Opton 900 transmission electron microscope

The samples for ultrastructural studies were fixed in a 3.6% buffered glutaraldehyde solution at pH 7.4 (Poly Scientific R&D Corporation, Bay Shore, NY1176, USA). They were then embedded in an Epon 812 epoxy resin (Sigma Aldrich, Poznan, Poland) and sliced into 1 µm-thick slices using an ultramicrotome. Subsequently, they were stained with toluidine blue and examined using a light microscope. Such ultra-thin sections were examined using electron microscopy. The photographic documentation was collected using an Opton 900 transmission electron microscope (Zeiss, Oberkochen, Germany).
The diagram of the above study flow description is shown in Figure 1.

The morphological changes in human ZR-75-1 and MDA-MB-231 cells were evaluated by transmission electron microscopy (TEM). Both cell lines (2.5 × 10⁵) were seeded in 2 mL of a medium in six-well plates. After 24 h, the medium was removed and replaced by the rGO suspensions in a medium at the concentration of 100 μg/mL. Subsequently, the ZR-75-1 and MDA-MB-231 cells were incubated for 24 h and 48 h. After incubation, the cells were centrifuged (1000× g, 5 min), fixed in a mixture of 2.5% glutaraldehyde and 2% paraformaldehyde in 0.1 M cacodylate buffer (CB) at pH 7.0, at 4 °C, for 1 h, and taken up into the agar blocks. Then, samples were washed in CB at 4 °C, for 1 h, post-fixed in 1% osmium tetroxide in CB at 4 °C for 1 h and next dehydrated through a graded series of ethanol and embedded in glycid ether 100 (Epon 812). Ultrathin sections were contrasted with uranyl acetate and lead citrate, mounted on nickel grids and evaluated in an OPTON 900 transmission electron microscope (Zeiss, Oberkochen, Germany).