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. 2020 Jul 24;20(15):4118.
doi: 10.3390/s20154118.

3D Microfluidic Devices in a Single Piece of Paper for the Simultaneous Determination of Nitrite and Thiocyanate

Peng Yu  1 , Muhan Deng  1 , Yi Yang  1 , Beixi Nie  1 , Shaoyu Zhao  1
Affiliations

3D Microfluidic Devices in a Single Piece of Paper for the Simultaneous Determination of Nitrite and Thiocyanate

Peng Yu et al. Sensors (Basel). .

Abstract

The concentrations of nitrite and thiocyanate in saliva can be used as the biomarkers of the progression of periodontitis disease and environmental tobacco smoke exposure, respectively. Therefore, it is particularly necessary to detect these two indicators in saliva. Herein, the three-dimensional single-layered paper-based microfluidic analytical devices (3D sl-μPADs) were, for the first time, fabricated by the spraying technique for the colorimetric detection of nitrite and thiocyanate at the same time. The conditions for 3D sl-μPADs fabrication were optimized in order to well control the penetration depth of the lacquer in a paper substrate. Then, the developed 3D sl-μPADs were utilized to simultaneously detect nitrite and thiocyanate and the limits of detection are 0.0096 and 0.074 mM, respectively. What is more, the μPADs exhibited good specificity, good repeatability, and acceptable recoveries in artificial saliva. Therefore, the developed 3D sl-μPADs show a great potential to determine nitrite and thiocyanate for the assessment of the human health.

Keywords: colorimetric analysis; nitrite; spraying; thiocyanate; three-dimensional microfluidic devices.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
The diagram of the spraying prototyping technique for fabricating the three-dimensional single-layered paper-based microfluidic analytical devices (3D sl-μPADs). (a) a sheet of filter paper and two PMMA boards with the same design. (b) the paper and two PMMA boards were stacked together. (c) the first spraying process. (d) the device was dried at room temperature for 10 min. (e) the filter paper and two PMMA boards with different designs. (f) the paper and two PMMA boards were stacked together. (g) the second spraying process. (h) the excess materials were trimmed. (i) the finished layout of the 3D sl-μPADs.
Figure 2
Figure 2
Optimization of the times for pressing the spray nozzle for the spraying process.
Figure 3
Figure 3
Optimization of the drying conditions for the fabrication of 3D sl-μPADs.
Figure 4
Figure 4
The intersection of the 3D sl-µPADs captured under an optical microscope.
Figure 5
Figure 5
(A) The photograph of the water droplet on both sides of the 3D sl-µPADs. (B) The pictures are taken at different times after adding food dye (18 µL) to the central reservoir from the top surface of the 3D sl-µPADs.
Figure 6
Figure 6
The optical micrographs of the lacquer barrier in the presence of different solutions.
Figure 7
Figure 7
The RGB measurements for the individual assay and the multiplex assay: (A) 1 mM nitrite, (B) 2 mM thiocyanate.
Figure 8
Figure 8
Assay results for nitrite (A) and thiocyanate (B) based on the developed 3D sl-µPADs.
Figure 9
Figure 9
The specificity of the fabricated 3D sl-μPADs. The concentrations of nitrite and thiocyanate are 0.5 and 5 mM, respectively. The concentrations of the interferents are all 50 mM. Error bars represent the standard deviation of four parallel experiments.
Figure 10
Figure 10
The pictures of the top surface of the 3D sl-μPADs after adding different concentrations of sodium carboxymethylcellulose (SCMC) solutions in the central well.
See this image and copyright information in PMC

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