Eu3+-doped Laponite as a new probe for combined confocal Raman imaging fluorescence

Laponite is a synthetic nanoclay highly attractive for medical applications, particularly as a platform for drug delivery and as an active material or bioimaging. The use of fluorescent dyes or even the functionalization of the nanoplatforms is a common practice to visualize the nanosystem within cell structures. However, these practices involve indirect characterization methods or could induce irreversible effects on the nanoparticle-cell interaction. Here, we introduce a methodology combining luminescence and confocal Raman microscopy to track the nanosystem and detect its cargo independently, using Eu 3+ as a fluorescent probe. Confocal Raman microscopy allow us to determine the localization of the nanoparticle by its unique Raman spectrum fingerprint while mapping the cell. At the same time, Eu 3+ luminescence serves to detect the cargo by its emission spectrum. Speciffically, we describe here the use of Eu-doped Laponite as a fluorescent probe, to track its uptake and incorporation into a macrophage cell line. To discard potential adhesion to the cell membrane, images were taken at different Z planes. In this way, we have observed that the cargo remains attached to the nanoparticle. Finally, the biocompatibility of the nanoplatforms and their cargo has been studied, showing no significant difference in the survival rate.