Heparin-containing block copolymers

Abstract

Newly synthesized heparin-containing block copolymers, consisting of a hydrophobic block of polystyrene (PS), a hydrophilic spacer-block of poly(ethylene oxide) (PEO) and covalently bound heparin (Hep) as bioactive block, were coated on aluminium, glass, polydimethylsiloxane (PDMS), PS or Biomer substrates. Surfaces of coated materials were characterized by transmission electron microscopy (TEM), contact angle measurements and X-ray photoelectron spectroscopy for chemical analysis (XPS), It was demonstrated by TEM that thin films of PS-PEO and PS-PEO-Hep block copolymers consisted of heterogeneous microphase separated structures. Using sessile-drop and Wilhelmy plate dynamic contact angle measurements, insight was provided into the hydrophilicity of the surfaces of the coatings. Measurements with hydrated coatings of PS-PEO and PS-PEO-Hep block copolymers revealed that the surfaces became more hydrophilic during immersion in water, due to relaxation/reorientation, or swelling of PEO or PEO-Hep domains, respectively. XPS results for PS, PEO, heparin and PS-PEO as powder agreed well with qualitative and quantitative predictions. XPS results for films of PS-PEO and PS-PEO-Hep block copolymers showed enrichments of PEO in the top layers of the coatings. This effect was more pronounced for hydrated surfaces. Only small amounts of heparin were detected at the surface of coatings of PS-PEO-Hep block copolymers.

Heparin-containing block copolymers

“…This is possibly due to the fact that the coating technique traps or buries part of the heparin molecules within the coating matrix, allowing only the detection of heparin at the surface that is actually bioactive. This was also found in the surface analysis of these materials using XPS and contact angle measurements [11].…”

“…It has been shown [11] that the coatings on PDMS expressed a higher content of the hydrophobic block on the surface than the coatings on glass. Thus, the heparin fragment seems to be buried under the PS fragment of the block copolymers when coated on PDMS.…”

“…The first articles of this series [11] was directed to the surface characterization of the PS-PEO-Hep block copolymers by XPS and contact angle measurements. The aim of this study is the evaluation of the blood compatibility of heparin-containing block copolymers as a function of the copolymer composition.…”

Selective Aerobic Oxidation of Methanol in the Coexistence of Amines by Nanoporous Gold Catalysts: Highly Efficient Synthesis of Formamides

“…There have been various efforts to minimize or eliminate thrombogenicity. To design nonthrombogenic polymers, there have been many approaches including (1) the grafting of hydrophilic groups to the bulk polymer or polymer surface, which prevents platelet adhesion by giving nonthrombogenicity to the polymer;13 (2) suppression of platelet adhesion and morphologic change of the adhered platelets by microphase‐separated structures of polymers such as 2‐hydroxy ethyl methacrylate/styrene block copolymer;14–16 and (3) the immobilization of pharmaceutical reagents such as urokinase or heparin to the polymer 17–20. Urokinase decomposes fibrin to dissolve the thrombus.…”

Photocycloaddition‐induced preparation of nanostructured, cyclic polymers using biscinnamated or biscoumarinated oligo(ethylene glycol)s

“…For example, Langmuir‐Blodgett membranes have been produced on gas–liquid interfaces by hydrophobic association of amphiphilic molecules for the fabrication of electronic,16–18 optical,19–21 and sensor materials 22, 23. Amphiphilic polymers including hydrophilic‐hydrophobic block chains have been used for the surface design of medical devices24–26 and various industrial materials27–29 because of their ability to adsorb onto the surfaces of hydrophobic substrates in an aqueous solution. Alkanethiolates form self‐assembled monolayers at high densities on gold by chemical adsorption of thiol residues specific to a gold surface and subsequent hydrophobic assembly of alkyl residues 30, 31.…”