Concentration and distribution of silica nanoparticles in colon cancer cells assessed by synchrotron based X-ray techniques

The quantitative uptake of Silica nanoparticles (SiNPs), although representing an essential prerequisite for their theranostic use, is difficult to address and it is still not utterly investigated. In this study, we tested the uptake and toxicity of two different types of luminescent core–shell silica–PEG (polyethylene glycol)nanoparticles SiNP and their carboxylate analogues on human adenocarcinoma cell line LoVo. We assessed the intracellular spatial distribution and concentration of Si element in the cell by a state-of-the-art approach merging synchrotron-based X-ray techniques (XRFM)with scanning transmission X-Ray microscopy (STXM). The concentration maps of Si obtained reflect the distribution of the SiNPs. In addition, we calculated the number of SiNPs per volume unit in each single cell, quantitating the exact amount of conveyed particles. The absence of effects on proliferation and cell death was confirmed by viability assays, morphological analysis and cytofluorimetric evaluation of ROS content. The three-dimensional analysis of intracellular uptake of both types of nanoparticles (with different surface charge)was performed by confocal fluorescence microscopy, which showed a main localization in the cytosolic region with no sign of nuclear uptake.