Development of a modified graphene oxide-alginate electrochemical impedance aptasensor for rapid E. coli detection

The study presents a sensitive and rapid electrochemical impedance aptamer-based biosensor (aptasensor) was developed for detecting Escherichia coli (E. coli) ATCC 25922, a model that offers diagnostic tools using a modified graphene oxide (MGO)–alginate composite platform. Electrochemical aptasensors employ ssDNA aptamers as selective bioreceptors, offering a promising alternative to conventional bacterial detection methods. Because of the high surface area of MGO and alginate biocompatibility, the combination as a composite sensing platform improves immobilization stability and signal amplification, hence boosting biosensor performance. The MGO–alginate-based aptasensor exhibited a concentration-dependent decrease in charge-transfer resistance upon E. coli binding, as measured by electrochemical impedance spectroscopy (EIS). Under optimized conditions (50 nM aptamer, 2 mg/mL modified GO, 30 min incubation at 37 °C), the sensor detected E. coli over a wide range from 10 2 to 10 8 CFU/mL ( p < 0.05, n = 3). MGO-alginate-based aptasensor has shown remarkable sensitivity in identifying E. coli , with charge transfer resistance dropping when bacteria attach to the immobilized aptamers. The biocompatible alginate enhances sensitivity and provides structural stability, making it suitable for real-world bacterial detection applications requiring strong stability, quick response, and high sensitivity. • MGO–alginate composite enables stable and sensitive EIS-based E. coli detection. • Electrochemical aptasensor detects E. coli from 10 2 to 10 8 CFU/mL. • Charge-transfer resistance decreases upon specific E. coli –aptamer binding. • Alginate suppresses GO aggregation and enhances sensor stability and reproducibility.