Chelated platinum is an ionized form of platinum that forms two or more bonds with a counter ion. [1] Some platinum chelates are claimed to have antimicrobial activity.
Although the concept and practical use of metal chelation is common, chelation of inert metals, such as platinum, has been rarely reported and the yield was extremely low. [2] To produce chelated platinum solution, tetraammonium EDTA, NTA, DTPA or HEDTA type chelating agent was mixed with platinum or platinum chemical compounds. The resulting chelated platinum would be in 4 forms:
The core technique was the usage of a bridge-type heterogeneous chelation architecture to capture metal in a stable water-soluble state. Surprisingly, platinum ion in this particular multi-phase bridged chelated state is amazingly stable. Chelated platinum solution is in the form of high energy dielectric aqueous solution.
Silver, platinum and gold are best known precious metals. However, from a more comprehensive and chemistry point of view, they should be described as inert metals. Inert metals are very stable. They are difficult to participate directly in ordinary acid-base reactions and turn into metal compounds. Therefore, they can stay alone in the form of single element in nature. To turn silver, platinum and gold into metal complex, it can only be performed in very special and particular reaction environment. Furthermore, it is much more difficult to make inert metals into its chelated form which is stable in acidic and basic conditions. The critical reason is that it should undergo a treatment process that involve a great amount of energy in order to achieve a water-soluble state.
Generally, it is not a simple process to turn an inert precious metal directly into its water-soluble ionic state. Material under high energy treatment would gain certain amount of energy according to energy storage effect. Therefore, when inert metal directly turns into its ionic water-soluble state under high energy treatment, it is certain that this aqueous solution would possess large amount of energy. Due to the high energy state and dielectric properties of platinum metal ion in chelated state, the energy conversion at the contact point between platinum ion and bacteria, which is similar to the situation of electrical short circuit, would lead to cell burst and trigger bactericidal effect. Furthermore, platinum ion in chelated state is much more stable than ordinary metal ion in aqueous solution. Also, the concentration and density of chelated platinum ion can be freely adjusted, this characteristic provides effective concentration for anti-microbial and anti-viral activity. Besides, platinum is known to be the best catalyst in the world. The concept of catalyst is that on one hand it triggers catalyzing and reversible reactions, but on the other hand, it does not involve directly in the chemical reaction. Thus, during the microbial eliminating process, there is no deterioration in chelated platinum ion content, such that the bactericidal effective can be continued and sustainable.
Besides the effect surface energy, it is also speculated that the antimicrobial and antiviral properties of platinum would involve the following aspects. Same as other antimicrobial and antiviral metal ions, such as silver, [3] gold, [4] and copper [5] platinum ion is also positively charged. Based on the chemical characteristics, the surface of either Gram-positive and Gram-negative bacteria is negatively charged [6] Meanwhile, similar surface characteristics could be found in fungi and enveloped virus. [7] The positively charged platinum ions would be attracted by the negatively charged cell surface through electrostatic interaction and involved in electron transfer. With the destabilization of cell membrane, change in membrane potential, pH and local conductivity, the permeability of the membrane would be significantly increased, leading to the rupture of microbe or virus outer membrane layer. Furthermore, some functional group of proteins might bind to metal ion that would cause protein denaturation. Eventually cell death or disruption of virus structure would be triggered. [5] [7] [8] [9] [10] Apart from the structural damage of membrane, metal ions also contribute to the generation of reactive oxygen species (ROS) inside the cell. ROS would oxidize glutathione, which is vital compound in bacteria carry out antioxidant defense system to combat against ROS. [8] Consequently, the cell would be destructed due to the reduction of intracellular ATP level, cellular enzyme denaturation, interruption of protein synthesis and DNA damage contributed by the oxidative stress or direct interaction with the metal ion. [11] [12] Since the interaction of metal ion with some atoms, such as nitrogen, oxygen and sulphur, which are abundant in most cellular biomolecules, is very strong and non-specific, therefore, metal ion could possess a broad spectrum of antimicrobial property. [13]
Regarding safety concern, platinum cannot be absorbed by the body. Platinum has widely been used in numerous kinds of medical implants, such as dental alloys, aneurysm coils, medical device electrodes, coronary stents and catheters. [14] Allergy of platinum metal in human has rarely been reported. Only platinum compounds which possess labile leaving groups coordinated to platinum, such as complex halogenated platinum salts or cisplatin, show hypersensitivity and/or toxicity to human. [15] [16] Since the chelated platinum ion is tightly bound to the chelating agent in the form of macromolecule, therefore, toxicity problem would not be an issue.
Chelation is a type of bonding of ions and molecules to metal ions. It involves the formation or presence of two or more separate coordinate bonds between a polydentate ligand and a single central metal atom. These ligands are called chelants, chelators, chelating agents, or sequestering agents. They are usually organic compounds, but this is not a necessity, as in the case of zinc and its use as a maintenance therapy to prevent the absorption of copper in people with Wilson's disease.
Ethylenediaminetetraacetic acid (EDTA), also called edetic acid after its own abbreviation, is an aminopolycarboxylic acid with the formula [CH2N(CH2CO2H)2]2. This white, water-soluble solid is widely used to bind to iron (Fe2+/Fe3+) and calcium ions (Ca2+), forming water-soluble complexes even at neutral pH. It is thus used to dissolve Fe- and Ca-containing scale as well as to deliver iron ions under conditions where its oxides are insoluble. EDTA is available as several salts, notably disodium EDTA, sodium calcium edetate, and tetrasodium EDTA, but these all function similarly.
Chelation therapy is a medical procedure that involves the administration of chelating agents to remove heavy metals from the body. Chelation therapy has a long history of use in clinical toxicology and remains in use for some very specific medical treatments, although it is administered under very careful medical supervision due to various inherent risks, including the mobilization of mercury and other metals through the brain and other parts of the body by the use of weak chelating agents that unbind with metals before elimination, exacerbating existing damage. To avoid mobilization, some practitioners of chelation use strong chelators, such as selenium, taken at low doses over a long period of time.
Proton-exchange membrane fuel cells (PEMFC), also known as polymer electrolyte membrane (PEM) fuel cells, are a type of fuel cell being developed mainly for transport applications, as well as for stationary fuel-cell applications and portable fuel-cell applications. Their distinguishing features include lower temperature/pressure ranges and a special proton-conducting polymer electrolyte membrane. PEMFCs generate electricity and operate on the opposite principle to PEM electrolysis, which consumes electricity. They are a leading candidate to replace the aging alkaline fuel-cell technology, which was used in the Space Shuttle.
Gadolinium(III) chloride, also known as gadolinium trichloride, is GdCl3. It is a colorless, hygroscopic, water-soluble solid. The hexahydrate GdCl3∙6H2O is commonly encountered and is sometimes also called gadolinium trichloride. Gd3+ species are of special interest because the ion has the maximum number of unpaired spins possible, at least for known elements. With seven valence electrons and seven available f-orbitals, all seven electrons are unpaired and symmetrically arranged around the metal. The high magnetism and high symmetry combine to make Gd3+ a useful component in NMR spectroscopy and MRI.
Nitrilotriacetic acid (NTA) is the aminopolycarboxylic acid with the formula N(CH2CO2H)3. It is a colourless solid that is used as a chelating agent, which forms coordination compounds with metal ions (chelates) such as Ca2+, Co2+, Cu2+, and Fe3+.
Pentetic acid or diethylenetriaminepentaacetic acid (DTPA) is an aminopolycarboxylic acid consisting of a diethylenetriamine backbone with five carboxymethyl groups. The molecule can be viewed as an expanded version of EDTA and is used similarly. It is a white solid with limited solubility in water.
Ethylenediamine-N,N'-disuccinic acid (EDDS) is an aminopolycarboxylic acid. It is a colourless solid that is used as chelating agent that may offer a biodegradable alternative to EDTA, which is currently used on a large scale in numerous applications.
Green nanotechnology refers to the use of nanotechnology to enhance the environmental sustainability of processes producing negative externalities. It also refers to the use of the products of nanotechnology to enhance sustainability. It includes making green nano-products and using nano-products in support of sustainability.
Shewanella oneidensis is a bacterium notable for its ability to reduce metal ions and live in environments with or without oxygen. This proteobacterium was first isolated from Lake Oneida, NY in 1988, hence its name.
Platinum nanoparticles are usually in the form of a suspension or colloid of nanoparticles of platinum in a fluid, usually water. A colloid is technically defined as a stable dispersion of particles in a fluid medium.
In coordination chemistry, denticity refers to the number of donor groups in a given ligand that bind to the central metal atom in a coordination complex. In many cases, only one atom in the ligand binds to the metal, so the denticity equals one, and the ligand is said to be monodentate. Ligands with more than one bonded atom are called polydentate or multidentate. The denticity of a ligand is described with the Greek letter κ ('kappa'). For example, κ6-EDTA describes an EDTA ligand that coordinates through 6 non-contiguous atoms.
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Polymers with the ability to kill or inhibit the growth of microorganisms such as bacteria, fungi, or viruses are classified as antimicrobial agents. This class of polymers consists of natural polymers with inherent antimicrobial activity and polymers modified to exhibit antimicrobial activity. Polymers are generally nonvolatile, chemically stable, and can be chemically and physically modified to display desired characteristics and antimicrobial activity. Antimicrobial polymers are a prime candidate for use in the food industry to prevent bacterial contamination and in water sanitation to inhibit the growth of microorganisms in drinking water.
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In coordination chemistry, a spectator ligand is a ligand that does not participate in chemical reactions of the complex. Instead, spectator ligands occupy coordination sites. Spectator ligands tend to be of polydentate, such that the M-spectator ensemble is inert kinetically. Although they do not participate in reactions of the metal, spectator ligands influence the reactivity of the metal center to which they are bound. These ligands are sometimes referred to as ancillary ligands.
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Ferric EDTA is the coordination complex formed from ferric ions and EDTA. EDTA has a high affinity for ferric ions. It gives yellowish aqueous solutions.
Transition metal amino acid complexes are a large family of coordination complexes containing the conjugate bases of the amino acids, the 2-aminocarboxylates. Amino acids are prevalent in nature, and all of them function as ligands toward the transition metals. Not included in this article are complexes of the amides and ester derivatives of amino acids. Also excluded are the polyamino acids including the chelating agents EDTA and NTA.