Surface-enhanced Raman spectroscopy for facile DNA detection using gold nanoparticle aggregates formed via photoligation.

We present a new type of nanoparticle-based DNA sensor using surface-enhanced Raman scattering (SERS) on gold nanoparticle (Au NP) aggregates formed by DNA photoligation. The DNA sensor exploits the photoligation reaction between oligodeoxynucleotides (ODNs) attached to the surfaces of Au NPs in the presence of target DNA (T-DNA). When hybridization takes place between the ODNs and T-DNA, Au NPs are covalently crosslinked to form aggregates via photoligation. Once the NP aggregates are formed, the interspace between Au NPs in the aggregate act as a stable "hot spot", and a SERS signal from the Raman-active molecules (sodium cacodylate) present in the hot spot is easily and sensitively detected. In contrast, a SERS signal is not detected if the hybridization is unsuccessful, because the stable hot spot does not form. This DNA sensor does not require an enzymatic reaction, fluorescent dye, precise temperature control, or complicated operating procedures.