Institute for Measurement Systems and Sensor Technology, Technical University of Munich, Munich 80333, Germany.
West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu 610041, China.
Anal Methods. 2021 Oct 8;13(38):4361-4369. doi: 10.1039/d1ay01209f.
Colorimetric tests for at-home health monitoring became popular 50 years ago with the advent of the urinalysis test strips, due to their reduced costs, practicality, and ease of operation. However, developing digital systems that can interface these sensors in an efficient manner remains a challenge. Efforts have been put towards the development of portable optical readout systems, such as smartphones. However, their use in daily settings is still limited by their error-prone nature associated to optical noise from the ambient lighting, and their low sensitivity. Here, a smartphone application (Colourine) to readout colorimetric signals was developed on Android OS and tested on commercial urinalysis test strips for pH, proteins, and glucose detection. The novelty of this approach includes two features: a pre-calibration step where the user is asked to take a photo of the commercial reference chart, and a CIE-RGB-to-HSV color space transformation of the acquired data. These two elements allow the background noise given by environmental lighting to be minimized. The sensors were characterized in the ambient light range 100-400 lx, yielding a reliable output. Readouts were taken from urine strips in buffer solutions of pH (5.0-9.0 units), proteins (0-500 mg dL) and glucose (0-1000 mg dL), yielding a limit of detection (LOD) of 0.13 units (pH), 7.5 mg dL (proteins) and 22 mg dL (glucose), resulting in an average LOD decrease by about 2.8 fold compared to the visual method.
比色法检测技术在 50 年前随着尿液分析试条的问世而变得流行起来，因为它降低了成本、提高了实用性并简化了操作。然而，开发能够有效连接这些传感器的数字系统仍然是一个挑战。人们一直在努力开发便携式光学读出系统，如智能手机。然而，它们在日常环境中的使用仍然受到光学噪声和环境光照带来的错误、以及灵敏度低的限制。在此，我们开发了一个用于读取比色信号的智能手机应用程序（Colourine），并在商业尿液分析试条上对 pH 值、蛋白质和葡萄糖的检测进行了测试。该方法的新颖之处包括两个特点：用户被要求拍摄商业参考图表的预校准步骤，以及对采集数据进行 CIE-RGB 到 HSV 颜色空间的转换。这两个元素允许将环境照明产生的背景噪声降到最低。在 100-400 lx 的环境光范围内对传感器进行了表征，得到了可靠的输出。在 pH（5.0-9.0 单位）、蛋白质（0-500 mg dL）和葡萄糖（0-1000 mg dL）的缓冲溶液中进行了尿液试条的读取，得出的检测限（LOD）分别为 0.13 个单位（pH）、7.5 mg dL（蛋白质）和 22 mg dL（葡萄糖），与视觉方法相比，平均 LOD 降低了约 2.8 倍。
