Effect of molecular crowding on the response of an electrochemical DNA sensor.
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 stem-loop 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. We find 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.
Ricci
Francesco
F
Department of Chemistry and Biochemistry, Department of Physics, and Institute for Polymers and Organic Solids, University of California, Santa Barbara, California 93106, USA.
Lai
Rebecca Y
RY
Heeger
Alan J
AJ
Plaxco
Kevin W
KW
Sumner
James J
JJ
D004247:DNA / Q000032:analysis*; D004563:Electrochemistry; D004566:Electrodes; D004583:Electrons; D005296:Ferrous Compounds / Q000737:chemistry*; D000075163:Metallocenes; D008751:Methylene Blue / Q000737:chemistry*
D005296:Ferrous Compounds; D000075163:Metallocenes; D004247:DNA; D008751:Methylene Blue; C004998:ferrocene