrapure poly(vinyl alcohol) (PVA) hydrogels were prepared by exposing an aqueous solution of 15 or 20 wt% PVA to repeated cycles of freezing for 6 or 12 h at -20°C and thawing for 2 hours at 25°C. The adhesive characteristics of the PVA gels in contact with a reconstituted mucus surface were quantified using a tensile technique. As the number of freezing/thawing cycles increased, the work of fracture (adhesion) decreased due to the increase in the PVA degree of crystallinity. Crystallinity was determined using differential scanning calorimetry. PVA gels prepared from the 20 wt% solution and exposed to two cycles of freezing/ thawing exhibited the largest work of adhesion. Drug delivery studies were conducted with ketanserin, a wound healing enhancer. Release studies were conducted using PVA samples prepared from a 20-wt% solution that were exposed to two or three freezing cycles for 12 h followed by thawing for 2 h. Results from the release of the drug from the PVA sample exposed to two cycles showed that approximately 80% of the ketanserin was released within 4 h.

ISSN:0920-5063    

DOI:10.1163/156856296X00543

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Spherical microporous matrix type microspheres composed of 330 kD P(HB-HV) (10.8% HV) 20%PCL II containing a range of %BSA loadings have been fabricated using a single emulsion technique with solvent evaporation. Microspheres were generated in high yield (>75%) and the percentage incorporation of BSA had no significant effect on microsphere size distribution, typically 6-50 μm in diameter with a mean of 26.28 ± 2.34 μm, n = 25, for 20% BSA loaded microspheres. The loss of BSA both by partitioning into the aqueous continuous phase and through micropores generated during the precipitation of the fabrication polymer concomitant with solvent evaporation resulted in a low encapsulation efficiency (<15%). When the total cumulative release of BSA was expressed as a percentage of the actual total BSA incorporated, BSA release was only marginally influenced by the theoretical percentage loading suggesting that the amount and duration of BSA release in vitro was initially influenced as much by micropore number and diameter as by the extent of matrix BSA loading and detectable levels of BSA release could be monitored for up to 24 days.

ISSN:0920-5063    

DOI:10.1163/156856296X00552

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Spherical BSA loaded microporous matrix type microspheres composed of P(HB-HV) blended with 20% PCL II and fabricated using 0/w emulsification with solvent evaporation have been incubated in Hanks' buffer, pH 7.4; newborn calf serum; 1.5% pancreatin and synthetic gastric juice over 30 days and their percentage weight loss (PWL) and changes in ultrastructural morphology monitored by gravimetry and SEM respectively. The greatest percentage weight loss was observed after incubation in newborn calf serum and decreased in the order newborn calf serum > pancreatin > synthetic gastric juice > Hanks' buffer. Only incubation in synthetic gastric juice and Hanks' buffer produced a significant increase in PWL with increasing theoretical percentage loading. Incubation in Hanks' buffer produced limited surface erosion leading to an increase in micropore diameter and the coalescence of micropores to form surface pits. With pancreatin, surface erosion led to the disappearance of surface micropores and a reduction in microsphere diameter. Subsequent fracturing of the microsphere surface facilitated the breakup of the matrix. In synthetic gastric juice there was little surface erosion and surface flaking and bulk erosion were responsible for the breakup of the matrix. In newborn calf serum, spherical shape was maintained despite a reduction in microsphere diameter. Bulk erosion in the form of large macroporous pits extending deep into the matrix gave the microspheres a hollow appearance. The enhanced biodegradation in NCS and significant surface erosion in pancreatin was assumed to be due to the effects of exogenous enzyme activity in addition to simple ester hydrolysis.

ISSN:0920-5063    

DOI:10.1163/156856296X00561

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

cis-Dichloro(cyclohexane-trans-l-1,2-diamine)platinum(II) (Dach-Pt(chlorato)), is a platinum complex which is expected to exhibit higher antitumor activity than, and show no cross resistance with, cisplatin. However, its strong side-effects and low water-solubility have also been cited. We report that polymer/ antitumor drug conjugates shows reduced side-effects and high antitumor activity. In order to provide a macromolecular prodrug of Dach-Pt having reduced side-effects and high water-solubility, we synthesized polymer conjugates of Dach-Pt and dextran derivatives having carboxylic acid groups, oxidized-dextran (OX-Dex)/Dach-Pt conjugate, and carboxymethyl-dextran(CM-Dex)/Dach-Pt conjugate. The cytotoxic activities of the conjugates were investigated against p388D1lymphocytic leukemia cells in vitro. The OX-Dex/Dach-Pt conjugate showed almost the same level of cytotoxic activity as free Dach-Pt(chlorato). Although the cytotoxic activity of free Dach-Pt(chlorato) was decreased by incubation in medium with serum, the OX-Dex/Dach-Pt conjugate kept its cytotoxic activity in higher level after 24 h incubation in medium with serum. These results suggested that the stability of Dach-Pt molecule in the medium was increased and cytotoxic activity of Dach-Pt was not decreased by fixing to OX-Dex.

ISSN:0920-5063    

DOI:10.1163/156856296X00570

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The orientation effect of galactose ligand on hepatocyte attachment was investigated. Poly(N-p-vinylbenzyl-o-β-D-galactopyranosyl-D-gluconamide)(PVLA, a β-galactose-carrying styrene homopolymer, was used as a model ligand for the asialoglycoprotein receptors on hepatocytes. PVLA was transferred onto the poly(γ-benzyl L-glutamate) (PBLG) or PBLG/poly(ethylene glycol) (PEG)PBLG Langmuir-Blodgett (LB) films as the monolayer level. The dichroic fluorescence values of the confocal microscope indicated that the PVLA transferred onto the LB films was located with a preferential orientation of its molecular axes with regard to the direction of the α-helix of polypeptide. Hepatocyte recognized well-oriented galactose moieties of the surface of PVLA through asialoglycoprotein receptors.

ISSN:0920-5063    

DOI:10.1163/156856296X00589

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Non-polar hydrophobic poly(isobutylene)glycol (PIBG) was substituted for poly(tetramethylene ether)glycol (PTMEG) in poly(ether urethanes) based on 4,4'-methylenebis-(phenylisocyanate) (MDI) and 1,4-butanediol (BD) as chain extender. Two series of polyurethanes differing in their soft segment length, polymer composition, and hard segment content were studied by dynamic mechanical analysis (DMA) and static, as well as dynamic, contact angle measurements. The thrombogenicity of these polymers was characterized by studying the adhesion and activation of platelets using ELISA for GMP 140 and fluorescence microscopy. It was found by DMA that in PIBG-containing polyurethanes (PUE) exist soft domains containing hard segments, strictly separated hard segment domains, and hard segments partially mixed with soft segments. Contact angle measurements revealed that 25% PIBG or even less, are sufficient for a remarkable enrichment of these non-polar soft segments on the polymer surface. The platelet adhesion/activation on these materials was demonstrated to increase with the rise in hard segment content, as well as with an enhancement of the PIBG content. However, comparison of PIBG-containing PUE with medical applied polypropylene and pellethane expressed that PUE with PIBG content equal or less 25% have excellent haemocompatibility.

ISSN:0920-5063    

DOI:10.1163/156856296X00598

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Porous ceramic supports have been developed and utilized for the immobilization of yeast cells to produce ethanol by the fermentation of glucose. The relationship between the porous structure of the ceramic support and the quantity of yeast cells immobilized and the production of ethanol by the fermentation have been investigated. A comparison of the properties of the ceramic supports with those of a calcium alginate gel indicated that the ceramics are the better of the two types of material and have potential for industrial application.

ISSN:0920-5063    

DOI:10.1163/156856296X00606

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor