Defining virulence factor as a pre-screening strategy for gram negative bacterial infection: A GO-Fe₃O₄-based electrochemical siderosensor for detection of virulent Escherichia coli

Infections caused by antibiotic resistant bacteria pose a multifaceted threat to global health. Sensors targeting key virulence factors such as siderophores, offer an unconventional yet selective detection approach for determination of bacterial virulence and pathogenicity, as siderophore production rate reflects both traits. This study presents a graphene oxide-Fe₃O₄ composite based electrochemical sensor for detection of enterobactin, an archetypal siderophore from E. coli. The developed sensor exhibited a tenfold increase in current compared to bare screen-printed carbon electrode and achieved a detection limit of 0.1 μM for standard enterobactin, with a linear detection range of 0.1-100 μM and an R² value of 0.99. Siderophore production was confirmed, quantified and demonstrated as a marker for metabolically active bacteria in iron-limited environments with a response time of 4 min. This study establishes a label-free, biorecognition element free, precise detection of siderophores in real-world samples, such as urine, serum and river water (0.1-50 μM), (1-100 μM) and (0.5-10 μM) respectively with an error of less than 9% for five months of use. This sensor enables the identification of virulence activation in metabolically active E. coli in iron restricted environments as an indicator of possible pathogenicity. Independently it serves as an indicator of iron deficiency in physiological specimen. It may also be utilized to access possible faecal contamination in environmental aqueous specimen. The value proposition of this sensor is as a preliminary screening tool of clinicians in primary healthcare setups of resource constrained settings as an indicator of possible E. coli infections.