Cytotoxicity and TNF-α secretion in RAW264.7 macrophages exposed to different fullerene derivatives

Fullerene derivatives have been reported as potential nanomedicines, however the role of surface chemical modification on the biological effects remains unclear. In this study, five kinds of water soluble C-60 derivatives with different surface chemical modification, C-60-(OH)(20) (HFD), C-60-(beta-Ala)(10.1) (AFD), C-60-(Lys)(8.7) (KFD), C-60-(Arg)(8.6) (RFD) and C-60-(NH(CH2)(2)NH2)(8.8) (NFD) were synthesized. Their cytotoxicity as well as TNF-alpha secretions were evaluated in RAW264.7 macrophage cell line. The results show that no significant cytotoxicity can be observed upon 24 h exposure to C-60 derivatives at less than 50 mu g/mL. However, higher concentration (>100 mu g/mL) of these C-60 derivatives decreases the proliferation of RAW264.7. The cytotoxicity of these fullerene derivatives is probably through the apoptosis pathway, while the extent of cytotoxicity varies with the different surface charges. Higher celluar uptake of HFD was observed in RAW264.7 cells than AFD, which correlates with the more toxic effect of HFD over AFD. The secretion of cytokine tumor necrosis factor alpha (TNF-alpha) was determined to evaluate the immunostimulating activity of these fullerene derivatives. The data show that the fullerene derivatives with negative surface charges secrete more TNF-alpha, whereas derivatives with positive charges show insignificant effect. The possible influence of various surface charge property on the observed biological effects is discussed.