Researchers from the General Physics Institute of the Russian Academy of Sciences (GPI RAS; Russia) and the Moscow Institute of Physics and Technology (MIST; Russia) have developed a novel biosensor device based on magnetic nanoparticles. The aim of the device is to provide highly accurate measurements of the concentration of proteins, which can be used to monitor and diagnose disease, in varying samples. Their work was recently published recently in Biosensors and Bioelectronics.
The device relies on a plate, which contains a line of test antibodies, a line of control antibodies and magnetic nanoparticles attached to an antibody. When a liquid sample containing antigens is added to the plate it spreads due to capillary action, leading to the antigen binding to the complimentary antibody attached to the magnetic nanoparticle. The liquid then reaches the test line and control line.
The test line antibodies are complimentary to the antigen and therefore capture the antigen (protein), which is attached to the antibody magnetic nanoparticle marker complex. The control line only binds to the antibody–magnetic particle complex and therefore does not capture the target antigen (protein). The control line will be activated if the test is undamaged and suitable for use.
The detector system uses a patented magnetic particle quantification method to precisely count magnetic nanoparticles by their nonlinear magnetization. This method involves the application of two different frequencies of magnetic field to the nanoparticles. The response at the frequency that is their linear combination, the combinatorial frequency, is then monitored.
The test can be performed quickly and does not require specially trained medical staff and could therefore be used in field conditions. The test is also highly sensitive and can be used to accurately determine protein concentration in an unambiguous manner.
As noted by Alexey Orlov, corresponding author of the study and a Research Fellow of GPI RAS, the test also has a wide dynamic range: “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 system was tested using 0.025 ng/mm of prostate-sepcific antigen (PSA) in blood. PSA is a commonly monitored marker in clinical examinations of men as it is a marker for prostate cancer. The researchers compared their results to those obtained using ELISA, the current gold standard for determining PSA, and found they were just as accurate.
The next step is to take the device from a laboratory prototype to a mass producible product, which the researchers are hopeful will happen due to the reliability, accessibility, high accuracy and sensitivity of the method.
Sources: Orlov AV, Bragina VA, Nikitin MP, Nikitin PL. Rapid dry-reagent immunomagnetic biosensing platform based on volumetric detection of nanoparticles on 3D structures. Biosensors and Bioelectronics 79, 423–429 (2016); Scientists have put a high precision blood assay into a simple test strip