Figure 4.

Overview of characterization of NPs before and after corona formation. An overview of the characterization tests done on nanoparticles A) before and after B) formation of protein corona in the 470 manuscripts included in this study. DLS, EM, and zeta potential are the major characterization methods performed on NPs. Other characterization tests relate to the chemical properties or functional properties of the nanoparticles and are not performed for most nanoparticles. C) The use of at minimum two complementary characterization methods was tested for the parameter of NP size. While almost half of reported studies (54.5%) used the recommended two methods for NP size determination, fewer than 5% of nanoparticles following protein corona formation has been characterized by two complementary size analysis methods. D) SD as an indicator of repeatability of the experiment is not commonly reported in NP characterization experiments. Around 40% of manuscripts (including 1702 NPs) did not report SD for key analyses such as DLS, zeta potential, and PDI. Data from EM experiments is generally not performed according to relevant standards such as ISO 21 363: “Nanotechnologies—Measurements of particle size and shape distributions by transmission electron microscopy”. Most nanoparticles (64.5%) had no reported values for SD in EM analysis. E) The reporting of SD drops following protein corona formation on NPs, which is an indicator of poor experimental repeatability of the nanoparticle protein corona literature and confirming that coronated nanoparticles are under characterized.