摘要:

Regeneration of organizationally complex tissue requires regulation of spatial distributions of particular cell types in three dimensions. In this paper we demonstrate an integration of polymer processing and selective polymer surface modification using methods suitable for construction of three-dimensional polymer scaffolds which may aid such cell organization. Specifically, the surfaces of degradable polyesters were modified with poly(ethylene-oxide) (PEO)-poly(propylene-oxide) (PPO) copolymers using a process compatible with a solid free-form fabrication technique, the 3DP™ printing process. We demonstrate inhibition of cell (hepatocyte and fibroblast) adhesion to regions of two-dimensional poly(lactide) (PLA) substrates modified with PEO-PPO-PEO copolymers. We further show that PEO-PPO-PEO-modified surfaces which are not adhesive for hepatocytes or fibroblasts can be made selectively adhesive for hepatocytes by covalent linkage of a carbohydrate ligand specific for the hepatocyte asialoglycoprotein receptor to the PEO chain ends. Our approach may be generally useful for creating regionally selective, microarchitectured scaffolds fabricated from biodegradable polymers, for spatial organization of diverse cell types.

ISSN:0920-5063    

DOI:10.1163/156856298X00451

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Novel hydrophilic-hydrophobic block copolymers - poly(2-hydroxyethyl methacrylate-block-4-bis(trimethylsilyl)methylstyrene) (poly(HEMA-block-BSMS) or BH polymer) - were prepared as materials potentially useful for blood-contacting devices. Among the BH(X) series including poly(HEMA) itself, platelet adhesion and activation are minimum on the surface of BH(10), the block copolymer composed of 10 mol% of the hydrophobic segment. The unique physicochemical characteristics of BH(10) such as the high free water content and the increased mobility of PHEMA segments seem to play an important role in the prevention of platelet adhesion and activation. The water content of BH(10) was twice that of poly(HEMA) itself, even in the presence of 10 mol% of the hydrophobic moiety [poly(BSMS)]. Further, an anomalous increase in free water content was observed for the BH(10) sample measured by DSC. The glass transition temperature of BH(10) in the dry state was determined to be c. 10°C, which was much lower than that observed for each of the homopolymers (c.f.: Tg[poly(HEMA)] = 70°C; Tg [poly(BSMS)] = 160°C), suggesting an increased mobility of tethered PHEMA segments in the BH(10) film.

ISSN:0920-5063    

DOI:10.1163/156856298X00460

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Octadecyltrichlorosilane (OTS) and [2-(perfluorooctyl)ethyl]trichlorosilane (FOETS) monolayers and their mixed monolayer were polymerized on a water subphase and subsequently immobilized onto a silicon wafer surface by covalent bonding. Atomic force microscopic (AFM) observation of the mixed (OTS/FOETS) monolayer revealed the formation of a phase-separated structure. Protein-adsorption behavior onto the monolayers was investigated in situ on the basis of an attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectroscopic flow cell method and the morphology of the monolayer surface-adsorbed bovine serum albumin (BSA) was observed by AFM. Protein adsorption behavior observed by ATR-FT-IR flow cell method revealed that the amount of BSA adsorption onto the OTS and FOETS monolayers increased remarkably at an initial experimental stage and attained a steady state within a few minutes at pH 7.5. The amount of steady state adsorption was c. 0.18-0.2 μgcm-2. AFM observation of the monolayer after exposure to BSA solution suggested that BSA adsorbed in the end-on adsorption state on OTS monolayer and side-on one in the FOETS monolayer, respectively. However, in the case of the mixed (OTS/FOETS) monolayer, ATR-FT-IR flow cell experiment revealed that the amount of steady state adsorption of BSA was suppressed. Also, AFM observation revealed that at pH 7.5, BSA preferentially adsorbed onto the FOETS phase of the mixed (OTS/FOETS) monolayer, which had a higher interfacial free energy against water. On the other hand, BSA adsorbed homogeneously onto the OTS and FOETS phases at the isoelectric point of BSA (pH 4.7). These results indicate that the preferential adsorption of BSA onto the FOETS phase in the mixed (OTS/FOETS) monolayer system is due to: (1) the minimization of the interfacial free energy between a monolayer surface and an aqueous solution; and (2) the electrostatic repulsion between BSA molecules bearing negative charges.

ISSN:0920-5063    

DOI:10.1163/156856298X00479

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The kinetics of competitive adsorption of proteins onto hexadecyltrichlorosilane coated glass (HTS-glass) from model solutions containing fluorescein isothiocyanate (FITC)-labeled human serum albumin (HSA-FITC) and gamma-globulin (HGG-FITC) were studied by total internal reflection fluorescence (TIRF) spectroscopy. The processes of displacement of HSA-FITC by HGG are independent of the conformational state of HSA adsorbed onto glass. On HTS-glass, displacement of protein is hindered by the presence of large numbers of CH3-terminated alkyl tails which induce conformational (reorientational) changes in HSA-FITC and HGG-FITC adsorbed from simple solutions. In contrast to HSA, adsorption of HGG onto HTS-glass from a simple solution is characterized by the absence of irreversible adsorption in the initial portion of the kinetic curve. Competition between HSA and HGG-FITC induces replacement of end-on adsorbed HGG-FITC on HTS-glass surface with subsequent desorption of the HGG-FITC into solution. Upon further increase in the HSA concentration in solution the competition of HSA for adsorption sites prevails, which leads to a decrease in the amount of adsorbed HGG-FITC and, consequently, to a decrease in the rate of its displacement.

ISSN:0920-5063    

DOI:10.1163/156856298X00488

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Sulfonated poly(ethylene oxide) (PEO-SO3)-grafted polyurethane (PU) copolymer (PU-PEO-SO3) was developed for utilization as a material for biomedical applications. Its bulk properties and biocompatibility were investigated and the results were compared to those of PU and PU-PEO (not sulfonated). PU-PEO-SO3copolymer showed higher water uptake than PU and PU-PEO, indicative of increased hydrophilicity due to the grafting of PEO-SO3. Compared with PU, PU-PEO-SO3displayed lower glass transition temperature (Tg) and melting endotherm from DSC analysis, suggesting the increase of microphase separation and the suppression of hard-segment packing. PU-PEO-SO3had practically similar mechanical properties to PU, indicating that the chemical modification of PU was accomplished without reducing its bulk properties. From the results of biocompatibility tests, PU-PEO-SO3copolymer showed significantly lower adhesion of platelets and S. epidermidis than PU control and PU-PEO. In addition, the platelet factor 4 (PF4) released from platelets was the lowest in PU-PEO-SO3among the test materials. PU-PEO-SO3copolymer, which has excellent mechanical properties and biocompatibility, is expected to be useful as coating, molding, and blending materials for artificial organs and medical devices.

ISSN:0920-5063    

DOI:10.1163/156856298X00497

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Dye-incorporated [poly(EGDMA-HEMA)] microspheres were investigated as a new chelate-forming polymer for iron overload. Poly(EGDMA-HEMA) microspheres, in the size range of 150-200 μm, were produced by a modified suspension polymerization of EGDMA and HEMA. The reactive dye-ligands (i.e. Cibacron Blue F3GA, Alkali Blue 6B and Congo Red) were covalently incorporated to the microspheres. The maximum dye incorporations were 16.5 μmol Cibacron Blue F3GA g-1, 23.7 μmol Alkali Blue 6B g-1, and 14.5 μmol Congo Red g-1. The maximum Fe(III) adsorptions on the dye-incorporated microspheres from aqueous solutions containing different amounts of Fe(III) ions were 51.0, 37.3, and 25.1 mg g-1for the Cibacron Blue F3GA, Alkali Blue 6B, and Congo Red carrying microspheres, respectively. The maximum Fe(III) adsorptions were observed at pH 4.0 in all cases. Fe(III) removal from human plasma was also investigated. The maximum adsorption capacities of Fe(III) ions from human plasma for Cibacron Blue F3GA, Alkali Blue 6B, and Congo Red, were of 12.0, 7.5, and 3.8 mg g-1polymer, respectively. It was observed that Fe(III) could be repeatedly adsorbed and desorbed without significant loss in adsorption capacity.

ISSN:0920-5063    

DOI:10.1163/156856298X00505

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In order to analyze the alginate components of alginate dressings and the fractions which are released when the dressing is in contact with model biological fluids, the use of various analytical methods was considered. The first step was the conversion of a calcium alginate batch to pure sodium alginate. The recovery of the latter from either insoluble or soluble mixed sodium/calcium alginates was performed by complexation of calcium ions with sodium citrate followed by ultrafiltration. Comparisons were made between sugar analysis,1H NMR and circular dichroism (CD) data to determinate the contents in guluronic and mannuronic acids of sodium alginate chains. It was shown that CD measurements afford a rapid and nondestructive method for determination of %G when one takes the ratio200/220into account. Fractionation of crude alginate (generally ranging from 30 to 70% G) was achieved by the triangle dissolution/precipitation method in order to increase the range of alginate in sugar composition. The various validated procedures were applied to investigate the effects of irradiation sterilization on alginate dressings. It was shown that sugar composition is retained whereas molecular weight decreased dramatically due to chain scission.

ISSN:0920-5063    

DOI:10.1163/156856298X00514

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor