Electrochemiluminescent immunoassay for the lung cancer biomarker CYFRA21-1 using MoO_x quantum dots

Molybdenum oxide quantum dots (MoO_x QDs) were synthesized by a one-pot method and used as a versatile probe in an electrochemiluminescent (ECL) immunoassay of the non-small cell lung cancer biomarker cytokeratin 19 fragment 21-1 (CYFRA21-1) as a model analyte. The MoO_x QDs exhibited stable and strong cathodic green ECL, with an emission peak at 535 nm, in the presence of K₂S₂O₈ within the potential range of -2.0 to 0 V. On exposure to CYFRA21-1, the ECL decreases because of the immunoreaction between CYFRA21-1 and its antibody which generates a barrier for electron transfer. The determination of CYFRA21-1 with favorable analytical performances was successfully realized under the optimal conditions. ECL decreases linearly in the 1 pg mL^-1 to 350 ng mL^-1 CYFRA21-1 concentration range, and the detection is as low as 0.3 pg mL^-1. Excellent recoveries from CYFRA21-1-spiked human serum indicate that the assay can be operated under physiological conditions. Graphical abstractSchematic representation of the fabrication of molybdenum oxide quantum dots (MoO_x QDs) and the electrochemiluminescent (ECL) immunoassay based on the use of the MoO_x QDs ECL probe for cytokeratin 19 fragment 21-1 (CYFRA21-1).