A wireless-electrodeless quartz crystal microbalance method for non-enzymatic glucose monitoring

Continuous glucose monitoring (CGM) in vivo is required for tight glycaemic control. Enzyme-free glucose sensors were proposed to solve the problems of daily invasive calibration and short lifespan of the current enzyme based continuous glucose monitors. In this report, a wireless-electrodeless quartz crystal microbalance method that tracks film dissipation was developed and proposed as a basis for a miniaturized implantable glucose monitor. An AT-cut blank quartz disc (14 mm in diameter) was stimulated wirelessly by a planar copper coil and working in the ring-down mode at a fixed frequency point (˜6 MHz). A 600–800 nm (3-acrylamidopropyl) tri-methylammonium chloride modified poly(acrylamide- co -3-acrylamideophenylboronic acid) hydrogel film was coated on the quartz disc for glucose sensing. The viscosity variations of the polymer film induced by the glucose binding were observed by measuring the dissipation change of the sensor. The linear relationship between the dissipation response and the glucose concentration was achieved in the range of ˜0 to 10 mM, with a sensitivity of 2 × 10 −5  mM −1 and a response time of around 5 min at 37 °C. Furthermore, the response of the modified film to other interferences including the fructose, galactose, mannose, uric acid was dramatically reduced. The results suggest the wireless-electrodeless quartz crystal microbalance with dissipation system has the potential to be used as a subcutaneously implanted real-time glucose monitor.