Author
M. Khoshsima
Other affiliations: Adelphi University
Bio: M. Khoshsima is an academic researcher from New York University. The author has contributed to research in topics: Whispering-gallery wave & Biosensor. The author has an hindex of 3, co-authored 7 publications receiving 1715 citations. Previous affiliations of M. Khoshsima include Adelphi University.
Papers
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TL;DR: In this article, an optical biosensor with unprecedented sensitivity for detection of unlabeled molecules is presented. But the method relies on the use of a dielectric microparticle (whispering gallery modes) as the physical transducing mechanism.
Abstract: We present an optical biosensor with unprecedented sensitivity for detection of unlabeled molecules. Our device uses optical resonances in a dielectric microparticle (whispering gallery modes) as the physical transducing mechanism. The resonances are excited by evanescent coupling to an eroded optical fiber and detected as dips in the light intensity transmitted through the fiber at different wavelengths. Binding of proteins on the microparticle surface is measured from a shift in resonance wavelength. We demonstrate the sensitivity of our device by measuring adsorption of bovine serum albumin and we show its use as a biosensor by detecting streptavidin binding to biotin.
955 citations
TL;DR: The theoretical shift for adsorption of a single protein is found to be extremely sensitive to the target region, with adsor adaptation in the most sensitive region varying as 1/R(5/2).
Abstract: Biosensors based on the shift of whispering-gallery modes in microspheres accompanying protein adsorption are described by use of a perturbation theory. For random spatial adsorption, theory predicts that the shift should be inversely proportional to micorsphere radius R and proportional to protein surface density and excess polarizability. Measurements are found to be consistent with the theory, and the correspondence enables the average surface area occupied by a single protein to be estimated. These results are consistent with crystallographic data for bovine serum albumin. The theoretical shift for adsorption of a single protein is found to be extremely sensitive to the target region, with adsorption in the most sensitive region varying as 1R 52 . Specific parameters for single protein or virus particle detection are predicted. © 2003 Optical
770 citations
TL;DR: In this article, a dielectric microparticle is evanescently coupled with an optical fiber for the resonance stimulation, and a shift of the resonance wavelength is measured to monitor protein monolayer formation on the surface.
Abstract: We report on molecular weight dependence measurements for an optical resonance biosensor. A dielectric microparticle is evanescently coupled with an optical fiber for the resonance stimulation, and a shift of the resonance wavelength is measured to monitor protein monolayer formation on the microparticle surface. Wavelength shifts for proteins over two orders of magnitude in molecular weight are measured. We show that the shift is proportional to molecular weight to the one-third power. Our result demonstrates that the optical resonance biosensor provides protein size information upon detection. This molecular weight dependency differentiates optical resonance sensing from electrical detection using field-effect transistors.
49 citations
TL;DR: In this article, the authors describe a harmonic oscillator with two phase, right and left expansions of spacetime, and the equilibrium position for a two phase universe is the fabric of space with surge of stored energy in a singularity, expanding into the next phase of expansion.
Abstract: Energy field waves propagate in the fabric of spacetime. Interaction between spacetime field propagation and matter will generate physical photons. There are three regions of spacetime; (1) events in timelike region corresponding to the expanding universe, (2) events in lightlike region, the fabric of spacetime corresponding to spacetime with no expansion, (3) events in spacelike region corresponding to residual or evanescent universe. Universe is similar to a harmonic oscillator with two phase, right and left expansions. The equilibrium position for a two phase universe is the fabric of spacetime with surge of the stored energy in a singularity, expanding into the next phase of expansion. The evanescent universe is the spacelike event region where mass will decay. Expansion of universe and creation of matter is due to energy field propagation and superposition of energy fields in the fabric of spacetime.
4 citations
01 Jan 2004
3 citations
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Proceedings Article•
01 Jan 2005TL;DR: In quantum optical devices, microcavities can coax atoms or quantum dots to emit spontaneous photons in a desired direction or can provide an environment where dissipative mechanisms such as spontaneous emission are overcome so that quantum entanglement of radiation and matter is possible.
Abstract: Microcavity physics and design will be reviewed. Following an overview of applications in quantum optics, communications and biosensing, recent advances in ultra-high-Q research will be presented.
2,857 citations
06 Jun 2003
TL;DR: This work demonstrates a process for producing silica toroid-shaped microresonators-on-a-chip with Q factors in excess of 100 million using a combination of lithography, dry etching and a selective reflow process, representing an improvement of nearly four orders of magnitude over previous chip-based resonators.
Abstract: We demonstrate microfabrication of ultra-high-Q microcavities on a chip, exhibiting a novel toroid-shaped geometry. The cavities possess Q-factors in excess of 100 million which constitutes an improvement close to 4 orders-of-magnitude in Q compared to previous work [B. Gayral, et al., 1999].
2,177 citations
TL;DR: This article reviews the recent progress in optical biosensors that use the label-free detection protocol, in which biomolecules are unlabeled or unmodified, and are detected in their natural forms, and focuses on the optical biosENSors that utilize the refractive index change as the sensing transduction signal.
2,060 citations
TL;DR: The enhancement mechanisms responsible for the extreme sensitivity of the WGM biosensor are described, its current implementations and applications are reviewed, and its future possibilities are discussed.
Abstract: Optical label-free detectors, such as the venerable surface plasmon resonance (SPR) sensor, are generally favored for their ability to obtain quantitative data on intermolecular binding. However, before the recent introduction of resonant microcavities that use whispering gallery mode (WGM) recirculation, sensitivity to single binding events had not materialized. Here we describe the enhancement mechanisms responsible for the extreme sensitivity of the WGM biosensor, review its current implementations and applications, and discuss its future possibilities.
1,621 citations
TL;DR: A highly specific and sensitive optical sensor based on an ultrahigh quality (Q) factor (Q > 108) whispering-gallery microcavity is reported and label-free, single-molecule detection of interleukin-2 was demonstrated in serum.
Abstract: Current single-molecule detection techniques require labeling the target molecule. We report a highly specific and sensitive optical sensor based on an ultrahigh quality (Q) factor (Q > 10^8) whispering-gallery microcavity. The silica surface is functionalized to bind the target molecule; binding is detected by a resonant wavelength shift. Single-molecule detection is confirmed by observation of single-molecule binding events that shift the resonant frequency, as well as by the statistics for these shifts over many binding events. These shifts result from a thermo-optic mechanism. Additionally, label-free, single-molecule detection of interleukin-2 was demonstrated in serum. These experiments demonstrate a dynamic range of 10^(12) in concentration, establishing the microcavity as a sensitive and versatile detector.
1,189 citations