Neutrophil adhesion on phosphorylcholine-containing polyurethanes

Polyurethanes have been synthesized using glycerophosphorylcholine (GPC) as a chain extender. By altering the ratio of GPC to butanediol (BD), a series of polymers was obtained composed of different contents of phosphorylcholine. Bulk and surface characterization of the polymers was carried out. Differential scanning calorimetry and dynamic mechanical analysis showed that the polymer with the highest phosphorylcholine content (PU-GPC-20) had the lowest soft segment Tg and the highest tensile strength and Young's modulus among the polymers studied. This is due to the high degree of microphase separation in PU-GPC-20 as a result of by ionic aggregation and hydrogen bonding from the zwitterionic phosphorylcholine moiety. PU-GPC-20 contained approximately 20 wt%, of glycerophosphorylcholine. Dynamic contact angle analysis showed that these polymers, especially the ones with high phosphorylcholine content, rearranged themselves to minimize their interfacial tension upon contacting an aqueous environment. Under shear rates of from 20 to 120 s(-1), neutrophils did not adhere to PU-GPC-20. Under similar conditions neutrophil adhesion was observed only at 20 s(-1) on PU-GPC-10, PU-GPC-5 and on the control polyurethane (PU-base). Cell spreading was observed on the control polyurethane but not on any of the other surfaces. The incorporation of phosphorylcholine into the polyurethane backbone effectively reduced neutrophil adhesion and thus potentially could result in lower inflammatory and foreign body responses.