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 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 the IISER Bhopal team are promising routes to take.
 

Speaking about his research, Prof. Saptarshi Mukherjee, Professor, Department of Chemistry, IISER Bhopal, said, “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.

“Generally, silver nanomaterials are produced using toxic precursors that often generate harmful by-products inside the system,” said the lead researcher, a problem the IISER Bhopal team has overcome in their recent research activity. 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.

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 that 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 elevates the cellular stress and consequently breaks 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.

“As our product comprises two components, it can be utilized for multiple purposes: from photophysical studies to applications in biological systems,” said Prof. Mukherjee, on the practical implications of this research work.