Dual-recognition gold nanoparticle-based sandwich SERS biosensors for detecting Pseudomonas aeruginosa in milk.

Abstract

Pseudomonas aeruginosa is an opportunistic pathogen frequently encountered in raw milk and dairy processing environments, where it accelerates milk spoilage and poses potential risks to public health. Rapid and ultrasensitive detection of pathogenic bacteria in complex food matrices remains a long-standing challenge due to matrix interference, nonspecific adsorption, and limited signal reproducibility. Herein, we report two dual-recognition sandwich-type surface-enhanced Raman scattering (SERS) biosensing platforms that integrate magnetic enrichment with plasmonic signal amplification for the ultrasensitive detection of P. aeruginosa in milk. Gold nanoparticle-coated chitosan starch magnetic beads functionalized with either antibody or aptamer were employed as capture probes, while aptamer-modified gold nanoparticles served as SERS signal tags. The synergistic combination of magnetic separation and spatially separated dual-recognition significantly enhanced capture efficiency and signal stability in complex matrices. The antibody-based and aptamer-based SERS platforms achieved detection limits of 1.78 and 1.29 CFU/mL, respectively, with relative standard deviations below 5%. Both systems exhibited excellent selectivity against non-target bacteria and maintained reliable quantitative performance in spiked milk samples, yielding recoveries of 93.33-105.84%. Notably, a systematic comparison between antibody- and aptamer-based recognition strategies within the same sensing framework revealed comparable analytical sensitivity but superior operational simplicity and matrix tolerance for the aptamer-based system. This work establishes a modular and matrix-tolerant dual-recognition SERS sensing framework that enables ultrasensitive bacterial detection and provides mechanistic insights into the practical trade-offs between antibody and aptamer recognition. Moreover, the adaptable design allows straightforward extension to other foodborne pathogens, offering a generalizable strategy for advanced biosensing in food safety applications.

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