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

• Broad spectrum microcystin detection using Adda-specific monoclonal antibodies.
• Highly stable and sensitive bio-platform made from polytyramine and gold nanoparticles.
• Low detection limit of 2.1 × 10−14 M MC-LR standard and stability for 30 regeneration-assay cycles.
• Short analytical time and real-time information on antigen–antibody binding kinetics.
• Biosensor can be used for microcystin evaluation in environmental matrix with minimal sample preparation.

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.

Specific monoclonal antibodies were immobilized on a gold surface modified with polytyramine and gold nanoparticles. Introduction of the target microcystin in the immunosensor resulted in a capacitance decrease whereas in the blank sample it remained unchanged.Figure optionsDownload as PowerPoint slide