Peroxidase activity of enzymes bound to the ends of single-wall carbon nanotube forest electrodes

This communication reports the first example, to our knowledge, of enzymes covalently attached onto the ends of vertically oriented single-wall carbon nanotube (SWNT) forest arrays used as electrodes. Quasi-reversible Fe-III/Fe-II voltammetry was observed for the iron heme enzymes myoglobin and horseradish peroxidase coupled to carboxylated ends of the nanotube forests by amide linkages. Results suggest that the trees in the nanotube forest behaved electrically similar to a metal, conducting electrons from the external circuit to the redox sites of the enzymes. Electrochemically manifested peroxidase activity of myoglobin and horseradish peroxidase attached to the SWNT forests was demonstrated, with detection limits for hydrogen peroxide in buffer solutions of similar to100 nM. These prototype SWNT-forest biosensors are easy to prepare, and enzyme layers were stable for weeks. (C) 2003 Elsevier Science B.V. All rights reserved.