An Ultrasensitive Electrochemical Immunosensor for in Situ Detection of GABA in Plant Leaves

Gamma-aminobutyric acid (GABA) is involved in the signal transduction and metabolism of various substances in plants. Its in vivo detection in plants is of great importance for understanding its physiological role. In this study, an ultrasensitive electrochemical immunosensor is developed for in vivo detecting GABA in plants based on screen printed electrode (SPE) electrode. Gold nanoparticles (Au NP) was electrodeposited on the SPE to improve the conductivity of the electrode. Nanocomposite of ferrocene-Carboxylated graphene oxide-carboxylated multi-walled carbon nanotubes (Fc-GO-MWCNT) was fabricated on the electrode to improve the electrochemical properties of the sensor, and Fc was used to generate electrochemical signals. Then polydopamine (PDA) was electropolymerized on the electrode to improve the electrochemical activity of the sensor and increase the loading amount of GABA antibody. The as-prepared immunosensor shows the widest detection range of 10 fM to 10 mM, and lowest detection limit of 1.9 fM (S/N=3) for GABA. This immunosensor was applied for in vivo detecting GABA in the cucumber leaves under salt stress. Our sensor is the first electrochemical immunosensor for in vivo detecting GABA in plant. It proposes a new strategy for the development of immunosensor for in vivo detection of biomolecules in plants.