Acoustic biosensor for monitoring antibody immobilization and neurotransmitter GABA in real-time

The conventional detection methods for neurotransmitter γ-aminobutyric acid (GABA) have concentrated on using high performance liquid chromatography (HPLC) and enzymatic reaction, which do not allow for much needed real-time monitoring. Here we report a novel acoustic impedance immunosensor for real-time measurement of GABA in buffer solution. The adsorption process of anti-GABA on a well-defined gold electrode surface of the quartz crystal and the immuno-interaction between GABA and anti-GABA in liquid were measured in real-time by a network analyzer and changes in the electrical equivalent circuit parameters (Δf, C0, R1, L1, C1) were recorded simultaneously. These impedance parameters were used to analyze changes in the interfacial viscoelastic properties during adsorption of liquid anti-GABA in air and during binding between GABA and anti-GABA in liquid phase. It was found that water plays a critical role in the antibody immobilization process. We also found that the proposed immunosensor can detect down to 38.0 μM of GABA in buffer solution. The specificity of this immunosensor against common neurochemical interferents, like l-aspartic acid, was also investigated. The electrode surface of sensor was also characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). We conclude that the acoustic immunosensor offers a novel and promising approach to monitor the dynamics of neurotransmitter GABA concentration in liquid in real-time.