Electrochemiluminescence immunoassay based on site-specific labeling using a histidine-binding iridium(III) solvento complex.

Histidine bound bis-cyclometalated iridium (III) complexes were found to be luminescent in previous studies. This work demonstrates that the luminophores could be excited electrochemically and the electrogenerated chemiluminescence was observed in both homogeneous solutions and on the surface of magnetic beads. The findings laid a foundation for novel ECL immunoassay methodology featuring site-specific labeling of antibodies and on-site formation of signal-generating units. Taking use of the findings and the unique advantages of the site-specific labeling approach, a sandwich immunoassay for a clinically important biomarker was conceptually proved. The limit of detection of <1 ng/mL procalcitonin in human plasma could be achieved from the unoptimized assay.