Photoimmobilisation of poly(N-vinylpyrrolidinone) as a means to improve haemocompatibility of polyurethane biomaterials

A novel method to improve the haemocompatibility of polymeric biomaterials (in particular: polyurethane elastomers) is reported. The new approach esse ntially rests upon photochemical immobilisation of the highly biocompatible polymer poly(N-vinylpyrrolidinone) (poly(NVP)) onto the biomaterial's surf ace. One of the key steps in the surface modification procedure is the prep aration of a copolymer of NVP and the photoreactive building block 4-[4'-az idobenzoyl]-oxo-n-butylmethacrylate (1). This copolymer is first dissolved in a volatile solvent, then sprayed onto the biomaterial's surface, and sub sequently immobilised via irradiation with ultraviolet light. The paper des cribes: (i) preparation of 1, (ii) preparation of the copolymer (NVP + 1), (iii) physico-chemical characterisation of the modified surfaces, and (iv) results of two in vitro haemocompatibility assays (i.e. thrombin generation and adhesion of blood platelets from recalcified human platelet-rich plasm a). Furthermore, the surface modification was performed with a microporous polyurethane vascular graft (Chronoflex (R)), which is already in clinical use. The in vitro experiments revealed that significant improvement of the haemocompatibility of polyurethanes can be achieved through this method. (C ) 1999 Elsevier Science Ltd. All rights reserved.