Sensitive detection of nucleic acids with rolling circle amplification and surface-enhanced Raman scattering spectroscopy.

Detection of specific DNA sequences is important to molecular biology research and clinical diagnostics. To improve the sensitivity of surface-enhanced Raman scattering spectroscopy (SERS), a variety of signal amplification methods has been developed, including Raman-active-dye, polymerase chain reaction (PCR) technology, molecular beacon, SERS-active substrates, and SERS-tag. However, the combination of rolling circle amplification (RCA) with SERS for nucleic acid detection has not been reported. Herein, we describe a new approach for nucleic acid detection by the combination of RCA reaction with SERS. Because of the binding of abundance repeated sequences of RCA products with gold nanoparticle (Au NP) and Rox-modified detection probes, SERS signal is significantly amplified and the detection limit of 10.0 pM might be achieved. The sensitivity of RCA-based SERS has increased by as much as 3 orders of magnitude as compared to PCR-based SERS and is also comparable with or even exceeds that of both RCA-based electrochemical and RCA-based fluorescent methods. This RCA-based SERS might discriminate perfect matched target DNA from 1-base mismatched DNA with high selectivity. The high sensitivity and selectivity of RCA-based SERS makes it a potential tool for early diagnosis of gene-related disease and also offers a great promise for multiplexed assays with DNA microarrays.