Dual-mode detection and efficient annihilation of pathogenic bacteria based on the construction of a ratiometric electrochemiluminescent/electrochemical sensor

Sensitive, reliable, and selective detection of pathogenic bacteria is a key objective for the assessment of public health. Here, a ratiometric electrochemiluminescent/electrochemical (ECL/EC) sensor sensitized with a two-step signal amplification strategy was designed for the dual-mode detection of pathogenic bacteria. Target-induced releasing of multi-DNA strands, as the first-step amplification, transformed Staphylococcus aureus (S. aureus) into abundant intermediate DNA strands, which then hybridized with the block DNA (W). New splice sites were formed via hybridization of the releasing swing arm with EC indicator-labeled anchor DNA. With the introduction of nicking endonuclease, DNA walker was activated as the second-step amplification, yielding abundant single-stranded DNAs on the sensing interface. ECL emitter-labeled probe DNA was hybridized with the left DNAs, resulting in a significant increase in ECL/EC ratio value to achieve sensitive monitoring of S. aureus. Taking advantage of the two-step signal amplification strategy, this method exhibited a high sensitivity for S. aureus analysis with a low detection limit of 1 CFU/mL. Concurrently, this sensing strategy brought about satisfactory results for S. aureus assay when interfering bacterial strains and complex matrices appeared. Furthermore, aptamer encapsulated silver nanoclusters (aptamer-Ag NCs) exhibited striking bactericidal performance against S. aureus during the experiment, which opened a promising antifouling avenue to eliminate bacteria.