Length difference of multi-walled carbon nanotubes generates differential cytotoxic responses.

Carbon nanotubes have recently been rated as an effective biomaterial owing to their functionalization ability. However, the safety of multi-walled carbon nanotubes (MWCNTs) has yet to be clearly understood. To investigate how cells differentially react to minor geometric differences, we prepared well-dispersed and stable long and short MWCNTs showing an approximately 100-nm length difference in an in vitro system. Through an optimal combination of bovine serum albumin (BSA) and fetal bovine serum (FBS) biosurfactants and ultrasonication, we first confirmed that the MWCNTs were maintained without aggregation throughout the experiments. Internalized MWCNTs in human coronary artery smooth muscle cells were then quantified in a label-free manner using coherent anti-Stokes Raman scattering, followed by an analysis of their localization via two-photon excitation fluorescence. Intracellular MWCNTs were found to primarily localize in mitochondria with abnormal morphologies. Mitochondrial dysfunction, which was found to result from early stages of oxidative stress that consequently lead to cell death, was then proved via decreasing mitochondrial membrane potentials, with short MWCNTs showing significantly greater cytotoxicity than long MWCNTs. Our results suggest that even small length differences of MWCNTs may lead to differential responses in cells.

Antioxidant and anti-inflammatory activities of Orostachys japonicus

Objective: To determine the bioactive compounds of Orostachys japonicus (O. japonicus) (Maxim.) A. Berger extraction by different solvents (70％ ethanol or water) and to evaluate the in vitro antioxidant and anti-inflammatory activities.Methods: Total polyphenol, flavonoid, and anthocyanin contents in O. japonicus extract were measured. Antioxidant activities were determined by DPPH, ABTS, and superoxide radical-scavenging ability assays. Anti-inflammatory activities were evaluated by nitric oxide production, tumor necrosis factor-α, and interleukin-6 expression techniques. Results: Extraction with 70％ ethanol yielded the highest total polyphenol (60.03 mg/g dry weight) and flavonoid (55.50 mg/g dry weight) contents. The total anthocyanin contents in 70％ ethanol and water extracts were 57.25 and 91.71 mg/g dry weight, respectively. The 70％ ethanol extract also showed stronger antioxidant activity than the water extract. Antioxidant activity and reducing power increased with the increasing concentration of O. japonicus extract. O. japonicus extract at 0-400 μg/mL did not affect the growth of RAW 264.7 cells, whereas dose-dependent inhibition of nitric oxide, tumor necrosis factor-α, and interleukin-6 production was observed. Conclusions: O. japonicus inhibits oxidative and inflammatory reactions with potentially positive health-related effects.