Dental floss embedded with saliva sensors detects cortisol accurately in real-time, providing a practical method for monitoring stress and improving health.
(Nanowerk Spotlight) Stress is a widespread issue impacting physical, emotional, and cognitive health, yet measuring stress accurately remains challenging. Traditional approaches rely on subjective assessments like self-reported surveys or clinical evaluations, methods that can introduce bias and lack immediacy.
Objective methods involving cortisol—often called the body’s “stress hormone”—usually require invasive blood tests, which are not suitable for frequent, everyday monitoring. Saliva-based cortisol tests offer a simpler, noninvasive alternative but have traditionally involved complex equipment and inconvenient sample processing, limiting their practicality for routine use.
Recent advances in wearable technology and flexible sensors have opened new avenues for health monitoring. Sensors embedded in everyday objects like mouthguards and wristbands have demonstrated potential, but these devices are often uncomfortable, conspicuous, or require conscious user effort. The challenge has been to find a subtle, intuitive, yet scientifically rigorous method to integrate sensitive hormone detection seamlessly into daily routines.
(a) Role of cortisol in stress response; (b) Proposed saliva sensing dental floss use case with the embedded cort-eMIP sensor. The floss is connected to a portable potentiostat for readout and signal transmission to a mobile device; Step-by-step process flow for fabrication of sensing dental floss device. (Image: reprinted with permission by American Chemical Society) (click on image to enlarge)
This dental floss innovation centers on a technology called molecularly imprinted polymers, or MIPs. In simple terms, MIPs are synthetic materials created to recognize and selectively capture specific molecules—in this case, cortisol. Think of MIPs as microscopic molds designed specifically to trap cortisol molecules from saliva. This selective binding ensures the sensor accurately identifies cortisol, even among many similar substances naturally present in saliva.
The sensor is built on a flexible graphene electrode, a thin, carbon-based material known for its superior electrical conductivity, flexibility, and durability. The electrode is coated with an electropolymerized MIP film that incorporates cortisol-specific binding sites and an internal chemical signal system using Prussian blue—a compound that facilitates electrical signal generation when cortisol binds to the sensor. The researchers ensured these reactions occur reliably and quickly, eliminating the need for additional chemical reagents or complicated sample preparation.
The device operates simply: as users floss, saliva moves along a specially prepared cotton thread embedded within the floss structure. Capillary action—a natural property where liquids spontaneously flow along narrow fibers—transports saliva effortlessly to the cortisol sensor. Within minutes, the sensor detects cortisol, and the results are wirelessly sent to a smartphone or other portable device, providing immediate feedback.
In extensive laboratory testing, the floss demonstrated remarkable sensitivity, accurately detecting cortisol at concentrations as low as 0.048 picograms per milliliter. This is more than adequate for typical human saliva cortisol levels, which range from very low levels during relaxation to significantly higher concentrations under stress. When compared against traditional laboratory methods such as enzyme-linked immunosorbent assays (ELISA), the floss-based sensor consistently showed high accuracy, matching laboratory results closely. This validation underscores the sensor’s reliability in real-world applications.
A critical strength of this floss-based technology is its selectivity. Saliva contains numerous substances chemically similar to cortisol, including hormones like cortisone and testosterone, as well as common metabolites like glucose and lactate. The researchers rigorously tested the floss sensor and confirmed it could accurately distinguish cortisol from these other substances, minimizing false readings and ensuring trustworthy results.
Practical usability was another focal point. The device proved robust, flexible, and comfortable, suitable for integration into routine oral hygiene practices without additional burden or inconvenience to the user. From saliva collection to wireless data transmission, the entire measurement process takes around 11-12 minutes, making it highly feasible for regular, daily monitoring.
The sensor also demonstrated good stability. When stored at 4°C, it maintained consistent performance for up to four weeks, with less than a 5% change in signal. This durability is essential for practical, repeated use in real-world settings. Additionally, because the composition of saliva can vary slightly from person to person, the researchers tested the sensor’s performance across a range of pH levels. They found that pH 7.4 produced the most reliable results and designed the sensor to maintain accuracy under typical physiological conditions.
Looking ahead, the researchers suggest this dental floss sensor could be adapted to measure other significant health markers detectable in saliva. Potential applications include monitoring blood sugar levels for diabetes, hormone balances for endocrine disorders, or biomarkers associated with cardiovascular diseases. Such flexibility highlights the potential of this technology as a versatile diagnostic tool in personalized healthcare.
This saliva-sensing dental floss represents a meaningful advancement in the ongoing effort to simplify health monitoring. By embedding sophisticated sensing technology into a familiar and mundane daily activity, this innovation brings continuous, accurate, and effortless health tracking closer to practical reality. Such accessible and immediate feedback on stress levels could empower individuals to manage stress proactively, significantly enhancing preventive care, wellness management, and overall quality of life.
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