Antithrombogenic surfaces: characterization and bioactivity of surface immobilized PGE1-heparin conjugate

Strong anionic polyelectrolyte microgels

We report a facile synthesis of highly uniform poly(styrene sulfonic acid) microgels, which carry a strong polyelectrolyte group at every repeating unit.

Preparation and characterization of polymeric coatings with combined nitric oxide release and immobilized active heparin

A new dual acting polymeric coating is described that combines nitric oxide (NO) release with surface-bound active heparin, with the aim of mimicking the nonthrombogenic properties of the endothelial cell (EC) layer that lines the inner wall of healthy blood vessels. A trilayer membrane configuration is employed to create the proposed blood compatible coating. A given polymeric substrate (e.g., the outer surface of a catheter sleeve, etc.) is first coated with a dense polymer layer, followed by a plasticized poly(vinyl chloride) (PVC) or polyurethane (PU) layer doped with a lipophilic N-diazeniumdiolate as the NO donor species. Finally, an outer aminated polymer layer is applied. Porcine heparin is then covalently linked to the outer layer via formation of amide bonds. The surface-bound heparin is shown to possess anti-coagulant activity in the range of 4.80-6.39 mIU/cm2 as determined by a chromogenic anti-Factor Xa assay. Further, the surface NO flux from the underlying polymer layer containing the diazeniumdiolate species can be controlled and maintained at various levels (from 0.5 to 60 x 10(-10) mol cm(-2)min(-1)) for at least 24 h and up to 1 week (depending on the flux level desired) by changing the chemical/polymer composition of the NO release layer. The proposed polymeric coatings are capable of functioning by two complementary anti-thrombotic mechanisms, one based on the potent anti-platelet activity of NO, and the other the result of the ability of immobilized heparin to inhibit Factor Xa and thrombin (Factor IIa). Thus, the proposed polymeric coatings are expected to exhibit greatly enhanced thromboresistivity compared to polymers that utilize either immobilized heparin or NO release alone.

Preparation and evaluation of polyurethane surfaces containing immobilized plasminogen

Plasminogen has been immobilized onto a segmented polyurethane containing amino groups, using glutaraldehyde as coupling agent. It was also aspecifically adsorbed, for sake of comparison, onto polyurethane films containing different functional groups and, in particular, epsilon-amino caproic acid and lysine residues. The differently immobilized plasminogen has been converted to plasmin by activation with urokinase, and the percentage of active plasmin for the various polymer films was determined using a tripeptide (S-2251) as a synthetic substrate. The biological behaviour of the differently treated polymer films has been evaluated in vitro by measurements of partial thromboplastin time (PTT) and platelet adhesion.

Platelet adhesion and cellular interaction with poly(ethylene oxide) immobilized onto silicone rubber membrane surfaces

Cellular interaction and platelet adsorption were investigated on poly(ethylene oxide) (PEO) immobilized silicone rubber membrane (SR) which has polyacrylic acid grafts on the surfaces. Polyacrylic acid (PAA) had been introduced to the SR surface after Ar plasma treatment of SR surfaces to introduce peroxide groups. Surface characterizations were made using ATR-FTIR, ESCA, SEM, and contact angle measurements. Experimental results obtained by ESCA high resolution curve fitting spectra indicated that the amount of bisamino PEO of different molecular weights immobilized onto SR surfaces were similar, which showed that the influence of the length of molecular chains (-C-C-O-) on the reactivity of terminal amino group is negligible. The wettability of modified SR surfaces increased with an increase in PEO molecular weight. Biological studies such as corneal epithelial cell culture and blood platelet adhesion were performed to understand the biocompatibility of modified SR surfaces. Biological studies using corneal epithelial cells showed that cell migration, attachment and proliferation onto PEO-20000 immobilized SR surface were suppressed, whereas these biological activities on PEO-600 were enhanced. Another study on platelet adhesion revealed that many platelets attached to PEO-600 immobilized SR, while platelet deposition was rarely observed on SR grafted with PEO-3350. The effects of different PEO molecular chains on biological response were discussed.

Synthesis and nonthrombogenicity of polyetherurethaneurea film grafted with poly(sodium vinyl sulfonate)

Synthesis of nonthrombogenic materials without using biologically active substances was explored. Poly(sodium vinyl sulfonate) is a water-soluble synthetic polymer and activates antithrombin III to exert nonthrombogenicity that was dependent on the molecular weight. Polyetherurethaneurea film was plasma-treated and graft-polymerized with sodium vinyl sulfonate. The graft film showed excellent in vitro and ex vivo nonthrombogenicity by suppressing interactions with plasma proteins and platelets as well as by inactivating blood-clotting factors.

In vitro non-thrombogenicity of a thrombin-substrate-immobilized polymer surface by the inhibition of thrombin activity

Derivatives of thrombin substrate were synthesized and immobilized on a poly(acrylic acid)-grafted polyurethane film. The carboxyl terminal of the thrombin substrate peptide should be blocked for a higher inhibitory effect of the thrombin activity. Immobilization of the thrombin substrate peptide enhanced adsorption and inactivation of thrombin on the polymer film to prolong the time for fibrin network formation, and suppressed adhesion and deformation of platelets on the film. Consequently, in vitro thrombus formation on the polymer film was strongly suppressed.