Abstract
The blood glucose meter (BGM) is the most successful and widely used portable device for point-of-care (POC) tests. However, its usage is limited to self-monitoring of blood glucose level only. To expand the targets that BGM can monitor while taking advantage of more than 50 years of technology development, we report herein the use of BGM to detect and quantify insulin and glycated hemoglobin (HbA1c), which are useful hormone for diabetes treatment and biomarker for diabetes monitoring, respectively. The method is based on invertase enzyme-linked immunosorbent assay (iELISA) and phosphatase enzyme-linked immunosorbent assay (pELISA) that convert BGM-inert sucrose or glucose-1-phosphate into glucose in the presence of insulin and glycated hemoglobin, respectively. In both assays, monoclonal antibodies specific to the targets (insulin or HbA1c) are immobilized onto magnetic beads to capture the targets in samples, followed by the formation of sandwich complex with the polyclonal antibodies conjugated to either invertase or phosphatase. The quantification of the targets is then realized by the production of glucose from the biochemical reactions catalyzed by the polyclonal antibody-enzyme conjugates bound on the surface of the magnetic beads. Such a method can be generally applied to a wide range of other biomarkers using the corresponding antibodies.