Plasmonic SERS Molecular Sentinels. A New Biosensing Approach
This chapter describes the detection of specific target DNA sequences using a novel 'molecular sentinel' (MS) biosensing approach using surface-enhanced Raman scattering (SERS) detection. The SERS-based MS nanoprobe consists of a metal nanoparticle and a stem-loop DNA molecule tagged with a Raman label. The nanoprobe utilizes the specificity and selectivity of the DNA hairpin probe sequence to detect a specific target DNA sequence of interest. In the normal configuration and in the absence of target DNA, the stem-loop configuration maintains the Raman label in close proximity to the metal nanoparticle, inducing an intense SERS effect that produces a strong Raman signal upon laser excitation. Upon hybridization of a complementary target DNA sequence to the nanoprobe, the stem-loop configuration is disrupted, causing the Raman label to physically separate from the metal nanoparticle, thus quenching the SERS signal. Due to the possibility of performing simple homogeneous bioassays, the SERS-MSs provide useful diagnostic probes for multiple biological targets. The potential for combining the spectral selectivity and high sensitivity of the SERS process with inherent molecular specificity of MS nanoprobes to diagnose molecular target sequences is discussed.
