How gold nanoparticles can be used to quickly test drinking water for bacteria

A group of researchers at a Nova Scotia university, in partnership with international colleagues, have developed a test to rapidly detect bacteria contamination in drinking water by using gold nanoparticles, antibiotics and light.

The technology devised by St. Francis Xavier University researchers is simpler and faster than other laboratory methods of finding bacteria in water, some of which take up to 18 hours and involve many more steps.

Geniece Hallett-Tapley, an associate professor of chemistry at St. FX in Antigonish, N.S., along with Maria Jazmin Silvero, from Argentina, are the heads of the research on the project. Hallett-Taply and Silvero had been friends for 10 years when they decided to work on a project together to help people in their respective countries.

"We came up with this idea that one of the big commonalities in both of our countries is the inadequate and inequitable access to clean drinking water, like, across the board," said Hallett-Tapley.

"We know this is a huge, ongoing crisis in the First Nations communities across Canada, and we know that one of the big problems is bacterial contamination of this water."

Detecting bacteria

Hallett-Tapley, Silvero and a research team began their work in 2019. Due to COVID-19, Silvero was not able to return to Nova Scotia, but they were still able to make breakthroughs with their technology that uses tiny gold nanoparticles, visible light and medicine to test for bacteria.

"We took our little tiny, little-bitty nanoparticles and we were able to kind of decorate them with antibiotic molecules," said Hallett-Tapley.

The scientists were then able to take the gold, antibiotic-covered nanoparticles and put them in the presence of a contaminated solution. If the antibiotic interacted with the bacteria, the researchers would see a quick colour change. 

"Our nanoparticles would go from vibrant pink to dark blue. And it would only occur if the antibiotic was responsive to the bacteria that was in the water," said Hallett-Tapley.

"So we were able to actually design a system that allows for a really quick naked-eye indication that whatever your water source is might not be so good right now, there might be some bad stuff in there."

The work done on detecting bacteria led the team to another possibility — the nanoparticles can also kill the bacteria, according Charlotte Elliott, a former member of the research team who is now a medical student at Memorial University.

"If we're looking at a contaminated waterway, we can not only detect the bacteria there, but we might be able to, in a smaller volume of water, actually kill the bacteria present," said Elliott.

'A promising technology'

The bacteria-detection research has been published and peer reviewed. More work and non-academic partners are now needed so the science can be applied to a real-world reality, but the team has confidence in the future of the technology.

The research team is now focusing on producing a strip-like version of the rapid tests that will be even easier for the public to use.

"The detection mechanism is very straightforward and can be used by non-experts," said Mita Dasog, an associate chemistry professor at Dalhousie University who is not connected to the research work. 

"As long as nothing else in the water interferes with the sensing process, this is a quick and easy way to detect pathogens. For disinfection, cost will play a big role and scaling this up using gold might be difficult and not practical.

"It is a promising technology, and I hope an actual sensing device comes out of it that is useful to the community."

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