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

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 m² 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.