SERS platforms for high density DNA arrays

Abstract

Surface Enhanced Raman Scattering (SERS) gives rise to analytical applications with much promise. In our approach three steps are necessary. We require a SERS platform of high enhancement. This has been achieved using the special technique of Island Lithography, combined with Ag deposition by galvanic exchange, yielding an enhancement factor of 10⁸. Probe oligonucleotide molecules are attached to a specific area on the platform, at the optimized surface concentration, using thiolated single stranded (ss) DNA molecules. The optimum surface concentration has been determined and interpreted in the light of the polyelectrolyte behaviour of ssDNA. Finally the change in SERS produced by hybridisation of the probe molecules to a target DNA molecule is measured. Highly discernible changes have been obtained. No change in probe signal is seen when presented with one base mismatched target. From this work it is concluded that the prospects for label-free DNA detection in high-density arrays is now close to achievement.