Abstract
In this work, a label-free colorimetric assay was developed for the determination of urine glucose using smartphone ambient-light sensor (ALS). Using horseradish peroxidase—hydrogen peroxide—3,3′,5,5′-tetramethylbenzidine (HRP-H2O2-TMB) colored system, quantitative H2O2 was added to samples to-be-determined for deepest color. The presence of glucose oxidase in urine led to the formation of H2O2 and the reduction of TMBred. As a result of this, the color of the urine faded and the solution changed from deep blue to light blue. We measured the illuminance of the transmitted light by a smartphone ambient light sensor, and thereby color changes were used to calculate the content of urine glucose. After method validation, this colorimetric assay was practically applied for the determination of urine samples from diabetic patients. Good linearity was obtained in the range of 0.039–10.000 mg/mL (R2 = 0.998), and a limit of detection was 0.005 mg/mL. Our method was had high accuracy, sensitivity, simplicity, rapidity, and visualization, providing a new sensor to be potentially applicable for point-of-care detection of urine glucose.
Highlights
Diabetes is a metabolic disease with high incidence rate in modern society, and there are globally millions of people suffering from this disease [1]
As there was correlation between glucose content in the sample solution and light intensity acquired by the smartphone, the transformation of solution color to light intensity could be the basis for quantitative calculation
We developed a label-free colorimetric assay using a smartphone ambient-light sensor that could directly determine the urine glucose at the point-of-care
Summary
Diabetes is a metabolic disease with high incidence rate in modern society, and there are globally millions of people suffering from this disease [1]. Frequent blood-glucose monitoring can bring benefits to the health of diabetic patients [2], the disinfection process and stabbing pain during blood collection lead to very poor compliance. The content of urine glucose is another important index for the clinical diagnosis and routine self-monitoring of the patients [3,4,5]. As urine glucose detection is non-invasive, patients’ compliance is good, and more emphasis was placed on urine glucose determination. Colorimetric analysis is a method to determine the content of a substance to-be-measured by the color of the solution that features good stability, low cost, and implementation simplicity, making it widely applied to clinical diagnosis and detection, including in glucose analysis [3,6,7,8]. Though colorimetric analysis is strongly dependent on measurement, specific equipment such as ultraviolet-visible spectrometer, fluorescence spectrometer, Raman spectrometer, or an electrochemical workstation is required for data collection
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