THE ANTIBACTERIAL PROPERTIES OF SILVER
HISTORY OF THE USE OF SILVER AS AN ANTIMICROBIAL AGENT
Silver is a powerful natural antibiotic used for thousands of years.
The medical properties of silver were already known in ancient Greek times.
It was noted that in families where people ate using silver utensils, they became less ill and infections were rare.
This knowledge has been passed down between kings, emperors, czar Sultans among their family members and court members.
It was eaten on silver dishes, silver cutlery was used, food was stored in silver containers and, over time, small quantities of silver mixed with food.
So it was observed that after a generation or two, the benefits of silver made it virtually immune to any infectious disease.
These royal lineages were called "Blue Blood" for the characteristic bluish tint of their blood due to the minimal traces of pure silver.
The common red-blooded people, on the other hand, ate from terracotta dishes using iron utensils and often fell ill, while royalty were not subject to infectious diseases, even from conception.
In 1893 the antibacterial activity of some metals was demonstrated and this property was called the oligodynamic effect. Subsequently it was discovered that of all metals the one that showed the greatest antibacterial property was silver which also had the least toxicity which was then adopted in the medical field and in particular to soldiers of the First World War who were injured to minimize microbial growth.
With the discovery of antibiotics, the use of silver as an antimicrobial agent dropped dramatically but the presence of antibiotic-resistant bacterial strains led to a renewed interest in silver.
Only in recent years has the availability of innovative technologies such as the use of radioactive isotopes and electron microscopy made it possible to study the mechanism of action of silver as an antibacterial. There are various hypotheses regarding the mechanism of action of silver as an antibacterial.
It is believed that silver binds to thiol -SH groups present in enzymes causing their deactivation: silver forms stable S-Ag bonds with compounds containing -SH groups present in the cell membrane which are involved in energy production and ion transport. Silver could also take part in catalytic oxidation reactions that lead to the formation of RSSR disulfide bonds. The formation of disulfide bridges catalyzed by silver therefore leads to a change in the structure of the enzymes, influencing their function.
In another of the suggested mechanisms relating to the antimicrobial activity of silver it has been proposed that the Ag + ion enters the cell and intercedes between the complementary bases purine and pyrimidine with consequent denaturation of the DNA molecule. While this has yet to be proven, it is certain that silver ions associate with DNA once they enter the cell.
However, most of the proposed mechanisms foresee that silver enters cells damaging them and it is believed that, to do this, it can make use of membrane proteins which have, among other things, the function of transporting molecules across the membrane by means of of specific pores, ion channels, ion pumps or carriers.
In order to carry out its antimicrobial activities, silver must be in an ionic form such as, for example, in the form of silver nitrate or in a zeolite matrix or in the form of nanoparticles . The latter are of particular interest for their ease of production as well as for their high antimicrobial action and the possibility of being able to adhere to many products such as surgical masks, cotton fibers and endotracheal tubes.