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MOSCOW, 25 January. /TASS/. Researchers from the General Physics Institute of the Russian Academy of Sciences (GPI RAS) and MIPT have developed a new biosensor test system based on magnetic nanoparticles. It is designed to provide highly accurate measurements of the concentration of protein molecules (e.g. markers, which indicate the onset or development of a disease) in various samples, including opaque solutions or strongly colored liquids, according to the press service of the MIPT.
“The biosensor can be used not only to diagnose diseases, but also for a number of other applications. It’s able to conduct analyses on food products and medicines; it will also be able to be used to conduct environmental monitoring”, said the press release.
At molecular level, the magnetic nanoparticles “link” with antibodies to the required protein and then they are placed on a porous plate close to the intended point of contact with the test solution. The liquid, which spreads along the plate due to capillary action, captures the magnetic particles. It then meets two lines – the test line and the control line. The test line contains antibodies that capture the protein in question and also the magnetic markers that became attached to molecules of the protein due to the fact that the nanoparticles are also “linked” to the antibodies. The control line only captures the antibodies with magnetic markers, and it will be activated in any case, if the test strip is usable. The control line serves as an indicator as to whether the test is suitable for use, the protein antibodies in it have not been destroyed due to improper storage, and the test liquid has been applied correctly (see Figure 1)
Figure 1. The antigen is the test protein (e.g. PSA). MP is the magnetic nanoparticle, the upside down Y is the antibody to the test protein. The test antibodies (the blue Ys) capture the test protein, and the control antibodies (the yellow Ys) capture the antibodies with the nanoparticlesMIPT
Alexey Orlov, the corresponding author of the study and a Research Fellow of GPI RAS): “Normally, tests that can be performed not only under lab conditions but also in the field, use fluorescent or colored markers and the results are determined visually, by sight or by using a video camera. In our case, we are using magnetic particles, which have a significant advantage: they can be used to conduct analyses even if the test strip is dipped into a completely opaque liquid, to determine the substances in whole blood for example. The precise numerical measurement is conducted entirely electronically using a portable device. This completely excludes any ambiguity.”
The scientists note that along with the high level of sensitivity of determining the concentration of a protein, the new test system also allows measurements to be taken over a wide dynamic range: the upper limit of the test concentration is more than 4000 times greater than the lower limit.
The new system was tested by measuring 0.025 nanograms per milliliter of prostate-specific antigen in the blood (the normal rate is anything up to 4 nanograms). Prostate-specific antigen is one of the most commonly monitored markers in clinical examinations on men.
“Prostate-specific antigen, PSA, is one of the possible markers for prostate cancer”, – said Alexey Orlov. “It is also used in forensics to detect traces of semen. Both applications have certain limitations and they are not able to conclusively provide a diagnosis/prove the guilt of a suspect, but the new biosensor platform will be able to do more than analyse PSA; this particular protein was simply chosen as a demonstration”
The combination of reliability, accessibility, and high accuracy and sensitivity of the new method means that it is likely to make a rapid transition from a laboratory prototype to mass production, but developers have not yet given a specific timeframe. The paper was published in Biosensors and Bioelectronics.