Cells Undergo Major Changes in the Quantity of Cytoplasmic Organelles after Uptake of Gold Nanoparticles with Biologically Relevant Surface Coatings

Abstract

Here, we use cryo soft X-ray tomography (cryo-SXT), which delivers 3D ultrastructural volumes of intact cells without chemical fixation or staining, to gain insight about nanoparticle uptake for nanomedicine. We initially used dendritic polyglycerol sulfate (dPGS) with potential diagnostic and therapeutic applications in inflammation. Although dPGS-coated gold nanoparticle (dPGS-AuNP) uptake followed a conventional endocytic/degradative pathway in human lung epithelial cell lines (A549), with cryo-SXT, we detected ∼5% of dPGS-AuNPs in the cytoplasm, a level undetectable by confocal light microscopy. We also observed ∼5% of dPGS-AuNPs in a rarely identified subcellular site, namely, lipid droplets, which are important for cellular energy metabolism. Finally, we also found substantial changes in the quantity of cytoplasmic organelles upon dPGS-AuNP uptake over the 1−6 h incubation period; the number of small vesicles and mitochondria significantly increased, and the number of multivesicular bodies and the number and volume of lipid droplets significantly decreased. Although nearly all organelle numbers at 6 h were still significantly different from controls, most appeared to be returning to normal levels. To test for generality, we also examined cells after uptake of gold nanoparticles coated with a different agent, polyethylenimine (PEI), used for nucleic acid delivery. PEI nanoparticles did not enter lipid droplets, but they induced similar, albeit less pronounced, changes in the quantity of cytoplasmic organelles. We confirmed these changes in organelle quantities for both nanoparticle coatings by confocal fluorescence microscopy. We suggest this cytoplasmic remodeling could reflect a more common cellular response to coated gold nanoparticle uptake.

Oxidative Stress and Apoptotic Responses Elicited by Nostoc-Synthesized Silver Nanoparticles against Different Cancer Cell Lines

“…An increase in number of mitochondria is associated with the use of stored cellular energy reserves in response to nutrient deprivation or exercise [ 67 ]. Thus, the intensive stress caused by N-SNPs may cause an increase in the number of mitochondria in cells, in order to generate more energy and avoid this stress [ 68 ]. Moreover, the dose-dependent increase in number of peroxisomes observed in all tested cells after exposure to N-SNPs may indicate that N-SNPs kill cancer cells via inducing oxidative stress, as ROS can be generated in peroxisomes by the production of H 2 O 2 during fatty acid oxidation [ 69 , 70 ].…”

Amelioration of ulcerative colitis via inflammatory regulation by macrophage-biomimetic nanomedicine

“…Free Cy5 and Cy5 loaded NPs without membrane coating (Cy5-N) and Cy5 loaded membrane coated NPs (Cy5-MN) (each containing the same content of Cy5) were added into the medium of BMDM and Caco-2 cells with the final concentration of Cy5 as 10 μg/mL and the concentration of NPs as 0.19 mg/mL. The internalization of free Cy5 and Cy5 loaded NPs was determined by flow cytometry in 4 hours and 24 hours, respectively according to the previous studies 30 , 31 and the mean fluorescence intensity was statistically analyzed.…”

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“…143 Also, it was found that Au-NPs increase number of mitochondria and decrease the number of lipid droplets indicating that cells produce more energy in trial to remove the stress caused by NPs. 142 Furthermore, the high incidence of, autophagic vacuoles, endosomes, cytoplasmic vacuoles were observed after treatment cancer cells with Ag-NPs. 142,144 Another study showed that Ag-NPs and copper NPs resulted in increasing lipid droplets that may be return to nanotoxicity that impaired the lipid catabolic activity.…”

“…142 Furthermore, the high incidence of, autophagic vacuoles, endosomes, cytoplasmic vacuoles were observed after treatment cancer cells with Ag-NPs. 142,144 Another study showed that Ag-NPs and copper NPs resulted in increasing lipid droplets that may be return to nanotoxicity that impaired the lipid catabolic activity. The authors reported also that high incidence of peroxisomes as well as lysosomes and low distribution of endoplasmic reticulum indicating necrosis.…”

“…A recent study demonstrated the direct interaction between NPs and cellular organelles such as LDs, endosomes, mitochondria, etc. 142 Barkhade et al showed that cells treated with titanium dioxide NPs exhibited swallowing mitochondria and influence the mitochondrial membrane permeability. 143 Also, it was found that Au-NPs increase number of mitochondria and decrease the number of lipid droplets indicating that cells produce more energy in trial to remove the stress caused by NPs.…”