Amperometric sensing of norepinephrine at picomolar concentrations using screen printed, high surface area mesoporous...

Norepinephrine (NE) is detected amperometrically using the enzyme Phenylethanolamine N-methyl transferase and cofactor S-(5'-Adenosyl)-l-methionine chloride dihydrochloride with disposable screen printed mesoporous carbon electrodes. The role of internal surface area and pore size of the mesoporous carbon is systematically examined using soft-templated, mesoporous silica-carbon powders with highly microporous walls obtained from etching of the silica to produce powders with surface areas ranging from 671-2339 m(2)g(-1). As the surface area increases, the sensitivity of the biosensor at very low NE concentrations (0-500 pg mL(-1)) in phosphate buffered saline (PBS) increases just as the current signal increases with respect to the NE concentration of 81-1581 μA mL ng(-1) cm(-2) for the mesoporous carbons. The best performing electrode provides similar sensitivity in whole rabbit blood in comparison to PBS despite no membrane layer to filter the non-desired reactants; the small (<5 nm) pore size and large internal surface area acts to minimize non-specific events that decrease sensitivity.