Researchers from the Moscow Institute of Physics and Technology (MIPT) and the Prokhorov General Physics Institute of the Russian Academy of Sciences have developed a next-generation rapid test for diagnosing myocardial infarction. The method is 45 times more sensitive than existing alternatives and can detect a damage marker from a single drop of blood in just six minutes. The findings were published in the international journal Biosensors and Bioelectronics.

Acute myocardial infarction remains one of the leading causes of death from cardiovascular disease worldwide. Emergency physicians and hospital admission units operate under intense time pressure: the earlier the diagnosis is confirmed, the higher the patient’s chances of survival, according to Scientific Russia. However, existing laboratory tests take 30–60 minutes and require specialized equipment and trained personnel. Rapid tests, on the other hand, often lack the sensitivity to detect early signs of heart muscle damage, leading to false-negative results.

This gap between speed and accuracy is what Russian scientists have managed to overcome, resulting in a fundamentally new testing system.

The test requires only a single drop of blood, which is applied to a test strip similar to a pregnancy test. The liquid is absorbed and moves along the strip, while a rotating magnetic field is activated. As the blood flows, nanochains mix the sample, capture the target protein marker, and accumulate at the test line. The entire process takes six minutes.

The result is read by a portable magnetic device. Unlike optical systems, which only detect signals on the surface of the strip, the magnetic field penetrates its full thickness. This allows for accurate readings even if the blood sample is cloudy or dark.

The test measures marker concentrations in the range of 0.02 to 50 ng/mL, with a detection limit of 21 picograms per milliliter. This makes it 45 times more sensitive than conventional magnetic bead-based tests and significantly more sensitive than most commercial rapid tests. Importantly, it provides not just a yes-or-no answer, but an exact quantitative value.

“Rapid tests have long faced a trade-off: either speed and simplicity or laboratory-level accuracy. Here, we were able to overcome this limitation in a fundamentally new way—not by improving traditional labels, but by replacing them with actively functioning ones. Nanochains in a rotating magnetic field mix the sample during analysis and self-concentrate on the test line. At the same time, we did not need to redesign the test strip—we use a standard nitrocellulose membrane, meaning all innovation lies in the labels themselves and in the detection method,” said the study’s lead author, Alexey Orlov, a senior researcher at the Prokhorov Institute and an MIPT graduate.

The scientists focused on a specific protein—fatty acid-binding protein (FABP). Among the many substances released into the blood during heart damage, this protein plays a particularly important role. Unlike troponins—the current “gold standard” in cardiac diagnostics, which require multiple measurements over 1–3 hours—FABP appears in the blood within the first hour after the onset of an attack. It serves as an early warning signal, but detecting it requires highly sensitive tools.

To label this protein, the researchers used a new type of magnetic marker: elongated nanochains instead of conventional spherical particles. These chains, made of iron oxide and about one micrometer long (hundreds of times thinner than a human hair), are coated with antibodies that bind to FABP, effectively turning them into traps for the cardiac marker.

In a stationary liquid, protein molecules move randomly and take a long time to find antibodies. To accelerate this process, the scientists placed the nanochains in a rotating magnetic field. The chains begin to spin, actively mixing the blood around them and allowing antibodies to bind to the protein dozens of times faster.

The researchers also observed an unexpected effect: nanochains already captured on the test line begin to attract additional chains carrying the protein from the flowing blood. This creates a self-amplifying process—the more markers accumulate, the more actively they attract others. At the same time, rotation disrupts random, non-specific binding, reducing background signals by about half. This combination—enhanced useful signal and reduced noise—achieves a level of sensitivity unattainable by each factor alone.

“The key finding is the synergy between rotation and immunochromatography. Intuitively, one might expect that directed fluid flow along the membrane would interfere with the rotation of nanochains. In reality, the opposite is true: capillary flow continuously delivers fresh analyte, while rotation ensures efficient mixing at the binding surface. Together, they perform better than separately,” said the study’s first author, Yuri Malkerov, a young researcher at the Prokhorov Institute.

Accuracy is just as critical as sensitivity. The team tested the system against a panel of significant proteins, including cardiac markers (troponin, NT-proBNP) and cancer markers, and observed no false positives.

“For potential clinical use, this is critically important, as it opens the possibility of creating a reliable rapid test that can help save lives,” said co-author Alexandra Rakitina, a graduate student at MIPT.

According to the study’s supervisor, Petr Nikitin, head of the laboratory at the Prokhorov Institute, the system does not require modification of standard test strips, keeping them inexpensive and easy to mass-produce.

“All the ‘magic’ lies in the detection method and the properties of the nanochains themselves. A portable version of the magnetic nanolabel detector based on nonlinear remagnetization, powered by standard batteries, has already been demonstrated. The next step is integrating the magnetic rotator and detector into a single compact device,” he said.

Before clinical implementation, the technology will need to undergo large-scale patient testing, device miniaturization, and regulatory approval. However, the platform itself is универсальный: magnetic nanochains in a rotating field can be adapted to detect other hard-to-capture biomarkers—from cancer markers to food toxins. According to the authors, the technology opens the way for test systems capable of simultaneously detecting multiple cardiac damage markers from a single drop of blood.