A team of researchers from the Indian Institute of Science Education and Research (IISER) Bhopal has developed a safe and easy procedure to produce silver nanomaterials that can be used as antimicrobial agents.
Antibiotic resistance is a serious condition in which bacteria and other microbes that invade the human body become resistant to the antibiotics/antimicrobials that are meant to kill them.
The World Health Organization (WHO) has declared bacterial antibiotic resistance as one of the worst crises to human health today, notwithstanding Covid-19. This problem is also serious in India, known as the antimicrobial resistance capital of the world, due to the rampant and indiscriminate use of antibiotics in humans, livestock, and agriculture.
“Silver, the common ornamental metal, when present as nano-sized particles — one hundred thousand times smaller than the width of a single human hair — have good antimicrobial properties,” said Saptarshi Mukherjee, Professor, Department of Chemistry, IISER Bhopal, in a statement.
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Medical practitioners have used silver in various forms to prevent infections and promote healing from ancient times.
“Generally, silver nanomaterials are produced using toxic precursors that often generate harmful by-products inside the system,” said the lead researcher.
But in the new study, published in the journal of the American Chemical Society – ACS Applied Materials and Interfaces, the IISER team used the amino acid Tyrosine to produce nanomaterials of silver that had excellent antimicrobial properties. Tyrosine is present in many food items, including meat, dairy, nuts, and beans.
The researchers treated silver nitrate, the main component of the ‘election ink’ used to stain nails after voting in India, with tyrosine in the presence of caustic soda.
Tyrosine functioned as a reducing agent and capping agent to produce silver nanomaterials. On examining the product under high-resolution microscopes (TEM and SEM), they found two forms of silver nanostructures — nanoclusters and nanoparticles.
The nanoparticles were found to kill microbes such as S. cerevisiae (associated with pneumonia, peritonitis, UTI, etc.), C. Albicans (oral and genital infections), E. coli (stomach infection), and B. cereus (stomach infection), in about four hours.
The research group has also elucidated the mechanism by which the nanoparticles kill microbes. They found that the nanoparticles generate “singlet oxygen species” that elevate the cellular stress and consequently break open/disrupt the cell membrane of the microbes and cause leakage of proteins from the cells, thereby killing them.
While the nanoparticles produced by the above process had microbicidal action, the smaller-sized nanoclusters are luminescent and can be used as bioimaging probes.