Polyadenine-Modulated DNA Conformation Monitored by Surface-Enhanced Raman Scattering (SERS) on Multibranched Gold Nanoparticles and Its Sensing Application.

This work proposes a facile way to modulate the conformation of DNA from the "Lie-Down" to the "Stand-Up" conformation on the surface of multibranched gold nanoparticles (AuNPs). This is realized by regulating the length of polyadenine (polyA) linked to the DNA sequence and/or the hybridization of this sequence with the target DNA, and can be monitored by the Raman signal owing to the excellent performance of multibranched AuNPs (AuNSs) as a surface-enhanced Raman scattering (SERS) substrate and the distance change between the Raman reporter and the substrate. The probable mechanism, which depends on the repulsion of polyA from the sequence and the tip assembly, has also been probed through theoretical simulation using the finite difference time domain method. By virtue of this strategy, a conformation-transformation-based DNA@AuNS sensor is constructed for the identification of a specific oligonucleotide, which has been used for the detection of DNA sequences associated with Severe Acute Respiratory Syndrome (SARS). This strategy leads to a novel sensing platform with good extendibility for DNA analysis, and provides a powerful protocol for facilitating the cognition of DNA conformation on metal surfaces.