Fei tecnai t20 microscope

HeLa cells were grown in standard culture medium on borosilicate glass coverslips; fixed with 2.5% glutaraldehyde, 2% formaldehyde, and 2 mM CaCl₂ in 0.1 M sodium cacodylate (pH 7.4) for 60 minutes; postfixed in 1% osmium tetroxide; and stained en bloc with aqueous 2% uranyl acetate overnight. Samples were dehydrated in increasing concentrations of ethanol, penetrated with epoxy resin, and subsequently polymerized at 65°C for 60 h. Coverslips were removed by hydrofluoric acid, and blocks were cut out and remounted on a microtome holder. Thin sections (80 nm) were cut parallel to the surface of the block, mounted on copper grids covered with formvar/carbon film, and stained with uranyl acetate and lead citrate. Samples were analyzed with an FEI Tecnai T20 microscope (Thermo Fisher Scientific) at 120 kV, and images were recorded with an AMT XR81 CCD camera (AMT, Woburn, MA, USA).

The ultrastructure of leaf mesophyll cells situated immediately above the basal meristem was examined at various stages of dehydration. This zone was selected as this tissue is most likely to retain viability relative to older and thus more naturally senescent leaf tips. A band of tissue one cm from the leaf base was removed from randomly selected leaves from three plants and these were further dissected into smaller segments (1–2 mm). These were fixed and embedded according to the method of Sherwin and Farrant [41 (link)]. Embedded samples were sectioned at 95 nm using a Diatome diamond knife (Diatome, Nidau, Switzerland) on a Reichert Ultracut S Ultra-microtome (Leica, Wien, Austria) and mounted onto copper grids. Sections were stained with uranyl acetate and lead citrate as described by Reynolds [42 (link)] for 10 min each before being viewed with a FEI Tecnai T20 microscope (Thermo Fisher Scientific, Waltham, MA, USA).

To prepare the samples for TEM analysis, human BCa cell line EJ28 (University of Frankfurt, Frankfurt, Germany) were seeded and incubated with 1.51 × 10⁻² mg mL⁻¹ CS_MWCNT for 24 h in Eagle’s Minimum Essential Medium. After co-incubation, the medium was removed and the cells were detached and fixed with 2% glutaraldehyde solution at 4 °C. After washing, cells were dehydrated with increasing concentrations of acetone and embedded in a solution (50:50) of EPOXI resin. Then EPOXI resin was cut in 70 nm thin slices.
The samples were analyzed by transmission electron microscopy (TEM) using a FEI Tecnai T20 microscope (Thermo Fisher Scientific, Hillsboro, OR, USA) and operating at 200 keV.