PCR-free quantification of multiple splice variants in a cancer gene by surface-enhanced Raman spectroscopy.

We demonstrate a surface-enhanced Raman spectroscopy (SERS) based array platform to monitor gene expression in cancer cells in a multiplex and quantitative format without amplification steps. A strategy comprising DNA/RNA hybridization, S1 nuclease digestion, and alkaline hydrolysis was adopted to obtain DNA targets specific to two splice junction variants, Delta(9,10) and Delta(5), of the breast cancer susceptibility gene 1 from MCF-7 and MDA-MB-231 breast cancer cell lines. These two targets were identified simultaneously, and their absolute quantities were estimated by a SERS strategy utilizing the inherent plasmon-phonon Raman mode of gold nanoparticle probes as a self-referencing standard to correct for the variability in surface enhancement. The results were then validated by reverse-transcription polymerase chain reaction. Our proposed methodology could be expanded to a higher level of multiplexing for quantitative gene expression analysis of any gene without any amplification steps.