2-Step lectin-magnetic separation (LMS) strategy combined with AuNPs-based colorimetric system for S. aureus detection in blood

A novel 2-step lectin-magnetic separation (LMS) method combined with gold nanoparticle (AuNPs) -based colorimetric system for specifically and quantitatively detecting S. aureus in blood samples was established. In this study, wheat germ agglutinin lectin from Triticum vulgaris (wheat) (WGA) was applied for the first time as a recognition agent in a 2-step magnetic separation method using magnetic nanoparticles (MNPs) for effective and low-cost bacteria enrichment. A quantitative detection strategy based on the long dsDNA amplicons stabilized with AuNPs against salt-induced aggregation was investigated. The 2-step LMS method resulted in a high enrichment efficiency even at low concentrations (100-102 CFU/mL) of S. aureus in pure culture and blood samples. The AuNPs-based colorimetric system was applied for quantitative detection of S. aureus with a limit of detection (LOD) at 3.5 × 100 CFU/mL. The complete process starting with the blood samples treatment, 2-step LMS, and AuNPs-based colorimetric detection took only 7 h. The low cost and sensitive 2-step LMS combined with AuNPs-based colorimetric detection holds considerable potential for early sepsis diagnosis.