Intracellular uptake of magnetite nanoparticles: A focus on physico-chemical characterization and interpretation of in vitro data

Comprehensive characterization of nanoparticles associated with investigation of their cellular uptake creates the basis on which fundamental in vitro and in vivo studies can be built. In this work, a complex analysis of various surface-modified magnetite nanoparticles in biologically relevant environment is reported and the promotion of incorrect characterization into the results obtained from model biological experiments leading to false conclusions is demonstrated. Via a bottom-up approach from particle characterization by DLS towards interpretation of biological data based on cellular uptake, this work draws attention to the systematic propagation of errors stemming from inaccurate determination of input parameters for DLS, improper selection of particle size distribution, inadequate sampling, unknown colloidal behavior and the omission of fraction of particles complying with the internalization threshold. In addition, cellular uptake depending on the number of treated cells is shown. The definition of cellular uptake efficacy reflecting the size distribution of particles beside their absolute internalization is postulated. Proper characterization of particles is critical for reliable correlation and interpretation of experimental data and must be seen as a necessary prerequisite for understanding the relationship between the properties of particles and their performance in vitro or in vivo. [Display omitted] •Particle characterization plays a critical role in interpretation of in vitro data.•Dependence of characteristics on multiple variables complicates data generalization.•Superficial particle characterization may propagate into false conclusions.•Step-by-step guide for the use of particles in biological experiments is provided.