A low-cost, portable and easy-operated salivary urea sensor for point-of-care application

Kuan Hsun Wang, Ju Chun Hsieh, Chang Chiang Chen, Hsiao-Wen Zan*, Hsin-Fei Meng, Sheng Yu Kuo, Minh Trâm Ngọc Nguyễn

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


Salivary urea was reported to be a useful biomarker to reflect the blood urea nitrogen in chronic kidney disease patients. However, as a new biomarker, enormous clinical trials are required to define the intended-use and to verify the specification. In this report, we demonstrated a low-cost easy-operated real-time sensing system (optical fiber-urea-sensing, OFUS, system) to detect salivary urea. We aim to make the system easily reproduced by the community to stimulate abundant clinical tests worldwide. The OFUS system is composed of a simple three-dimensional printed tank to link with two optical fibers, one connecting with a commercial light-emitting diode to deliver the input light signal, the other connecting with a commercial cadmium sulfide photo-conductive cell to detect the sensing signal. To allow on-site detection without any sample pretreatment, only 1 μl saliva is needed to be mixed with 10 μl urease solution and 90 μl pH indicator solution in the reaction tank and the detection time is only 20 s. A stable and reproducible calibration curve can be easily built with a detection range as 24–300 mg/dL. The OFUS system successfully detected saliva with added synthetic urea and samples from chronic kidney disease patients. A good agreement between the OFUS system and the commercial kit was obtained. A good correlation between salivary urea and the blood urea nitrogen was also confirmed.

Original languageEnglish
Pages (from-to)352-359
Number of pages8
JournalBiosensors and Bioelectronics
StatePublished - 1 May 2019


  • Non-invasive
  • Optical fiber
  • Point-of-care
  • Real-time
  • Salivary urea


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