The effect of surface modification of single-wall carbon nanotubes on cytotoxicity reduction in the liver cell model (HEPG2)

Carbon nanotubes (CNTs) that their surface hydrophilicity has been modified are important vehicles in drug delivery and diagnostic application. This study aimed to evaluate the cytotoxicity of original and functional CNTs on human cells. In an interventional study, lateral surfaces of single wall-carbon nanotubes were coated by polyethylene glycol, as an amphiphilic polymer, via charged functional groups (the amine or carboxylic group). Original and functional carbon nanotubes were exposed to human hepatoma (HEPG2) cells, as a cellular model of liver. Exposure times were 24, 48 and 72 hours and CNT suspension applied in concentrations of 100, 200, 400 and 600µg/ml. Morphologic changes of cells were analyzed using an inverted microscope. Viability percentage of HEPG2 cells was also evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. The naked CNTs after 72 hours exposure showed toxicity on HEPG2 in concentrations more than 100 µg/ml, while surface modification of CNTs with amine or carboxylic polyethylene glycol (PEG) led to a better biocompatibility of CNTs to 200 and 400 µg/ml, respectively. In 400µg/ml concentrations of CNTs and more, PEG-CNTs via carboxilic functional groups showed severe morphological changes in the HEPG2 cells, while amine mediated PEG-CNTs, in the same experimental time were more biocompatible. The results of the MTT test showed that carboxylic PEG-CNTs in concentrations more than 200 µg/ml, and amine PEG-CNTs in more than 400 µg/ml decreased viability of HEPG2 cells significantly (P<0.05). Accumulation of charged functional groups on the surface of CNTs can be an interesting pathway to render CNTs as biocompatible nanoparticles for application in drug delivery and diagnostic systems.