Endogenous Free-Electron-Involved Coreactant-Free Electrochemiluminescence from Nanoclusters and Its Immunoassay...

Area of Science:

• Nanomaterials Science
• Analytical Chemistry
• Biomedical Engineering

Background:

• Commercial electrochemiluminescence (ECL) immunoassays typically require a coreactant and operate at +1.40 V (vs Ag/AgCl).
• Exogenous coreactants can introduce variability and complicate assay procedures.
• Developing coreactant-free ECL systems is desirable for simplified and robust immunoassays.

Purpose of the Study:

• To propose a novel sulfur-vacancy-involved and free electron strategy for coreactant-free ECL immunoassays.
• To utilize gold nanoclusters (AuNCs) as anodic electrochemiluminophores.
• To demonstrate the application of this strategy for detecting human carcinoembryonic antigen (CEA).

Main Methods:

• Synthesis of methionine-capped gold nanoclusters (Met-AuNCs) with sulfur vacancies.
• Investigation of the electron-rich nature and endogenous free electrons in Met-AuNCs using electron paramagnetic resonance (EPR).
• Development of a coreactant-free ECL immunoassay by oxidizing Met-AuNCs at the anode (+0.86 V).

Main Results:

• Met-AuNCs exhibit a sulfur-vacancy-involved, electron-rich nature due to deficient coordination.
• Endogenous free electrons in Met-AuNCs facilitate light emission through direct combination with exogenous holes.
• The coreactant-free ECL immunoassay successfully quantified human carcinoembryonic antigen (CEA) from 10 to 5000 pg/mL, with a limit of detection of 5 pg/mL.

Conclusions:

• A novel coreactant-free ECL immunoassay strategy based on sulfur vacancies and free electrons in AuNCs was successfully developed.
• This approach simplifies ECL immunoassay operations by eliminating the need for external coreactants.
• The strategy shows significant promise for designing advanced nanoelectrochemiluminophores for improved immunoassay performance.