Graphical and SERS dual-modal identifier for encoding OBOC library

‘Split-and-mix’ synthetic methods are widely utilized to prepare extensively large numbers of combinatorial libraries. For this, a simple and reliable encoding/decoding method is required to identify a lead compound, especially when it comes to combinatorial peptide/peptoid libraries. Here, we report a simple, efficient, and reliable on-bead peptoid ligand identification method using dual-modal identifiers (DM-IDs), which have a graphical pattern and a Raman signal. The DM-ID was designed to encode the sequence and the type of peptoid side chain by the number of holes and the surface-enhanced Raman scattering (SERS) signals, respectively. Using this dual encoding strategy, 5832 (183)-individual peptides/peptoids can be encoded with 3 holes and 18 Raman label compounds. In addition, the method can be easily extended to encode more than one hundred billion ligands by expanding to 9 patterns with 3 holes in binary code. After pentapeptoids were encoded with DM-IDs during solid phase synthesis, the peptoid’s affinity towards streptavidin is successfully evaluated, and the on-bead peptoid sequence is determined by the graphical patterns and the SERS signatures of the DM-IDs. We believe that this encoding method using DM-IDs is a promising tool to construct one-bead-one-compound (OBOC) combinatorial libraries for drug discovery.