On measuring nanoparticle toxicity and clearance with Paramecium caudatum

As the extent to which aquatic environments are polluted with nano-scale objects is becoming known, we are presented with an urgent need to study their effects on various forms of life and to clear and/or detoxify them. A range of methods exist to these ends, but a lack of inter-study comparability arising from an absence of experimental standardisation impedes progress. Here we present experiments that demonstrate measurement of orchestrated uptake and clearance of two environmentally-relevant nano- and micromaterials by a model aquatic microoraganism, Paramecium caudatum. Experiments were based on a simple, modular, multi-chamber platform that permits standardised control of organism behaviour and measurement of variables relevant to the study of nanotoxicology, including nanomaterial chemotaxis assays, bioaccumulation and deleterious effects on cell motility systems. Uptake of internalised materials may be estimated through the addition of a low-cost fluorescence spectrometer. P. caudatum cells can clear an estimated 0.7 fg of contaminant materials (or 161 of the particles used) per cell over a 5 mm distance per 6 hour experiment, whilst suffering few short-term adverse effects, suggesting that the organism and the platform used to investigate their properties are well-suited to a range of laboratory and field-based nanotoxicological studies.