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 4 , 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.