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A team of researchers from the Indian Institute of Science Education and Research (IISER), Bhopal, have developed a safe and easy procedure to produce silver nanomaterials that can be used as antimicrobial agents.
The World Health Organisation (WHO) has declared bacterial antibiotic resistance as one of the most important crises to human health today, notwithstanding Covid. This problem is serious for India, the ‘antimicrobial resistance capital of the world’, due to rampant and indiscriminate use of antibiotics in humans, livestock, and agriculture. There is, thus, a dire need for antibiotic substitutes, and nanotechnological solutions such as those studied by IISER, Bhopal, team are promising routes to take.
“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. Medical practitioners have used silver in various forms to prevent infections and promote healing from ancient times,” said Saptarshi Mukherjee, Professor, Department of Chemistry, IISER Bhopal.
Mukherjee said that generally, silver nanomaterials are produced using toxic precursors that often generate harmful byproducts inside the system.
The researchers 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.
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“The researchers treated silver nitrate, the main component of ‘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 microscope, they found two forms of silver nanostructures, nanoclusters and nanoparticles. The nanoparticles were found to kill microbes in about four hours,” he said.
The research group has also elucidated the mechanism by which the nanoparticles kill microbes. They found that the nanoparticles generate “singlet oxygen species” that elevates the cellular stress and consequently breaks open and disrupts the cell membrane of the microbes and causes 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. As our product comprises two components, it can be utilized for multiple purposes: from photophysical studies to applications in biological systems,” said Mukherjee, on the practical implications of the research work.
