Development of a novel activity-based ratiometric electrochemical probe for real-time detection of Listeria monocytogenes in human blood and milk samples.

Listeria monocytogenes (LM) is a prevalent food-borne pathogen that causes listeriosis, life-threatening disease. Current methods for detecting LM in turbid samples require multistep and complex-liquid extraction. Thus, an alternative tool is needed. A typical enzyme-biomarker for LM, PI-PLC, is secreted by LM. This study, we designed and prepared a PI-PLC (Phosphatidylinositol-specific phospholipase C) activity-targeted-electrochemical probe, termed PL-AFc, for detecting LM in turbid samples. PI-PLC catalyzes the hydrolysis of the phosphoether linkage between phosphatidylinositol and the phenol moiety in PL-AFc, inducing a reaction cascade that releases the unmasked signaling molecule, aminoferrocene. PL-AFc exhibits a wide linear detection range against PI-PLC (0.00001-0.1 unit/ml) and LM (3 × 106-1 × 108 cfu/ml), with detection limit of 2.703 ng/ml and 1.44 × 105 cfu/ml. Practical application, PL-AFc demonstrated the ability to sense LM in human blood and milk samples with a simple dilution procedure, suggesting the platform has significant potential for detecting LM.