Dynamic Monitoring of Metal Oxide Nanoparticle Toxicity by Label Free Impedance Sensing

TLDR

The growing use of nanoparticles in industry and medicine demands accurate, high‑throughput in‑vitro toxicity screening, yet conventional viability assays risk false positives from nanoparticle interactions with labels or optical readouts. The study aims to use impedance spectroscopy for real‑time, reagent‑free detection of toxicity of ZnO, CuO, and TiO₂ nanoparticles. The method employs real‑time impedance spectroscopy combined with image analysis to detect rapid cellular responses, showing that ZnO and CuO activate ATP‑dependent MRP/1 pumps to export glutathione, thereby increasing ROS and triggering apoptosis. Impedance measurements yield IC₅₀ values comparable to standard assays (ZnO 55 µg/mL, CuO 28 µg/mL) and identify a 6‑h window of rapid toxicity; the targeted strategy reveals glutathione depletion, ROS surge, and dose‑dependent apoptosis, providing richer information than conventional assays and highlighting potential in‑vivo cell‑nanoparticle interactions.

Abstract

The increased use of nanoparticles in industrial and medical products is driving the need for accurate, high throughput in vitro testing procedures to screen new particles for potential toxicity. While approaches using standard viability assays have been widely used, there have been increased reports of the interactions of nanoparticles with their soluble labels or optical readouts which raise concerns over the potential generation of false positive results. Here, we describe the use of an impedance spectroscopy approach to provide real-time reagent free detection of toxicity for a panel of metal oxide nanoparticles (ZnO, CuO, and TiO2). Using this approach, we show how impedance measurements can be used to track nanoparticle toxicity over time with comparable IC50 values to those of standard assays (ZnO-55 μg/mL, CuO-28 μg/mL) as well as being used to identify a critical 6 h period following exposure during which the nanoparticles trigger rapid cellular responses. Through targeted analysis during this response period and the use of a novel image analysis approach, we show how the ZnO and CuO nanoparticles trigger the active export of intracellular glutathione via an increase in the activity of the ATP dependent MRP/1 efflux pumps. The loss of glutathione leads to increased production of reactive oxygen species which after 2.5 h triggers the cells to enter apoptosis resulting in a dose dependent cytotoxic response. This targeted testing strategy provides comprehensive information beyond that achieved with standard toxicity assays and indicates the potential for cell-nanoparticle interactions that could occur following in vivo exposure.