Sensing of electrolytes in urine using a miniaturized paper-based device - PubMed (original) (raw)
Sensing of electrolytes in urine using a miniaturized paper-based device
Fariba Ghaderinezhad et al. Sci Rep. 2020.
Abstract
Analyzing electrolytes in urine, such as sodium, potassium, calcium, chloride, and nitrite, has significant diagnostic value in detecting various conditions, such as kidney disorder, urinary stone disease, urinary tract infection, and cystic fibrosis. Ideally, by regularly monitoring these ions with the convenience of dipsticks and portable tools, such as cellphones, informed decision making is possible to control the consumption of these ions. Here, we report a paper-based sensor for measuring the concentration of sodium, potassium, calcium, chloride, and nitrite in urine, accurately quantified using a smartphone-enabled platform. By testing the device with both Tris buffer and artificial urine containing a wide range of electrolyte concentrations, we demonstrate that the proposed device can be used for detecting potassium, calcium, chloride, and nitrite within the whole physiological range of concentrations, and for binary quantification of sodium concentration.
Conflict of interest statement
The authors declare no competing interests.
Figures
Figure 1
Schematic procedure of measuring the concentration of cations. (a) Chromatography paper cut with laser cutter (Ø = 0.25 in). (b) Depositing 2 μl of fluorescent probe (Sodium green, PBFI, and Fluozin) on paper. (c) Adding the solution that contains the Na+, K+, or Ca2+ ions. (d) Reading the fluorescent intensity by a smartphone-enabled platform. (e) Chelation mechanism of fluorescent probes (from top to bottom: sodium green, PBFI, and Fluozin). (f) Illustration of the portable smartphone-based reader.
Figure 2
Investigating the effect of elapsed time on fluorescent intensity of probes for (a) Na+, (b) K+ and (c) Ca2+ ions for a range of concentrations. Elapsed time refers to the time passed between depositing the ion solution on the paper and reading the intensity: elapsed time varied from 0 to 3 h. Pink shaded area shows the physiological ion concentration range in human urine.
Figure 3
Selectivity of fluorescent probes. Selectivity of 25 μM (a) Sodium green, (b) PBFI, and (c) Fluozin towards different ions in Tris buffer solution (150 mM, pH 7.4) at concentrations of 1, 10, 100 mM, and their maximum physiological concentration. Excitation/Emission wavelength of Sodium Green (λex/λem: 485 nm/541 nm), PBFI (λex/λem: 360 nm/450 nm), and Fluozin (λex/λem: 485 nm/541 nm). Error bars represent the standard error of the mean (n = 6).
Figure 4
Na+, K+, Ca2+, Cl−, and NO2- ion concentration measurements in Tris buffer (150 mM, pH 7.4) using fluorescent probes (Sodium Green, PBFI, and Fluozin, respectively) and the RGB model. Calibration curves of (a) Na+, (b) K+, and (c) Ca2+ ions on paper matrix at a constant probe concentration of 25 μM in DMSO (Sodium Green (λex/λem: 485 nm/541 nm), PBFI (λex/λem: 360 nm/450 nm), and Fluozin (λex/λem: 485 nm/541 nm)). Red, Blue, and Green channels of the RGB model for different concentrations of (d) Cl− and (e) NO2- ions. Insets in (a) and (b) show the logarithmic scale of Na+ and K+ concentrations, respectively. Error bars represent standard error of the mean (n = 6). Pink shaded area shows the physiological ion concentration range in human urine.
Figure 5
Na+, K+, Ca2+, Cl−, and NO2- ion measurements in artificial urine (pH 6) using fluorescent probes (Sodium Green, PBFI, and Fluozin, respectively) and the RGB model. Calibration curves of (a) Na+, (b) K+, and (c) Ca2+ ions on paper matrix at a constant probe concentration of 25 μM in DMSO (Sodium Green (λex/λem: 485 nm/541 nm), PBFI (λex/λem: 360 nm/450 nm), and Fluozin (λex/λem: 485 nm/541 nm)). Red, Blue, and Green channels of the RGB model for different concentrations of (d) Cl− and (e) NO2- ions. Insets in (a) and (b) show the logarithmic scale of Na+ and K+ concentrations, respectively. Error bars represent standard error of the mean (n = 6). Pink shaded area shows the physiological ion concentration range in human urine.
Figure 6
Na+, K+, and Ca2+ ion measurements in artificial urine (pH 6) using smartphone-enabled platform. Calibration curves of (a) Na+, (b) K+, and (c) Ca2+ ions on paper matrix at a constant probe concentration of 250 μM in DMSO (Sodium Green (λex/λem: 485 nm/541 nm), PBFI (λex/λem: 360 nm/450 nm), and Fluozin (λex/λem: 485 nm/541 nm)). Insets show the logarithmic scale of Na+, K+, and Ca2+ concentrations, respectively. Error bars represent standard error of the mean (n = 6). Pink shaded area shows the physiological ion concentration range in human urine.
References
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