Title page for ETD etd-02172001-014116

Type of Document Master's Thesis
Author Martin, Jennifer E.
URN etd-02172001-014116
Title Composite Films for Modifying Evanescent Wave Characteristics in Long-Period Grating Biosensors
Degree Master of Science
Department Chemical Engineering
Advisory Committee
Advisor Name Title
Velander, William H. Committee Chair
Davis, Richey M. Committee Member
Forsten-Williams, Kimberly Committee Member
  • biosensor
  • evanescent wave
  • long-period gratings (LPG)
  • affinity ligand film
  • titanium dioxide
Date of Defense 2001-02-09
Availability unrestricted
Biosensors are detection devices that couple biological recognition elements to physiochemical transducers to generate quantifiable signals. Immunosensors are biosensors that use antibodies as the recognition element. The highly specific nature of antibody-antigen binding is exploited to create immunosensors that are sensitive to analytes in complex mixtures and demonstrate a rapid response. Fiber optical immunosensors based on long-period gratings have limited sensitivity at the refractive index of ordinary aqueous solutions (~1.33). A composite film was designed to raise the local refractive index of the sensor, thus increasing sensitivity. Titanium dioxide deposition raised the refractive index of the sensor to ~1.42. Bovine serum albumin was immobilized onto a dextran hydrogel and attached to the LPG element via reductive amination. The thickness of the hydrogel was estimated to be 500 nm using Environmental Scanning Electron Microscopy. The affinity film was probed by an evanescent wave to detect changes in refractive index due to the binding of anti-BSA IgG. Under these conditions, the sensor yielded a signal ratio of approximately 10-4 refractive index units per nm signal. Reproducible binding was shown over multiple exposures, with no cross reactivity for non-specific antibodies and other proteins. Anti-BSA IgG (20 µg/mL) in whole serum was recycled through the fiber holder with an accompanying peak wavelength shift that averaged 2 nm on an Optical Spectrum Analyzer with a noise level of 0.1 nm. The BSA affinity film was regenerated 50 times and showed a baseline shift of -1.3 nm.
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