Metallic wires with an adherent lubricious and blood-compatible polymeric coating and their use in the manufacture of novel slippery-when-wet guidewires: possible applications related to controlled local drug delivery.

A new procedure was developed for the controlled application of adherent hydrophilic and biocompatible coatings onto the surface of "endless" metallic wires. Use of copolymers of 1-vinyl-2-pyrrolidinone and alkylmethacrylates provided coatings with excellent adherence and lubricity, and markedly low thrombogenicity. Coated wires could be spiralized without damaging the coating; the resulting coils are potentially useful as lubricious guidewires for use in, for example, interventional cardiology or urology. This study demonstrates that the lubricity of the coating is dependent on the composition (hydrophilicity) of the coating biomaterial, as well as on the thickness of the coating. Furthermore, the results imply that the adherence of the hydrophilic coating is essentially due to entanglement of the binder polymer chains and the hydrophilic copolymer chains. Moreover, the idea to use the hydrophilic coating on the wire as a temporary depot for controlled local drug delivery was explored. The coating was loaded with the dye rhodamine, and release of the dye upon immersion of the coated wire in water was studied. This work revealed that release of the drug is dependent on the composition of the coating. The potential utility of such wires with a drug-charged coating for controlled local drug delivery is discussed briefly.

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 essentially rests upon photochemical immobilisation of the highly biocompatible polymer poly(N-vinylpyrrolidinone) (poly(NVP)) onto the biomaterial's surface. One of the key steps in the surface modification procedure is the preparation of a copolymer of NVP and the photoreactive building block 4-[4'-azidobenzoyl]-oxo-n-butylmethacrylate (1). This copolymer is first dissolved in a volatile solvent, then sprayed onto the biomaterial's surface, and subsequently immobilised via irradiation with ultraviolet light. The paper describes: (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 plasma). Furthermore, the surface modification was performed with a microporous polyurethane vascular graft (Chronoflex), 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.