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Proceedings Paper

Development of label-free microsphere optical resonator bio/chemical sensors
Author(s): Niranjan M. Hanumegowda; Ian M. White; Caleb J. Stica; Bijal C. Patel; Hesam Oveys; Xudong Fan
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Paper Abstract

Whispering Gallery Modes (WGMs) in microsphere ring resonators enable excellent sensitivity due to the high Q-factor (> 106) that significantly increases the light-matter interaction. The analytes attached to the sphere surface change the local refractive index, leading to a spectral shift in the resonances of the WGM. A practical microsphere-based sensor must detect minute changes in the refractive index. In addition, the microsphere surface should be functionalized for subsequent binding of bio/chemical molecules. Both functionalization and binding processes should be monitored in order to better anchor the captured molecules and to acquire quantitative and kinetic binding information. In this work, we have carried out a series of experiments towards developing highly sensitive fused silica microsphere based sensors. A fiber prism is used to couple the light from a tunable diode laser to the sphere. A fluidic well is built to allow for injection and withdrawal of samples. The sensor sensitivity of refractive index is characterized by using the mixture of water and alcohol. It is shown that our system is able to detect changes in refractive index as low as 10-7. We further monitor the kinetics of layer deposition when the sphere surface is functionalized with silane solution. Finally we monitor the protein binding to and peptide cleavage from the functionalized microsphere. Our results should lead to highly sensitive microsphere bio/chemical sensor arrays with applications in biomedical sciences, environmental monitoring, and drug discovery.

Paper Details

Date Published: 10 November 2005
PDF: 12 pages
Proc. SPIE 6004, Fiber Optic Sensor Technology and Applications IV, 60040I (10 November 2005); doi: 10.1117/12.630062
Show Author Affiliations
Niranjan M. Hanumegowda, Univ. of Missouri (United States)
Ian M. White, Univ. of Missouri (United States)
Caleb J. Stica, Univ. of Missouri (United States)
Bijal C. Patel, Univ. of Missouri (United States)
Hesam Oveys, Univ. of Missouri (United States)
Xudong Fan, Univ. of Missouri (United States)


Published in SPIE Proceedings Vol. 6004:
Fiber Optic Sensor Technology and Applications IV
Michael A. Marcus; Brian Culshaw; John P. Dakin, Editor(s)

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