Functionalization-dependent cytotoxicity of single- and multiwalled carbon nanotubes.

Recently developed functionalization schemes have extended the application spectrum of carbon nanotubes (CNTs) enabling the implementation of new functions that cannot otherwise be acquired by pristine nanotubes. Functionalization has been shown to impact on the biological response to CNTs suggesting that toxicological profile rnay also be modified. In this study, the cytotoxicity of single-walled CNTs (SW), multi-walled CNTs (MW) and functionalized MW (MW-COOH, MW-N H2) was investigated in human astrocytoma D384 and lung carcinorna A549 cell cultures using MTT assay and calcein propidium iodide (PI) staining. The test nanomaterials were characterized by themal analysis (TGA), infrared spectroscopy, and atomic force rnicroscopy to assess the degree of purity and functionalization. The cells were exposed to the CNTs (0.1-1 00 ug/ml) for 24, 48, 72h in medium containing 70% FCS. Quartz (Si02) and carbon black were also similarly tested. In both cell types. MTT data revealed strong cytotoxicity (50% loss of cell viability) of SW after 24h-exposure already at 0.1 ug/ml, without further changes at higher concentrations or longer incubation times. At all time-points, MTT metabolism was decreased by about 50% by all the other compounds at 10 uglml and with no exacerbation at the higher dose. Parallel assays using calcein-PI staining did not confirm MTT cytotoxicity data neither in D384 nor in A549 cells. Cell viability was not affected by any CNT type at any concentration or time of exposure, whereas extensive cell killing was observed in the preparation exposed to the positive control Si02. The results indicate that CNTs can interact with certain types of dye markers that are commonly used in cell culture experiments. This may lead to artefactual data. A study design using multiple tests is recommended in investigations examining CNT toxicity in vitro. (Grant from the Italian Ministries of Health, Education and Research). Citation: L.Manzo, E.Roda, D.Sangiannis. G.Cimint~Reale, P.Mustarelli, AProfumo, T.Coccini. FUNCTIONALIZATION - DEPENDENT CYTOTOXICIW OF SINGLE - AND MULTI - WALLED CARBON NANOTUBES.. Abstract No. 221 1. 2009 Itineary Pianner. Baltimore, MD: Society of Toxicolog