Microstructured Polymer Optical Fibers (mPOFs) based sensors for label-free detection of biomolecules

Project description

The project aims at the development of Microstructured Polymer Optical Fibers (mPOFs) based sensors for label-free detection of biomolecules. Such fibers are characterized by having a pattern of micrometer- sized air holes along the entire length of the fiber. The optical field from modes guided through the fiber core penetrates into the air holes where a significant fraction of the field propagates as an evanescent wave. By carefully optimizing the relevant fiber parameters, such as the air hole size and distance between neighboring air holes, the fraction of the field that propagates in the evanescent wave will be substantial. The optical field can hence probe aqueous solutions of biomolecules positioned in the air holes or biomolecules captured at the polymer-air interface.

Today, several optical techniques based on obtaining a response from a fluorescent label-molecule attached to the biomolecule of interest, exist. Recently, there has been a growing interest in the development of sensors for the detection of biomolecules, without adding the label molecules, the so-called label-free detection. Some techniques have matured into of-the-shelf products, such as Surface Plasmon Resonance, but the equipment for these techniques is usually very expensive, and simpler more cost-effective techniques will have a huge impact on the biosensor market, potentially capturing large shares of this very large market.

As the COM Center (DTU) is currently acquiring a drawing tower for fabrication of mPOFs, the first part of the project is dedicated to the development of techniques for fabrication of such fibers. In fact, polymer based fibers have the advantage over silica based Photonic Cristal Fibers, that many biological substances are more compatible with polymers than with silica. The preparation of the air holes with the deposition of a sensor layer should be easier and hence more reliable and reproducible. After fabricating the mPOFs, their performance in sensor applications will be evaluated with studies comparing the benefits and problems concerning different air hole patterns and polymers.

The long term goal of the project is to perform the label-free detection by measuring changes in the refractive index profile in the mPOFs when the biomolecules are captured at the air-polymer interface. The target is to demonstrated selective capture of labeled biomolecules in sensor layers immobilized inside the air holes of these fibers. Some modeling has indicated that substantial changes in the resonance wavelength of Bragg gratings or long period gratings inscribed in microstructured fibers will occur when the specific biomolecules are captured. Alternatively, changes in a photonic band gap upon capture can be used as an indicator. Modifications of the refractive index profile in such photonic band gap fibers will shift the position of the transmission windows defined by the band gaps. The detection can then be through measuring the position of the band gaps or by monitoring the intensity of a single-wavelength signal with a wavelength at a band gap edge.

back to previous page