Variably Sized and Multi-Colored Silica-Nanoparticles Characterized by Fluorescence Correlation Methods for Cellular Dynamics

Controlling the uptake of nanoparticles into cells so as to balance therapeutic effects with toxicity is an essential unsolved problem in the development of nanomedicine technologies. From this point of view, it is useful to use standard nanoparticles to quantitatively evaluate the physical properties of the nanoparticles in solution and in cells, and to analyze the intracellular dynamic motion and distribution of these nanoparticles at a single-particle level. In this study, standard nanoparticles are developed based on a variant silica-based nanoparticle incorporating fluorescein isothiocyanate (FITC) or/and rhodamine B isothiocyanate (RITC) with a variety of accessible diameters and a matching fluorescent cobalt ferrite core-shell structure (Fe2O4/SiO2). The physical and optical properties of the nanoparticles in vitro are fully evaluated with the complementary methods of dynamic light scattering, electron microscopy, and two fluorescence correlation methods. In addition, cell uptake of dual-colored and core/shell nanoparticles via endocytosis in live HeLa cells is detected by fluorescence correlation spectroscopy and electron microscopy, indicating the suitability of the nanoparticles as standards for further studies of intracellular dynamics with multi-modal methods.