Optofluidic in-fiber SERS biosensor with 4-MBA for monitoring of pyocyanin secretion under PAHs stress

Novel integrated optofluidic in-fiber SERS probe based on 4-MBA/Ag NPs for high-stability, label-free detection of PYO. • Ultrafast PYO fingerprint identification within 5 s via a competitive coordination recognition strategy. • Quantitative evaluation of PAHs-triggered bacterial virulence enhancement, providing reliable technical support for marine environmental risk assessment and coastal public health early warning. The activation of virulence in Pseudomonas aeruginosa under environmental stress is of great significance for studying the mechanism of bacterial-environment interaction. Pyocyanin (PYO), a key phenazine virulence factor secreted by P. aeruginosa , serves as a direct indicator of bacterial pathogenicity. Herein, we developed a highly integrated optofluidic in-fiber surface-enhanced Raman scattering (SERS) biosensor for rapid, label-free detection of PYO secretion by Pseudomonas aeruginosa under environmental stress. 4-Mercaptobenzoic acid (4-MBA) serves as a molecular recognition linker anchored onto silver nanoparticle (Ag NPs) surfaces, which can undergo competitive coordination with pyocyanin to suppress non-specific interference from coexisting impurities. The nitrogen atoms on the phenazine ring of PYO form Ag–N coordination bonds along with π–metal coupling interactions with Ag NPs. This competitive substitution displaces the Ag–S bonds between 4-MBA and Ag NPs, leading to a concentration-dependent reduction in the characteristic peak intensity of 4-MBA at 1077 cm⁻¹ . The sensor specifically identifies PYO via its characteristic peak at 1345 cm⁻¹ within 5 s, and exhibits a linear range of 10 −5 M to 10 −14 M. The limit of detection (LOD) was calculated as 1.0 × 10⁻ 14 M. Through the sampling tests, we confirm that 50 μM PAHs stress triggers a 1.5-fold increase in PYO secretion of P. aeruginosa , verifying PAHs-induced bacterial virulence enhancement. Benefiting from the specific competitive recognition between 4-MBA and PYO, the sensor exhibits robust anti-interference performance in complex natural seawater matrices. This work provides a sensitive, rapid, and cost-effective SERS platform for bacterial virulence monitoring, offering valuable insights into pollutant-bacterium interactions and public health early warning. Download: Download high-res image (164KB) Download: Download full-size image