Toxicity and applications of internalised magnetite nanoparticles within live Paramecium caudatum cells

The nanotechnology revolution has allowed us to speculate on the possibilities of hybridising nanoscale materials with live substrates, yet significant doubt still remains pertaining to the effects of nanomaterials on biological matter. In this investigation we cultivate the ciliated protistic pond-dwelling microorganism Paramecium caudatum in the presence of excessive quantities of magnetite nanoparticles in order to assess both potential beneficial applications for this technique as well as any deleterious effects on the organisms health. Our findings indicate that these nanoparticles are well-tolerated by paramecia, who were observed to consume in quantities exceeding 10% of their body volume: cultivation in the presence of magnetite nanoparticles does not alter P. caudatum cell volume, swim speed, growth rate or peak colony density and cultures may persist in nanoparticle-contaminated medium for many weeks. We demonstrate that P. caudatum cells ingest starch coated magnetite nanoparticles which facilitates their being magnetically immobilised whilst maintaining apparently normal ciliary dynamics, thus demonstrating that nanoparticle biohybridisation is a viable alternative to conventional forms of ciliate quieting. Ingested magnetite nanoparticle deposits appear to aggregate, suggesting that (a) the process of being internalised concentrates and therefore detoxifies nanomaterial suspensions in aquatic environments and (b) P. caudatum is a candidate organism for programmable nanomaterial manipulation and delivery.