Colloidal silver ( Latin argentum colloidale , from Greek kolla , glue-like) is a form of use of silver . It was used medically to fight infection until the first half of the 20th century , when more effective means were not yet available. Later, however, it took a back seat because of the high manufacturing costs and manufacturing quality problems. No medical efficacy or health benefit has been proven for any of the claimed applications when used internally.
When colloidal silver is ultrafine particles of elemental silver (nano-silver), or sparingly soluble silver compounds or their liquid dispersions . For the latter, the terms silver sol and silver water are used synonymously . Silver colloid dispersions or silver sols are to be distinguished from solutions of soluble silver salts . The colloid particles are between 1 and 100 nm in size and cannot be seen with the eye or with a light microscope . The individual particles contain around 1,000 to 1 billion silver atoms or molecules of the corresponding silver compound. In contrast to saline solutions, colloids scatter laterally incident light ( Tyndall effect ) towards the observer.
Colloidal silver can be made by several processes:
- mechanical grinding in colloid mills
- electrolytically using various processes
- purely chemical processes ( reduction of silver salts, e.g. wet-chemical, sonochemical)
Colloidal silver shows an antimicrobial effect in vitro (ie outside of a living organism) and inactivates a number of bacteria and fungi in even small concentrations . Effective agents are silver cations , which are always released in tiny amounts from elemental silver or from sparingly soluble silver compounds and inhibit the metabolism of microorganisms. The minimum inhibitory concentration (MIC) is around 8 to 100 ppm silver ions, gram-positive bacteria are considered to be somewhat more sensitive than gram-negative bacteria . However, the methods for determining the susceptibility of germs to silver have not yet been sufficiently standardized. The inhibition comes about through the reaction of silver cations with sulfur-containing functional groups of certain amino acids and proteins , which are thereby inactivated. This mechanism of action, also known as the oligodynamic effect , is not only inherent in silver , but is also observed with other metals (e.g. with mercury , copper , tin , iron , lead , bismuth and gold ). The ability to attack different parts of the cell metabolism at the same time explains the broad spectrum of antimicrobial effects of silver and silver compounds. The surface that releases metal ions is particularly large in colloids.
The strong antimicrobial effectiveness of nanosilver is associated with its ability to penetrate cell walls and membranes and to work inside the cell. In vitro, colloidal silver is also effective against viruses by binding nanosilver particles to their surface and suppressing the virus' binding to host cells.
Externally, because of its antimicrobial properties, colloidal silver is used in cosmetic products such as soaps, creams, lotions, etc. In view of the incomplete data, it is questionable whether a caring treatment of healthy skin with silver makes sense. The effectiveness in the therapy-accompanying care of atopic skin diseases was investigated in smaller studies and observational studies. A number of dressing materials and wound dressings are also made antibacterial with colloidal silver.
For medical use, the European Pharmacopoeia characterizes “colloidal silver for external use” , a silver-protein compound with a content of 70 to 80 percent elemental silver.
Preparations with colloidal silver for internal use are mainly advertised on the Internet as a panacea for numerous areas of application, which are mainly justified with the antimicrobial, but also with other alleged effects. Various products are offered as "colloidal silver", "silver water", "silver water" or " Hunza water". No medical efficacy or health benefit has been proven for any of the claimed applications.
It cannot be assumed that colloidal silver is marketable as a dietary supplement in Germany. No physiological function is known for silver. Food supplements may not serve any therapeutic purpose and may not be advertised in relation to diseases. The Federal Institute for Drugs and Medical Devices takes the view that finished preparations with colloidal silver for ingestion should be classified as medicinal products . As a result, in accordance with the provisions of the pharmaceutical law, they may only be manufactured with a permit and only be placed on the market with a corresponding drug approval. In the past, cases of illegal distribution were punished as a violation of the Medicines Act. Silver colloids are used as alternative medical, highly diluted finished medicinal products, e.g. B. for homeopathy , legally marketable.
In the United States , in 1999 the FDA classified over-the- counter drugs for both internal and external use that contain silver salts or colloidal silver as a concern and a separate government agency practice was established. As a result, the agency has repeatedly warned companies about the inadmissible application of colloidal silver for antibiotic or other medical uses. The National Center for Complementary and Alternative Medicine (NCCAM) of the National Institutes of Health presents the observed side effects and risks as well as the lack of evidence on positive effects on health in a fact sheet.
Preparations with a high silver content can cause irreversible silver deposits (silver accumulation) in the organism, especially when used over a longer period of time, which can lead to a. can lead to argyria (dark discoloration of the skin), argyrosis (local deposits, especially on the eye) and neurological impairments. Silver is also deposited in blood vessels and internal organs such as the liver , kidneys , spleen and in the central nervous system . In connection with this, chronic epigastric pain and central nervous diseases such as taste and gait disorders, dizziness or seizures have been described.
There are concerns that ultrafine particles such as nanoparticles , including colloidal silver, could penetrate the skin and be toxic when applied topically. The European Parliament has taken this into account by amending Regulation (EC) No. 1223/2009 on cosmetic products . In the future, cosmetics manufacturers will have to declare nanomaterials in cosmetics as such and also prove their harmlessness.
Some studies provide evidence of the genotoxicity of nanosilver. "There is evidence of DNA damage, and after subcutaneous injection of nanoparticulate silver, the development of malignant tumors ( sarcomas ) was observed in rats ."
Overall, however, there is still a lack of scientific knowledge that would enable the authorities to make an appropriate assessment. The Federal Ministry of Health sums up: "However, there is still insufficient data for a comprehensive risk assessment of nanosilver - threshold values or dose-effect relationships are not known." And warns: "Large-scale and low-dose use of nanosilver in consumer products could, in the opinion of Rather, experts and scientific advisory bodies favor the development of allergies and the selection of "multi-resistant" pathogens. There is therefore a risk that silver will no longer be available as an important weapon against pathogenic germs in the medical field. ”This is problematic for experts, especially because a positive effect of nanosilver in consumer products such as cosmetics has not yet been proven. Overall, this results in an increased risk situation in the area of consumer products, which is offset by no proven benefit.
Formation of resistance
Silver-sensitive microorganisms can become silver- resistant over time. The resistance mechanism between different types of bacteria can be exchanged via plasmids . Silver-resistant microorganisms were detected in water filters and in patients with burn injuries who were treated with agents containing silver. The clinical significance is estimated to be rather low so far.
It is unclear whether the colloidal silver that got into the wastewater has ecotoxicological effects on sewage treatment plants and bodies of water. It used to be assumed that it was largely converted into insoluble silver sulfide that was bound to biological particles in sewage sludge. In the experiment, however, poorly soluble silver chloride was formed, even if only a few chloride ions were present in the solution.
In Germany, with regard to the problem of product delimitation , the Drugs Act , the Medical Devices Act as well as the Food, Consumer Goods and Feed Code and various subordinate legal provisions ( Cosmetics Ordinance , Food Supplements Ordinance ) are particularly relevant.
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