An Electrochemical Sensor for the Detection of Bacteria in Water Using Cationic Manganese Ferrite Nanoparticles

We report a fully synthetic bio‐label‐free electrochemical sensor for the detection of bacteria in aqueous environments by using 2‐(3‐(3,4‐dihydroxyphenyl)propanamide)‐ N , N , N ‐trimethylethanaminium chloride‐capped manganese ferrite nanoparticles (DPTMA‐MnFe 2 O 4 NPs). These cationic DPTMA‐MnFe 2 O 4 NPs were synthesized by postfunctionalization of 3,4‐dihydroxydihydrocinnamic acid (DOHCA)‐capped MnFe 2 O 4 NPs. This postfunctionalization imparted a positive surface charge to these nanoparticles due to the presence of terminal quaternary ammonium groups. The nanoparticles, being electroactive materials, were immobilized on a glassy carbon electrode (GCE) to construct bio‐label‐free electrochemical sensor. The DPTMA‐MnFe 2 O 4 NPs acted as both transducer and recognition element by electrostatically interacting with the negatively charged surface of bacteria. Square wave voltammetry (SWV) was employed due to its rapid response and sensitivity to detect a change in electrochemical response in proportion to various concentrations of bacteria. This simple, rapid, and cost‐effective bio‐label‐free electrochemical sensor resulted in bacterial detection down to 10 2 cfu/mL in water, with the sensitivity of the electrode calculated to be 1.46 cfu/mL. This sensor may be adapted for a wide range of bacterial total load detection without needing selective receptors. This platform offers a promising label‐free electrochemical sensor alternative to conventional bio‐based sensing methods. However, future development aims to enhance selectivity and robustness in complex real‐world samples.