Forms of Silver and Their Medicinal Uses

Silver offers its own very special way to fight bacteria, and this is very useful in a great and ever-growing number of medical applications today. With increasing efforts to promote healing and reduce infection, products such as medical uniforms, surgical thread, hospital duct-work, catheters, and wound dressings are beginning to incorporate silver in some form.[1] Let’s take a look at some of these in more detail.

Silver Salts

In chemistry, there are acids and bases. Since these terms have different definitions depending on which theory is being used, this book will define them in terms of their properties. An acid generally tastes sour and has a pH of less than seven. Strong, inorganic acids dropped onto metals may generate hydrogen gas. A base usually tastes bitter, has a pH of greater than seven, and feels slippery. When an acid and a base combine, a salt can form. There are a wide variety of silver salts. Some of those used for antimicrobial/antibacterial purposes include:

  • silver chloride: a component of bandages and wound healing products
  • silver fluoride : a tooth decay preventative
  • silver nitrate: a wart treatment
  • silver sulfadiazine: the most powerful, topical dressing for burns[2]
  • silver sulfate: an ingredient in topical creams and bandages

Microbe Wiki, a student-edited information project of Kenyon College in Ohio, states that one advantage of the salt form of silver is that it “is effective at providing a large quantity of silver ions all at once.”[3]

Silver Nanoparticles (AgNP)

Nanoparticles (NP) are very small metal entities. Their dimensions are measured in nanometers (nm), 1nm being equal with 3.93700787 by 10-8 inches; a nanometer is roughly 400 million times smaller than an inch. Depending on the size, a nanoparticle can contain anywhere from a few hundred to several tens of thousands atoms of silver. Currently, silver nanoparticles are considered as perhaps the best form for internal antimicrobial purposes. Microbe Wiki suggests that this may be due to “their simple synthesis and highly effective, observed antibacterial activity.”[4] Research points to nanoparticle size and shape as the reasons for this increased effectiveness. Some studies suggest that the smaller particle size enables the nanoparticle to dissolve easier in liquid environments and more easily pass through cell membranes and cell walls. Nanoparticles come in a variety of forms, including spheres, platelets, needles, and wires. Obviously, the transportation of spheres through the body poses far fewer issues than the other forms. The fewer facets (sides) the particle has, the better its chances of preventing bacterial growth. In addition, nanocrystalline silver dressings have been shown to be anti-inflammatory.[5]

Silver nanoparticles are basically balls comprised of hundreds or thousands of atoms in a metallic state, as explained earlier. When these are placed in a liquid environment, a small fraction of atoms leaves the particle, and these are converted into silver ions (Ag+), following their interaction with oxidizing species (oxygen in the external environment). The silver ion is the species responsible for the antibacterial activity. The metallic silver itself does not offer antibacterial activity, but it does function as a reservoir, providing a slow release of silver ions.

Silver Powder

Silver powders are aggregates of very large silver crystals. They have been used with good results in treating wounds resulting from pressure, sores, and burns. The powder is generally placed in or on the wound site, either directly or as a dispersion in an acceptable cream, then covered with a bandage.

In addition to the above forms, gels and sprays containing silver are also in common use today.

It is certainly not uncommon for medical equipment production to incorporate some silver components. Studies have shown that urinary catheters containing silver alloys more effectively prevent urinary tract infection (UTI). Compared with non-silver-containing catheters, the reduction in infection incidence is ~300 percent.

These and other results have given rise to the use of silver-based antimicrobial coating on items such as prosthetic heart valves and vascular grafts. The general current opinion is that, “despite the initial higher cost of the silver-bearing products, the longer-term benefits of reduced spending on aftercare may justify the economic cost of using these materials.”[6]

“This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.”

[1] It appears that when silver is a part of a wound dressing, the dressing adheres or sticks less to the wound. This makes it more comfortable when changing dressings. However, the frequency of dressing changes may also be lessened due to the antimicrobial action of the silver.   

[2] First Majestic Silver Corporation. “Why Silver?”

[3] “Silver as an Antimicrobial Agent”. Microbe Wiki.

[4] Ibid.

[5] “Anti-inflammatory Activity of Nanocrystalline Silver-derived Solutions in Porcine Contact Dermatitis.” Journal of Inflammation.

[6] Silver Institute, The. “The Future of Silver.”