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 C60 derivatives with different surface chemical modification, C60-(OH)20 (HFD), C60-(beta-Ala)10.1 (AFD), C60-(Lys)8.7 (KFD), C60-(Arg)8.6 (RFD) and C60-(NH(CH2)2NH2)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 C60 derivatives at less than 50 microg/mL. However, higher concentration (> 100 microg/mL) of these C60 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.

Although surfactant micelles usually exhibit superlow friction at the nanoscale due to the formation of the hydration layer, the load-bearing capacity (LBC) is limited. In this study, the friction behaviors of two different surfactant micelles (fluorinated and hydrocarbon surfactants, denoted as F-surfactant and H-surfactant) were compared, with the results showing that both can achieve superlow friction (μ = 0.001−0.002) when the self-assembled micelle layers on the two surfaces were not ruptured. Although the two different surfactant micelles have the similar friction behaviors, the LBC of superlow friction for the F-surfactant is 2.5 times larger than that for the H-surfactant. The mechanisms of the superlow friction and the reasons for different LBC were investigated using an atomic force microscopy. The superlow friction can be attributed to the formation of hydration layer on the surfactant headgroups, whereas the higher LBC for F-surfactant originates from the fatness of its carbon chain, which produces the larger hydrophobic attraction and meanwhile increases the stiffness of the micelle layer.