Optimization of DNA immobilization on gold electrodes for label-free detection by electrochemical impedance spectroscopy

S D Keighley, P Li, Pedro Estrela, P Migliorato

Research output: Contribution to journalArticle

155 Citations (Scopus)

Abstract

The ability to immobilize DNA probes onto gold substrates at an optimum surface density is key in the development of a wide range of DNA biosensors. We present a method to accurately control probe DNA surface density by the simultaneous co-immobilization of thiol. modified probes and mercaptohexanol. Probe surface density is controlled by the thiol molar ratio in solution, with a linear relationship between thiol molar ratio and probe density spanning (1-9) x 10(12)/cm(2). The probe surface density per microscopic surface area was determined using chronocoulometry, and a detailed analysis of the method presented. Using this sample preparation method, the effect of probe density and hybridization on the charge transfer resistance with the negatively charged ferri/ferrocyanide redox couple was determined. Above a threshold probe surface density of 2.5 x 10(12)/cm(2), electrostatic repulsion from the negatively charged DNA modulates the charge transfer resistance, allowing hybridization to be detected. Below the threshold density no change in charge transfer resistance with probe density or with hybridization occurs. The probe surface density was optimized to obtain the maximum percentage change in charge transfer resistance with hybridization.
Original languageEnglish
Pages (from-to)1291-1297
Number of pages7
JournalBiosensors and Bioelectronics
Volume23
Issue number8
Early online date4 Dec 2007
DOIs
Publication statusPublished - 14 Mar 2008

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