Printed Organic Transistor‐Based Enzyme Sensor for Continuous Glucose Monitoring in Wearable Healthcare Applications

Abstract

A printed extended‐gate‐type organic transistor‐based enzyme sensor for the continuous monitoring of D‐glucose has been developed through a simple modification of the electrical circuit. The sensor is composed of a glucose oxidase (GOx)/Prussian blue (PB)‐modified extended‐gate electrode and an Ag/AgCl reference electrode, which are connected to the gate and source electrodes of an organic transistor, respectively. The GOx/PB‐modified extended‐gate electrode and Ag/AgCl reference electrode were short‐circuited by an external resistor to spontaneously induce redox cycling of PB. Continuous monitoring of the source‐drain current of the organic transistor for various concentrations of D‐glucose was successfully demonstrated in this system. This is the first report of the transistor‐based enzyme sensor exhibiting reversible response to the analytes in physiologically buffered solution without the addition of any chemical reagents. This new type of printed organic transistor‐based enzyme sensor will greatly contribute to the development of wearable biosensors for non‐invasive monitoring of biomarkers in externally secreted bodily fluids such as tears, saliva, and sweat.

Recent Advances in Immobilization Strategies for Biomolecules in Sensors Using Organic Field-Effect Transistors

“…Since the redox reaction of PB is irreversible after an enzymatic reaction, the response of traditional extendedgate enzyme sensors to the analyte is one-time only. Mano et al [27] fixed GO x /chitosan on an extended-gate electrode modified by PB-carbon. By introducing an external resistor and simply modifying the circuit design, the extendedgate electrode was short-circuited with a reference electrode (compare Fig.…”

“…c Schematic illustrations of the reac-tion process of enzyme and PB in an enzyme electrode on the sensor chip (reprinted from [25] with permission from MDPI). d Schematic view of the structure of extended-gate type organic transistor-based enzyme sensor (reprinted from [27] with permission from Wiley) for the realization of direct interaction between the OSC and an analyte. However, most organic thin films cannot remain stable in the process of chemical modification.…”

An L-lactate Biosensor Based on Printed Organic Inverter Circuitry and with a Tunable Detection Limit

“…The fabrication process for the sensor device was similar to that in our previous report. (28) In short, silver nanoparticle ink in a hydrocarbon-based solution (Harima Chemicals, NPS-JL) was printed on a glass slide or a polyethylene naphthalate (PEN) film substrate (125 μm thickness) as a gate electrode using an inkjet printer (Fujifilm, Dimatix DMP2831). After sintering silver nanoparticles for 30 min at 120 ℃ in air ambient, a 150-nm-thick parylene (KISCO, diX-SR) gate dielectric layer was formed by chemical vapor deposition.…”

“…The fabrication process for the electrode was similar to our previous report. (28) In summary, a Au electrode pattern composed of an active area (3 × 5 mm 2 ) connected to a narrow lead line pattern (1 mm width, 3 cm length) was fabricated by thermal evaporation on a PEN film substrate (125 μm thickness) through a stencil mask. The active area was modified with carbongraphite ink including a redox compound of Prussian blue (PB-carbon) (C2070424P2, Gwent Inc.) and 10 µL of a mixture solution composed of 1 U µL −1 lactate oxidase (LOx, TOYOBO Co., Ltd.) in 100 mM phosphate buffer (pH 6.8, Nakalai Tesque) and 0.1 wt% chitosan (Junsei Chemical) in 50 mM HCl (pH 5.4) at the ratio 1.4 : 10.…”

Towards organic neuromorphic devices for adaptive sensing and novel computing paradigms in bioelectronics

“…23,24 Using these concepts, a wide variety of sensors have been developed, ranging from in vitro to in vivo or wearables. The latter is useful for non-invasive monitoring of biomarkers such as long-term and continuous glucose monitoring 25 or pH sensing. 9 Towards this direction, cheap and disposable devices were recently shown, such as a fully inkjet-printed glucose sensor.…”