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Lab Chip. 2009 Dec 7;9(23):3360-3. doi: 10.1039/b912076a. Epub 2009 Oct 1.

Label-free and highly sensitive biomolecular detection using SERS and electrokinetic preconcentration.

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Biomolecular Nanotechnology Center, Department of Bioengineering, University of California, Berkeley, California 94720, USA.


In this paper, we present a method combining surface-enhanced Raman scattering (SERS) spectroscopy to detect biomolecules in a label-free way with an electrokinetic preconcentration technique (electrophoresis) to amplify biomolecular signals at low concentrations. A constant electric field is applied to charged biomolecules in solution, attracting them to an oppositely charged electrode, which is also used as a SERS substrate. Within 5 min, we observed that the SERS signal of 10 fM adenine was amplified to the level of the signal of non-preconcentrated 1 microM adenine (sensitivity improvement by 8 orders of magnitude) and the method was effective over a wide range of concentrations (10 fM to 1 microM). The signals were further amplified under stronger electric field and longer application: The increase of the signal intensity was observed to be 51 times at -0.6 V cm(-1) after 25 min. The effectiveness of this method allows the creation of label-free, target-specific, and highly sensitive monitoring applications.

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