Multiplex Smartphone Diagnostics
Increasing computing power in smartphones allows for their transformation into point-of-care diagnostic devices. Mobile medical diagnostic applications enable utilization of the processing capabilities of smartphones through their cameras. Hardware attach
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Introduction Smartphone applications utilizing their built-in cameras have been developed for dermatology [1], microscopy [2, 3], ophthalmology [4], chemical analyses [5], and paper-based diagnostic devices [6–8]. Although they are normally optimized for photography, smartphone camera algorithms can be modified so that sufficient information can be extracted to enable their use as diagnostic tools. Here, we describe the use of a stand-alone smartphone application that compensates for lighting variability and fully utilizes the sensor capabilities of smartphone cameras. This mobile application is capable of analyzing multiple colorimetric tests allowing for multiplex molecular analyses in scenarios such environmental monitoring, veterinary screening, and medical diagnostics. Specifically, we describe the detailed methodology for a three-analyte commercial test (glucose, protein, and pH) that can be extrapolated for 12 or more analytes. The device uses test strips similar to commercial kits that are utilized for monitoring kidney and liver functions, or screening for diabetes [9]. Although these analytes are commonly measured in laboratories, there is an increasing demand for home
Paul C. Guest (ed.), Multiplex Biomarker Techniques: Methods and Applications, Methods in Molecular Biology, vol. 1546, DOI 10.1007/978-1-4939-6730-8_26, © Springer Science+Business Media LLC 2017
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or workplace monitoring due to expanding healthcare expenditures. It is important for diagnosed patients or individuals at risk to continuously monitor their conditions to limit disease progression.
2 2.1
Materials (See Note 1) Artificial Urine
1. Prepare artificial urine stock solutions by varying the concentrations of protein and glucose, and the pH level following previously reported protocols [10] and as shown in Table 1. 2. Prepare 200 mL of each stock solution in individual 10 mL vials. 3. The protein concentrations should be 0 mg/dL; 30 mg/dL; 100 mg/dL; and 500 mg/dL. 4. Adjust the pH values to 5, 6, 7, 8, and 9. Table 1 Stock concentrations of reagents in artificial urine Component
Quantity (g) Concentration (mM)
Peptone L
37
1
Yeast extract
0.005
N/A
Lactic acid
0.1
1.1
Citric acid
0.4
2
Sodium bicarbonate
2.1
25
Urea
10
170
Uric acid
0.07
0.4
Creatinine
0.8
7
Calcium chloride (2H2O)
0.37
2.5
Sodium chloride
5.2
90
Iron II sulphate (7H2O)
0.0012
0.005
Magnesium sulphate (7H2O)
0.49
2
Sodium sulphate (10H2O)
3.2
10
Potassium dihydrogen phosphate
0.95
7
Dipotassium hydrogen phosphate
1.2
7
Ammonium chloride
1.3
25
Distilled water to 1 L Hydrochloric acid to specific pH Sodium hydroxide to specific pH
Multiplex Smartphone Diagnostics
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5. The glucose values should be 0 mg/dL; 50 mg/dL; 100 mg/ dL; 300 mg/dL; and 1000 mg/dL.
3 3.1
Methods (See Note 2) Basic Protocol
1. Calibrate the smartphone using three test strips dipped into each of the 15 vials prepared as above. 2. Dip the test strip into artificial urine for 1 s and ensure th
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