Silica interlayer-protected colorimetric-fluorescent dual-signal microbial tag mediate lateral flow immunoassay for flexible and ultrasensitive detection of sepsis biomarkers

Rapid, accurate, and timely detection of inflammatory markers is essential for diagnosing sepsis and assessing its progression; however, challenges remain. Herein, we proposed a colorimetric and fluorescent dual-signal microorganism tag (EASi-QDs) for rapid monitoring of sepsis biomarkers by sequentially coating a layer of Au nanoparticles (NPs), a layer of silica (SiO₂) shell, and two layers of quantum dots onto the surface of Escherichia. coli. The introduction of the SiO₂ interlayer into EASi-QDs significantly enhances the structural stability of bacterial cell and effectively suppresses the quenching of fluorescence signal by the inner Au NPs, thereby ensuring high sensitivity and accuracy in detecting sepsis biomarkers on the lateral flow immunoassay (LFIA). The EASi-QDs-LFIA features both colorimetric and fluorescent detection modes, enabling rapid qualitative detection and quantitative analysis of two important biomarkers—procalcitonin (PCT) and interleukin-6 (IL-6). This method achieves detection limits of 29.5 pg/mL and 4.7 pg/mL for PCT and IL-6, respectively, exceeding those of traditional enzyme-linked immunosorbent assays and AuNP-based colorimetric LFIA by at least 15-fold and 339-fold, respectively. The clinical utility of the EASi-QDs-LFIA was validated through diagnostic testing of 20 plasma samples from real sepsis patients, demonstrating the significant potential of this technology for bedside real-time monitoring of sepsis.