Biosensors and Bioelectronics 26 (2010) 1500–1506 Contents lists available at ScienceDirect Biosensors and Bioelectronics journal homepage: www.elsevier.com/locate/bios Bipodal PEGylated alkanethiol for the enhanced electrochemical detection of genetic markers involved in breast cancer O.Y.F. Henry a,∗ , J. Lluis Acero Sanchez a , C.K. O’Sullivan a,b,∗∗ a Nanobiotechnology and Bioanalysis Group, Departament d’Enginyería Química, Univeritat Rovira I Virgili, 26 Paisos Catalans, 43007 Tarragona, Spain b Institució Catalana de Recerca i Estudis Avanc ¸ ats, Passeig Lluís Companys 23, 08010 Barcelona, Spain article info Article history: Received 22 April 2010 Received in revised form 15 July 2010 Accepted 25 July 2010 Available online 7 August 2010 Keywords: DNA Co-immobilisation Electrochemical PEG alkanethiol abstract 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 technolo- gies 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- as a model system. PEGylated DNA capture probes for oestrogen receptor- 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 sensitiv- ity 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- 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 electrochemi- cal sensitivity and resistance to fouling believed to result s from an enhanced electron permeability and surface hydrophilicity. © 2010 Elsevier B.V. All rights reserved. 1. Introduction In the post-genome era, many efforts have focused on the devel- opment of DNA/RNA analysis platforms directed at developing new personalised therapeutics (Manolopoulos, 2007). Often coined theranostics, the promises of individualised therapy have been acclaimed as the next grand evolution in point-of-care diagnos- tics, with cancer diagnostics and pharmacogenomics being rapidly expanding research fields (Amir-Aslani and Mangematin, 2010). One of the major limiting factors in the widespread acceptance of genetic screening prior to drug administration is economically driven (Veenstra and Higashi, 2000), with the lack of inexpensive, simple and rapid genetic tests being a major contributing factor in the failure to achieve the promised developments in patient care (Manolopoulos, 2007). ∗ Corresponding author. Tel.: +34 977 558577; fax: +34 977 559667. ∗∗ Corresponding author at: Institució Catalana de Recerca i Estudis Avanc ¸ ats, Pas- seig Lluís Companys 23, 08010 Barcelona, Spain. E-mail addresses: olivier.henry@urv.cat, henry olivier@yahoo.com (O.Y.F. Henry), ciara.osullivan@urv.cat (C.K. O’Sullivan). One of the biggest challenges in developing diagnostic tests is the ability of the immobilised recognition elements to sense its tar- get in a given solution, whilst the supporting material resists any non-specific interaction (Sharma et al., 2004; Vaisocherová et al., 2009). As such, currently accepted genetic screening tools, such as high-density DNA microarrays, typically require long hybridi- sation times and repeated stringency washes that can take up to 24 h before delivering an answer (De Lellis et al., 2008). Although the amount of information gathered from such arrays is extremely valuable in given areas, e.g. research to identify disease associ- ated genes, whole genome expression analysis, the time and effort required to render the test prohibitively expensive for point-of-care diagnostics (McShea et al., 2006). On the other hand, low-density microarrays, focused on the detection of narrow sets of genetic sequences have the potential to deliver rapid and low-cost tests, enabling, e.g. the rapid screening of an individual for a particular disease/disease strain, the identification of cancer progression or the susceptibility of an individual to develop adverse drug reac- tions, combining to facilitate a better management of the disease (Henry et al., 2009; Marchand et al., 2008). Electrochemical techniques offer great promise for the devel- opment of robust low-density DNA arrays. Electrodes can easily 0956-5663/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.bios.2010.07.095