Quiet the noise Find the signal

How do you read a faint biological signal when the background is louder than the target itself?

Detecting very low concentrations of biomarkers in blood, saliva or urine commonly relies on fluorescent labels that bind the target and emit light that can be measured. The difficulty appears at the low end of the range: the light emitted by the bound labels can be swamped by background signals originating in the sample itself, in the assay reagents and in scattered light.

In the laboratory of Prof. Amos Danielli at the Bar-Ilan Institute of Nanotechnology and Advanced Materials (BINA), doctoral student Shmuel Burg and the laboratory team developed a straightforward way to separate the signal of interest from that background.

The new method, Chopped Optical Biosensing (COB), uses magnetic particles that capture the target molecule. At the start of the measurement the particles are dispersed throughout the solution and the system records mainly background. A magnet then concentrates the particles into a small spot, bringing the fluorescent labels bound to the target into the same region. The system measures again and subtracts the background recorded a moment earlier, isolating the weak target signal from everything around it.

The outcome is a measurement scheme that detects very weak fluorescent signals inside complex biological samples using a comparatively simple and compact optical system. The work was not confined to clean laboratory solutions: the technology was evaluated on 64 clinical serum samples in a dengue serological assay, and classified all positive and negative samples in agreement with the reference test.

The commercial angle is notable, because the work continues a technological line that has already moved beyond academic research. The group previously developed Optical Modulation Biosensing (OMB), which now serves as its commercial platform. The new study shows that high sensitivity and effective background separation can be preserved while significantly simplifying the optical setup. COB may therefore form the basis for a simpler, more compact and more cost-effective generation of sensitive fluorescence detection systems, with potential for portable and point-of-care diagnostics.

Congratulations to Prof. Amos Danielli and the team of the Optics and Biosensing Laboratory at BINA, Bar-Ilan University.

Read the full paper published in Talanta: https://doi.org/10.1016/j.talanta.2026.129666