A team of researchers from the Indian Institute of Science Education and Research (IISER), Bhopal, have developed a new way to produce silver nanomaterials (AgNMs) which can be used as antimicrobial agents. The process is proved to be safe and easy compared to existing methods to produce silver nanomaterials. The investigation shows the enhanced combating ability of our the newly developed AgNMs system against pathogenic strains like C. albicans and E. Coli. The nanoparticles generate ‘singlet oxygen species’ which elevate the cellular stress and break open and disrupt the cell membrane of the microbes. The research was undertaken by Subhajit Chakraborty, Preeti Sagarika, Saurabh Rai, Dr Chandan Sahi, and Saptarshi Mukherjee.
Silver Nanoparticle
Silver nanoparticles are nanoparticles of silver of between 1 nanometre (nm) and 100 nm in size. They are one hundred thousand times smaller than the width of a single human hair. AgNMs have good antimicrobial properties. Medical practitioners have been using silver in various forms, since ancient times, to prevent infections and promote healing. But AgNMs are produced using toxic precursors which often result in formation of harmful products. The new procedure of developing AgNMs by the IISER scientists overcomes this problem.
Some Findings of the Research
In the study, a small amino acid, L-tyrosine (Tyr), was used as a ligand for the preparation of AgNMs. 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’, which is used to stain nails after voting in India) with tyrosine in the presence of caustic soda. Tyrosine functioned as reducing and capping agent to produce AgNMs. (A reducing agent is used for the synthesis of nanomaterials, while capping agent is used for stabilising the nanoparticles.)
When the newly developed product was examined under high-resolution microscopes—scanning electron microscopy (SEM) and transmission electron microscopy (TEM)—the researchers found two forms of AgNMs—nanoclusters and nanoparticles. The smaller silver nanoclusters are responsible exclusively for the photophysical properties. The larger silver nanoparticles are responsible exclusively for the antimicrobial properties.
The study demonstrates the promising antimicrobial properties of AgNMs against microbes such as Saccharomyces cerevisiae, Candida albicans, Escherichia coli, and Bacillus cereus cell lines. S. cerevisiae is associated with pneumonia, peritonitis, and urinary tract infections (UTI). C. albicans is associated with oral and genital infections, E. coli is associated with stomach infections and B. cereus causes serious infectious diseases. The nanoparticles were found to kill these microbes in about four hours.
The researchers also elucidated the mechanistic aspects of the antimicrobial activity of the AgNMs using various methods such as propidium iodide staining, monitoring reactive oxygen species generation, leakage of proteins, DNA cleavage, etc. It was found that the nanoparticles generate ‘singlet oxygen, (1O2)’ species which elevates the cellular stress and consequently breaks open/disrupt the cell membrane of the microbes. This causes leakage of proteins from the cells, thereby killing them.
This study can pave the way towards elucidating the role of a small molecule, Tyr, in the formation of nanomaterials, and describe the use of new nanomaterials in potential antimicrobial applications. As the product comprises two components, it can be utilised for multiple purposes: from photophysical studies to applications of biological systems. The details and results of the work have been published in the journal of the American Chemical Society–ACS Applied Materials and Interfaces.
Significance
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 for human health today. This is serious problem in India due to rampant and indiscriminate use of antibiotics in humans, livestock, and agriculture. Many patients in India also suffer from multiple drug resistance. As such, there is an urgent need for antibiotic substitutes like nanotechnological solutions, such as the one provided by IISER Bhopal scientists which have the potential to address the problem.
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