Self-contained microelectrochemical immunoassay for small volumes using mouse IgG as a model system

Area of Science:

• Electrochemistry
• Immunoassay Development
• Microfluidics

Background:

• Traditional immunoassays often require larger sample volumes, limiting their application in certain research areas.
• Microfabricated devices offer potential for miniaturization and increased sensitivity in analytical techniques.
• Enzyme-linked immunosorbent assays (ELISA) are widely used but can be time-consuming and require significant reagent volumes.

Purpose of the Study:

• To develop a self-contained microelectrochemical immunoassay utilizing ultra-small sample volumes.
• To demonstrate the assay's capability for rapid detection of mouse IgG using a sandwich-type format.
• To evaluate the performance of the microfluidic device for sensitive electrochemical detection.

Main Methods:

• Fabrication of a microfluidic chip with individually addressable microelectrodes within a microcavity.
• Covalent attachment of primary antibodies to a gold recessed microdisk electrode (RMD) using self-assembled monolayers (SAMs).
• Electrochemical detection of enzymatically generated species via cyclic voltammetry using a gold nanoband electrode.

Main Results:

• Successful development of a microelectrochemical immunoassay using only 1 microL of antigen and secondary antibody-enzyme conjugate.
• Achieved rapid detection of enzymatically generated species in less than 30 seconds.
• Demonstrated high sensitivity with detection limits for mouse IgG as low as 56 fM (9 pg/mL) and for p-aminophenyl phosphate (PAPR) as low as 4.4 nM (6.4 ng/mL).

Conclusions:

• The developed microelectrochemical immunoassay is highly efficient, requiring minimal sample and reagent volumes.
• The proximity of electrodes to the antibody-modified surface enhances detection sensitivity and speed.
• The device shows promise for ultra-small volume analysis, potentially down to picoliter volumes.