Gold nanoparticles can kill bacteria through a special physical mechanism

Finding alternatives to antibiotics is one of the greatest challenges to the research community. Bacteria are becoming increasingly resistant to drugs, and this resistance kills more than 25,000 people worldwide every year. A group of researchers found that bacteria can be fought with gold nanoparticles.

Since the days of ancient Egypt, gold has been used for various medicinal purposes, and more recently, for the diagnosis and treatment of diseases such as cancer. The fact is that gold is a chemically inert material: it does not react or change upon contact with the body. In the scientific community, nanoparticles are known for making tumors available for detection with their applications in nanomedicine.

A new study has shown that chemically inert gold nanoparticles can kill bacteria through a physical mechanism that deforms the cell wall. To demonstrate this, the researchers synthesized gold nanoparticles in the form of spheres and stars, all 100 nanometers in size (8 times thinner than a hair) in the laboratory. Scientists have analyzed how these particles interact with living bacteria.

“We found that in the presence of these nanoparticles, bacteria deform and deflate like a ball from which air comes out before death,” explained Vladimir Baulin, a researcher in the chemical engineering department of URV. The researchers say the bacteria appear to have died after being damaged, “as if the cell wall had spontaneously exploded.”

Scientists thought that a physical mechanism might be responsible for the death of bacteria. They performed numerical simulations to analyze how a uniform layer of individual nanoparticles can apply sufficient mechanical stress to the bacterial cell wall. It eventually breaks, stretching out like a balloon that inflates from different points until it explodes.

The researchers created an artificial model of the bacterial cell membrane to evaluate its reaction upon contact with 100 nm gold nanoparticles to confirm this hypothesis. “We found that the model spontaneously contracted until it collapsed completely, thereby confirming the hypothesis that nanoparticles mechanically stretch the bacterial cell membrane,” the scientist concludes.

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