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24 February 2010 Immunoassay demonstration using a local evanescent array coupled biosensor
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A Label-free optical waveguide immunosensor is investigated both theoretically and experimentally. The local evanescent array coupled (LEAC) biosensor is based on a local evanescent field shift mechanism, which differs from those of other evanescent waveguide sensors. Antigens specifically bound by immobilized antibodies on the waveguide surface increase the refractive index of the upper cladding of the waveguide, and hence shift the evanescent field distribution up. This local detection mechanism grants the LEAC sensor multi-analyte ability in a single optical path. Compared to traditional biosensors, including surface plasmon resonance and ring resonance biosensors, the nonresonant and temperature/wavelength insensitive properties of the LEAC biosensor relax its requirement on the optical source. It requires no accessory off-chip instruments such as spectrometers, making it a chip-scale biosensing platform. The on-chip detection is accomplished by integrating buried polysilicon detector arrays into silicon nitride waveguide in a commercial complementary metal oxide semiconductor (CMOS) process. Protein antigens and IgG producing biologically relevant antibody-antigen interactions were used to test the clinical utility of the LEAC biosensor platform. Advanced analysis beam propagation method (BPM) simulations and chips with different geometric parameters were used to study the relationship between the sensitivity and structure of LEAC biosensor.
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Rongjin Yan, Luke C. Kingry, Richard A. Slayden, and Kevin L. Lear "Immunoassay demonstration using a local evanescent array coupled biosensor", Proc. SPIE 7559, Optical Fibers and Sensors for Medical Diagnostics and Treatment Applications X, 75590D (24 February 2010);

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