Smartphone assisted portable biochip for non-invasive simultaneous monitoring of glucose and insulin towards precise diagnosis of prediabetes/diabetes

Diabetes is a chronic disease with metabolic disorders. Prediabetes is a condition in which the blood glucose levels are not high enough to be diagnosed as diabetes, but insulin resistance and β-cell dysfunction are simultaneously present. Glucose and insulin are important biomarkers for diagnosing diabetes/prediabetes. It is critical and essential to monitor glucose and insulin levels to achieve the early and precise diagnosis, timely prevention and scientific management of diabetes/prediabetes. Here, an electrochemical aptasensor on screen-printed carbon electrode (SPCE) was developed for non-invasive simultaneous real-time detection of glucose and insulin in saliva. Two thiolated aptamers specific to glucose and insulin, respectively, were fabricated onto gold nanoparticles (AuNPs) decorated SPCE through Au-S bonds to form the sensing interface terminated with redox probes methylene blue (SPCE-AuNPs-GluApt-MB and SPCE-AuNPs-InsApt-MB). With the electrochemical signal readout on SPCE, the sensing interface responded to glucose linearly in the range of 0.1-50 mM with a detection limit of 0.08 mM, and responded linearly to insulin in the range of 0.05-15 nM with a detection limit of 0.85 nM. Integration of a SPCE based sensing interface with a portable wireless biochip, the continuous real-time detection of glucose and insulin in saliva was successfully realized with smartphone signal readout in a non-invasive way, demonstrating its potential as a non-invasive and reliable tool for precise diagnosis of diabetes/prediabetes in a point of care fashion.