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Abstract
In this research, a selective, cost-efficient, highly sensitive Ag nanostructure Surface Enhanced Raman Spectroscopy (SERS) sensor was developed as a methodological approach to rapidly detect a targeted-ss-DNA (stx2) in STEC (Shiga toxin-producing Escherichia coli). The Ag nanostructure-based SERS substrate was functionalized by two type of thiols: thiol-ss-DNA for bonding targeted-ss-DNA and 6-Mercapto-1-hexanol (HS(CH2)6OH) for blocking the Ag nanostructure surface. Methylene Blue (MB) was used as a Raman marker to quantify targeted-ss-DNA, as well as a model molecule to characterize the electrodeposited Ag nanostructure SERS substrate. Ag nanostructure SERS substrates showed good sensitivity and repeatability towards MB detection, with a LOD = 0.3158 μM, RSD = 12.48% (at 45 different random points). More importantly, the Ag nanostructure/ss-DNA SERS substrate showed good selectivity towards STEC O157 stx2 targeted DNA, as well as good linearity and sensitivity towards its detection in a buffer solution. A limit of detection of 0.4900 aM in a wide linear range from 1 aM to 100 pM was demonstrated. The SERS sensors were able to identify target DNA ( stx2) in an STEC strain and the study showed proof of principle that SERS substrate has potential as a cost effective, highly selective, highly sensitive DNA and bacteria sensor without the aid of DNA amplification. With further development and validation, this methodological approach has the potential for use in the point-of-use detection for instance on a farm or in the food industry.
