Extensive research efforts continue to be invested in the development of low-density electrochemical DNA sensor arrays for application in theranostics and pharmacogenomics. Rapid and low-cost technologies are thus required for genosensor arrays to impact on current medical practice, with sensors clearly being required to detect their targets with high sensitivity and specificity, whilst resisting biofouling and avoiding interfering signals from the sample matrix. We report on the performance of three polyethylene glycol (PEG) co-immobilisation strategies used in the preparation of DNA sensors, using the detection of the breast cancer marker oestrogen receptor-α as a model system. PEGylated DNA capture probes for oestrogen receptor-α were co-immobilised in the presence of either a PEG alkanethiol, a mixture of PEG alkanethiol and mercaptohexanol or a bipodal aromatic PEG alkanethiol. Electrochemical impedance spectroscopy and pulsed amperometry were employed to characterise the prepared surface and sensitivity of the sensor. A surface plasmon resonance study was additionally carried out to confirm the results obtained electrochemically. Finally, the best co-immobilisation system, consisting of the co-assembly of oestrogen receptor-α capture probes and bipodal aromatic PEG alkanethiol in a ratio of 1:100, was used for the electrochemical analysis of a PCR product resulting from the amplification of the genetic material extracted from 20 MCF7 cells. This novel co-immobilisation system exhibited both high electrochemical sensitivity and resistance to fouling believed to results from an enhanced electron permeability and surface hydrophilicity.
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