Hollow rhombic dodecahedron Ag particles decorated electrochemical aptasensor for rapid and onsite detection of E. coli

The present study has reported the development of sensitive, straightforward and ready-to-use aptasensor for the spontaneous detection of Escherichia coli in water based on the electrochemical oxidation of Ag. The working electrode of screen-printed carbon electrodes (SPCE) was decorated with novel hollow rhombic dodecahedron-shaped Ag particles deposited by electrodeposition at optimised chronoamperometry (CA) parameters. The aptasensor does not require the administration of an external redox probe for signal generation. The electrodeposited hollow rhombic dodecahedron Ag particles serve a dual purpose by providing a large stable platform for aptamer immobilization and functioning as an electrochemical signal generator through Ag oxidation. The resistance to Ag oxidation acts as an electrochemical indicator for bacterial detection. Therefore, quantitative detection of bacteria was carried out by analysing the Ag oxidation peak using differential pulse voltammetry (DPV). The current signals were observed to be decreasing in proportion to the rise in E. coli concentration. The regression line of the sensing signal was obtained as ?I = 4.84 log C + 10.5 (R2 = 0.988) for the detection range 50 cfu/ml to 106 cfu/ml. During aptasensor validation in E. coli-spiked tap water, a relative standard deviation (RSD) of 4.98% for three replicates and an error of �4% were noted, suggesting good accuracy and reproducibility. The aptasensor achieved a minimum detection limit of 50 cfu/ml for E. coli and an incubation period of 15 min. The developed aptasensor was found to be selective to E. coli and stable when preserved at 4 �C.