Noninvasive Colorimetric Detection of Insulin Using a Chromogenic Substrate

At the peak of technologies such as continuous glucose monitoring and insulin delivery are available today, they still pose a challenge on the individuals to continuously monitor their glucose levels to keep their hypoglycemia in check. Apart from being expensive, the constant needles pricking, delay in reading venous blood glucose are common drawbacks of such technologies. The other methods for detecting insulin are enzyme-linked immunosorbent assay (ELISA), chemiluminescence immunoassay (CLIA), radioimmunoassay (RIA), chromatography. Especially in the pandemic era access to such device-based test methods is becoming increasingly difficult for resource-limited countries due to the economic collapse from the year 2020. To address the changing needs, in our lab, we have focused on developing a colorimetric noninvasive, highly selective, and rapid detection method for insulin detection as the model bioanalyte. Our sensor is based on taking advantage of the magnetic property of functionalized nanoparticles with sandwich immunoassay. The method is selective and accurate. Insulin-bound HRP conjugate upon addition of the chromogenic substrate, 3′, 5, 5′-tetramethylbenzidine develops a blue color. The intensity of the color directly correlates with the insulin concentration. Our method can detect picomolar insulin within five mins in buffer solutions. Testing real biofluids is our ongoing effort.