Application of mass fabricated silicon-based gold transducers for amperometric (bio)sensors

Robert Ziółkowski 1Łukasz Górski 1Elzbieta Malinowska 

1. Warsaw University of Technology, Faculty of Chemistry, Noakowskiego 3, Warszawa 00-664, Poland

Abstract

Development of biosensors has increased tremendously over the past few years. The large area of possible applications powers the ongoing research over the immobilization methods of recognition elements, the signal transduction and detection or simply the stability of biosensors in specific environmental conditions.

Thanks to composition of biosensor recognition layer, there is a possibility to investigate various biologically important analytes for example glucose, antigens or DNA. As the nucleotides sequence of the DNA strand may be the indicator of blood contamination with pathogenic bacteria, genetically modified food or mutations being the cause of different genetic disorders, it is one of the most interesting target for biosensors. Since the early stage of any DNA examination techniques, there always was need for good and reliable signal detection methods. These promote the implementation of electrochemical methods in protocols dealing with nucleic acids. The most important advantages of such a methods over the traditional ones are their insensitivity to sample cloudiness, cost effectiveness, operating comfort and most of all the extremely low detection limit.

The surface quality is an important factor affecting results obtained with electrochemical methods especially when self assembled monolayers (SAM) are applied to build recognition layer of a biosensor. In the presented study three types of gold electrode surfaces have been compared, presented in Figure (a-c): commercially available chips with screen printed gold layer (a), silicon chips with vacuum evaporated gold layer and backside contact (b) and typical gold disc electrode (c). For the preliminary examination of the surface roughness the 6-(ferrocenyl)-hexanethiol was chosen as the indicator.

elektrody.jpg

The gold surfaces ware exposed to the 10-3 M 6-(ferrocenyl)-hexanethiol solution. The electrochemical examination was carried out in 50 mM phosphate buffer with 0.3 M NaCl (pH 7.0) as electrolyte. As expected, the best stability and response were obtained on the silicon chips with the evaporated gold layer - probably due to their perfect smoothness compared to screen printed and polycrystalline gold disc electrode. These encouraged us to creation of DNA biosensor based on the silicon chip with vacuum evaporated gold layer. The electrochemical analysis in methylene blue solution of bare gold electrode, with ssDNA and after hybridization ware conducted. The change in height and the potential shifts of reduction peaks of methylene blue due to immobilization and hybridization process corresponds to these well described in literature. Moreover the compact size of our chips allows to significantly reduce the required volume of solutions to be tested.

Acknowledgement: This work was co-financed by the Polish Ministry of Science and Higher Education within a framework of the Operational Programme – Innovative Economy, Priority I, Action 1.3, Sub-Action 1.3.1, Project No. PO1G.01.03.01-00-014/08-00.

 

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Presentation: Poster at SMCBS'2009 International Workshop, by Robert Ziółkowski
See On-line Journal of SMCBS'2009 International Workshop

Submitted: 2009-08-31 13:52
Revised:   2009-08-31 13:52
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