Electrogenerated chemiluminescence biosensors for the detection of pathogenic bacteria using antimicrobial peptides as capture/signal probes

Two electrogenerated chemiluminescence (ECL) biosensors for selective and sensitive detection of Escherichia coli O157:H7 were first designed by employing the antimicrobial peptide Magainin I as a biological recognition element and the ruthenium complex (Ru1) as an ECL label. In a direct format, the biosensor (I) was fabricated by self-assembling the Ru1-labeled peptide taken as a capture and signal probe onto the gold electrode surface. This system showed that the decreased ECL intensity was logarithmically proportional to the concentration of E. coli O157:H7 in the range of 1.0 x 10(3) - 5.0 x 10(5) CFU/mL, with a detection limit of 2.3 x 10(2) CFU/mL. In a sandwich format, the biosensor (II) was fabricated by self-assembling the modified Magainin I taken as capture probe onto the gold electrode surface. After E. coli O157:H7 was captured by the capture probe on the biosensor (II) and then bound with the Ru1-labeled peptide as the signal probe, the increased ECL intensity was logarithmically proportional to the concentration of E. coli from 5.0 x 10(2) CFU/mL to 5.0 x 10(5) CFU/mL, with a detection limit of 1.2 x 10(2) CFU/mL. Importantly, the designed ECL biosensors showed a satisfactory selectivity in discriminating the gram-negative E. coli O157:H7 from gram-positive bacteria, and pathogenic from nonpathogenic E. coli. The strategy of using a Ru1-labeled peptide as a capture/signal probe is a promising approach to designing ECL biosensors for highly sensitive and rapid detection of E. coli O157:H7; this approach could be extended to the design of ECL biosensors for other desired bacteria as well. (C) 2015 Published by Elsevier B.V.