An international team of collaborators found that when bacteria come into contact with the gold nanoparticles, their cell walls deform and eventually burst, causing the material inside the cells to leak and die.
As bacterial resistance grows, more than 25,000 people worldwide now die each year from infections for which there are no effective antibiotics. Researchers hope to find other ways to deal with the bacterial threat.
Since the time of ancient Egypt, gold has been widely used for a variety of medical purposes. More recently, doctors have used gold to help diagnose and treat cancer. Gold is an inert metal that does not react or change when it comes into contact with living organisms. Gold can be used to make cancer cells visible, as well as in nanomedicine.
The new research has uncovered the mechanism by which gold nanoparticles kill bacteria.
In the lab, the researchers synthesized stars and near-perfect spherical nanoparticles, each about 100 nanometers in diameter (an eighth of the diameter of a human hair), and observed how they interacted with bacteria.
“What we found is that the bacteria around these nanoparticles, they start to deform and then deflate and die like a deflated balloon.” ‘It looks like the cell wall exploded,’ said Vladimir Baulin, one of the researchers from the Chemical engineering department at the University of Rovira Wiljilly.
To test the mechanism, the researchers built models of bacteria and observed their interactions with gold particles as small as 100 nanometers in diameter.
It turns out that the uniform properties of the surface layer of the nanoparticles create a mechanical force that stretches the cell walls of the surrounding bacteria, causing the bacteria to rupture in the end, much like a balloon being stretched from different points of action leading to bursting.
The study, published recently in Advanced Materials, was a collaboration between The Universitat Rovira I Virgili in Spain, the University of Grenoble in France, Universitat des Saarlandes in Germany and RMIT University in Australia.
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