Lasers combine with gold nanodisks to fry bacteria within seconds

The team found that their new technique, involving gold nanodisks and infrared light, killed the bacterial cells within 25 seconds

On any given day, around one in 25 hospital patients in the US will fall victim to healthcare associated infection, according to the Center for Disease Control and Prevention. Antibiotics and current sterilization methods can provide some respite from the spread of harmful bacteria, but they do have their pitfalls. Researchers have developed a new approach to killing off these germs that may provide a more efficient path forward, using porous gold nanodisks and infrared light to destroy them in a matter of seconds.

Based on earlier research, scientists at the University of Houston had known that gold nanoparticles are able to absorb light very well, swiftly turning the photons into heat to produce temperatures high enough to destroy nearby cells. In 2013, they crafted a gold disk-like nanoparticle littered with pores to further boost its heating efficiency. While a human hair measures between 50,000 and 100,000 nanometers in diameter, the microscopic disk measures just a few hundred.

Looking to investigate its germ-killing capabilities, the scientists applied bacteria, including E. Coli and two forms of heat-resistant bacteria, to the surface of the disks. They then directed infrared light from a laser onto the disk, bringing the surface temperature to 180 degrees Celsius (356 ° F) almost instantly, which in turn created thermal shocks throughout the material.

Using cell viability tests and Scanning Electron Microscopy (SEM), they confirmed that the technique killed all of the bacterial cells within 25 seconds. E. Coli was shown to be the most susceptible, enduring only five seconds of the intense heat. The other two heat-resistant types, which have been found to thrive in the hot springs of Yellowstone National Park, took 25 seconds.

According to the researchers, this is a marked improvement on current approaches to sterilization that can take up to an hour, such as boiling water or dry-heat ovens. And they say it is also faster acting than other germ-killing nanoparticle arrays that have been recently developed, some of which can take up to 20 minutes.

The team is currently exploring the possibility of using the nanoparticles as a bacteria-repellant coating for catheters, which could help to cut the rate of urinary tract infections in hospitals. Another potential use for the technique is in water filtering, where the nanodisks could be worked into membranes to boost water quality.

The research was published in the journal Optical Materials Express.

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