Mixing gold flakes and DNA may sound like the recipe for a wild night on the town, but University of Toronto researchers have found that a drop of blood, a bit of water, and a powdered DNA-and-gold mixture makes for a stellar diagnostic test.
Their rapid, accurate screening technique could make testing for malaria, HIV, HPV and other infectious diseases available to millions in the developing world, with no need for multiple blood tests and no chance that the testing solution will degrade over time.
Kyryl Zagorovsky, a Ph.D. student, and Professor Warren Chan of the University of Toronto’s Institute of Biomaterials and Biomedical Engineering (IBBME) spearheaded the research and have published their initial findings in the German chemistry journal Angewandte Chemie.
How Does the Diagnostic Cocktail Work?
An over-the-counter pregnancy test is a good example of a biosensor that takes advantage of the unique properties of gold. Gold nanoparticles—about 1,000 times smaller than the thickness of human hair—appear very bright, and change color depending on whether the particles are separate (red) or clumped together (purple).
Researchers first clump the gold nanoparticles together using strands of DNA, and then immerse them in a solution called DNAzyme. The DNAzyme acts like a pair of molecular scissors. When the gene for, say, HPV is introduced, the DNAzyme is activated, "snipping" the DNA strands between the gold particles and turning the sample red.
The DNAzye is highly efficient—very little of the disease gene needs to be present for the DNAzyme to be activated and the sample to change color. This means that the test could potentially be used to screen for a number of diseases at once using only a single drop of blood or saliva.
“A single unit of genetic material present is translated into many DNA strands that get cleaved. This significantly improves the sensitivity of pathogen detection,” Zagorovsky said in an interview with Healthline. “The technique is still in the developing stage. We have not yet investigated or optimized the detection of pathogens from actual bodily fluids, such as blood or saliva, but consider these as feasible potential applications. Our assay can work with only two microliters of sample, which is the size of a very small droplet.”
The Quest for Simple, Portable Diagnostic Tests
Inexpensive, at-home tests for everything from pregnancy complications to UTIs to blood oxygen levels are taking medicine cabinets by storm. Soon, patients will be able to conduct their own screening and diagnostic tests and bring the results to their doctors, without waiting or paying for laboratory work.
"There's been a lot of emphasis in developing simple diagnostics. The question is, how do you make it simple enough, portable enough?" Chen, also the Canada Research Chair in Nanobiotechnology, said in a press release. "We've now put all the pieces together.”
Zagorovsky says that the team is exploring industrial collaborations to develop the technology further, though it will likely be a while before they begin testing with human subjects.