A USC-led research team claims to have made a significant improvement in a new type of electronic sensors for detecting viruses and other biological substances - a development that could serve as a valuable addition in the fight against epidemics.
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A USC-led research team claims to have made a significant improvement in a new type of electronic sensors for detecting viruses and other biological substances - a development that could serve as a valuable addition in the fight against epidemics. The detector consists of a synthetic antibody segment anchored to a nanowire attached to an electrical base, all immersed in a liquid.
When the protein, with which the antibody reacts, is in the liquid, it binds to these antibodies while immediately receiving a sharp and measurable voltage jump through the nanowire.
The basic principle of biosensors for protein detection using nanotubes and nanowires was first demonstrated in 2001, but the cutting-edge design of the research team led by researchers Zhongwu Chou and Mark Thompson of the University of Southern California contains two completely new components.
First of all, the state-of-the-art detector takes advantage of bioengineered synthetic antibodies that are much, much smaller versions of the natural substances designed to bind exclusively to unique proteins, and only to them.
Second, the detector contains nanowires of indium oxide (In2O3) instead of zinc and other materials tested previously. Metal oxides, according to new research published in the journal ACS Nano, do not, unlike their form, develop over time "an isolated localized oxide layer that can reduce sensitivity."
The result, as claimed in the article, is a device capable of detecting its target species with the highest sensitivity rate available today, in a faster manner and without the use of additional chemicals. Also, the new detector is significantly cheaper than those on the market today.
"We believe," the researchers write, "that biosensing devices based on nanowires containing engineered proteins...could have important applications ranging from disease diagnosis to internal security."
In addition, the system can be useful in basic research, aiding in the understanding of important factors affecting two-component biological systems such as the antibody/target protein pair.
The prototype system was able to discover the characteristic protein (n-protein) of the SARS virus in question (SARS, severe acute respiratory syndrome), which was responsible for the infection of eight thousand people in 2003-2002, with the death of about ten percent of them, in the end .
Commercial systems that use ELISA (enzyme-linked immunosorbent assay) systems to detect the virus do exist on the market, but the new system has superior advantages such as saving time, cost and portability.
The first step in the research was the synthesis of the artificial antibody that contained both the active site designed to bind to the protein and its other end, a chemical "hook", which should bind to the nanowire at this point only. "This approach allows for each sensing particle anchored to the surface to retain its full activity - a clear advantage over other antibodies, which in most cases (in previous biosensor designs) are bound to the nanowire surface via amine residues randomly scattered over the surface of the antibody."
Researcher Zhou's laboratory, which has specialized in nanowire and nanotube technologies for years, carried out the complex series of procedures for preparing the nanowires, and examining the expected response of the detector to the presence or absence of the virus proteins. The reaction was completed in less than ten minutes, compared to several hours required by ELISA systems, where only a qualitative measurement of the presence or absence of the target substance is obtained without any quantification of its concentration. The next steps in the research focus on developing sensing capability in more complex environments, such as the blood serum or the whole blood fluid, by combining the nanobiosensors with microsystems such as microfluidic chips or microfilters.
