PULLMAN, Wash. — Researchers at Washington State University (WSU) have created a rapid test that enables individuals—especially astronauts and those in round-the-clock jobs—to monitor their biological rhythms using a single drop of blood, a paper test strip, and a smartphone reader.
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The interdisciplinary team developed an affordable test that takes just 15 minutes, employing fluorescent nanoparticles to assess melatonin levels, which vary according to a person's internal biological clock. This clock governs circadian rhythms, impacting functions such as digestion, metabolism, and alertness. Monitoring these rhythms is crucial, particularly in space where traditional day-night cycles are disrupted, potentially affecting mental performance and mission success.
The study, published in Nanoscale Horizons, details a melatonin assay linked with a 3D-printed fluorescence reader for smartphones, allowing precise quantification of melatonin relevant to identifying the onset of an individual's biological night.
Annie Du, a research professor in the College of Pharmacy and Pharmaceutical Sciences and the publication's corresponding author, explained that monitoring astronauts' circadian cycles was a primary motivation for the study. "We developed a sensing method connected with a smartphone reader that enables immediate measurement without needing to send samples to a lab. The method uses a lateral flow immunoassay based on a paper strip, similar to COVID or pregnancy tests, providing specific melatonin levels instead of a basic yes or no outcome."
This innovative test simplifies melatonin assessment in space. Du's work includes creating various test systems that monitor health conditions, such as exposure to wildfire smoke for firefighters. Additionally, she has investigated drug delivery techniques using nanomaterials for various diseases, including cancer and arthritis.
Melatonin, a hormone produced by the pineal gland, typically rises in the evening and declines in the morning, serving as a biological signal for nighttime. Understanding when physiological night begins can aid in scheduling high-performance tasks or addressing circadian rhythm sleep disorders caused by biological clock dysregulation.
Due to the low concentration of melatonin in blood, traditional detection methods are often ineffective. Researchers enhanced sensitivity by utilizing europium-based nanoparticles in their test strip, achieving a “gold standard” sensitivity of up to 10 picograms per milliliter. This precision indicates the start of physiological nighttime, a critical threshold where alertness and cognitive function may decline.
The team is currently validating the device using plasma samples from participants in WSU's Sleep and Performance Research Center. Du envisions a future continuous melatonin monitoring system, comparable to glucose monitors for diabetes management.
The project involved collaboration among WSU researchers from pharmaceutical science, engineering, and sleep science. Co-authors of the study include Zhansen Yang, Xinyi Li, Hans Van Dongen, Yuehe Lin, Yang Song, and Dan Du. The work received partial funding from the NASA-supported Biology in Space Consortium in Washington.