Aptamer-Functionalized Microchannel-Gated Field-Effect Transistor Biosensor for In Vivo Detection of Dopamine

Field-effect transistors (FETs) have been widely applied in biosensors due to their inherent signal amplification capabilities. Glass-based microchannels offer excellent mechanical rigidity and facile surface functionalization, which have been applied in vivo. In this study, a microchannel was coupled with a junction FET (JFET) to design a sensitive biosensor for dopamine (DA, chosen as a model target) detection. A specific, negatively charged DA aptamer was immobilized on the inner wall of the microchannel as the recognition element, and the microchannel served as an extended gate connected between the electrochemical workstation and the gate of the JFET. Acting as a tunable resistor, the microchannel modulates the voltage distribution within the circuit. Since DA is positively charged, specific binding of the target to the aptamer reduces the local negative charge density of the microchannel, thereby altering the effective gate voltage. The subtle resistance shift induced by DA resulted in a change in the gate voltage, leading to a significant change in channel current. The system response exhibits a linear relationship with the logarithm of the target concentration over the range from 1.00 nM to 10.0 μM, with a detection limit as low as 0.15 nM (S/N = 3). The constructed microchannel-gated JFET biosensor exhibited high sensitivity and selectivity and was successfully applied to detect the DA concentration in the human serum and striatum of Sprague-Dawley rats, demonstrating its promising potential for trace biomolecule detection in vivo.