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.

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A simple, fast, and highly sensitive direct competitive enzyme-linked immunosorbent assay (ELISA) based on bovine serum albumin (BSA) antigen labeled amine-terminated silicon dioxide (SiO-NH-BSA) nanoparticles was developed to determine residual BSA in vaccines. As nano-ELISA using nanomaterials with a very high surface-to-volume ratio has emerged as a promising strategy, SiO-NH-BSA nanoparticles were prepared in this study by the coupling of BSA to SiO nanoparticles modified with amidogen, followed by the quantification of BSA via a direct competitive binding of BSA-antigen-labeled SiO nanoparticles to anti-BSA antibody conjugated with horseradish peroxidase. The validation study showed that the linear range of this method was from 1 to 90 ng/mL (r = 0.998) and the limit of detection was 0.67 ng/mL. The intra-assay and interassay coefficients of variation were less than 10% at three concentrations (10, 40, and 70 ng/mL), and the recovery was 92.4%, indicating good specificity. As a proof of principle, this new method was applied in the analysis of residual BSA in five different vaccines. Bland-Altman plots revealed that there was no significant difference in the accuracy and precision between our new method and the most commonly used sandwich ELISA. From the results taken together, the new method developed in this study is more sensitive and facile with lower cost and thus demonstrated potential to be applied in the quality control of biological products. Graphical Abstract Illustration of the procedures of the direct competitive enzyme immunoassay.