Irina Kondyurina

Crosslinked Polyurethane Coating on Vascular Stents for Enhanced X-ray Contrast

A coating of polyurethaneurea was made from a solution on the surface of metal stents. The influence of cleaning, etching, chemical and ion beam modification (plasma immersion ion implantation) of the metal surface on the adhesion strength of the polyurethaneurea was analysed. Polyurethaneurea films imbedded with tantalum particles as a radiopaque filler maintained their strength and elasticity and produced clear X-ray contrast images of vascular stents.

Drug release from polyureaurethane coating modified by plasma immersion ion implantation

A crosslinked polyurethanurea (PUU) coating was synthesised from a solution on metal vascular stents. In the model system the glucocorticoid prednisolone was inserted into the film by the equilibrium swelling method; after this plasma immersion ion implantation (PIII) was applied to modify the coating for improved release kinetics. This treatment causes the formation of oxygen-containing and unsaturated carbon-carbon groups in the PUU and a destruction of the drug in the surface layer. As a consequence, the release rate of prednisolone to water becomes more stable with time than it is at the untreated coating. In this drug release system PIII treatment prevents an initial toxically high release of the drug. By this it allows the incorporation of a higher amount of the drug and an extended action.

Plasma mediated protein immobilisation enhances the vascular compatibility of polyurethane with tissue matched mechanical properties

Polyurethanes are a diverse class of polymers, with independently tunable mechanical and biodegradation properties making them a versatile platform material for biomedical implants. Previous iterations have failed to adequately embody appropriate mechanical and biological properties, particularly for vascular medicine where strength, compliance and multifaceted biocompatibility are required. We have synthesized a new polyurethane formulation with finely tuned mechanical properties, combining high strength and extensibility with a low Youngs modulus. Additional cross-linking during synthesis enhanced stability and limits leaching. Under cyclic testing, hysteresis was minimal following completion of the initial cycles, indicating the robustness of the material. Building on this platform, we used plasma immersion ion implantation to activate the polymer surface and functionalized it with recombinant human tropoelastin. With tropoelastin covalently bound to the surface, human coronary endothelial cells showed improved attachment and proliferation. In the presence of heparinized whole blood, tropoelastin-coated polyurethane showed very low thrombogenicity in both static and flow conditions. Using this formulation, we synthesized robust, elastic prototype conduits which easily retained multiple sutures and were successfully implanted in a pilot rat aortic interposition model. We have thus created an elastic, strong biomaterial platform, functionalized with an important regulator of vascular biology, with the potential for further evaluation as a new synthetic graft material.

Experimental investigation of plasma-immersion ion implantation treatment for biocompatible polyurethane implants production

Modification of the surface layer of polyurethane with plasma-immersion ion implantation (PIII) and studying its physical and chemical changes have been discussed in this paper. The goal of the research was to obtain carbonized layer allowing creating biocompatible polyurethane implants. The experiments of PIII treatment in various modes were performed. The investigation of the modified surface characteristics was carried out by observing the kinetics of free surface energy for two weeks after treatment. The regularities between treatment time and the level of free surface energy were detected. The explanation of high energy level was given through the appearance of free radicals in the surface layer of material. The confirmation of the chemical activation of the polyurethane surface after PIII treatment was obtained.