NanoH: Scientists Develop a 15-Minute Blood Test to Monitor Circadian Rhythms

esearchers at Washington State University have developed a test that can assess the state of a person’s internal biological clock in about 15 minutes. The test requires only a drop of blood, a paper test strip and a smartphone equipped with a specially designed reader. The findings were published in Nanoscale Horizons (NanoH).

The researchers developed a system to measure melatonin, a hormone whose concentration changes throughout the day and serves as one of the key markers of circadian rhythms. Melatonin levels typically rise in the evening, signaling the onset of the body’s physiological night, and decline in the morning.

The test combines a paper strip with a 3D-printed fluorescent smartphone reader. To increase sensitivity, the researchers used europium nanoparticles capable of producing a strong fluorescent signal. The system can detect melatonin concentrations as low as 10 picograms per milliliter of blood, a level corresponding to the early onset of physiological night.

Unlike conventional laboratory methods, the new technology could potentially provide results directly at the point of testing, without requiring blood samples to be sent to a laboratory. In principle, it works similarly to rapid diagnostic tests, but instead of providing a simple “yes” or “no” result, it measures the hormone quantitatively.

According to lead author Annie Du, one of the main goals of the technology is to monitor astronauts’ circadian rhythms. During spaceflight, the natural day-night cycle can be disrupted, potentially affecting sleep, alertness and performance.

The technology could also be useful for people who work at night or on rotating shifts, as well as for studying sleep disorders. The researchers are currently testing the system using actual plasma samples from volunteers.

In the future, the team hopes to develop a system capable of continuously monitoring melatonin levels, similar to devices used for continuous glucose monitoring.

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