Scientists have found a way to rapidly kill E. coli bacteria and other bacteria using nanoporous gold disks and light. Instead of traditional sterilization methods, requiring boiling water or dry-heat ovens that take minutes to an hour, this technique accomplishes the task in seconds.
Wei-Chuan Shih, a professor in the electrical and computer engineering department at the University of Houston of Houston in Texas and colleagues have recently published their findings in the journal Optical Materials Express.
We showed that all of the bacteria were killed pretty quickly … within 5-25 seconds. That’s a very fast process.
Previous research showed that gold nanoparticles absorb light strongly, converting the photons quickly into heat, reaching temperatures that can destroy bacterial and cancer cells.
In 2013, Shih and his colleagues created a new type of gold disk-like nanoparticles that measures a few hundred nanometers in diameter. The scientists created gold nanoparticles in the lab by dissolving gold, reducing the metal and smaller disconnected pieces until the size could be measured in nanometers. In comparison, a human hair is between 50,000 to 100,000 nanometers in diameter. Once materialized, they formed the particles into disks. The disks have sponge-like pores that increased their heating efficiency while maintaining their stability.
In their new study, they tested the antimicrobial properties of their new nanoparticles when activated by light. First, they grew E. coli and other types of heat-resistant bacteria in their lab. They then placed the bacteria cells on the surface of a single-layer coating of the gold disks and shone infrared light from a laser on them. Using a thermal imaging camera, they showed that temperatures reached up to 180-degrees Celsius, delivering thermal shocks to the bacteria cells. After, they used cell visibility tests and SEM imaging to see what percent of cells survived.
The results were amazing, in that all of the bacteria cells were dead within 25 seconds. The E. coli cells died within five seconds.
This technique can eventually be used in many biomedical applications. It could one day allow hospitals to treat common infections without antibiotics and help reduce the spread of antibiotic resistant bacteria. Researchers are investigating its use as a coating for catheters to help reduce the number of urinary tract infections in hospitals.
Any sort of light-activated procedure would be much easier to implement at the bedside of the patient.
Another application may be using nanoparticles with filter membranes in small water filters to improve water quality.
Scientists have only reached the tip of the golden iceberg when it comes to future applications for these gold bacteria-killing disks.