(Nanowerk Spotlight) Medical professionals constantly struggle with monitoring patients’ drug levels and vital electrolytes. Traditional monitoring requires repeated blood draws – an invasive process that needs trained staff and specialized equipment. While urine testing offers a gentler alternative, current methods still demand manual sample collection and time-consuming laboratory analysis, making continuous monitoring impossible.
This monitoring gap particularly affects patients receiving morphine for severe pain management. Morphine dosing requires careful balance – insufficient amounts leave patients in pain, while excess can cause dangerous breathing problems or even death. Doctors must also track potassium levels, as this electrolyte plays a crucial role in heart and muscle function. Both excessive potassium (hyperkalemia) and insufficient potassium (hypokalemia) can trigger dangerous heart rhythm problems. The ideal monitoring system would track these markers continuously without disrupting patient care.
Scientists have tried various approaches to solve this problem. Some developed skin patches with tiny needles, while others created sensors worn on the skin or in the mouth. These solutions often proved impractical – they were either uncomfortable, difficult to use, or too expensive for widespread adoption. The key challenge has been creating a monitoring system that fits naturally into existing patient care routines.
A research team from Prince of Songkla University in Thailand, has now developed a practical solution by adding chemical sensors directly to ordinary diapers. “This represents the first development of a wearable, printed sensing array capable of noninvasively and rapidly detecting drugs and electrolyte ions in body fluids,” lead researcher Professor Itthipon Jeerapan tells Nanowerk. The team’s new system, detailed in Chemical Engineering Journal (“A diaper-based printed sensing array for noninvasively and speedily detecting morphine and potassium ions”), can continuously measure both morphine and potassium levels in urine using flexible electronic sensors printed directly onto diaper material.
Diaper-based morphine and potassium sensors. (A) A diaper device designed for developing morphine and potassium sensors, featuring: (a) Application of diaper-based FLEX-CNT to the patient, (b) Illustration of custom-made ink preparation, (c) Photos of customized FLEX-CNT ink on a flexible plastic sheet, (d-e) Printing of Ag/AgCl patterns and working and counter electrodes on a substrate, and (f) Drop casting of a reference cocktail as the reference electrode for sensors and the potassium-selective solution on the working electrode of the potassium sensor. (B) Photo of the diaper-embedded morphine and potassium sensor. (C) Square wave voltammetry (SWV) response performed with a screen-printed FLEX-CNT electrode, increasing the concentration of morphine in artificial urine from 1 µM to 50 µM. SWV conditions: step potential 15 mV, modulation amplitude 50 mV, frequency 5 Hz. (D) Potentiometric response of the potassium selective-membrane-based sensor. (Image: Reprinted from Chemical Engineering Journal, Volume 485, Natcha Rasitanon, Warawut Sangsudcha, Itthipon Jeerapan, A diaper-based printed sensing array for noninvasively and speedily detecting morphine and potassium ions, 148898, 2024, with permission from Elsevier)
The researchers created a special electronic ink that combines three key materials: carbon nanotubes and graphite for electrical conductivity, plus a flexible polymer called SEBS that allows the sensor to bend and stretch. Using standard printing techniques, they apply this ink to create arrays of tiny sensors on the diaper’s surface.
The system uses two different methods to detect chemicals. The first, called electrochemical sensing, works like a tiny battery – it applies small electrical pulses to morphine molecules, causing them to release electrons that create measurable electrical signals. The sensor can detect morphine at concentrations as low as 0.024 micromolar (about 24 trillionths of a mole per liter) up to 1000 micromolar – spanning the entire range of clinically important levels. For potassium, the sensor uses a special membrane containing molecules that specifically capture potassium ions while ignoring other chemicals in urine. This selective detection works across a wide range of concentrations.
The researchers performed extensive durability testing, repeatedly bending and flexing the sensors to simulate real-world use. The sensors maintained accuracy even after 100 bending cycles at various angles. They also verified that common urinary compounds like glucose, creatinine, and uric acid did not interfere with the measurements.
The system’s wireless connection to a smartphone app enables immediate data access and analysis. When urine contacts the sensors, they can detect and report changes in morphine or potassium levels within 15 seconds. The system is particularly suited for “near-bed settings, continuous patient monitoring, emergency medical services for immediate diagnosis, and home healthcare for self-monitoring,” notes Jeerapan. It could also prove valuable for “detecting drug abuse in uncooperative individuals.”
(A) Images of our diaper-based FLEX-CNT electrodes for in-situ urine analysis. (B) Test results displayed on a smartphone app. (Image: Reprinted from Chemical Engineering Journal, Volume 485, Natcha Rasitanon, Warawut Sangsudcha, Itthipon Jeerapan, A diaper-based printed sensing array for noninvasively and speedily detecting morphine and potassium ions, 148898, 2024, with permission from Elsevier)
The technology marks an important advance in patient monitoring. By integrating sensors into diapers – items already used in many healthcare settings – the system overcomes practical barriers that have hindered previous monitoring attempts. The combination of continuous measurement and wireless reporting could help prevent dangerous complications from incorrect drug dosing or electrolyte imbalances.
Looking ahead, the researchers acknowledge several challenges, including “ensuring the durability and stability of sensors in everyday environments, improving the collection of networked signals, and incorporating AI to analyze and personalize data for each individual.” The team also emphasizes the importance of “reducing the size and cost of wireless electronics for integration into wearable devices” as crucial for widespread adoption.
This sensor platform lays the groundwork for monitoring a wide range of medical markers in urine. The flexible design and wireless capability could be adapted to detect indicators of kidney function, diabetes, bacterial infections, or even early signs of certain cancers. The same basic technology could potentially track hormone levels, metabolic markers, or other prescription medications. This versatility makes the platform particularly valuable for developing new diagnostic tools.
While clinical trials will be necessary to validate the system’s real-world performance, this work demonstrates a practical path toward continuous biological monitoring that could significantly improve patient care.
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