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Paper-Based Device for Detecting Lithium Ion Concentration in Blood

Research team from the Hokkaido University developed this device that is able to easily and cheaply measure lithium ion concentration in blood.

Lithium carbonate is used for treating bipolar disorder, a mental health condition that causes extreme mood swings. Caution should however be exercised when using this drug due to its narrow therapeutic concentration range in the blood. Japan’s Pharmaceuticals and Medical Devices Agency has warned doctors to regularly examine lithium ion concentration levels in the blood of patients given the drug.

Presently, testing methods for lithium ions in blood require a large amount of blood, special operations, and large, expensive devices. These methods are also only available to use in specific testing laboratories.

In this study led by Takeshi Komatsu, a doctoral student at Hokkaido University’s Graduate School of Chemical Sciences and Engineering, and Professor Manabu Tokeshi of the university’s Faculty of Engineering was conducted to address this problem by developing a user-friendly, low-cost method. The study was published in ACS Sensors.

The team successfully developed a colorimetric paper-based device that allows point-of-care testing in one step. It consists of two paper-based elements linked to each other: a blood cell separation unit and a colorimetric detection unit. The device uses high-purity cotton blotting paper and blood cell separation membrane as a substrate for each unit, respectively. It is also coated with hydrophobic ink to allow each liquid handling.

After a drop from a blood sample is placed on the end of the separation unit, plasma, or the liquid portion of the blood in the sample, is automatically separated and transported to the detection unit dry-coated with a reagent, which displays a diagnostic colour. This process takes about a minute to complete. To measure the colour, a digital camera obtains the image for analysis without any fixed light condition, a process that makes the conventional, special device for this task unnecessary. The researchers showed that the device’s detection ability is comparable to that of conventional instruments using the same colorimetric reaction.

“The device provides an alternative method for regularly monitoring lithium ion concentrations when treating bipolar disorder patients,” says Manabu Tokeshi. “In the future, we hope to develop a smartphone app for the image analysis so patients themselves or non-medical workers can check the lithium ion concentration in the blood.” The researchers also say that by tuning detection reagents and other components, the device can be used for measuring the concentration of blood components other than lithium ions. [APBN]