Nonthrombogenic, Biodegradable Elastomeric Polyurethanes with Variable Sulfobetaine Content

For applications where degradable polymers arelikely to have extended blood contact, it is often important forthese materials to exhibit high levels of thromboresistance.This can be achieved with surface modification approaches, butsuch modifications may be transient with degradation.Alternatively, polymer design can be altered such that thebulk polymer is thromboresistant and this is maintained withdegradation. Toward this end a series of biodegradable, elasticpolyurethanes (PESBUUs) containing different zwitterionicsulfobetaine (SB) content were synthesized from a polycaprolactone-diol (PCL-diol):SB-diol mixture (100:0, 75:25, 50:50, 25:75and 0:100) reacted with diisocyanatobutane and chain extended with putrescine. The chemical structure, tensile mechanicalproperties, thermal properties, hydrophilicity, biodegradability, fibrinogen adsorption and thrombogenicity of the resultingpolymers was characterized. With increased SB content some weakening in tensile properties occurred in wet conditions andenzymatic degradation also decreased. However, at higher zwitterionic molar ratios (50% and 75%) wet tensile strength exceeded15 MPa and breaking strain was >500%. Markedly reduced thrombotic deposition was observed both before and after substantialdegradation for both of these PESBUUs and they could be processed by electrospinning into a vascular conduit format withappropriate compliance properties. The mechanical and degradation properties as well as the acute in vitro thrombogenicityassessment suggest that these tunable polyurethanes could provide options appropriate for use in blood contacting applicationswhere a degradable, elastomeric component with enduring thromboresistance is desired.