Detection of protein biomarker using a blood glucose meter.

mHeath technologies are recognized to play important roles in the future of personal care and medicine. However, their full potentials have not been reached, as most of current technologies are restricted to monitoring physical and behavioral parameters, such as body temperature, heart rate, blood pressure, and physical movement, while direct monitoring of biomarkers in body fluids can provide much more accurate and useful information for medical diagnostics. A major barrier to realizing the full potential of mHealth is the high costs and long cycles of developing mHealth devices capable of monitoring biomarkers in body fluids. To lower the costs and shorten the developmental cycle, we have demonstrated the leveraging of the most successful portable medical monitoring device on the market, the blood glucose meter (BGM), with FDA-approved smartphone technologies that allow for wireless transmission and remote monitoring of a wide range of non-glucose targets. In this protocol, an aptamer-based assay for quantification of interferon-γ (IFN-γ) using an off-the-shelf BGM is described. In this assay, an aptamer-based target recognition system is employed. When IFN-γ binds to the aptamer, it triggers the release of a reporter enzyme, invertase, which can catalyze the conversion of sucrose (not detected by BGM) to glucose. The glucose being produced is then detected using a BGM. The system mimics a competitive enzyme-linked immunosorbent assay (ELISA), where the traditional immunoassay is replaced by an aptamer binding assay; the reporter protein is replaced by invertase, and finally the optical or fluorescence detector is replaced with widely available BGMs.