Detecting Glucose Concentration in Biological Fluids

Microfluidics paper-based diagnostics are novel and inexpensive point-of-care devices with significant potential for use in developing countries. These devices work on the principle of capillary action in a porous substrate in which the wicking distance is proportional to the square root of the time taken to travel across the porous substrate, illustrated by the Lucas-Washburn equation. These can be used to diagnose multiple diseases by measuring parameters like glucose levels and lipid levels in biological fluids. This paper focuses on an innovative and simple point-of-care diagnostic to measure glucose concentration in different solutions. The experimental device has a testing region coated with glucose oxidase-peroxidase mixed with potassium iodide. On reaching the testing zone, the glucose solution reacts with glucose oxidase to yield gluconic acid and hydrogen peroxide. In the next stage, hydrogen peroxide reacts with potassium iodide, liberating iodine. [The iodine develops colorimetric assays ranging from light pink to brown depending on the glucose concentration. A smartphone camera was used to capture the colorimetric assay, and the software ImageJ to convert it into an 8-bit image. The mean grey intensity of each colorimetric assay and the respective glucose concentrations were calculated using ImageJ. The results show a linear relationship, y=0.264x+67.3 (y: mean grey intensity, x: glucose concentration), between glucose concentration and mean grey intensity with a correlation coefficient of 0.97 (2 s.f), indicating a strong relationship between these variables. This innovation can be further developed to diagnose diabetes in low-income and rural communities and substitute for expensive and unaffordable diagnostic tools.