A magnetically enriched suspended liquid membrane-assisted SERS biosensing platform for ultrasensitive detection of Escherichia coli as a model bacterium

A suspended liquid membrane-assisted SERS biosensing platform was developed for ultrasensitive E. coli detection. • Dual-recognition “magnetic bead– E. coli –SERS tag” complexes enabled specific E. coli capture and signal amplification. • Under optimized conditions, a limit of detection of 10 CFU/mL was achieved. • The SERS platform enables favorable detection of E. coli in complex matrices. Sensitive detection of pathogenic bacteria with a shorter turnaround than conventional culture-based methods is essential for clinical diagnosis, public health monitoring, and food safety. Herein, we developed a magnetically enriched suspended liquid membrane (SLM)-assisted surface-enhanced Raman scattering (SERS) biosensing platform for the sensitive detection of Escherichia coli ( E. coli ). Wheat germ agglutinin (WGA)-functionalized carboxylated magnetic beads were used to capture and enrich bacteria, while aptamer-modified Au@4-mercaptobenzoic acid (MBA)@Ag core–shell nanoparticles served as SERS tags for specific recognition and signal amplification. By combining magnetic enrichment with the directional concentration effect of the SLM, the platform enabled favorable Raman detection with enhanced signal intensity and improved quantitative performance. Under optimized conditions, the platform enabled detection of E. coli at a lowest experimentally verified concentration of 10 colony-forming units per milliliter (CFU/mL), provided an 8–10-fold SERS signal enhancement compared with the non-enriched system, and exhibited a quantitative linear response over the range of 1 × 10 3 to 1 × 10 8  CFU/mL with an R 2 of 0.9634. The platform showed proof-of-concept feasibility for E. coli detection in pretreated and post-spiked complex matrices, including human seminal plasma (HSP), human urine and commercial fruit juice, with apparent recoveries ranging from 85.76% to119.94% for juice, 93.26% to 114.82% for human urine, and 79.38% to115.40% for HSP. Download: Download high-res image (173KB) Download: Download full-size image