Ratiometric fluorescent immunoassay mediated by alkaline phosphatase-catalyzed Eu3+ coordination polymers for the detection of Ochratoxin A

Eu-CP self-assembled at room temperature enables reverse regulation of dual fluorescence signals. • OTA LOD as low as 0.0273 ng/mL (0.4883–62.5 ng/mL linear range) with excellent sensitivity. • High specificity, good probe and inter-batch stability. • Qualified grain sample recovery, suitable for on-site primary screening. Ochratoxin A (OTA) contamination severely threatens global food safety. Herein, a ratiometric fluorescent immunoassay method was established for trace OTA detection based on an alkaline phosphatase (ALP)-catalyzed Eu 3+ coordination polymer (Eu-CP). The Eu-CP probe is self-assembled from ciprofloxacin, adenosine monophosphate, and Eu 3+ . Upon activation by the Mg 2+ cofactor, ALP drives the dephosphorylation and subsequent structural disassembly of the Eu-CP framework, which synchronously regulates dual-emission fluorescent signals. In indirect competitive reaction, OTA competes with bovine serum albumin-OTA for limited antibodies, and the bound ALP-labeled secondary antibody is inversely correlated with OTA concentration. Based on the ratiometric fluorescence signal (F 618 /F 418 ), the proposed method exhibited a reliable linear range of 0.4883–62.5 ng/mL (R 2  = 0.9909) and a limit of detection as low as 0.0273 ng/mL. Recoveries in corn, oat and rice were 97.07%–119.11% with inter-batch CV < 10%. This study provides a simple and sensitive method for trace OTA detection. Download: Download high-res image (194KB) Download: Download full-size image