Fig. 7

TEM image of cells treated with CoNPs and ALA for 24 h. a Control group. No abnormality in cell morphology and structure was found; b) Morphological characteristics of CoNPs. The CoNPs are round or oval, with size less than 50 nm; b Cells treated with CoNPs only group. Obvious characteristic changes in mitochondria can be found. The mitochondria shrunken, while the mitochondrial membrane is visible. The chromatin is condensed in granular form (red arrow). The blue arrow indicates the early stage of mitochondrial deformation, while the yellow arrow indicates the middle stage of mitochondrial deformation. Intracellular organelles are swollen and have many vesicle shapes (black arrow). CoNPs are aggregated and encapsulated in the cell (double black arrow); c Cells treated with CoNPs and ALA together, CoNPs inside the cells are wrapped to form vesicles (double black arrow) and are excreted from the cell. The cell morphology and structure are similar to those of the control group. d ALA group, the cell morphology, and structure are similar to those of the control group