Conjugated polyelectrolyte complexes with single-walled carbon nanotubes for amperometric detection of glucose with inherent anti-interference properties

Abstract

Supramolecular complexes between single-walled carbon nanotubes and the conjugated polyelectrolytes poly[3-(3-N,N-diethylaminopropoxy)thiophene] (PDAOT), poly[3-(3′-thienyloxy)propanesulfonate] (P3TOPS), and poly[2,5-bis(3-sulfonatopropoxy)-1,4-ethynylphenylene-alt-1,4-ethynylphenylene] (aPPE) were prepared in homogeneous aqueous solution, and mixed with the enzyme glucose oxidase. The resulting solutions were drop cast onto the surface of glassy carbon electrodes, producing uniform coatings that contained high concentrations of carbon nanotubes and the enzyme. It was found that electrochemical cells comprising the coated electrodes were responsive to the addition of glucose, resulting in biosensors having a detection limit of 5.0 μM and a linear dynamic range of 0.5 to 5.0 mM glucose. It was shown that sensitivity increased with increasing nanotube concentration up to 4 g L⁻¹, and increasing enzyme concentration up to 20 g L⁻¹. The high sensitivity of the nanotube-based sensors results from an effective increase in the surface area of the electrode as a result of contact with a percolation network of carbon nanotubes that is in close contact with glucose oxidase throughout the coating. By using the anionic conjugated polyelectrolyte aPPE in the coating, it was found that charge repulsion of anionic interferents such as uric acid and ascorbic acid could be achieved without the need for a Nafion overcoat. These results pave the way for development of new sensors to a variety of other analytes.