Amperometric Detection of Glucose Using a Conjugated Polyelectrolyte Complex with Single-Walled Carbon Nanotubes

The conjugated polymer, poly[3-(3-N,N-diethylaminopropoxy)thiophene] (PDAOT), was synthesized and employed in the supramolecular functionalization of single-walled carbon nanotubes (SWNTs). Highly stable aqueous solutions of PDAOT−SWNT complexes were obtained after sonication under mildly acidic conditions. UV−vis absorption and Raman spectroscopy studies showed that the noncovalent functionalization did not change the nanotube structure and retained its inherent properties. The reactions of [Fe(CN6)]3−/4− redox couple on Au electrodes modified with PDAOT and the PDAOT−SWNT films were studied using electrochemical impedance spectroscopy and cyclic voltammetry. A lower electron-transfer resistance and higher current response were observed on the Au/PDAOT−SWNT electrode compared with the Au/PDAOT electrode. We prepared glucose biosensors by entrapping glucose oxidase (GOx) within the PDAOT and PDAOT−SWNT films. Under optimized conditions, the Au/PDAOT−SWNT/GOx biosensor exhibited fast current response to glucose with a detection limit of 5 μM and a sensitivity of 700 ± 26 μA/mM·cm2. The responsiveness of the Au/PDAOT−SWNT/GOx biosensor can be attributed to the synergistic effect of the high conductivity and nondenaturing microenvironment of the PDAOT and the large active surface area and electrical conductivity provided by the SWNTs.