Summary: Maintaining alertness during space missions or overnight shifts depends on precise biological timing. Researchers at Washington State University have developed an affordable, 15-minute paper test that lets astronauts, shift workers, and clinicians monitor internal circadian timing using a single drop of blood and a smartphone-based reader.
The study presents a lateral flow test strip enhanced with bright europium fluorescent nanoparticles that delivers lab-grade melatonin measurements, pinpointing when an individual’s “physiological night” begins.
Key Facts
- Primary Use: Designed with NASA’s needs in mind, the test helps monitor astronauts whose 24-hour light/dark cues are disrupted in orbit, causing circadian dysregulation and impaired cognitive performance.
- Physiological Night: The assay detects dim-light melatonin onset (DLMO), the biological marker indicating the end of circadian-driven alertness and the start of physiological night—critical for scheduling high-risk operations.
- Rapid, Field-Ready: Unlike traditional melatonin assays that require specialized labs, this paper-strip system produces on-the-spot results for settings such as space stations, fire camps, or shift-work facilities.
- Broader Impact: Validation efforts are under way for clinical use in circadian sleep disorders and occupational health monitoring, including firefighter exposure studies.
- Future Goal: The team envisions evolving the approach into continuous melatonin monitoring, analogous to continuous glucose monitoring for diabetes management.
Source: Washington State University
A simple, fast melatonin test developed at Washington State University could let people in 24-hour operations check their internal clocks in minutes with one drop of blood, a paper strip and a smartphone reader.
An interdisciplinary team at WSU created a cost-effective, under-15-minute assay that uses europium-based fluorescent nanoparticles to measure melatonin, the hormone that reliably tracks the body’s internal 24-hour timing system. The method combines a lateral flow immunoassay on paper with a compact, 3D-printed fluorescence reader that attaches to a smartphone.
Circadian rhythms coordinate physiology and behavior across the day—affecting sleep, alertness, metabolism, and cognitive performance. In environments where natural light/dark cycles are absent or irregular—such as spacecraft or emergency-response scenes—these rhythms can become misaligned, reducing performance when it matters most.
Published in Nanoscale Horizons, the paper describes how the assay quantifies melatonin at concentrations relevant to identifying DLMO, conventionally defined when plasma levels cross about 10 pg/mL. Detecting this threshold accurately allows precise determination of when the biological clock shifts toward night-mode.
“Monitoring astronauts’ circadian timing was our initial application,” said Annie Du, research professor in the College of Pharmacy and Pharmaceutical Sciences and corresponding author. “We developed a lateral flow sensing method paired with a smartphone reader so measurements can be taken immediately, without sending samples to a lab. Unlike binary test strips, this system returns exact melatonin levels.”
Melatonin concentrations in blood are very low, which typically requires sensitive laboratory assays. To reach equivalent sensitivity on a paper strip, the team used europium nanoparticles—rare-earth particles that fluoresce intensely—boosting signal strength so the smartphone reader can detect tiny amounts.
After optimizing parameters such as nanoparticle size, antibody conjugation, reagent volumes, and membrane coatings, the platform achieved a detection limit near 10 pg/mL and reliable recovery for melatonin-spiked plasma samples. These performance metrics match the sensitivity needed to mark the start of an individual’s physiological night.
WSU researchers are now validating the device with plasma samples collected at the university’s Sleep and Performance Research Center. If validation continues successfully, the team hopes to extend the platform toward continuous monitoring and broader clinical applications for circadian rhythm management.
This project united expertise across pharmaceutical science, engineering, and sleep research. Coauthors include Zhansen Yang, Xinyi Li, Hans Van Dongen, Yuehe Lin, Yang Song, and Dan Du. Funding partially came from the NASA-supported Washington state Biology in Space Consortium, BioS-ENDURES.
Key Questions Answered:
A: In orbit, crew members may experience many sunrises and sunsets each day, disrupting the normal 24-hour light/dark signal. Even if they feel alert, their internal clock can be misaligned and reaction times reduced. Measuring melatonin provides objective information about when the brain is switching into night mode.
A: Potentially. Current treatments often rely on educated guesses about timing for melatonin or light therapy. An accurate, rapid melatonin measurement would let clinicians or apps tailor interventions to an individual’s true biological night.
A: For this application, yes. The sensitivity comes from the europium nanoparticles and the light-shielding 3D-printed reader. The smartphone captures the fluorescence signal, allowing detection at picogram-per-milliliter levels.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by staff to clarify applications and validation steps.
About this neurotech and circadian rhythm research news
Author: Shawn Vestal
Source: Washington State University
Contact: Shawn Vestal – Washington State University
Image: The image is credited to Neuroscience News
Original Research: Closed access.
“Europium nanoparticle label/lateral flow test strip integrated with a 3D-printed fluorescence smartphone reader for detection of melatonin in human blood” by Zhansen Yang, Xinyi Li, Hans P. A. Van Dongen, Yuehe Lin, Yang Song, and Dan Du. Nanoscale Horizons
DOI:10.1039/D5NH00853K
Abstract
Europium nanoparticle label/lateral flow test strip integrated with a 3D-printed fluorescence smartphone reader for detection of melatonin in human blood
Melatonin is secreted by the pineal gland mainly at night and is suppressed by bright light exposure. When measured under dim lighting, plasma melatonin accurately reflects the timing of the central circadian pacemaker in the hypothalamus. The evening rise in melatonin—commonly defined when plasma concentration exceeds 10 pg mL−1—is a gold-standard marker for the onset of physiological night.
Existing melatonin assays typically require costly equipment and trained personnel, or they lack the sensitivity and robustness needed for point-of-need use. To overcome these limitations, we developed a europium nanoparticle-based lateral flow immunoassay (EuNP-LFIA) paired with a 3D-printed smartphone fluorescence reader for on-site plasma melatonin detection.
We systematically optimized six parameters—readout time, EuNP size, antibody conjugation, Tween-20 concentration, EuNP deposition volume, and the concentration of melatonin–bovine serum albumin on the nitrocellulose membrane. After optimization, the platform demonstrated a limit of detection of 9.99 pg mL−1 in buffer and strong recovery (82.58%–114.70%) for melatonin-spiked plasma, indicating repeatability and reliability.
Overall, the method combines high sensitivity and accuracy with portability and speed (<15 min), offering a cost-effective, user-friendly approach for real-time plasma melatonin monitoring in field and clinical settings.