Electrochemical detection of adrenaline and hydrogen peroxide on carbon nanotubes

Adrenaline and hydrogen peroxide (H ₂ O ₂ ) have neuromodulatory functions in the brain, and peroxide is also formed during reaction of adrenaline. Considerable interest exists in developing electrochemical sensors that can detect their levels in vivo due to their important biochemical roles. Challenges associated with the electrochemical detection of hydrogen peroxide and adrenaline are that the oxidation of these molecules usually requires highly oxidising potentials (beyond 1.4 V against silver (Ag)/silver chloride (AgCl)) where electrode damage and biofouling are likely and the signals of adrenaline, hydrogen peroxide and adenosine overlap on most electrode materials. To address these issues, the authors fabricated pyrolysed carbon (C) electrodes coated with oxidised carbon nanotubes. Using these electrodes for fast-scan cyclic voltammetric measurements showed that the electrode offers reduced overpotentials compared with graphite and improved resistance to biofouling. Adrenaline oxidises on this electrode at 0.75 (±0.1) V and reduces back at −0.2 (±0.1) V, while hydrogen peroxide oxidation is detected at 0.85 (±0.1) V on this electrode. The electrodes are highly sensitive with a sensitivity of 16 nA/μM for adrenaline and 11 nA/μM for hydrogen peroxide on an 80 μm ² electrode. They are also suitable for distinguishing between adrenaline, hydrogen peroxide and adenosine. Thus, these probes can be used for multimodal detection of analytes.