Surface-enhanced Raman spectroscopy for drug discovery: peptide-RNA binding.

The ever-growing demand for new drugs highlights the need to develop novel cost- and time-effective techniques for drug discovery. Surface-enhanced Raman spectroscopy (SERS) is an emerging ultrasensitive and label-free technique that allows for the efficient detection and characterization of molecular interactions. We have recently developed a SERS platform for detecting a single protein molecule linked to a gold substrate (Almehmadi et al. Scientific Reports 2019). In this study, we extended the approach to probe the binding of potential drugs to RNA targets. To demonstrate the proof of concept, two 16-amino acid residue peptides with close primary structures and different binding affinities to the RNA CUG repeat related to myotonic dystrophy were tested. Three-microliter solutions of the RNA repeat with these peptides at nanomolar concentrations were probed using the developed approach, and the binding of only one peptide was demonstrated. The SER spectra exhibited significant fluctuations along with a sudden strong enhancement as spectra were collected consecutively from individual spots. Principal component analysis (PCA) of the SER spectral datasets indicated that free RNA repeats could be differentiated from those complexed with a peptide with 100% accuracy. The developed SERS platform provides a novel opportunity for label-free screening of RNA-binding peptides for drug discovery. Schematic representation of the SERS platform for drug discovery developed in this study.