Magnetic Resonance Contrast Agents for Medical and Molecular Imaging
Astrid Sigel, Helmut Sigel in Metal Ions in Biological Systems, 2004
Many types of molecules enhance contrast in MRI. While organic and inorganic materials can be MRI contrast agents, we restrict our discussion to metal containing agents. Some paramagnetic ions decrease T1 without causing substantial line broadening (e.g., gadolinium(III)), while others induce drastic line broadening (e.g., superparamagnetic iron oxide). The lanthanide ion Gd(III) is generally chosen as the metal atom for contrast agents because it has a high magnetic moment (μ2 = 63 BM2), and a symmetric electronic ground state, (S8) [7]. Transition metal ions such as high spin Mn(II) and Fe(III) are candidates due to their high magnetic moments (5 unpaired electrons) [4]. Free metal ions are toxic to biological systems, thus suitable ligands or chelates must bind the metal ions to form nontoxic complexes. Common ligands used to coordinate paramagnetic metal ions are shown in Figure 1.
For The Want of a Nail … Trace Elements in Health and Disease
Owen M. Rennert, Wai-Yee Chan in Metabolism of Trace Metals in Man, 2017
All trace metals interact with chemical groups called ligands and form complexes or chelates (from the Greek “claw”) (Figure 3). The ligands may be simple monodentate (“single toothed”) complexes; two or more ligand groups may be bound together in the same molecule, such as oxalate or nitrilotriacetate, to form polydentate chelates. Ferric iron is a metal that forms particularly strong chelates. It is able to react with dietary organic acids such as fumaric, oxalic, and citric acids and also with sugars. For years nutritionists scoffed at Popeye for eating spinach because they believed that the ferric oxalate in spinach was not absorbed. Recently it has been demonstrated that pure iron oxalate is a source of iron that can be rapidly assimilated by the body.24 Unfortunately, the tannins in spinach, like those of tea, may indeed inhibit iron absorption under some circumstances.25
Metals
Frank A. Barile in Barile’s Clinical Toxicology, 2019
Toxicity from metals and metallic elements depends largely on the route of exposure (inhalation, dermal, or oral), chemical species (inorganic, organic, or gaseous state), concentration, frequency, and duration. The management of toxicity generally entails instituting the ABCs of emergency treatment (see Chapter 3). In the case of a few chemical agents, antidotes are available for neutralizing, eliminating, or ameliorating the effects of metal exposure. Chelation therapy is generally associated with the treatment of metal poisoning for the particular goal of decreasing the body burden of the chemicals that have been absorbed and distributed to physiological compartments.* Chelators have one or more binding sites for particular compounds; their affinity varies according to their structure and properties.
Synergistic response of physicochemical reaction parameters on biogenesis of silver nanoparticles and their action against colon cancer and leishmanial cells
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2020
Bilal Javed, Zia-ur-Rehman Mashwani, Abdullah Sarwer, Naveed Iqbal Raja, Akhtar Nadhman
The spectrums obtained under different physicochemical reaction conditions were observed critically. The location, height, absorbance unit (Au) and the shape of the SPR band were observed. The location, height and symmetry of the peak depends on the size and shape of the nanoparticles. It was manifested that the 3 mM of the AgNO3 with plant extracts in the ratio of 1 to 9 (Plant: AgNO3) at 120 °C in acidic pH results in the optimised synthesis of SNPs after the incubation period of one hour (Figure 4(B)). The mechanism of the biosynthesis of the SNPs involves the reduction, chelation and stabilisation with the potential functional groups originate from the plant secondary metabolites. The reduction takes place by the redox chemical reactions that occur between the plant secondary metabolites and the silver salt. The redox reactions result in the formation of ions and molecules. During the phase of chelation, ions and molecules coordinate and results in the bonding of ions and molecules to the metal ions. The functional groups originate from the plant secondary metabolites cover the metallic core and help the biogenic nanoparticles to remain stable for a longer period [35,36]. However, the exact mechanism of the synthesis of nanoparticles by phyto-reduction still needs to be investigated.
Optimization of Ag2O nanostructures with strontium for biological and therapeutic potential
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2018
Farwa Ahmad Kiani, Umair Shamraiz, Amin Badshah, Saira Tabassum, Misbah Ambreen, Jahangir Ali Patujo
The antifungal potential of the catalysts was evaluated using three filamentous strains of fungi. Different antifungal inhibitory zones of growth are enlisted in Table 3. The data illustrate that 3% Sr/Ag2O shows significant growth against A. fumigatus and 5% strontium-doped silver oxide against N. niger that is believed to be ubiquitous fungi that affects corn by producing potential mycotoxins on the eatables (Figure 8). The key factor determining the sample’s antifungal activity is lipid solubility. The permeability of the cell is controlled by the lipid membrane that permits lipid-soluble substances in the cell. The polarity of the metal ion is decreased by chelation, owing to the ligand orbital overlap and partial sharing of metal ion’s positive charge with donor groups. An increase in lipophilicity causes easy penetration of the complexes in the lipid membrane, hence blocking the binding sites of metals on the enzymes of the microorganism [21].
Discovery of a new mitochondria permeability transition pore (mPTP) inhibitor based on gallic acid
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2018
José Teixeira, Catarina Oliveira, Fernando Cagide, Ricardo Amorim, Jorge Garrido, Fernanda Borges, Paulo J. Oliveira
As iron overload and loss of iron homeostasis are associated with oxidative stress37, and ultimately to mitochondrial dysfunction, the AntiOxBEN3 iron chelating properties were evaluated. Data show that AntiOxBEN3 can chelate ferrous iron, as observed for the significant decrease in [Fe(ferrozine)3]2+ complex formation. Still, EDTA, a well-known metal chelator, was the best chelating agent tested (Figure 3(A)), as the binding constant of EDTA for its complex with iron is higher than that of phenolic acids38. Most important, the TPP cation and the alkyl spacer did not have a relevant effect on AntiOxBEN3 chelation properties, when compared to gallic acid alone. AntiOxBEN3 metal chelation properties, which are similar to that presented by gallic acid, can be ascribed to the presence of the pyrogallol system and are likely involved in their antioxidant mechanism. As, gallic type systems have intrinsic metal chelating properties39, and this motif was not altered in AntiOxBEN3, one can consider that it is the moiety responsible for the observed iron chelation and antioxidant activities.
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