Raman-dielectrophoresis goes viral: towards a rapid and label-free platform for plant virus characterization

An innovative spectroscopic method that allows to chemically and structurallycharacterize viruses directly in suspension within few minutes was developed. Alibrary of five different plant viruses was obtained combining dielectrophoresis(DEP), performed with a device specifically designed to capture and agglomeratevirus particles, and Raman spectroscopy to provide a chemical fingerprint ofvirions. The tested viruses, purified from infected plants, were chosen for theireconomic impact on horticultural crops and for their different morphologicaland structural features. Using the Raman-DEP device, specific profiles for eachvirus were successfully obtained, relying on chemical differences occurringeven with genetically similar viruses belonging to the same taxonomic speciesand morphologically indiscernible by transmission electron microscopy (TEM).Moreover, we investigated the potentiality of Raman-DEP to follow dynamicchanges occurring upon heat treatment of tobacco mosaic virus (TMV) particles.Raman peak deviations linked to TMV coat protein conformation were observedupon treatment at temperatures equal or higher than 85°C, substantiating therod-to-spherical shape transitions observed by TEM and the concomitant drasticloss of infectivity following plant inoculation. Overall, the Raman-DEP methodcan be useful for the characterization of virus (nano)particles, setting the basis tocreate a database suitable for the study of viruses or virus derived-nanoparticlesrelevant for the agricultural, medical, or biotechnological fields.