Detection of single photoluminescent diamond nanoparticles in cell and study of the internalization pathway

International audienceDiamond nanoparticles are promising photoluminescent probes for tracking intracellular processes, due to embedded perfectly photostable color centers. In this work, we investigate the spontaneous internalization of such nanoparticles (diameter 25 nm) in HeLa cells by confocal microscopy and time-resolved techniques. Nanoparticles are observed inside the cell cytoplasm at the single particle and single color center level, assessed by time correlation intensity measurements. Improvement of the nanoparticles signal-to-noise ratio inside cell is achieved using a pulsed excitation laser and a time resolved detection taking advantage of the long radiative lifetime of the color center excited state, compared to cell auto-fluorescence. The internalization pathways are also investigated, with endosomal marking and colocalization analyses. The low colocalization ratio observed proves that nanodiamonds are not trapped in endosomes, a promising result in prospect of drug delivery by these nanoparticles. We also prove a low cytotoxicity of these nanoparticles in this cell line. Submitted to-