An extended-gate-type organic transistor-based enzymatic sensor for dopamine detection in human urine

Abstract

Given the increasing attention paid to health monitoring in daily life, the development of easy-to-handle sensor devices is desirable. Therefore, an appropriate sensor design for highly selective detection of a specific biomarker in human samples is required to obtain accurate analytical results. Hence, we report an extended-gate-type organic field-effect transistor (OFET)-based biosensor functionalized with a laccase-linked mediator for the detection of dopamine in human urine. In the detection mechanism, the oxidation of dopamine by laccase with a mediator (i.e., an N-ethylphenazonium moiety) induces an electron relay on the extended-gate electrode, resulting in a quantitative change in the transistor characteristics. Using an extended-gate electrode functionalized with an enzyme-linked self-assembled monolayer, the OFET selectively detected the target dopamine over the interferents. The limit of detection (i.e., 0.029 ppm, 0.19 μM) estimated by the 3σ method suggests the usability of the proposed OFET-based sensor for the detection of dopamine levels in human urine, taking into consideration of actual concentration of urinary dopamine (< 0.39 ppm, 2.5 μM). Notably, the demonstration of the spike-and-recovery test for non-diluted human urine samples without any pretreatment clarified the feasibility of the OFET-based biosensor for urinalysis, judging by the highly accurate recovery rate (97−104%). We believe that the designed OFET device for urinalysis is a potent sensor platform for accurate monitoring of biomarker levels.