Effect of Molecular Crowding on the Response of an Electrochemical DNA Sensor

Authors

Francesco Ricci, University of California, Santa Barbara
Rebecca Lai, University of Nebraska - LincolnFollow
Alan J. Heeger, University of California, Santa Barbara
Kevin W. Plaxco, University of California, Santa Barbara
James J. Sumner, U.S. Army Research Laboratory

Date of this Version

2007

Citation

Langmuir 2007, 23, 6827-6834

Comments

U.S. Government Work

Abstract

E-DNA sensors, the electrochemical equivalent of molecular beacons, appear to be a promising means of detecting oligonucleotides. E-DNA sensors are comprised of a redox-modified (here, methylene blue or ferrocene) DNA stemloop covalently attached to an interrogating electrode. Because E-DNA signaling arises due to binding-induced changes in the conformation of the stem-loop probe, it is likely sensitive to the nature of the molecular packing on the electrode surface. Here we detail the effects of probe density, target length, and other aspects of molecular crowding on the signaling properties, specificity, and response time of a model E-DNA sensor.Wefind that the highest signal suppression is obtained at the highest probe densities investigated, and that greater suppression is observed with longer and bulkier targets. In contrast, sensor equilibration time slows monotonically with increasing probe density, and the specificity of hybridization is not significantly affected. In addition to providing insight into the optimization of electrochemical DNA sensors, these results suggest that E-DNA signaling arises due to hybridization-linked changes in the rate, and thus efficiency, with which the redox moiety collides with the electrode and transfers electrons.