Development of a real-time capacitive biosensor for cyclic cyanotoxic peptides based on Adda-specific antibodies

The harmful effects of cyanotoxins in surface waters have led to increasing demands for accurate early warning methods. This study proposes a capacitive immunosensor for broad-spectrum detection of the group of toxic cyclic peptides called microcystins (∼80 congeners) at very low concentration levels. The novel analytical platform offers significant advances compared to the existing methods. Monoclonal antibodies (mAbs, clone AD4G2) that recognize a common element of microcystins were used to construct the biosensing layer. Initially, a stable insulating anchor layer for the mAbs was made by electropolymerization of tyramine onto a gold electrode surface, with subsequent incorporation of gold nanoparticles (AuNPs) on the glutaraldehyde (5%) activated polytyramine surface. The biosensor responded linearly to microcystin concentrations from 1 × 10⁻¹³ M to 1 × 10⁻¹⁰ M MC-LR standard with a limit of detection of 2.1 × 10⁻¹⁴ M. The stability of the biosensor was evaluated by repeated measurements of the antigen and by determining the capacitance change relative to the original response, which decreased below 90% after the 30th cycle.