A signal-off aptasensor for the determination of Acinetobacter baumannii by using methylene blue as an...

An electrochemical aptasensor has been developed to detect Acinetobacter baumannii (A. baumannii). The proposed system was developed by modifying carbon screen-printed electrodes (CSPEs) with a synthesized MWCNT@Fe₃O₄@SiO₂-Cl nanocomposite and then binding A. baumannii-specific aptamer using covalent immobilization on the modified electrode surface and the interaction of methylene blue (MB) with Apt as an electrochemical redox indicator. As a result of the incubation of the A. baumannii bacteria as a target on the proposed aptasensor, a cathodic peak current density (J_pc) of MB decreased due to the formation of the Apt-A. baumannii complex and MB being released from the immobilized Apt on the surface of the modified electrode. In addition to increasing the electron transfer kinetics, the nanocomposite provides a relatively stable matrix to improve the loading Apt sequence. The suggested aptasensor was demonstrated to be capable of detecting A. baumannii with a linear range of 10.0-1.0 × 10⁷ colony-forming unit (CFU) mL^-1 and a detection limit of 1 CFU mL^-1 (S/N = 3) using differential pulse voltammetry (DPV) studies at a working potential of ~0.29 V and a scan rate of 100 mV s^-1. The outcomes revealed that the aptasensor exhibited high A. baumannii detection sensitivity, stability, reproducibility, and specificity.