A simple method for ssDNA detection based on SERS signals and PNA slides is reported. Upon hybridization with ssDNA, the surface charge of the PNA slides changes from neutral to negative. Subsequent treatment with partly aggregated, positively charged silver nanoparticles results in selective electrostatic adsorption onto surfaces containing PNA/ssDNA duplexes. Addition of rhodamine6G gives rise to SERS signals characteristic of this dye, which are diagnostic of the hybridization event. Characterization by SERS maps and AFM reveals that the distribution of nanoparticles is random and that approximately 1 in 10 aggregate sites is responsible for the SERS spectra.
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