Researchers have shown that an off-the-shelf glucose meter can be used to test blood samples for a variety of substances, including cocaine, the pathogen-related protein interferon, the biochemical adenosine, and traces of uranium. The ability to measure such medically important targets without expensive lab testing could be particularly vital in developing countries.
The researchers modified the chemistry of blood samples in order to use glucose concentration as a proxy for detecting the concentration of these substances. The research was conducted by Yu Xiang and Yi Lu at the University of Illinois at Urbana-Champaign.
“There’s an elegant simplicity to their repurposing,” says Kevin Plaxco, professor of biochemistry at the University of California, Santa Barbara. “The development of a general sensing platform with the convenience and form-factor of the home glucose meter is the holy grail of biosensor research,” he says.
To achieve this, Xiang and Lu first modify a sample (typically blood) with a solution containing microscopic magnetic beads. Attached to these beads is a piece of DNA that binds to a desired target, as well as invertase, an enzyme that drives the breakdown of sucrose into glucose. When the target binds to the DNA, it releases invertase from the magnetic bead. Once the target is bound to the DNA—a process that takes anywhere from seconds to minutes, depending on the target—the solution is exposed to a magnet, which pulls out the remaining magnetic beads, which hold the unreleased invertase. The solution is then mixed into another that contains sucrose. The released invertase breaks the sucrose down into glucose—and the concentration of glucose is directly related to the concentration of the target. In a final step, the solution is put onto a test strip and into the glucose meter, giving a reading of the concentration of the target substance in the original sample.
“This paper sets an excellent example in combining novel sciences with existing technologies for translational research and development,” says Weihong Tan, a chemistry professor at the University of Florida. “This will revolutionize the field of biosensors and push biosensors to be practically useful in personalized medicine and in medical diagnosis.”
Colin Campbell, a professor of chemistry at the University of Edinburgh, says Xiang and Lu have “steered around one of the common questions asked of such technologies: ‘Can you really make it small enough and simple enough that anyone could use it?’ ” Furthermore, he says, “It is important and impressive that the authors have demonstrated detection in complex samples like blood.”
However, “several hurdles should be overcome if this technique is commercialized,” says Jaebum Choo, a professor of bio-nano engineering at Hanyang University. “First, there are not many target contents which can be captured by specific sequences of DNA.” He also sees the magnetic separation, which adds another step to the process, as a problem, calling it “another hurdle to be considered in the integration process for the commercialization.”
Lu hopes to make the process simpler by replacing the magnet with a filter that would separate the unreleased invertase from the mixture as it is injected into the sucrose solution via syringe. He hopes to see his research lead to commercially available chemical testing kits. “The science and technology are already well developed,” he says, “and there are only several engineering challenges that need to be overcome to reach this goal.”
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