How does the deposited dose of oxide nanomaterials evolve in an in vitro assay?

In this work, the evolution of some key physicochemical parameters of oxide engineered nanomaterial (ENM) dispersions was studied during an in vitro biological assessment. Commercial oxide ENMs, SiO2 and TiO2, were dispersed in aqueous solutions (20 μg/mL) to A549 cells and N-hTERT keratinocytes and were assessed at several incubation times: 6, 24, 48, and 72 hours. The ENMs deposited dose and its particle size distribution (PSD) were followed each time. Centrifuge Liquid Sedimentation (CLS) measured the PSD and the ENMs deposited dose from a particle entity perspective, while Particle-Induced X-ray Emission (PIXE) measured the ENMs deposited dose from an elemental mass perspective. No significant variations in PSD were observed for SiO2 ENMs during incubation in A549 cells and TiO2 ENMs in both cell lines, while a continuous evolution of the PSD is observed for SiO2 in N-hTERT keratinocytes. The deposited dose for TiO2 ENMs remained stable and similar in both cell lines due to a smaller specific surface area and a higher quantity of primary particles present during incubation. It is concluded that the observed differences in the deposited dose are related to an interaction between the proteins present in the media and the ENMs specific surface.