Spinning-disk self-referencing interferometry of antigen-antibody recognition

Area of Science:

• Nanotechnology
• Biophysics
• Optical Engineering

Background:

• Interferometry offers high sensitivity for detecting minute changes.
• Biosensors are crucial for rapid disease diagnosis and molecular detection.
• Developing label-free biosensing platforms is an ongoing challenge.

Purpose of the Study:

• To develop a spinning-disk interferometric biosensor for antigen detection.
• To utilize a gold ridge microstructure as a self-referencing interferometer.
• To demonstrate sensitive and specific molecular recognition of antigens.

Main Methods:

• Fabrication of a lambda/8 gold ridge microstructure on a high-reflectivity substrate.
• Illumination with a Gaussian laser beam and far-field observation.
• Selective immobilization of immunoglobulin G (IgG) antibodies and detection of antigen binding via phase shifts.
• Interferometric detection on spinning disks at 100 kHz sampling rate.
• Verification of signal integrity using two opposite quadratures to exclude dynamic light scattering.

Main Results:

• The gold microstructure functioned as a wave-front-splitting interferometer.
• Immobilized IgG antibodies specifically bound to target antigens, causing measurable phase shifts.
• Antigen binding was detected interferometrically with high sensitivity (100 kHz sampling rate).
• The biosensor demonstrated strong molecular recognition, distinguishing specific antigens from nontarget molecules.
• Signal verification confirmed the interferometric nature and ruled out artifacts.

Conclusions:

• The developed spinning-disk interferometric immunoassay (BioCD) shows potential as a sensitive biosensor.
• This platform enables label-free detection of molecular interactions.
• The technology is suitable for rapid, high-throughput screening and diagnostics.