Abstract
The purpose of the present study was to compare two neutral red retention methods, the more established but very labour-intensive microscope method (NRR) against the more recently developed microplate method (NRU). The intention was to explore whether the sample volume throughput could be increased and potential operator bias avoided. Mussels Mytilus sp. were exposed in vivo to 50, 250 and 500μgL−1 single (SWCNTs) or multi-walled carbon nanotubes (MWCNTs). Using the NRR method, SWCNTs and MWCNTs caused concentration dependent decreases in neutral red retention time. However, a concentration dependent decrease in optical density was not observed using the NRU method. We conclude that the NRU method is not sensitive enough to assess carbon nanotube ecotoxicity in vivo in environmentally relevant media, and recommend using the NRR method.
•Mussels Mytillus sp. were exposed in vivo to single (SWCNTs) and multi-walled carbon nanotubes (MWCNTs).•SWCNTs and MWCNTs caused concentration dependent decreases in neutral red retention time (NRR).•A concentration dependent decrease in optical density was not observed using the microplate method (NRU).•The NRU method is not sensitive enough to assess carbon nanotube ecotoxicity in vivo under environmentally relevant conditions.