Silver is widely used in medicine, and its antimicrobial efficacy is well described and documented. The modification of noble metal by means of nanotechnology has increased its therapeutic potential. It has been proven that silver nanoparticles (Ag nanoparticles, AgNPs) act to inhibit the growth and development of bacteria, fungi, protozoa and arthropods. They also demonstrate antiviral and antineoplastic activity. Extremely developed active surface of nanostructures translates into higher material efficiency, e.g. its antibacterial effect.
It is believed that silver nanoparticles can be used to fight pathogens that are difficult to eliminate due to their developed multi-drug resistance and can be an important supplement to classic infections of various etiology.
Due to nanotechnology, which enabled the acquisition of particles with nanometric dimensions, interest in silver increased significantly. However, the biological properties of this metal have been known since antiquity, when they were used to treat ulcers, wound healing, and food preservation. Replacing silver ions with nanoparticles has widened the possibilities of using the material in the diagnosis and treatment of many diseases. Some authors see AgNPs as a new generation of antibacterial agents.
Silver nanoparticles are structures of 1-100 nm in size, which exhibit unique physical, chemical and optical properties that condition large biological activity. Particles on the nanometer scale are silver atoms connected by metallic bonds, characterized by a much higher surface to volume ratio (and more effective operation).
Thanks to antibacterial properties, silver is used primarily for disinfection. Disinfectants with nanosilver are used, among others for the purpose of local decontamination of the skin and mucous membranes. Currently, silver is increasingly being used in medicine in the form of nanoparticles.
Nanosilver has a broad spectrum of activity, including against Gram-positive bacteria, Gram-negative bacteria, fungi, viruses, protozoa, as well as multi-drug resistant microorganisms.
Silver nanoparticles are able to adhere (adhere to) the surface of the bacterial cell efficiently and easily and penetrate into it. (Mammalian cells have a different coating, so silver does not work on their structures).
Very small concentrations of silver are enough to achieve the desired bacteriostatic effect (inhibiting the growth and multiplication of microorganisms) or bactericidal (toxic to microbes, leading to their death).
The mechanism of AgNPs antimicrobial activity is, among others, on:
• direct impact on extracellular sheaths (e.g., modification of cell membrane structure and increase of their permeability, which leads to cell destruction);
• increased production of reactive oxygen species (ROS) and causing oxidative stress;
• influencing cell metabolism, disturbing the process of obtaining energy (including impairing the functioning of the respiratory chain) and affecting the genetic material (eg, disturbing DNA and RNA synthesis, DNA damage).
Colloidal silver is a heterogeneous mixing: silver particles suspended in water. Considerable fragmentation of particles in colloidal silver increases the total surface area of the substance and its biological impact. Colloidal silver may have antibiotic-like properties with a broad spectrum of activity. It can be used internally or externally, e.g. as an irrigation fluid, for instillation of wounds, for local spreading on the skin or mucous membranes.
The progress of nanotechnology has expanded the possibilities of producing biologically active compounds based on silver. The biological activity of nanoparticles significantly exceeds the activity of analogous, larger structures. Due to the increasing resistance of microorganisms to antibiotics, chemotherapeutics and metal ions, the therapeutic potential of nanosilver is constantly gaining in importance. Silver nanoparticles are now increasingly used in traditional medicine, dentistry, pharmacy and cosmetology.