As shown in Fig 7, various metabolites were influenced by exposure of the cells to MSNs. Interestingly, most of these metabolic changes were already induced by low concentrations of MSNs (1, 10 μg/mL) while they were suppressed by high concentrations (100, 1000 μg/mL). For instance, the contents of amino acids, phosphoric acid, and tricarboxylic acid cycle-related metabolites increased or decreased when E. coli was exposed to low (1, 10 μg/mL), or high (100, 1000 μg/mL) concentrations of MSNs, respectively.