Micro Paper-Based Electrochemical Device for Small Molecule Diabetes Biomarkers

Abstract

Glucose monitoring has been widely established as a successful diabetes management system. However, non-glucose markers such as, autoantibodies, hormones, proteins, and other small molecules can provide better assessments for the prediction and management of the disorder. Nevertheless, the challenges our research community faces in designing an analytical device for such markers, especially the small molecules, are the dynamic range, limit of detection, selective isolation of the analyte, higher background noise due to clinical matrix, and ability to transform the system into a cheap point-of-care device. Here, we have designed a paper-based graphene amperometric sensor that can detect a model hormone (insulin, 5808 Da) from complex serum matrix. The paper platform provides for a cheap, on-site filtration system that limits the mobility of larger molecules, and upon combining with a double-blocking step before analyte detection greatly minimizes the background noise. Insulin aptamers acts as a capture probe to selectively identify and bind to insulin. Graphene, coated on working electrode, with its superior electrical conductivity provides for improved analytical features of the detection system. The amperometric signals are achieved by flowing a solution mixture of 1 mM hydroquinone mediator and 0.5 mM H2O2 and applying a constant potential of -0.1 V. The paper-based device exhibits a picomolar limit of detection for serum insulin with a reasonably good dynamic range. Our future prospect is to advance this device further for detecting even smaller molecules (< 500 Da) in complex clinical matrices, for which no current assay methods are available.