Scars. We all have them. Whether they come from a time when we fell on a bike while rushing on a bumpy road or remind us of a surgery that saved our lives when we had appendicitis, they are clearly distinguishable from other surfaces of our skin. In an ideal situation wound healing and tissue regeneration would occur after a skin injury, and the scar formation would be minimal. However, this is often not the case and many cuts, burns, etc. result in visible scar formation. This wound healing is dependent on a very careful interplay between several cell types, the cytokines, factors, proteins that they release, and slight changes might result in different healing outcomes which we see as more or less severe scarring.
Silver has been used in medical treatments of wounds for centuries already, as it was known for its antimicrobial activity but only since recently researchers have put more attention into the use of silver in inducing successful wound healing and prevention of formation of the so-called hyperthrophic scars.
Silver nanoparticles (AgNPs) are a perfect example of inorganic nanoparticles, which are nowadays becoming increasingly used in medical applications. AgNPs specifically can be produced in different ways, mainly through physical, (bio)chemical, and biological approaches, and their exact physicochemical structure depends on the way of their production (they can for example be coated with silica).
Their sizes vary from study to study but most AgNPs are of about 20 nm in size, which seems rather small as nanoparticles can have up to 100 nm.
The advantage of using these nanoparticles is that they can penetrate the cell membrane, and their large surface area to volume ratio allows for more interaction site, and provoke a quicker reaction. Interestingly, studies have shown that topical treatment with AgNPs results in faster wound healing. Even though the exact mechanisms of AgNPs actions that would mediate the healing and skin regeneration remain a question, studies have found that application of AgNPs to wounds mediates inflammatory cytokine expression. Particularly, the expression of INF-gamma, TGFbeta-1, and IL-6 are altered, and as a result the inflammation at the site of injury is limited with AgNPs are applied. This could possibly explain why AgNP-treated wounds heal with less scaring. Several interesting studies have also been able to show that applying silver to wounds is more beneficial to skin tissue regeneration when the silver is administered topically as AgNPs in solution, and not in other forms (in this case in a silver sulfadiazine cream), and seem to allow almost full recovery and re-epithelialization without scar formation.
Additionally, studies on human fibroblasts, a cell type especially important in the deposition of collagen-rich matrix that forms scars, have shown that upon treatment with AgNPs the fibroblast growth is largely inhibited. All of these exciting results further speak for the idea of using nanoparticles as drugs or in drug delivery which we recently discussed in class. It seems like AgNPs offer a promising means of mediating proper wound healing and diminishing scar formation which could be used in treatment of skin lesions and burns. Hopefully soon we will be able to use them!