Evaluation of the cytotoxicity of original and functional carbon nanotubes in human lung cells

Carbon nanotubes (CNT) are important carriers in drug delivery and medical application. This study aimed to investigate the cytotoxic effects of original and modified CNTs on A549 cells, as a cellular model of human lung. Single-wall CNTs were pegilated via different functional groups. Original and modified CNTs were exposed to A549 cells. Different concentrations (0-600 µg/ml) of CNTs were evaluated at exposure times of 24, 48 and 72 hours. Morphologic changes were observed by an inverted microscope and the viability percentage of A549 cells was determined using the methylthiazol tetrazolium (MTT) assay. Amine-mediated pegilated CNT (amin-PEG-CNTs) and carboxyl-mediated pegilated CNT (carboxyl-PEG-CNTs) in concentration of 600 µg/ml after 48 hours exposure led to severe morphologic changes in the A549 cells. These changes were also obvious after 72 hours. In concentrations of 100, 200 and 400 µg/ml of CNTs, in all times, amin-PEG-CNTs showed better biocompatibility than carboxyl-PEG-CNTs. The MTT results showed a significant reduction in viability of A549 cells in concentrations more than 200 µg/ml after carboxyl-PEG-CNTs exposure and more than 400 µg/ml after amin-PEG-CNTs exposure (P<0.05). While, original CNTs showed a cytotoxic effect on A549 cells in concentration of 100 µg/ml. It seems that the amine group in combination with positive charge in surface, with surface modification of CNTs, can be an interesting solution to safer application of CNTs as carriers.