Development of optical fiber biosensors with long period gratings.

摘要

This dissertation successfully developed a new sensitive optical fiber biosensor with Long Period Gratings (LPG), using the self-fabricated LPG and self-built demodulation system. The LPG biosensor is a in-fiber sensor which is especially suitable for sensing in remote and hostile environments. The biosensor is also unique in that it is a label-free sensor with the ability of real-time detection and the potential for multiplexing.;We began the research with detailed computer simulations, using a new simplified three-layer model for a cylindrical waveguide with doubly-cladded step-index profile. The simulation results showed the nonlinear relationship between the LPG spectral sensitivity and the ambient refractive index. It was also shown that, at the same ambient refractive index, higher LPG modes resulted in higher sensitivity. Simulations of biolayer formation on the LPG surface showed a linear relationship between the LPG spectral shift and the biolayer thickness and a linear relationship between the LPG spectral shift and the biolayer refractive index. In the case of antibody detection, the simulation results for the LPG biosensor suggested an estimated minimum detectable human Immuno-Globin G (hIgG) concentration of ∼1.0 picomole/mL.;By immobilizing Goat anti-human IgG (antibody) on the LPG surface, a LPG biosensor (immunosensor) was successfully developed for the sensitive detection of a specific antigen (human IgG). The binding of non-labeled hIgGs on the LPG surface was investigated by experiments in real time. It was observed that both the maximum output signal and the calculated initial signal slope were concentration dependent over a range of 2--100 mug/mL of homogeneous hIgG solutions in PBS. If applying initial signal slope determination, the target antigen hIgG concentration or the final signal level could be determined in approximately 10 minutes after the target solution was introduced into the flow chamber of the LPG immunosensor. Also, the dissertation found that the minimum detectable hIgG concentration for the LPG immunosensor was about 6.7 picomole/mL, which was pretty close to the estimated sensitivity of ∼1.0 picomole/mL based on the computer simulations. Finally, the specificity of the LPG immunosensor was positively verified, and the biosensor regeneration and re-treatment were successfully tested.