Development of interferometric biosensors on optical fiber assemblies for in vivo application


Thesis presented July 17, 2023

Abstract:
Diagnostics of internal disorders may require imaging techniques like magnetic resonance imaging, computed tomography, or endoscopy. Endoscopy is a minimally invasive technique widely used for in-vivo tissue imaging. However, it provides only visual examination and no biochemical information. The project attempts to improve the endoscopy technique by adding a biorecognition feature and creating a tool allowing “real-time optical biopsy”. Such a tool could bring significant progress in the medical field and help doctors diagnose diseases faster. In this context, this thesis aims to contribute to the development of new biosensors on optical fiber bundles of a micrometric size capable of real-time remote measurements and label-free multiple analyses.
To reach this goal, we propose a device design that consists of an optical fiber bundle on top of which are deposited two thin layers: an internal reflecting layer and a cavity. The detection principle is based on interferometry. By functionalizing the optical fiber bundle surface with biological probes, molecular interactions with target analytes can be followed through the modulation of the interferences. Thanks to the simulating of the interference phenomenon occurring at the fiber end, we have determined the geometrical and optical parameters of interferometric layers that give the optimal performance of the sensor to detect changes in the refractive index of the sensing medium. Then, fiber bundles with appropriate deposited interferometric layers were produced. They underwent optical characterization to examine the actual performance regarding spectral response, sensitivity, and resolution to the refractive index variation.
The experimental results were compared with the simulation showing agreement between the two approaches. After that, surface chemistries adapted to the composition of interferometric layers, like aminosilanization, were investigated and adapted to the geometry and size of the fiber bundle. Finally, the successfully functionalized fiber bundles with several different probes were used to demonstrate the proof-of-concept of real-time remote multiplexed biomolecular detection.

Keywords:
Biosensor, optical fiber assemblies, interferometry, multiplexed molecular detection, label-free biosensing, real-time

On-line thesis. ​