Development of a label-free impedimetric immunosensor for the detection of respiratory syncytial virus

Respiratory syncytial virus (RSV) is responsible for outbreaks of bronchiolitis, bronchitis, and pneumonia and is effective and lethal in children under five years old. Current RSV detection methods are expensive, time-consuming, and require highly skilled personnel. Therefore, we developed a cost-effective impedimetric immunosensor for the detection of RSV based on a pencil graphite electrode (PGE) modified with a polymeric film derived from 3-amino phenylacetic acid. The current responses in the potassium ferricyanide and methylene blue solutions suggest the presence of unchanged carboxylic acid groups in the polymer. With a similar number of electrons involved in the first step of the reaction and electron/proton ratio to those proposed for aniline, a mechanism for electropolymerization was proposed. The immunosensor was assembled by activating the carboxyl groups via an EDC/NHS nucleophilic substitution reaction with the amino groups present in the anti-RSV monoclonal antibody (mAb). The detection was performed using electrochemical impedance spectroscopy, and the data were evaluated using equivalent circuits. The charge transfer resistance values increased as PGE was modified in the following order: PGE < PGE/polymer < PGE/polymer/mAb < PGE/polymer/mAb/virus. 100 ng of mAb was used, and the immobilization times for mAb and blocker were 3 h and 50 min, respectively. The response time for RSV immobilization was 30 min. The limit of detection was 22.54 PFU mL⁻¹, and the limit of quantification was 75.12 PFU mL⁻¹, with a linear range from 50 – 2000 PFU mL⁻¹, demonstrating that the proposed immunosensor is a viable alternative for the detection of RSV.

Graphical abstract