Effects of Endohedral Gd-Containing Fullerenols with a Different Number of Oxygen Substituents on Bacterial Bioluminescence.

Gadolinium (Gd)-containing fullerenols are perspective agents for magnetic resonance imaging and cancer research. They combine the unique paramagnetic properties of Gd with solubility in water, low toxicity and antiradical activity of fullerenols. We compared the bioeffects of two Gd-containing fullerenols with a different number of oxygen groups-20 and 42: Gd@COH and Gd@COH. The bioluminescent bacteria-based assay was applied to monitor the toxicity of fullerenols, bioluminescence was applied as a signal physiological parameter, and bacterial enzyme-based assay was used to evaluate the fullerenol effects on enzymatic intracellular processes. Chemiluminescence luminol assay was applied to monitor the content of reactive oxygen species (ROS) in bacterial and enzymatic media. It was shown that Gd@COH and Gd@COH inhibited bacterial bioluminescence at >10 and >10 gL, respectively, revealing a lower toxicity of Gd@COH. Low-concentration (10-10 gL) bacterial bioluminescence activation by Gd@COH was observed, while this activation was not found under exposure to Gd@COH. Additional carboxyl groups in the structure of Gd@COH were determined by infrared spectroscopy and confirmed by quantum chemical calculations. The groups were supposed to endow Gd@COH with higher penetration ability through the cellular membrane, activation ability, lower toxicity, balancing of the ROS content in the bacterial suspensions, and lower aggregation in aqueous media.