A photochemical method for the surface modification of poly(etherurethanes) with phosphorylcholine-containing compounds to improve hemocompatibility

Abstract

Phosphorylcholine groups attached to polymer surfaces are known to improve hemocompatibility. A photochemical method is presented to couple phosphorylcholine-containing aryl azides to poly(etherurethane) surfaces (PEUs). Two aryl azides that consist of a photoactivatable 4-azidobenzoyl group, a short spacer chain, and a phosphorylcholine endgroup were synthesized. The two compounds differ only in the type of spacer used: triethylene glycol for compound 1 and hexanediol for compound 2. These compounds were physically adsorbed to PEU surfaces. Upon UV irradiation, reactive intermediates are formed that react with nucleophilic groups on the polymer surface. The modified surfaces showed decreased underwater contact angles, indicating that hydrophilic phosphorylcholine groups are present at the surface. ESCA measurements showed the presence of phosphorus and positively charged nitrogen atoms in the outermost polymer layers (analyzed depth about 50 A), which is a strong indication of the presence of phosphorylcholine groups. Hemocompatibility in vitro was tested with thrombin generation assays and platelet adhesion tests. In thrombin generation assays the clotting time of platelet-rich plasma in contact with the polymer surface is determined. Clotting times were clearly prolonged for the modified surfaces. Surfaces modified with compound 2 showed slightly higher clotting times than those modified with compound 1. Repeated surface modification with compound 2 further increased the clotting time. For the tested surfaces an increase in the clotting time corresponds to an increase in the concentration of phosphorylcholine groups at the surface (as measured by ESCA and contact angle). Platelet adhesion studies with scanning electron microscopy demonstrated that fewer platelets (showing less activation) adhered to the modified surfaces than to the unmodified polyurethane.

Zwitterionic phosphorylcholine-protected water-soluble Ag nanoparticles

“…They are prone to aggregation in high ionic strength solutions in which the van der Waals attraction outweighs the electrostatic and/or steric repulsion provided by surface-bound ligands (e.g., citrate). Phosphorylcholine, as a very polar and zwitterionic molecule, can bind a large amount of water [14,15] . Whitesides et al [16] have shown that the strong resistance of zwitterionic SAMs to protein adsorption on flat surfaces is due to their strong hydration capacity via electrostatic interactions.…”

Surface Modification of PDMS and Plastics with Zwitterionic Polymers

“…Therefore, a copolymer SB-Az Fig. 1 , which was a sulfobetaine polymer bearing photoreactive moiety, phenyl azide, was synthesized by AIBN polymerization, similarly 36,37 .…”

Surface modification of biomaterials by photochemical immobilization and photograft polymerization to improve hemocompatibility

“…Heiden et al [58] synthesized aromatic-azido polymers with phosphorylcholine groups and then grafted to biomaterial surface by UV irradiation (300-400 nm). The modified surface had high hydrophilicity, and much long clotting time.…”