Chemical Sensing by RIFTS-Reflective Interferometric Fourier-Transform Spectroscopy: A Robust, Self-Compensating Method for Label-Free Detection of Biomolecules

Background

Most optical transducers for label-free biosensing involve measurement of a change in the refractive index of a material induced upon analyte binding. While surface plasmon resonance (SPR) films, resonant and nonresonant diffraction gratings, reflectometric interference (RIFS) layers and Fabry-Perot interferometers show very sensitive responses to small changes in refractive index, these methods are all limited by zero-point-drift arising from changes in temperature, matrix composition, or nonspecific binding to the analytical surface.

A double-beam (Michelson-type) interferometer, in which one optical path acts as a reference channel, provides an excellent means of compensating for such effects. Various implementations of double-beam correction have been employed in micro-scale biosensor systems, generally involving two spatially distinct regions of a chip. However, because the sample and reference channels are separated in the X-Y plane, such designs pose significant alignment and manufacturability challenges, especially upon incorporation into high-throughput arrays.

Technology Description

This invention utilizes a novel self-compensating interferometric biosensor comprised of two layers of porous SiO 2, stacked one on top of the other. The reflectivity spectrum displays a complex interference pattern that arises from a combination of Fabry-Pérot interference from these layers. A ratio of the peak intensities in the fast Fourier transform (FFT) allows discrimination of target analyte from matrix effects arising from non-specific compositional changes in the analyte solution.

Applications

Label-free biosensing, high-throughput molecular sensing, array-based sensing, drug lead discovery, diagnostics, and characterization of kinetic and thermodynamic binding constants in biomolecular binding assays.

Advantages

The approach is very general. For example, the methodology should also work with other label-free transduction modalities in materials other than porous SiO 2 or porous Si that utilize refractive index changes, such as surface plasmon resonance or microcavity resonance. The built-in reference channel and Fourier method of analysis provides a general means to compensate for changes in sample matrix, non-specific binding, temperature, and other experimental variables.

State Of Development

The concept has been demonstrated with a Protein A capture probe and Human Immunoglobulin G as the target analyte. The system response is shown to be insensitive to the addition of 4000-fold excess sucrose or 80-fold excess bovine serum albumin.

Related Materials

1. Tinsley-Bown, A. M. et al. Tuning the Pore Size and Surface Chemistry of Porous Silicon for Immunoassays. Phys. Status Solidi A 182, 547-53 (2000).
2. Létant, S. E., Content, S., Tan, T. T., Zenhausern, F. and Sailor, M. J. Integration of Porous Silicon Chips in an Electronic Artificial Nose. Sens. Actuators B 69, 193-198 (2000).
3. Sailor, M. J. et al. in Unattended Ground Sensor Technologies and Applications III (ed. Carapezza, E. M.) 153-165 (SPIE, Orlando, FL, 2001).
4. Collins, B. E., Dancil, K.-P., Abbi, G. and Sailor, M. J. Determining Protein Size Using an Electrochemically Machined Pore Gradient in Silicon. Adv. Funct. Mater. 12, 187-191 (2002).
5. Cunin, F. et al. Biomolecular Screening with Encoded Porous Silicon Photonic Crystals. Nature Mater. 1, 39-41 (2002).
6. See Professor Michael Sailor's June 2005 Smart Dust presentation.
7. Lin, H., Mock, J., Smith, D., Gao, T. & Sailor, M. J. Surface-Enhanced Raman Scattering from Silver-Plated Porous Silicon. J. Phys. Chem. B 108, 11654 -11659 (2004).
8. Lin, H., Gao, T., Fantini, J. and Sailor, M. J. A Porous Silicon-Palladium Composite Film for Optical Interferometric Sensing of Hydrogen. Langmuir 20, 5104-5108 (2004).

Related Materials

• Ghadiri, M. R., Sailor, M. J., Motesharei, K., Lin, S.-Y. & Dancil, K.-P. S. Porous semiconductor-based optical interferometric sensor. See U.S. patent number 6,897,965. - 05/24/2005
• Ghadiri, M. R., Sailor, M. J., Motesharei, K., Lin, S.-Y. & Dancil, K.-P. S. Porous semiconductor-based optical interferometric sensor. See U.S. patent number 6,720,177. - 04/13/2004
• Ghadiri, M. R., Motesharei, K., Lin, S.-Y., Sailor, M. J. & Dancil, K.-P. Porous semiconductor-based optical interferometric sensor. See U.S. patent number 6,248,539. - 06/19/2001
• Létant, S. & Sailor, M. J. Molecular Identification by Time Resolved Interferometry in a Porous Silicon Film. Adv. Mat. 13, 335-338 (2001).
• Sohn, H., Létant, S., Sailor, M. J. & Trogler, W. C. Detection of Fluorophosphonate Chemical Warfare Agents by Catalytic Hydrolysis with a Porous Silicon Interferometer. J. Am. Chem. Soc. 122, 5399-5400 (2000).
• Dancil, K.-P. S., Greiner, D. P. & Sailor, M. J. A Porous Silicon Optical Biosensor: Detection of Reversible Binding of IgG to a Protein A-Modified Surface. J. Am. Chem. Soc. 121, 7925-7930 (1999).
• Janshoff, A. et al. Macroporous P-Type Silicon Fabry-Perot Layers. Fabrication, Characterization, and Applications in Biosensing. J. Am. Chem. Soc. 120, 12108-12116 (1998).
• Lin, V. S.-Y., Motesharei, K., Dancil, K. S., Sailor, M. J. & Ghadiri, M. R. A Porous Silicon-Based Optical Interferometric Biosensor. Science 278, 840-843 (1997).

Intellectual Property Info

A patent application is pending.

Patent Status