An immunobiosensor based on chelate-ring-containing iridium(III) complexes for electrochemiluminescence determination of TNF-α

Abnormal Tumor necrosis factor-α (TNF-α) levels in serum are closely linked to Alzheimer's disease onset, progression, and severity. Highly sensitive and specific detection of TNF-α offers a key biomarker for early diagnosis and disease evaluation, providing significant clinical value for improved disease management. In this study, an iridium complex [(piq)₂Ir(dpppy)] containing a cyclometalated ligand was used as a novel and highly efficient electrochemiluminescence (ECL) luminophore to construct an ultrasensitive electrochemical biosensor for the detection of TNF-α. First, the TNF-α antibody was immobilized in the microplate reactor, and a quasi-specific sandwich immunoassay was performed. Subsequently, aptamers modified with silver nanoparticles-which were in-situ generated on the C-rich sequence-modified aptamer, captured the TNF-α antigen. After dissociation with nitric acid, the solution containing Ag + was transferred to the electrode surface modified with the cyclometalated iridium complex for ECL signal detection. The constructed immunosensor not only exhibited a wide linear range of 0.001 ng mL −1 –100 ng mL −1 , but also showed excellent recovery in human serum samples, ranging from 98.6 % to 101.7 %, with a relative standard deviation of 0.66 %–3.8 %. This strategy not only enhanced the detection sensitivity due to the efficient performance of the iridium complex in the 3 LCπ − π* state, but also this strategy of this biosensor effectively maintained the specificity and stability.