Silver antimicrobial activity

Russell A.D. Hugo W.B. (1994) Antimicrobial activity and action of silver. InProgress inMedicinal Chemistry (eds G.P. Ellis D.K. Luscombe), vol. 39, pp. 351-370. Amsterdam Elsevier. 

Their antimicrobial activities were found to be improved compared with those of silver(i) nitrate. Encapsulation of 69 by electrospun tecophilic nanofibres for the formation of antimicrobial nanosilver particles was also achieved. 

Silver and its compounds have long been used as antimicrobial agents in medicine. The mechanisms of silver toxicity as they relate to human exposure to pharmaceuticals have been reviewed (328). Silver is active at low concentrations and has a low toxicity. The practice of instilling the eyes of infants with 1% of AgN03 solution immediately after birth is still common in some countries, for prevention of opthalmia neonatorum (329). Silver sulfadiazine 77 is clinically used as a topical antimicrobial and antifungal agent and applied as a cream to prevent bacterial infections in cases of severe burns. It is an insoluble polymeric compound and releases Ag(I) ions slowly. 

However the mechanism of the antimicrobial effect of silver nanoparticles is not well understood. It has been recently reported that Nanosilver represents a special physicochemical system which confers its antimicrobial activities via Ag-t [11]. According to Morones et al., the bactericidal effect of silver nanoparticles on microorganisms is connected not merely with the release of silver ions in solution [12]. Silver nanoparticles can also be attached to the surface of the cell membrane and drastically distnrb its proper function [12]. They could also penetrate inside the bacteria and canse farther damage by interacting with sulfur and phosphorus-containing componnds snch as DNA. 

To compare the bactericidal efficacy of silver nanoparticles and silver ions, the minimum inhibitory concentration (MIC) assays were conducted for gram-negative bacterium E. coli, gram-positive bacteria S. aureus and B. subtilis and fungus P. phoeniceum. The data on MICs are summarized in Table 18.1. The results demonstrated that the antimicrobial activity of silver ions was superior to that of silver nanoparticles against all microbes tested. 

In the environment of the burn the compound slowly dissociates into silver and sulfadiazine (30). The silver ion is the antimicrobially active part of the compound and acts by interaction with the micro-organism. Possibly sulfadiazine has a supportive antibacterial effect, but the concentration seems to be subinhibitory (30). The role of sulfadiazine may be to create a sustained delivery of silver ions into the wound environs. 

The purpose of this example is to demonstrate the antimicrobial activity of the silver-based composition of the present invention on bacterial endospores from the test organism Bacillus subtilis. This was accomplished by performing a standard kill-time assay using a suspension of B. subtilis endospores. Normally, bacterial endospores are resistant to killing. 

The 10 ppm silver composition of the present invention was tested and found to be both bacteriostatic and bactericidal for all organisms tested. In other studies, this composition was compared to other commercially available colloidal silver products and found to have a superior activity to all other preparations tested (data not shown). The most interesting observation was the broad spectrum that the 10 ppm silver composition possesses. The antimicrobial activity that was observed was fairly constant independent of the particular organism tested. With the exception of Streptococcus faecalis and Streptococcus aureus (which had MIC values of 10 ppm and 5 ppm, respectively), MIC values ranged between 1.25 ppm and 2.5 ppm for both gram... 

Exploration of new complexes with useful antimicrobial activities has stimulated extensive development of synthetic chemistry of silver(I) complexes. The incorporation of novel ligands can moderate the physical and chemical properties of complexes. For example, the bis(diphosphine)silver(I) complexes (which are analogues of the bis(diphosphine)gold(l) complexes with promising antitumor activity compromised by their antimitochondrial activity) were examined for antitumor and antimicrobial activity by... 

A very early, perhaps the first, report of the use of silver appeared in pre-dynastic Egypt around 3500 BC, where it was used for currency. Medicinally, it has been known since 1000 BC, and possibly before, that water kept in silver or copper vessels, exposed to light or filtered, could be rendered potable [1]. Certainly Alexander the Great (335 BC) was advised by Aristotle to store water in silver vessels and to boil it before use when he transported it on his many campaigns. It must be inferred that the antimicrobial activity of copper and silver was being exploited, albeit empirically, in those very early days and must have been based on shrewd observation. 

Several factors influence the antimicrobial activity of silver salts [19]. Silver has a marked tendency to adsorb to surfaces and bactericidal activity is reduced in the presence of phosphates, chlorides, sulphides and hard water. Activity is increased as the temperature is raised (Q,o = 1.6, that is, a 1.6-fold increase in activity per 10°C rise in temperature) and is pH-dependent, increasing with increasing pH [19, 20]. Sodium thioglycol-late has been recommended as a suitable neutralizing agent for use in... 

Polyoxyethylene stearates are unstable in hot alkaline solutions owing to hydrolysis, and will also saponify with strong acids or bases. Discoloration or precipitation can occur with salicylates, phenolic substances, iodine salts, and salts of bismuth, silver, and tannins.Complex formation with preservatives may also occur. The antimicrobial activity of some materials such as bacitracin, chloramphenicol, phenoxymethylpenicillin, sodium penicillin, and tetracycline may be reduced in the presence of polyoxyethylene stearate concentrations greater than 5% w/w. ... 

Biological activity of electroless-deposited silver on plasma-activated polyurethane was investigated by Gray et al.73 Silver was deposited onto polyurethane samples using commercially available solutions. Some antimicrobial activity of these samples was observed. 

The properties of the most widely used silver-based active ingredients for the antimicrobial treatment of... 

The antimicrobial activity and durability of peroxide-cured rabber formulations containing silver-based antimicrobials are discussed in depth. 20 refs. (ACSd ubber Div.,160th Fall Technical Meeting, 16th-19th Oct.2001, Cleveland, Ohio) Articles from this journal can be requested for translation by subscribers to the Rapra produced International Polymer Science and Technology. 

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