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

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 function-alized 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 & mu;M) estimated by the 3 & sigma; 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 & mu;M). Notably, the demonstration of the spike-and-recovery test for non-diluted human urine samples without any pretreatment clarified the feasi-bility 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.