SERS tags derived from silver nanoparticles and aryl diazonium salts for cell Raman imaging

The surface functionalization of silver nanoparticles (NPs) by Raman reporters has stimulated a wide interest in recent years for the design of Surface-Enhanced Raman Spectroscopy (SERS) labels. However, silver NPs are prone to oxidation and aggregation, which strongly limits their applications. The design of stable SERS tags based on Ag NPs still represents a major challenge for Raman bioimaging. We address this issue herein by taking advantage of aryl diazonium salt chemistry to obtain stable Ag NPs functionalized by multifunctional polyaryl layers bearing different Raman reporters (-NO2, -CN, -CCH). The resulting SERS-encoded Ag NPs were characterized by UV-vis absorption, transmission electron microscopy (TEM) and SERS. The formation of multilayers at the surface of Ag NPs gives access to new spectrally distinguishable SERS codes thus broadening the library of available Raman tags. Proof-of-concept Raman imaging experiments were performed on cancer cells (HeLa) after NP uptake, highlighting the large potentials of diazonium salt chemistry to design Ag NPs-based SERS labels for Raman bioimaging.

Automated summary

This study presents a method for obtaining stable silver nanoparticles (Ag NPs) functionalized with multifunctional polyaryl layers using diazonium salt chemistry. The resulting Ag NPs were characterized by UV-vis absorption, transmission electron microscopy (TEM), and surface-enhanced Raman spectroscopy (SERS). The formation of multilayers on the surface of Ag NPs allows for the generation of spectrally distinguishable SERS codes, thus expanding the library of available Raman tags. Proof-of-concept Raman imaging experiments on cancer cells demonstrated the potential of diazonium salt chemistry for designing Ag NPs-based SERS labels for Raman bioimaging.