Photonic ring resonance is a versatile platform for performing multiplex immunoassays in real time

Area of Science:

• Photonics and optical sensing
• Biotechnology and biosensing
• Nanotechnology and microfabrication

Background:

• Photonic ring resonators trap specific light wavelengths, enabling sensitive detection of refractive index changes.
• Biosensors utilize these ring resonators to detect the binding of biological material to their surface.
• Miniaturization of these sensors onto silicon chips allows for multiplexed array development.

Purpose of the Study:

• To describe the properties of silicon photonic ring resonator biosensors.
• To demonstrate their response to refractive index changes caused by ionic strength and macromolecular binding.
• To present a capture immunoassay for detecting anti-SS-A autoantibodies in patient serum.

Main Methods:

• Fabrication of miniaturized silicon chips with a 4x6mm array of ring resonators.
• Detection of resonant wavelength shifts due to changes in the surrounding medium's refractive index.
• Implementation of a capture immunoassay using SS-A antigen and anti-IgG amplification.

Main Results:

• The system demonstrated high precision with low variability (0.6% CV between rings, 0.5% CV between clusters, 1.8% CV between chips).
• Inter-instrument variation was within 3% after wavelength referencing improvements.
• The immunoassay showed high sensitivity, requiring only ~200 picograms of antigen and a few microliters of sample, with assay times under 10 minutes.

Conclusions:

• Silicon photonic ring resonator biosensors offer a miniaturized, highly sensitive, and rapid platform for biomolecular detection.
• The technology is suitable for developing multiplexed diagnostic arrays with minimal sample and reagent requirements.
• The demonstrated immunoassay highlights the potential for clinical diagnostics and personalized medicine.