Impedimetric aptasensor for Pseudomonas aeruginosa by using a glassy carbon electrode modified with silver...

An aptasensor is described for the ultrasensitive detection of Pseudomonas aeruginosa (P. aeruginosa). A glassy carbon electrode (GCE) was first modified by electrodeposition of silver nanoparticles (AgNPs). Immobilization of NH₂-aptamer was covalently attached to the AgNP/GCE surface. The morphology, distribution and size of the sensor were characterized by field emission scanning electron microscopy. Cyclic voltammetry and electrical impedance spectroscopy were used to study conductivity of the aptasensor and the electrochemical properties. Detection of P. aeruginosa was carried out by evaluation of the charge transfer resistance after and before the adding of P.aeruginosa and by using the hexacyanoferrate redox system as an electrochemical probe. The impedance increases on going from 10² to 10⁷ CFU·mL^-1 concentrations of P. aeruginosa, and the detection limit is 33 CFU·mL^-1 (for S/N = 3). The assay was successfully applied for the determination of P. aeruginosa in spiker serum samples. Graphical abstract Schematic representation of an impedimetric assay for Pseudomonas aeruginosa by using a [Fe(CN)₆]^3-/4- probe based on immobilization of amino-modified aptamer onto a glassy carbon electrode (GCE) modified with silver nanoparticles (AgNPs): Incubation with P. aeruginosa leads to an increase of the charge-transfer resistance.