Surface modification of the polymers present in a polysulfone hollow fiber hemodialyser by covalent binding of heparin or endothelial cell surface heparan sulfate: Flow characteristics and platelet adhesion

The present study addresses the problem of simultaneous surface modification of various polymers, i.e. polysulfone (PSU), polycarbonate (PC), and polyurethane (PU), which constitute the Ultraflux AV 600 S® hollow fibre hemodialyser. An investigation was first made into six different chemical routes aimed at introducing carboxyl groups onto the surface of PSU, PC, and PU model polymers to which heparin (HE) or endothelial cell surface heparan sulfate (ESHS) was covalently bound via the reaction of residual amino groups and a coupling reagent. Carboxyl groups were introduced using three specific reactions based on their nucleophilic or electrophilic introduction into aromatic repeating units of the polymers and three non-specific carboxylation reactions, i.e. UV, heat or redoxactivation via nitrene or radical species. Concentrations of 1-20 nmol COOH groups per cm-2 led to HE or ESHS surface concentrations corresponding to one or several layers. Two nonspecific carboxylation reactions followed by HE- or ESH...