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Methods and Protocols for In Vitro Animal Nanotoxicity Evaluation: A Detailed Review
Published in Vineet Kumar, Nandita Dasgupta, Shivendu Ranjan, Nanotoxicology, 2018
Venkatraman Manickam, Leema George, Amiti Tanny, Rajeeva Lochana, Ranjith Kumar Velusamy, M. Mathan Kumar, Bhavapriya Rajendran, Ramasamy Tamizhselvi
Measurement of intracellular ROS is another important strategy to assess the toxicity of nanoparticles. The ROS are mainly produced by two major components of the mitochondrial electron transport chain, complex I and complex III, especially when electron transport is slowed by high mitochondrial membrane potential (Δψm). Toxic levels of ROS thus generated can interfere with signaling pathways. Higher ROS levels can induce macromolecular damage (by reacting with DNA, proteins, and lipids) and further lead to apoptosis or necrosis (Figure 12.3). In 2,7-dichlorofluorescein-diacetate (DCFDA) assay, the fluorescent dye is used for quantification of hydroxyl, peroxyl, and other reactive oxygen species activity inside the cells. The diacetate form, H2DCFDA and its aceto-methyl ester, H2DCFDA-AM, are taken up by cells where nonspecific cellular esterase act upon it to cleave off the lipophilic groups, resulting in a charged compound trapped inside the cell. Oxidation of H2DCF by ROS converts the molecule to 2′, 7′ dichlorodihydrofluorescein (DCF), which is highly fluorescent. Fluorescence can be visualized by fluorescence microscopy or quantified by fluorescence spectroscopy with maximum excitation and emission spectra of 495 and 529 nm, respectively (Figure 12.10). There are also alternate colorimetric methods where the reduction of nitroblue tetrazolium (NBT) can be quantified during ROS estimation (Figure 12.11).
Silicon dots in radiotherapy
Published in Klaus D. Sattler, Silicon Nanomaterials Sourcebook, 2017
María L. Dell´Arciprete, Mónica C. Gonzalez, Roxana M. Gorojod, Mónica L. Kotler
On the other hand, in C6 cells, ionizing radiation resulted in a marked increase in SiDs-induced ROS generation. It is well known that induction of excessive ROS generation in cells promotes mitochondrial dysfunction, mitochondrial membrane permeability, and respiratory chain dysfunction triggering different types of cell death (Orrenius 2007). Mitochondrial dysfunction induces the release of electrons from the electron transport chain which in turn causes a second wave of ROS with complex I and complex III being sites of O2•- generation (St-Pierre et al. 2002). Interestingly, under our experimental conditions, ionizing radiation is not able to appreciably increase ROS generation in C6 cells in the absence of SiDs. In this regard, gliomas are highly resistant to ionizing radiation, due to their inability to generate ROS, and/or because of efficient ROS depletion by the cellular antioxidant defense system. Thus, our data employing SiDs represent a relevant contribution to the development of future radiotherapy strategies for the treatment of gliomas and other radio-resistant tumors.
Interfacial Catalysis at Oil/Water Interfaces
Published in Alexander G. Vdlkdv, Interfacial Catalysis, 2002
Plant mitochondria have two membranes: a smooth outer membrane that surrounds a invaginated inner membrane. The respiratory chain of mitochondria is an integral part of the inner mitochondrial membrane. It is composed of four electron-transporting protein complexes (NADH dehydrogenase complex I, succinate dehydrogenase complex II, cytochrome reductase complex III, and cytochrome c oxidase complex IV), ATP synthase (complex V), and the mobile electron carriers ubiquinone and cytochrome c. Plant mitochondria have additional enzymes not found in the mitochondria of animals: the cyanideinsensitive alternative oxidase, an internal rotenone-insensitive NADPH dehydrogenase, and an externally located NADPH dehydrogenase, which do not conserve energy. The alternative oxidase catalyzes the oxidation of ubiquinol to ubiquinone and the reduction of oxygen to water and is inhibited by salicylhydroxamic acid. In some photosynthetic cells the carbohydrates formed during photosynthesis can serve as the Gibbs free energy source for respiration, which leads to ATP synthesis and water and CO2 production. Oxygen reduction, catalyzed by cytochrome c oxidase accounts for a significant portion of the water eliminated from the mitochondria.
Influence of Antimycin A, a bacterial toxin, on human dermal fibroblast cell adhesion to tungsten-silicon oxide nanocomposites
Published in Journal of Experimental Nanoscience, 2019
Hassan I. Moussa, Gyeongsu Kim, Jessica Tong, D. Moira Glerum, Ting Y. Tsui
While a significant amount of progress has been made in our understanding of cell adhesion to engineered structures, there is little understanding of how natural (or synthetic) toxins, such as antimycin A, affect normal cell adhesion to biomaterial surfaces such as surgical implants. Antimycin A is a compound naturally produced by Streptomyces bacteria, which are commonly found in soil. Antimycin A, which serves as a defensive mechanism against microorganisms in the environment, is a potent inhibitor of Complex III of the mitochondrial respiratory chain, which is housed in almost all eukaryotic cells. Exposure to Antimycin A interferes with the production of adenosine triphosphate (ATP), modifies the electrical potential across the mitochondrial membrane and results in elevated production of the superoxide molecule, one of the family of reactive oxygen species (ROS) [20]. Antimycin A is also used as a piscicide in the aquaculture industry to control invasive fish populations. In large quantities, this chemical is lethal to fish, mammals, and plants. While high doses of Antimycin A are known to lead to cell apoptosis [21], sub-lethal doses of Antimycin A have been used as a means of depleting ATP in models of ischemia in renal dysfunction; transient exposure to Antimycin A was shown to cause actin rearrangements and lead to poor cell adhesion [22–24]. Interestingly, similar effects on the cytoskeleton and cell adhesion were observed when cells were treated with cyanide, a potent inhibitor of cytochrome c oxidase, which is the terminal electron acceptor of the mitochondrial respiratory chain [25, 26], suggesting that depletion of ATP leads to defects in cell structure and morphology. However, the effect of Antimycin A on mitochondrial morphology remains undocumented; likewise, the mitochondrial morphology in cells adhering to engineered surfaces remains unknown.