Evaluation of biocompatible dispersants for carbon nanotube toxicity tests

Dispersion is one of the key obstacles to evaluating the in vitro and in vivo toxicity of carbon nanotubes (CNTs), as the aggregation or agglomeration of CNTs in culture media or vehicles complicates the interpretation of the toxicity test results. Thus, to test the dispersion of CNTs in biocompatible solutions, 5 known biocompatible dispersants were selected that are widely used for nanomaterial toxicity evaluation studies. Single-wall nanotubes (SWCNTs) and multi-wall nanotubes (MWCNTs) were both dispersed in these dispersants and their macrodispersion evaluated using a light absorbance method. The dispersion stability of the dispersed SWCNTs and MWCNTs was also evaluated for 16 weeks, plus the dispersants were tested for their innate toxicity using trypan blue dye exclusion, lactate dehydrogenase (LDH) leakage, and neutral red assays. All the dispersants were found to be biocompatible in the cytotoxicity tests when compared with a positive control of 2% Triton X-100. In the dispersion tests, 0.02, 0.1, and 0.5% MWCNTs and SWCNTs were diluted in the respective dispersants. Distilled water and dimethylsulfoxide (DMSO) both showed a poor macrodispersion of only 1-13% for the various CNT concentrations. In 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), the 0.02 and 0.1% MWCNTs showed a macrodispersion of 11 and 74%, respectively, while the 0.02 and 0.1% SWCNTs showed a macrodispersion of 15 and 16%, respectively. In 0.5% bovine serum albumin (BSA), the 0.02, 0.1, and 0.5% MWCNTs showed a very good macrodispersion of 32, 53, and 70%, respectively, yet the 0.02% SWCNTs only showed a macrodispersion of 17%. In 1% Tween 80, the 0.02-0.5% SWNCTs exhibited a good macrodispersion of 27-81%, whereas the 0.02-05% MWCNTs only showed a macrodispersion of 13-23%. The dispersion stability of the CNTs during 16 weeks was in the following descending order of BSA, Tween 80, DPPC, and DMSO for the MWCNTs and BSA, DPPC, Tween 80, and DMSO for the SWNCTs. Thus, appropriate dispersants are proposed according to the type of CNT, experiment concentration, and treatment duration. Also, it is suggested that the dispersibility, dispersion stability, and biocompatibility of the selected dispersant should all be confirmed before a toxicity evaluation.