Colorimetric Schirmer strip for tear glucose detection

Abstract

Human tears have attracted attention with easy-accessible indicators of healthcare monitoring. Recently self-monitoring of tear glucose in place of blood glucose has been developed with microfluidic paper-based analysis for a non-invasive diagnosis of diabetes. However, most previous works still have many limitations in unstable sample collection, low sensitivity, and insufficient sample volume. Here, we report a colorimetric Schirmer strip with preconcentration for tear glucose detection. A wax barrier on a paper strip enables tear collection of a fixed quantity as well as biocompatible incorporation of tear collection and detection by preventing flow reversal of reagents. Additional solvent was injected on a sampling site after tear collection, which accumulates the dispersed glucose into active site by capillary-driven flow for signal amplification. Glucose concentration was quantitatively detected at 0.1-2 mM by using a simple colorimetric method without any further image processing. The color changes in glucose concentration were clearly distinguishable between normal and diabetic patient-level. The colorimetric paper strip allows straightforward sensing platform for noninvasive diagnosis of diabetes and direct application of paper-based technology to the human body fluids.