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Copper and its alloys (brasses, bronzes, cupronickel, copper-nickel-zinc, and others) are natural antimicrobial materials. Ancient civilizations exploited the antimicrobial properties of copper long before the concept of microbes became understood in the nineteenth century.〔Dollwet, H.H.A. and Sorenson, J.R.J. Historic uses of copper compounds in medicine, ''Trace Elements in Medicine'', Vol. 2, No. 2, 1985, pp. 80–87.〕〔(Medical Uses of Copper in Antiquity )〕 In addition to several copper medicinal preparations, it was also observed centuries ago that water contained in copper vessels or transported in copper conveyance systems was of better quality (i.e., no or little visible slime formation) than water contained or transported in other materials. The antimicrobial properties of copper are still under active investigation. Molecular mechanisms responsible for the antibacterial action of copper have been a subject of intensive research. Scientists are also actively demonstrating the intrinsic efficacies of copper alloy "touch surfaces" to destroy a wide range of microorganisms that threaten public health. ==Mechanisms of antibacterial action of copper== The oligodynamic effect was discovered in 1893 as a toxic effect of metal ions on living cells, algae, molds, spores, fungi, viruses, prokaryotic and eukaryotic microorganisms, even in relatively low concentrations.〔v. Nägeli K.W. 1893. Über oligodynamische Erscheinungen in lebenden Zellen. Neue Denkschr. Allgemein. Schweiz. Gesellsch. Ges. Naturweiss. Bd XXXIII Abt 1.〕 This antimicrobial effect is shown by ions of copper as well as mercury, silver, iron, lead, zinc, bismuth, gold, and aluminium. In 1973, researchers at Battelle Columbus Laboratories〔Dick, R.J., Wray, J.A., and Johnston, H.N. (1973), A Literature and Technology Search on the Bacteriostatic and Sanitizing Properties of Copper and Copper Alloy Surfaces, Phase 1 Final Report, INCRA Project No. 212, June 29, 1973, contracted to Battelle Columbus Laboratories, Columbus, Ohio, US.〕 conducted a comprehensive literature, technology and patent search that traced the history of understanding the “bacteriostatic and sanitizing properties of copper and copper alloy surfaces” which demonstrated that copper, in very small quantities, has the power to control a wide range of molds, fungi, algae and harmful microbes. Of the 312 citations mentioned in the review across the time period 1892–1973, the observations below are noteworthy: *Copper inhibits ''Actinomucor elegans, Aspergillus niger, Bacterium linens, Bacillus megaterium, Bacillus subtilis, Brevibacterium erythrogenes, Candida utilis, Penicillium chrysogenum, Rhizopus niveus, Saccharomyces mandshuricus, and Saccharomyces cerevisiae'' in concentrations above 10 g/L.〔Chang, S.M., and Tien, M. (1969), Effects of Heavy Metal Ions on the Growth of Microorganisms, Bull. Inst. Chem., Acad. Sinica, Vol. 16, pp. 29–39.〕 *''Candida utilis'' (formerly, ''Torulopsis utilis'') is completely inhibited at 0.04 g/L copper concentrations. *''Tubercle bacillus'' is inhibited by copper as simple cations or complex anions in concentrations from 0.02 to 0.2 g/L.〔Feldt, A. (no year), Tubercle Bacillus and Copper, ''Munch Med. Wochschr.,'' Vol. 61, pp. 1455–1456〕 *''Achromobacter fischeri'' and ''Photobacterium phosphoreum'' growth is inhibited by metallic copper. *''Paramecium caudatum'' cell division is reduced by copper plates placed on Petri dish covers containing infusoria and nutrient media.〔Oĭvin, V. and Zolotukhina, T. (1939), Action Exerted From a Distance by Metals on Infusoria, ''Bull. Biol. Med. Exptl.'' USSR, Vol. 4, pp. 39–40.〕 *''Poliovirus'' is inactivated within 10 minutes of exposure to copper with ascorbic acid. A subsequent paper probed some of copper’s antimicrobial mechanisms and cited no fewer than 120 investigations into the efficacy of copper’s action on microbes. The authors noted that the antimicrobial mechanisms are very complex and take place in many ways, both inside cells and in the interstitial spaces between cells. Examples of some of the molecular mechanisms noted by various researchers include the following: *The 3-dimensional structure of proteins can be altered by copper, so that the proteins can no longer perform their normal functions. The result is inactivation of bacteria or viruses 〔 *Copper complexes form radicals that inactivate viruses. *Copper may disrupt enzyme structures, and functions by binding to sulfur- or carboxylate-containing groups and amino groups of proteins. *Copper may interfere with other essential elements, such as zinc and iron. *Copper facilitates deleterious activity in superoxide radicals. Repeated redox reactions on site-specific macromolecules generate OH- radicals, thereby causing “multiple hit damage” at target sites. *Copper can interact with lipids, causing their peroxidation and opening holes in the cell membranes, thereby compromising the integrity of cells. This can cause leakage of essential solutes, which in turn, can have a desiccating effect. *Copper damages the respiratory chain in ''Escherichia coli'' cells. and is associated with impaired cellular metabolism. *Faster corrosion correlates with faster inactivation of microorganisms. This may be due to increased availability of cupric ion, Cu2+, which is believed to be responsible for the antimicrobial action.〔Michels, H.T., Wilks, S.A., Noyce, J.O., Keevil, C.W. (2005), (Copper Alloys for Human Infectious Disease Control ), Presented at Materials Science and Technology Conference, September 25–28, 2005, Pittsburgh, PA; Copper for the 21st Century Symposium〕 *In inactivation experiments on the flu strain, H1N1, which is nearly identical to the H5N1 avian strain and the 2009 H1N1 (swine flu) strain, researchers hypothesized that copper’s antimicrobial action probably attacks the overall structure of the virus and therefore has a broad-spectrum effect. *Microbes require copper-containing enzymes to drive certain vital chemical reactions. Excess copper, however, can affect proteins and enzymes in microbes, thereby inhibiting their activities. Researchers believe that excess copper has the potential to disrupt cell function both inside cells and in the interstitial spaces between cells, probably acting on the cells’ outer envelope.〔BioHealth Partnership Publication (2007): (Lowering Infection Rates in Hospitals and Healthcare Facilities - The Role of Copper Alloys in Battling Infectious Organisms ), Edition 1, March.〕 Currently, researchers believe that the most important antimicrobial mechanisms for copper are as follows: *Elevated copper levels inside a cell causes oxidative stress and the generation of hydrogen peroxide. Under these conditions, copper participates in the so-called Fenton-type reaction — a chemical reaction causing oxidative damage to cells. *Excess copper causes a decline in the membrane integrity of microbes, leading to leakage of specific essential cell nutrients, such as potassium and glutamate. This leads to desiccation and subsequent cell death. *While copper is needed for many protein functions, in an excess situation (as on a copper alloy surface), copper binds to proteins that do not require copper for their function. This “inappropriate” binding leads to loss-of-function of the protein, and/or breakdown of the protein into nonfunctional portions. These potential mechanisms, as well as others, are the subject of continuing study by academic research laboratories around the world. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Antimicrobial properties of copper」の詳細全文を読む スポンサード リンク
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