Amazing stuff!
"... Tears, one of the less invasive bodily fluids to collect, contain biomarkers such as serotonin that can reveal information about people’s stress and mood. To collect and analyze tears in real time, researchers devised a “lab-on-a-contact lens” that consisted of an electrochemical serotonin sensor on a soft hydrogel lens. Testing the device for 28 days using artificial tears revealed that it could read out serotonin levels while withstanding being folded, twisted, and stretched.
After ruling that the device was safe and biocompatible, the researchers moved to live subjects, including pigs and mice, and even conducted a pilot study with 30 humans asked to do stressful tasks such as public speaking and arithmetic. The trials revealed that chronic stress indeed caused reduced serotonin in tears. ..."
From the abstract:
"Stress-related endocrine responses are critical for understanding human performance and mental health. Conventional assessments rely heavily on subjective self-report questionnaires or invasive sampling such as venipuncture. Tears offer a noninvasive source of neurochemical biomarkers, including serotonin, a key regulator of stress and mood. However, real-time and continuous monitoring of tear serotonin has not yet been fully realized.
Here, we present a reversible lab-on-a–contact lens platform that integrates a printable, stretchable ferrocene-based electrochemical sensor for in situ detection of serotonin in tear fluid. The device is fabricated on a soft hydrogel lens and uses an electrochemically refreshable redox surface to restore baseline between measurements.
Calibration in artificial tears established a limit of detection of 72 picomolar and a dynamic range of 0.1 to 500 nanomolar.
Function was maintained for more than 28 days in a tear-like environment and under repeated mechanical deformations (flipping, folding, stretching, and twisting), with stability confirmed by periodic redox cycling.
Ocular safety and biocompatibility were demonstrated in a porcine eye model. In a chronic stress mouse model, tear serotonin concentrations inversely correlated with cortisol in both serum and tears, and a first-in-human pilot study further supported the relationship between tear serotonin and stress with off-line analysis by the lab-on-a–contact lens platform. This platform could enable applications in decentralized, noninvasive endocrine monitoring and holds promise as a clinically translatable tool for real-time mental health biomarker assessment."
Serotonin measurement by lab-on-a–contact lens in porcine and human tears (no public access)
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