Electrochemical biosensor for detection of Escherichia coli 0157:H7 gene based on amino acid-derived nanomaterials

This work presents a novel biosensor platform designed for the detection of Escherichia coli O157:H7, an important foodborne illness-causing bacteria. Carbon quantum dots based on tyramine were synthesized and characterized by UV-Vis, photoluminescence and FT-IR. Printed carbon electrodes were modified with these quantum dots and arginine monolayer. Specific DNA probe for E. coli O157:H7 was immobilized onto the working electrode and used for analysis of lysate solution of complementary or non-complementary target, detected by square wave voltammetry, using methylene blue as an intercalator of the duplex. The modified electrodes were characterized by cyclic voltammetry, electrochemical impedance spectroscopy, dynamic force microscopy and scanning electron microscopy. The platform's effectiveness in detecting the E. coli O157:H7 rfbE gene is demonstrated with electrochemical and morphological methods, having a detection limit in the attomolar range (1.65 aM), making it possible to successfully detect E. coli samples in milk, without purification steps, and differentiate them from other bacteria. Additionally, the proposed genosensor was able to distinguish real milk samples contaminated with E. coli, showing a 3.7-fold difference in response compared to a sample contaminated with B. subtilis. The biosensor demonstrates significant potential for real-world applications due to its high sensitivity, specificity, and ease of use, making it particularly well-suited for food safety, medical diagnostics, and environmental monitoring of E. coli strains. This work contributes to the ongoing efforts to construct increasingly simple and cost-effective biosensors, which are crucial for various applications, including food safety, medical diagnostics and environmental monitoring.