Specific bio-recognition reactions observed with an integrated Mach-Zehnder interferometer

Area of Science:

• Optoelectronics
• Biotechnology
• Surface Chemistry

Background:

• Integrated Mach-Zehnder interferometers (iMZI) offer label-free biosensing capabilities.
• Microfluidic systems enable precise control and manipulation of biological samples.
• Supramolecular chemistry provides tools for creating highly specific molecular recognition interfaces.

Purpose of the Study:

• To develop and characterize an integrated biosensor combining iMZI, microfluidics, and supramolecular binding layers.
• To demonstrate the sensor's capability for sensitive detection of specific biomolecular interactions.
• To validate the sensor's performance against theoretical predictions.

Main Methods:

• Fabrication of a fluidic microchannel system with an integrated Mach-Zehnder interferometer.
• Formation of a self-assembled monolayer of a silane-compound on the iMZI channel rib.
• Utilizing the specific streptavidin-biotin interaction as a model biosensing event.
• Measuring the phase shift of light in the iMZI upon streptavidin injection.

Main Results:

• A streptavidin-biotin binding event formed a protein monolayer of 2.8 nm effective thickness.
• This monolayer induced a significant phase shift of 6π in the sample light relative to the reference channel.
• The experimental results closely matched the theoretical sensitivity of 2.9π/nm for a protein layer.

Conclusions:

• The integrated iMZI-microfluidic system with supramolecular interfaces is a highly sensitive biosensing platform.
• The sensor effectively detects specific biomolecular binding events in real-time.
• This technology holds promise for various applications in diagnostics and biochemical analysis.