Electrochemiluminescence Modulation by a Versatile Organic Redox Mediator.

Area of Science:

• Electrochemistry
• Analytical Chemistry
• Biochemistry

Background:

• Iridium complexes enhance electrochemiluminescence (ECL) but are costly and complex.
• Existing methods face challenges with high cost, synthesis, and background signal.

Purpose of the Study:

• To explore nortropine N-oxyl (NNO) radical as a non-emissive redox mediator for ECL.
• To investigate NNO's mechanism in modulating co-reactant ECL emission.
• To assess NNO's performance in various ECL sensing formats.

Main Methods:

• Utilized nortropine N-oxyl (NNO) radical as a redox mediator.
• Investigated hydride transfer reactions with amine co-reactants (TPrA, DBAE).
• Employed density functional theory (DFT) for mechanistic studies.
• Tested NNO in homogeneous solution and heterogeneous formats (bead-based immunosensing, single cells).

Main Results:

• NNO catalyzed co-reactant oxidation, decreasing homogeneous ECL but amplifying heterogeneous ECL.
• Achieved 7.3-fold amplification with TPrA and 12.5-fold with DBAE in bead-based assays.
• Demonstrated 5.4-fold amplification on single cells.
• DFT calculations elucidated the background-free ECL modulation mechanism.

Conclusions:

• NNO provides a cost-effective, non-emissive redox mediator for ECL.
• NNO significantly amplifies heterogeneous ECL signals, improving biosensing sensitivity.
• This approach offers new possibilities for ECL bioassays, microscopy, and biosensing design.