Enzyme mimetic microgel coating for endogenous nitric oxide mediated inhibition of platelet activation

Abstract

Nitric oxide (NO) continuously generated by healthy endothelium prevents platelet activation and maintains vascular homeostasis. However, when artificial surfaces, like of extracorporeal membrane oxygenator comes in contact with blood, protein adsorption and thereby platelet activation takes place, which eventually leads to thrombus formation. To overcome this, we present an antifouling microgel coating mimicking the function of enzyme glutathione peroxidase to endogenously generate NO in the blood plasma from endogenous NO-donors and maintain a physiological NO flux. Microgels are synthesized by copolymerization of highly hydrophilic N–(2–hydroxypropyl)methacrylamide (HPMA) and glycidyl methacrylate (GMA) with diselenide crosslinks. For immobilization of the microgels on hydrophobic poly(4-methylpentene) (TPX) membranes bioengineered amphiphilic anchor peptides with free thiols are used. The anchor peptide attaches to the TPX membranes by hydrophobic interactions while the free thiols are presented for crosslinking with the microgels. The hydrophilic nature of the microgel coating prevents protein adsorption while the reversible diselenide bridges make the microgels responsive to the reducing environment and lead to the formation of reactive selenols/selenolates. The generated selenols/selenolates provide an efficient and sustained NO-release from endogenous S-nitrosothiols (RSNOs) mimicking the enzymatic function of glutathione peroxidase. On exposure to the whole blood, the microgel coating inhibited platelet activation and prolonged the blood clotting time.