Label-Free tomographic imaging of cellular morphology after uptake of polystyrene nanoparticles

Study Summary

We studied the cellular uptake of nanosized organic particles such as nanoplastics which is of high interest for the fields of nanotoxicology, the analysis of medical nanoparticle mediated effects and the interdisciplinary field of label-free quantitative phase imaging such as a holotomography.

We investigated the surface charge-dependent uptake of polystyrene nanoparticles (PS-NPs) into alveolar cells and their cytotoxicity in the presence of cyclic stretches that can mimic human breathing conditions.

The internalization of positively- or negatively-charged PS-NPs through the plasma membrane, their intracellular distribution, and the integrity of the plasma membrane were time-lapse imaged by the label-free three-dimensional (3D) holotomography for further quantitative analysis. In comparison with negatively-charged PS-NPs, the higher cytotoxicity of positively-charged PS-NPs were associated with the rapid increase of ROS level, structural instability of the plasma membrane, loss of mechanoadaptive capacity when the cyclic stretch was applied to the alveolar cells. These biochemical and morphological disruption was eventually linked to apoptotic fate in the early stage whereas the unstretched cell showed either marginal changes upon the treatment of negatively-charged PS-NPs or lower apoptosis in the late stage upon the treatment of positively-charged PS-NPs.

[Figure 1] Surface charge-dependent uptake of PS-NPs into alveolar cells and their cytotoxicity in the presence of cyclic stretches

[Figure 2] 3D holotomographic images of nPS-NPs- and pPS-NPs-treated cells in two different conditions: unstretched and 15% CS at defined time points.

This work will be a significant contribution to demonstrate the charge-dependent uptake of PS-NPs into the alveolar cells and their impacts on the cell viability in the breath-mimicking condition. Our approach that combined the cell-stretching system and long-term 3D holotomography will be extended to the in vitro cytotoxicity of other nanoparticles such as metallic nanoparticles or viral particles.