Modification of Polyurethane with Polyethylene Glycol–Corn Trypsin Inhibitor for Inhibition of Factor Xlla in Blood Contact

In previous work using gold as a model substrate, we showed that modification of surfaces with poly(ethylene glycol) (PEG) and corn trypsin inhibitor (CTI) rendered them protein resistant and inhibitory against activated factor XII. Sequential attachment of PEG followed by CTI gave superior performance compared to direct attachment of a preformed PEG-CTI conjugate. In the present work, a sequential method was used to attach PEG and CTI to a polyurethane (PU) substrate to develop a material with applicability for blood-contacting medical devices. Controls included surfaces modified only with PEG and only with CTI. Surfaces were characterized by water contact angle and X-ray photoelectron spectroscopy. The surface density of CTI was in the range of a monolayer and was higher on the PU substrate than on gold reported previously. Biointeractions were investigated by measuring fibrinogen adsorption from buffer and plasma, factor XIIa inhibition and plasma clotting time. Both the PU-PEG surfaces and the PU-PEG-CTI surfaces showed low fibrinogen adsorption from buffer and plasma, indicating that PEG retained its protein resistance when conjugated to CTI. Although the CTI density was lower on PU-PEG-CTI than on PU modified only with CTI, PU-PEG-CTI exhibited greater factor XIIa inhibition and a longer plasma clotting time, suggesting that PEG facilitates the interaction of CTI with factor XIIa. Thus sequential attachment of PEG and CTI may be a useful approach to improve the thromboresistance of PU surfaces.