Application of low-energy scanning transmission electron microscopy for the study of Pt-nanoparticle uptake in human colon carcinoma cells

Abstract

High-angle annular dark-field scanning transmission electron microscopy (HAADF STEM) in a scanning electron microscope facilitates the acquisition of images with high chemical sensitivity and high resolution. HAADF STEM at low electron energies is particularly suited to image nanoparticles (NPs) in thin cell sections which are not subjected to poststaining procedures as demonstrated by comparison with bright-field TEM. High membrane contrast is achieved and distinction of NPs with different chemical composition is possible at first sight. Low-energy HAADF STEM was applied to systematically study the uptake of Pt-NPs with a broad size distribution in HT29 colon carcinoma cells as a function of incubation time and incubation temperature. The cellular dose was quantified, that is, the amount and number density of NPs taken up by the cells, as well as the particle-size distribution. The results show a strong dependence of the amount of incubated NPs on the exposure time which can be understood by considering size-dependent diffusion and gravitational settling of the NPs in the cell culture medium.

Assessment of in vitro particle dosimetry models at the single cell and particle level by scanning electron microscopy

“…The striking difference in particle numbers on cells and in the intercellular regions was further analyzed. First, we investigated cellular uptake of particles by STEM and FIB/SEM, techniques successfully used to quantify number of particles per cell at the highest possible resolution [ 21 , 22 ]. In line with studies with bronchial epithelial cells (BEAS-2B), we could not detect substantial amounts of silica particles in A549 cells [ 23 ].…”

Extracellular Vesicles as Vehicles for the Delivery of Food Bioactives

“…1 Although the emergence of nanotechnology and the use of nanoparticles has markedly improved the bioavailability of food bioactives, nanoparticles may also demonstrate non-desired effects as they may cause immune reactions and sometimes even cytotoxicity. Cellular clearance of nanoparticles is also of concern because nanoparticles have been shown to be taken up by, e.g., intestinal cells 2,3 but no cellular excretion mechanism has yet been identified. Within the last few decades, a new class of cellular secretion products, namely, extracellular vesicles (EVs), has emerged that demonstrates an enormous potential to achieve highly efficient delivery of bioactive compounds while overcoming many of the mentioned issues.…”

On the Progress of Scanning Transmission Electron Microscopy (STEM) Imaging in a Scanning Electron Microscope

“…Although STEM detectors have already been available in SEMs for many years, low-energy STEM has not been extensively exploited up to now and only few methodological studies were published (Merli & Morandi, 2005; Morandi & Merli, 2007; Morandi et al, 2007; Volkenandt et al, 2010; Pfaff et al, 2011; Klein et al, 2012; Volkenandt et al, 2014). A few dedicated investigations have appeared in the past few years where low-energy STEM in a SEM was specifically applied to study organic materials (organic solar cells and biological cells) which substantially profit from higher contrast at low electron energies (Hondow et al, 2011; Pfaff et al, 2012; Blank et al, 2014). The initial marginal interest in low-energy STEM in SEM can be partly attributed to the fact that resolution has been limited to about 1 nm.…”