Development of polydopamine functionalized Co-EDTA complex-based electrochemical aptasensor for precise monitoring of Pseudomonas aeruginosa

Abstract

Despite a myriad of electrochemical sensors, the challenge of achieving sensitive and selective detection of the opportunistic pathogenic bacterium Pseudomonas aeruginosa (P. aeruginosa) in low concentrations remains. To meet this need, herein we developed a novel sensing platform based on polydopamine (PDA)-functionalized cobalt–nitrogen–carbon (Co–NC) nanoparticles (NPs) (PDA@Co–NC-NPs) at the surface of a graphitic pencil electrode (GPE) for rapid, ultrasensitive, and selective detection of P. aeruginosa. Ethylene diamine tetraacetic acid (EDTA) acts as a nitrogen precursor as well as a surface-stabilizing agent for cobalt–nitrogen–carbon nanoparticle (Co–NC NPs) synthesis, while PDA-based surface functionalization boosts the conductivity and biocompatibility of the synthesized aptasensor. The PDA@Co–NC-NPs/GPE with excellent conductivity and biocompatibility was then used to conjugate with the specific P. aeruginosa aptamer as a sensing element. Morphological and compositional analyses of the Co-EDTA complex-derived Co–NC NPs were performed using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analysis. Each step in the fabrication of PDA@Co–NC-NPs/GPE was optimized and characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The fabricated aptasensor exhibits high sensitivity and reproducibility, a wide linear detection range of 10¹–10⁶ CFU mL⁻¹, a low limit of detection (LOD) of 2.8 CFU mL⁻¹ for detection of P. aeruginosa, and was also capable of accurate detection and determination of P. aeruginosa in spiked cow's milk as a real-world sample.