SERS and ECL dual-mode sensing of bacterial lipopolysaccharide based on bifunctional DNA strands mediated transformation from Au@Ag nanocubes to silver nanoclusters.

Bacterial contamination is a very serious health and environmental problem, with the main source of toxicity being lipopolysaccharides in the cell walls of Gram-negative bacteria. Therefore, the development of effective analytical methods is crucial for the detection of lipopolysaccharide content. This work facilitates the efficient generation of precisely adjustable dual-mode signals for LPS detection in surface-enhanced Raman spectroscopy (SERS) and electrochemiluminescence (ECL) by inducing anisotropic morphological evolution of Au@Ag nanocubes (Au@AgNCs) through poly-cytosine (poly-C) DNA. In the presence of LPS, the released probe triggers rolling circle amplification (RCA) and generates cyclic poly-C DNA, which subsequently induces the etching of Ag composites on Au@AgNCs. This etching process leads to changes in both the morphology and composition of Au@AgNCs composite materials, resulting in a decrease in SERS signals. The poly-C DNA was subsequently adsorbed with Ag and then reduced to silver nanoclusters (AgNC) by NaBH, serving as an ECL signal source. Under optimal experimental conditions, both SERS and ECL demonstrated linear ranges spanning from 1 fg/mL to 1 ng/mL, with detection limits of 0.29 fg/mL and 0.14 fg/mL, respectively. Moreover, the SERS-ECL dual-mode sensor facilitates the accurate discrimination of Gram-negative bacteria in diverse real samples. It demonstrates promising applications in the areas of food safety, water quality monitoring, and clinical bacterial detection.