Integrating metabolic analysis with biological endpoints provides insight into nanotoxicological mechanisms of graphene oxide: From effect onset to cessation

Metabolomics is a new tool used in nanotoxicology to provide comprehensive insight into overall stress responses, while the relationships between global metabolic disturbance and the alterations of biological endpoints remain unclear from effect onset to cessation. Herein, single-cell Chlorella vulgaris was exposed to graphene oxide (GO). The inhibition of cell division and chlorophyll a biosynthesis and the enhancement of reactive oxygen species (ROS) and cell plasmolysis were observed under GO exposure; these adverse effects returned to normal levels when the cells were placed in fresh medium, suggesting that the tested effects were recoverable. Using the data collected from biological effect onset to cessation, the metabolic endpoints (X variables) and biological endpoints (Y variables) were integrated using the orthogonal partial least squares discriminant analysis. It was found that fatty acid metabolism greatly contributed to chlorophyll a and ROS levels, while carbohydrate metabolism had a dominant influence on GO-induced cell plasmolysis. This study proposes the reversibility of GO nanotoxicity and provides deeper insight into nanotoxicological mechanisms via integrating metabolomics with biological endpoints than using metabolic analysis alone.