Composite Films for Modifying Evanescent Wave Characteristics in Long-Period Grating Biosensors

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.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Chemical Engineering

Department dc:contributor.department

Chemical Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2001

Author dc:creator

• Martin, Jennifer E.

Chair dc:contributor.committeechair

• Velander, William H.

Committee members dc:contributor.committeemember

• Forsten-Williams, Kimberly
• Davis, Richey M.

• biosensor
• evanescent wave
• long-period gratings (LPG)
• affinity ligand film
• titanium dioxide

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

etd-02172001-014116

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/31253