Heparin surface immobilization through hydrophilic spacers: Thrombin and antithrombin III binding kinetics

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Abstract
The immobilization of heparin onto polymeric surfaces using hydrophilic spacer groups has been effective in curtailing surface induced thrombus formation. In this study, the effect of hydrophilic spacers (PEO) on the binding kinetics of immobilized heparin with antithrombin III (ATIII) and thrombin was investigated. Monodispersed, low molecular weight heparin was fractionated on an ATIII affinity column to isolate high-ATIII affinity heparin. This high-ATIII affinity fraction was immobilized onto a styrene/p-amino styrene random copolymer surface using hydrophilic poly(ethylene oxide) (PEO) spacer groups. Styrene/p-amino styrene random copolymer was chosen as the model surface to provide quantitative and reproducible surface concentrations of available amine groups, grafted PEO spacers, and immobilized heparin. The polymer substrate was coated onto glass beads, tolylene diisocyanate modified PEO was covalently coupled to the surface, followed by heparin immobilization. The bioactivity of immobilized hepar...