ISFET and Dex-AgNPs based portable sensor for reusable and real-time determinations of concanavalin A and glucose on smartphone

In this paper, a portable real-time sensing device was built for Concanavalin A (Con A) and glucose detection using a smartphone. The ion-sensitive field-effect transistor (ISFET) functioning at a low working point was selected as a small-size, low-power transducer, and dextran-capped silver nanoparticles (Dex-AgNPs) served as sensitive nanoprobes on the ISFET gate. Using the affinity between Con A and carbohydrates, Con A can be captured, and thus directly detected by the ISFET/Dex-AgNPs unit; then glucose can be determined indirectly by removing Con A from the ISFET/Dex-AgNPs/Con A unit via competition with dextran . The mechanism of this competition does less harm to the sensor, allows the reusability of the sensing device, and overcomes the Debye screening of the FET device in saline solutions . Powered by a button cell, the handheld device attains excellent Con A (0.16 ng mL −1 ) and glucose (10 nM) detection limit, and can practically be used for at least 20 days.