Blood heparin sensor made from a paste electrode of graphite particles grafted with molecularly imprinted polymer

A real-time heparin monitor could be used to optimize the dosage of heparin during extracorporeal circulation procedures. This report describes the development of a graphite-paste (GP) electrode with molecularly imprinted polymer (MIP) grafted onto it. Heparin-imprinted poly (methacryloxyethyltriammonium chloride -co- acrylamide -co- methylenebisacrylamide) was grafted directly onto graphite particles. The grafted particles were thoroughly mixed with oil to fabricate the MIP-GP electrode. Traditional cyclic voltammetry was performed with the electrode in physiological saline or bovine whole blood containing 5 mM ferrocyanide and 0–8 units/mL heparin. The current intensity increased with heparin concentration, due to expansion of the effective surface area resulting from heparin-promoted mobility of the oil in the MIP-GP electrode. No significant difference was found in the sensitivity of the current to unfractionated heparin among the electrodes fabricated because of the electrode homogenization resulting from thorough mixing of the MIP-grafted particles and oil. (A previous MIP-grafted indium tin oxide electrode exhibited lower sensitivity in blood than in saline.) Only 60 s were needed to stabilize the current. The current at the MIP-GP electrode was also sensitive to low-molecular-weight heparin in blood, but insensitive to chondroitin sulfate C (CSC), which is a heparin analog. The non-imprinted polymer (NIP)-grafted electrode was insensitive to heparin. Thus, the MIP-GP electrode, which operated through a new heparin-sensing mechanism, is an excellent candidate for application as a disposable sensor to monitor heparin levels in blood.