Live E. coli bacteria label-free sensing using a microcavity in-line Mach-Zehnder interferometer

Area of Science:

• Optical biosensing
• Fiber optic sensors
• Biotechnology

Background:

• Label-free biosensing offers advantages for real-time biological monitoring.
• Microcavity in-line Mach-Zehnder interferometers in optical fibers are promising sensing platforms.
• Achieving specificity in optical fiber sensors often requires complex surface functionalization.

Purpose of the Study:

• To develop and demonstrate a selective, label-free biosensor using a microcavity in-line Mach-Zehnder interferometer.
• To investigate the use of immobilized bacteriophages for specific bacterial detection.
• To achieve real-time monitoring of live bacteria with high sensitivity.

Main Methods:

• Fabrication of microcavity structures in single-mode optical fiber using femtosecond laser micromachining.
• Chemical surface treatment for immobilization of MS2 bacteriophages as recognition elements.
• Real-time monitoring of E. coli C3000 bacteria interactions with the sensor surface.

Main Results:

• The developed biosensor demonstrated ultrahigh refractive index sensitivity (15,000 nm/RIU).
• Selective detection of live E. coli C3000 bacteria was achieved.
• Detection of E. coli concentrations as low as 100 colony forming units/mL in picoliter volumes was possible.

Conclusions:

• The study presents the first selective label-free biosensing application of a microcavity in-line Mach-Zehnder interferometer in optical fiber.
• The sensor enables specific and sensitive detection of live bacteria through immobilized bacteriophages.
• This technology holds potential for real-time, high-sensitivity microbial detection in various applications.