In vitro thrombogenicity investigation of new water-dispersible polyurethane anionomers bearing carboxylate groups

New segmented polyurethane (PU) anionomers based on hydroxytelechelic polybutadiene were synthesized via an aqueous dispersion process. Incorporation of carboxylic groups was achieved using thioacids of different length. Surface properties were investigated by mean of water absorption analysis and static contact-angle measurements using water, diiodomethane, formamide and ethylene glycol. Blood compatibility of the PUs was evaluated by in vitro adhesion assays using 111In-radiolabeled platelet-rich plasma and [125I]fibrinogen. Morphology of the adhered platelets was examined by scanning electron microscopy (SEM). Results were compared to two biomedical-grade PUs, namely Pellethane and Tecoflex. Insertion of carboxylic groups increased surface hydrophilicity and limited water uptake ( < 8% for an ion content of 5% by weight). Surface energy of all synthesized PUs was between 40 and 45 mJ/m2. Platelet adhesion and fibrinogen adsorption on the PU anionomer surfaces were affected as a function to the increase of graft length; thiopropionic was the most haemocompatible, followed by thiosuccinic and then thioglycolic acid. SEM analyses of all ionic PU samples exhibited low platelet adhesion to surfaces with no morphological modification. In conclusion, increased hydrophily, dynamic mobility and charge repulsion are synergistic key factors for enhanced haemocompatibility.

Hemocompatibilty of new ionic polyurethanes: influence of carboxylic group insertion modes

New segmented polyurethane (PU) anionomers based on hydroxytelechelic polybutadiene (HTPB) were synthesized via two environment-friendly chemical routes. The effects of carboxylic content and ion incorporation mode on the surface properties were investigated by mean of water absorption analysis and static contact angle measurements using water, diiodomethane, formamide and ethylene glycol. Blood compatibility of the PUs was evaluated by in vitro adhesion assay using 111In-radiolabeled platelet rich plasma and 125I-fibrinogen. The morphology of platelet adhesion was also observed by scanning electron microscopy (SEM). Results were compared with a biomedical-grade PU, Pellethane. Insertion of the carboxylic groups on the soft segments (S-alpha series), using thioglycolic acid (TGA), increases surface hydrophilicity, limits water uptake (5%, for an ion content of 3.6 wt%), and reduces platelet adhesion and fibrinogen adsorption on the PUs' surfaces. In contrast, the classical insertion onto the hard segment (H-alpha series), using dimethylolpropionate (DMPA) as chain extender, leads to high water uptake (18%, for an ion content of 3.6 wt%) and promotes platelet and fibrinogen adhesion. SEM analyses of the non-ionic PUs exhibited surfaces with adhered platelets which underwent morphological modification. Similarly, the H-alpha ionic PUs show adherent and activated platelets. On the contrary, no platelet morphology changes were observed on the S-alpha ionic surfaces. In conclusion, insertion of carboxyl groups on the soft segments of PUs reduces their thrombogenicity.