At Hokkaido University, a research group has designed a paper-based device that can measure the concentration of lithium ions in blood simply and inexpensively. The device could be of great assistance to bipolar disorder patients.
Lithium carbonate is used for the treatment of bipolar disorder, which is a mental health condition that leads to severe mood swings. However, this drug should be cautiously used since the therapeutic concentration range of lithium ions in the blood is narrow and nearer to the toxic range.
The Pharmaceuticals and Medical Devices Agency of Japan alerts doctors to routinely analyze the lithium-ion concentration levels in the blood of patients who have been prescribed with the drug.
But present examination techniques need special operations, a huge amount of blood, and big, costly devices. Such techniques can be carried out only by some testing laboratories.
The current study by Takeshi Komatsu, a doctoral student at Hokkaido University’s Graduate School of Chemical Sciences and Engineering, and Professor Manabu Tokeshi from the university’s Faculty of Engineering was carried out to overcome this issue by designing an easy-to-use, affordable method.
The study has been published in the ACS Sensors journal.
The scientists have successfully developed a colorimetric paper-based device that enables point-of-care testing in a single step. The device includes two paper-based elements connected to each other—a colorimetric detection unit and a blood cell separation unit.
A blood cell separation membrane and high-purity cotton blotting paper, which are both commercially available, have been utilized as a substrate for both the units, respectively. Easy handling of liquid was enabled by the hydrophobic ink coated on the device.
Once a drop of a blood sample is added to the end of the separation unit, plasma (i.e. the liquid portion of the blood in the sample) is segregated automatically and conveyed to the detection unit that is dry-coated with a reagent, which exhibits a diagnostic color.
About a minute’s time is needed to complete this process. The color is measured with a digital camera that gets the image for analysis without any set light condition—this process avoids the need for the traditional, exclusive device used for this task. The scientists demonstrated that the detection ability of the device is equivalent to that of traditional instruments that use a similar colorimetric reaction.
The device provides an alternative method for regularly monitoring lithium ion concentrations when treating bipolar disorder patients. 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.
Manabu Tokeshi, Professor, Faculty of Engineering, Hokkaido University
The researchers added that detection reagents and other components could be tuned to use the device for measuring the concentration of blood components apart from lithium ions.
This work was financially supported by the Urakami Foundation for Food and Food Culture Promotion and the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant (JP20H02760).
Komatsu, T., et al. (2020) Paper-Based Device for the Facile Colorimetric Determination of Lithium Ions in Human Whole Blood. ACS Sensors. doi.org/10.1021/acssensors.9b02218.