Synthesis and spectroscopic study of dual self-encoded polymer microbeads with Raman scattering and surface-enhanced Raman scattering

The unique Raman spectra of various polymers render polymeric microbeads to be attractive in Raman-based multiplex analysis and simultaneous biomolecular recognition as self-encoded supports. The combination of polymer Raman signals with highly sensitive surface-enhanced Raman scattering (SERS) codes will be able to significantly enhance the combinatory library in bioanalysis. However, there is lack of study on the preparation and spectroscopic analysis of self-encoded microbeads with both Raman and SERS signatures. This study establishes a robust synthesis and spectral analysis protocol of the microbeads with bi-codes, namely Raman and SERS. As modal examples, surface carboxylic acid functionalized monodisperse microbeads of polystyrene and poly(4-tert-butylstyrene) were conjugated with the amine group of 4-aminothiophenol, followed by the adsorption of gold nanoparticles (AuNP) on microbead surfaces. The thiol group of 4-aminothiophenol forms self-assembled monolayers with AuNPs. The resulting microbeads are Raman and SERS dual self-encoded as evident from their Raman spectroscopic and imaging analysis. The synthesis and spectroscopic analysis of the Raman and SERS dual-encoded systems suggest the potential expansion of multiplex library in suspension bioassays.