An Alternative In Vitro Method for Examining Nanoparticle-Induced Cytotoxicity

Conventional in vitro assays are often used as initial screens to identify potential toxic effects of nanoparticles (NPs). However, many NPs have shown interference with conventional in vitro assays, resulting in either false-positive or -negative outcomes. Here, we report an alternative method for the in vitro assessment of NP-induced cytotoxicity utilizing Fluoro-Jade C (FJ-C). To provide proof of concept and initial validation data, Ag-NPs and Au-NPs were tested in 3 different cell cultures including rat brain microvessel endothelial cells, mouse neural stem cells, and the human SH-SY5Y cell line. Conventional 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) and lactate dehydrogenase (LDH) assays were run in parallel with the new method and served as references. The results demonstrate for the first time that FJ-C labeling can be a useful tool for assessing NP-induced cytotoxicity in vitro. Using these approaches, it was also demonstrated that removal of Ag-NPs—while keeping the Ag-ions that were released from the Ag-NPs in culture media—abolished the measured cytotoxicity, indicating that Ag-NPs rather than Ag-ions in solution contributed to the observed cytotoxic effects. Further, co-treatment of Ag-NPs with N-acetyl cysteine (NAC) prevented the observed cytotoxicity, suggesting a protective role of NAC in Ag-NP-induced cytotoxicity. Thus, this alternative in vitro assay is well suited for identify potential cytotoxicity associated with exposure to NPs.