Cellular uptake and cytotoxic impact of chemically functionalized and polymer-coated carbon nanotubes

The impact of nanomaterials such as carbon nanotubes on biological matter is a topic of increasing interest and concern and requires a multifaceted approach to be resolved.  A modifi ed cytotoxic (lactate dehydrogenase (LDH)) assay is developed in an attempt  to offer a valid and reliable methodology for screening carbon nanotube toxicity  in vitro. Two of the most widely used types of surface-modifi ed multiwalled carbon nanotubes (MWNTs) are tested: ammonium-functionalized MWNTs (MWNT-NH 3+) and Pluronic F127 coated MWNTs (MWNT:F127). Chemically functionalized MWNTs show signifi cantly greater cellular uptake into lung epithelial A549 cells compared to the non-covalently Pluronic F127-coated MWNTs. In spite of this, MWNT:F127 exhibit enhanced cytotoxicity according to the modifi ed LDH assay. The validity of the modifi ed LDH assay is further validated by direct comparison with other less reliable or accurate cytotoxicity assays. These fi ndings indicate the reliability of the modifi ed LDH assay as a screening tool to assess carbon nanotube cytotoxicity and illustrate that high levels of carbon nanotube cellular internalization do not necessarily lead to adverse responses.