Free-labeled nanoclay intracellular uptake tracking by confocal Raman imaging

[Display omitted] •Exploring the cell uptake of the free labelled nanocarrier Laponite by confocal Raman imaging.•Tracking the nanomaterial from the cell surface to the inner cell, without dye-labeling steps.•Raman spectroscopy is sensitive to detect Laponite signalling when it is dispersed in serum and in cell cultures.•Mapping the intracellular structures allows to discard Laponite adhesion to the membrane surface of the cell. Laponite is a nanoplatform that has been successfully used as a new biomaterial for drug delivery, tissue engineering and bioimaging at the nanoscale. In general, a deep knowledge of the mechanism interaction of the nanomaterial with biological components in a physiological environment is highly desirable for properly characterizing its therapeutic efficacy and toxicology. Up to know, the use of fluorescent dyes labelling both, the nanomaterial and cell components, has been a requirement to characterize the cell uptake and to visualize the entrance of the nanomaterial into the cytosol and the cell nucleus. The used of fluorophores usually perturb the physiological medium and can interfere in the nanomaterial cell interaction. A new Raman imaging methodology to track the uptake and internalization of Laponite nanoparticles into J774 macrophages line cells is presented in this work. The combination of Raman spectroscopy and confocal microscopy provides direct information about the localization of the nanoparticle into the cell, through its unique vibrational fingerprint without labelling or adding dyes, and taking advantage of the fact that Laponite and biological molecules bands can be clearly differentiated.