By Danny Freedman
Chemical structure analysis is a bit like solving a jigsaw puzzle—a really tiny one with a heap of microscopic pieces. But a new technique developed at GW may make it easier for scientists to find the big picture by breaking molecular puzzles into larger and fewer pieces.
As a result, the new method could enhance efforts to quickly identify trace amounts of biomolecules, like sniffing the air for biological warfare agents or a budding virus in the bloodstream, says chemistry professor Akos Vertes, leader of the study team and co-director of GW’s Institute for Proteomics Technology and Applications.
The research was done in collaboration with Oak Ridge National Laboratory in Tennessee and funded by the Department of Energy.
The new technique applies to the field of mass spectrometry, which is used to determine the mass, quantity and structure of molecules, among other things.
To do this, molecules are placed in a mass spectrometer and then hit with a dose of energy that breaks apart the molecules and ionizes them—that is, the molecules are given an electrical charge. The charged molecules then are pushed through an analyzer, where they are broken down into their component parts, and the results are read by a detector.
There are several ways of ionizing molecules for mass spectrometry, depending on the work to be done, and Dr. Vertes’ team has introduced a new one. The technique, he says, offers a better way to analyze low-mass molecules, allowing for ions to be produced from smaller samples while maintaining a high sensitivity for detecting trace amounts of a target, and making it easier to shatter the ions into bigger—and more readily identifiable—pieces.
The new approach is able to do that by using photons—particles of light, in this case produced by a laser—as the source of energy for ionizing molecules. The laser offered a higher degree of control than other methods since key variables could be adjusted, such as the strength and direction of laser energy.
The technique, says Dr. Vertes, represents the first convergence of photonics, mass spectrometry and biomedicine.
The team fabricated an array of tiny, nano-scale silicon posts—each of which would be dwarfed by a human hair—for the sample molecules to sit on. Then the nanoposts collected photons from the incoming laser light and used that energy to ionize the sample.
The university is seeking a patent on the technique, says Dr. Vertes.
The advance could factor into ongoing work by scientists to cram all the functions of a chemistry lab onto a single chip, says Dr. Vertes. “One piece of this [chip] device will be something that will identify molecules,” he says, and since his new process requires a smaller sample size and uses the microscopic nanoposts, “it can naturally be integrated into these so-called lab-on-a-chip devices.”
The Department of Energy has funded the researchers’ work for another three years, as they begin using the technique to study microorganisms. Dr. Vertes envisions growing bacteria and viruses on the nanoposts to study how they respond to the process and the kinds of ions they produce. His team already has been able to do this with yeast.
These studies eventually may lead to a better understanding of how microorganisms respond to adverse conditions, like malnutrition or intense heat, and perhaps even allow scientists to rapidly differentiate run-of-the-mill microorganisms in the environment from those of a biological attack.
“Of course, this is way down the line,” he says. “But in order to get there we need to understand how microorganisms behave on the posts in the presence of strong laser light and what kind of ions we get.”