A phosphorylation-sensitive tyrosine-tailored magnetic particle for electrochemically probing free organophosphates in blood.

A simple, rapid, sensitive, selective, and field-deployable detection protocol has been initially proposed for the early warning and diagnosis of exposure to organophosphates (OPs) by electrochemically monitoring the direct biomarkers of free OPs in blood. Phosphorylation-sensitive tyrosine (Tyr), which was tested with unique electroactivity, was bound onto Fe3O4 particles mediated by the mussel-inspired dopamine to form Fe3O4@Tyr particles with well-defined shape and well-retained Tyr electroactivities, as characterized separately by electron microscopy and electrochemical measurements. A "lab-on-a-particle"-based detection procedure combined with a magnetic electrode was thus developed by employing Fe3O4@Tyr particles as capturing probes for detecting free OPs in blood, dimethyl-dichloro-vinyl phosphate (DDVP) as an example. A significant difference in electrochemical responses could be obtained for Fe3O4@Tyr particles before and after DDVP exposure, based on the phosphorylation-induced inhibition of electroactivities of loaded Tyr. Investigation results indicate that highly specific and sensitive phosphorylation for the inhibition of Tyr electroactivities by sensitive electrochemical outputs could endow the OP detection with high selectivity and sensitivity (i.e., down to about 0.16 nM DDVP in blood). Moreover, strong and stable Tyr-OP bindings especially irreversible electrochemical oxidization of the Tyr probe could facilitate the OP evaluation with high reproducibility and stability over time. In particular, the simple "lab-on-a-particle"-based detection procedure equipped with a portable electrochemical transducer can be tailored for the field-deployable or on-site monitoring of the exposure to various nerve agents and pesticides.