Document Type


Publication Date



The novel positive-contrast magnetic resonance imaging (MRI) marker C4 consists of an aqueous solution of cobalt chloride (CoCl 2 ) complexed with the chelator N-acetylcysteine (NAC). We evaluated whether the presence of C4 or its components would produce reactive oxygen species (ROS, including hydroxyl, peroxyl, or other reactive oxygen species) in cultured cells. Human cancer or normal cells were incubated with 1% (w/v) CoCl 2 ·6H 2 O or 2% NAC or a combination of both (1% CoCl 2 ·6H 2 O: 2% NAC in an aqueous solution, abbreviated as Co: NAC) in the presence or absence of H 2 O 2 . Intracellular ROS levels were measured and quantified by change in relative fluorescence units. Student's t-tests were used. In all cell lines exposed to 1000 μM H 2 O 2 , the Co: NAC led to ≥94.7% suppression of ROS at 5 minutes and completely suppressed ROS at 60 and 90 minutes; NAC suppressed ROS by ≥76.6% at 5 minutes and by ≥94.5% at 90 minutes; and CoCl 2 ·6H 2 O suppressed ROS by ≥37.2% at 30 minutes and by ≥48.6% at 90 minutes. These results demonstrate that neither Co: NAC nor its components generated ROS; rather, they suppressed ROS production in cultured cells, suggesting that C4 would not enhance ROS production in clinical use.


© Journal of Toxicology. Original version available at:

Publication Title

Journal of Toxicology





To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.