# Developing a Multi-Method Approach for Understanding Cellular Uptake and Biological Response: Investigating Co-Exposure of Macrophage-like Differentiated THP-1 Cells to Al2O3 and CeO2 Nanoparticles

## TL;DR

This study explores how cells respond when exposed to two types of nanoparticles together, using multiple methods to better understand their combined effects.

## Contribution

The paper introduces a multi-method approach to assess cellular responses to co-exposure of Al2O3 and CeO2 nanoparticles at sub-toxic concentrations.

## Key findings

- Combined analytical techniques reveal changes in biological responses and cellular metal content across exposure scenarios.
- Exposure concentrations below acute toxicity levels were found to still impact cellular responses.
- The study emphasizes the importance of realistic exposure scenarios involving multiple nanoparticles for health risk assessment.

## Abstract

The use of different nanoparticles (NPs) is increasing in a wide variety of everyday products. Nevertheless, most studies concerning NP risk assessment have evaluated exposure scenarios involving a single kind of NP. A stepwise study distinguishing between the effects resulting from exposure to one kind of NP and those resulting from different co-exposure scenarios to Al2O3 and CeO2 NPs at concentrations below acute toxicity was conducted with different analytical techniques. As a starting point, WST-1 viability assays were performed to assess whether the chosen exposure concentrations resulted in any acute loss of viability, which would hamper further insight into the cellular response to NP exposure. Then, data on NP dissolution and uptake were obtained via single-particle inductively coupled plasma–mass spectrometry (spICP-MS) and microwave-assisted ICP-MS. Additionally, time-of-flight secondary ion mass spectrometry (ToF-SIMS) was performed to check for differences in the biological response to the exposure scenarios at the single-cell level. It was found that the proposed combined techniques provide insight into changes in biological responses as well as cellular metal contents among the exposure scenarios. In this work, a comprehensive tiered analytical strategy for evaluating the biological responses to challenging exposure scenarios is provided. The results highlight the necessity of selecting situations more closely resembling real life—including concentrations below acute toxicity and potential interactions due to multiple NPs—when estimating potential health risks. These findings thus provide a foundation and an incentive for further research into the complex processes leading to the observed effects.