Polypyrrole functionalized (Ti3C2Tx–SnO2 NPs) nanocomposite-based hybrid capacitive electrode for electrochemical detection of Klebsiella pneumoniae

Abstract

Bacterial detection is crucial for accurate clinical diagnostics and effective environmental monitoring. Particularly, Klebsiella pneumoniae, a pathogenic bacterium, can cause a wide range of infections, including meningitis, bloodstream infections, pneumonia, urinary tract infections, and wound or surgical site infections. Herein, a polypyrrole (PPy) functionalized Ti₃C₂T_x–tin dioxide nanoparticle (SnO₂ NPs) nanocomposite-based hybrid capacitive electrode for the electrochemical detection of Klebsiella pneumoniae ATCC 700603 is developed. The PPy layer was coated onto the Ti₃C₂T_x–SnO₂ NPs via drop-casting, followed by immobilization of bacteriophages through a potentiostatic, charge-directed chronoamperometric approach. The resulting Ti₃C₂T_x–SnO₂ NPs/PPy/phage biosensor exhibited a wide dynamic detection range of 10 to 10⁶ CFU mL⁻¹, with excellent linearity confirmed by differential pulse voltammetry and electrochemical impedance spectroscopy. The nanocomposite was characterized by using a suite of techniques including FTIR, XRD, elemental mapping, cyclic voltammetry, and galvanostatic charge–discharge to understand its composition, structure, and electrochemical properties. The developed Ti₃C₂T_x–SnO₂ NPs/PPy hybrid electrode demonstrated typical supercapacitor behavior with a specific capacitance of 806.67 F g⁻¹ at 2.0 A g⁻¹ of current density, and exhibited exceptional cycling stability, storing 98.3% of its capacitance after 10⁴ consecutive cycles. The selectivity of the modified electrode to detect K. pneumoniae while minimizing interference from various bacterial cells was assessed, exhibiting remarkable resilience, and remaining unaffected. Additionally, after eleven successive weeks of storage, the proposed sensor showed no discernible reduction current (∼98.1%), demonstrating an excellent stability. Despite the presence of background bacterial interference in the environmental sample, K. pneumoniae detection remained highly reliable and consistent with recovery efficiency ranging from 99.75 to 99.90%.