Together, they are developing versatile technology that will enable such breakthroughs as rapid evaluation of the effectiveness of potential antiviral drugs by their ability to block a virus' bond with a cell receptor, as well as high-precision detection of cancer biomarkers using molecular binding as a means for biorecognition. While it is common to utilize these natural molecular binding processes to identify biological agents, Dmitri Litvinov's research distinguishes itself by how these processes are detected.
Usually scientists attach tags, also referred to as labels, to biomolecules - proteins, DNAs or RNAs - that allow these biomolecules to be tracked. This tracking tells researchers the location of the biomolecules and whether the biomolecules have bonded with a specific substrate, such as a healthy cell.
"Common tags used by researchers are fluorescent beads that are detectable by their colouring, but many of the tags currently used in research are much larger than the biomolecules being studied", Dmitri Litvinov stated. "Because of this, these tags often interfere with the formation of bonds. This complicates research and brings into question the accuracy of experiments."
In Dmitri Litvinov's research, the tags are magnetic spheres measuring about 50 nanometers - 1000 times smaller than the width of human hair. At such a size, they better conform to the size of the biomolecules to which they are attached, thereby minimizing their interference with the binding processes. While these spheres have already been developed and are available to scientists, their small size makes them extremely difficult to track and detect.
Dmitri Litvinov, Richard Willson and John Wolfe are developing an array of magnetic-field sensors capable of detecting the presence of these tiny magnetic spheres. These sensors, dubbed giant magnetoresistive (GMR) sensors, are widely used in the data storage industry and are small enough that a million of them can be fit in a single square millimeter of space.
This work is being done in the Center for Nanomagnetic Systems that specializes in the development and application of novel magnetic materials and devices at nanoscale dimensions, such as those directly related to current and future magnetic storage technologies.
For applications in antiviral drug development, the GMR sensors will be coated with cell receptors that bind with a specific virus protein. When the virus protein bonds with the cell receptor, these sensors will detect magnetic spheres, letting researchers know that a bond has occurred. Should an antiviral drug be added to the mix, it will block the cell receptors, preventing them from binding with the virus protein. For example, virus proteins will bind with cell receptors in the body to generate infections. The process imitates the biological development of illnesses within the body.
It is this process that will enable Dmitri Litvinov's tool to screen potential drug candidates. By adding potential medications to a mixture containing viruses, the GMR sensor array will, in effect, detect whether a drug blocks a particular virus from binding with a cell receptor. If it does, further clinical trials with the drug likely will follow. Because so many sensors can reside in a small area, hundreds - even thousands - of drug candidates can be screened at once, cutting down the time it takes to bring new drugs to market. In addition to testing the viability of potential drug candidates, the technology being developed by Dmitri Litvinov's team also may be put to use in other areas of health care.
Though this technology initially is funded for drug development, it can be used for other high-throughput molecular screening applications, such as in cancer studies. Such an application would work in a similar way as the tests for potential drug candidates. A small biological sample suspected of being cancerous would be extracted from a patient using a nearly painless technique - fine needle aspiration. Nanoparticles known to bond with that particular form of cancer would then be exposed to the biological sample, and medical professionals would be able to determine if cancer is present depending on whether or not the nanoparticles and biological samples bond. Should bonding occur, the presence of cancerous cells would be confirmed.
The key advantage of such a system, according to Richard Willson, is that it would combine the non-invasive nature of fine needle aspiration with the reliability of conventional highly invasive techniques, such as open surgery. This would provide results with far greater accuracy than traditional testing methods.
"The way they evaluate fine needle aspiration biopsies for the presence of cancer is by looking at a biological sample under a microscope, relying heavily on the experience of the person evaluating the sample and the quality of the sample", he stated. "Here, the idea is to automate the process to make it foolproof and eliminate the human-error factor without resorting to surgery."
Whether used as a diagnostic tool or to screen drug candidates, the use of GMR sensors in medical applications has the potential to simplify many areas of medical research.
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