1 DNA Detection by Differential Perturbation of two ...sphere S1 is detected by an increase of the...
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R DNA Detection by Differential Perturbation of two Microsphere Cavities Frank Vollmer 1 , Stephen Arnold 2 , Dieter Braun 1 , Iwao Teraoka 2 , Albert Libchaber 1 1 Center for Studies in Physics and Biology, The Rockefeller University, New York, NY 10021 email: [email protected] 2 Microparticle Photophysics Lab, Polytechnic University, Brooklyn, NY 11201 www.poly.edu/microparticle We report the detection of unlabeled DNA oligonucleotides on microsphere probes from a response of their photonic resonance modes. Narrow linewidth resonant modes (called whispering-gallery-modes, WGMs) occur from a light ray orbitting inside the microsphere due to total internal reflection. The reso- nance wavelength increases when dielectric material such as nucleic acid is added on the microparticles surface. Each microsphere is modified with an oligonucleotide probe of interest. The kinetics of an hybridization event is detected with millisecond time resolution from an increase of a sphere spe- cific resonance wavelength. We demonstrate that the narrow, microsphere specific resonances are separated by several linewidths which allows multi- plexing of signals from two (or more) different microparticle probes coupled to the same waveguide. We show that the differential signal of two micro- spheres can be used to identify a single nucleotide mismatch in a label-free 11-mer oligonucleotide. This approach to hybridization measurements is par- ticularly sensitive, with the typical differential signal for a single nucleotide mismatch at 54:1. λ ... wavelength (1.3 µm) δλ ... wavelength shift α ex ... excess polarizability of the bound protein σ s ... surface density of the bound protein n 1 , n 2 ... refractive indices of the sphere and the buffer solution, respectively R ... orbital radius ε 0 ... vacuum permittivity FV is supported by a fellowship of the Boehringer Ingelheim Fonds, DB by a Fellowship of the Deutsche Fors- chungsgemeinschaft, research at the Polytechnic is supported by a National Science Foundation grant. microsphere eroded optical fiber A light ray can be confined inside a dielectric sphere due to total internal reflection at the sphere surface. The long confinement time (high Q) allows the light to circumnavigate the sphere for many orbits. If used for biosensing, such an optical resonance (WGM) enables the light to interact with the same analyte molecule for several thousand times. The resonance thus improves the detection limit by orders of magnitude as compared to existing single pass techniques. The ulti- mate detection limit of an optical cavity has been estimated to be on the order of a single, unlabeled macromolecule. Resonances in glass microspheres can be excited by the light transmitted through an optical fiber. Coupling of light between fiber and sphere occurs only for specific resonance wave- lengths. Experimentally, a resonance is detected as a dip in the spectrum of the light intensity transmitted through the fiber-sphere system. Detection of biomolecules is possible due to the evanescent field which extends from the microsphere surface. Dielectric material such as DNA and protein molecules polarize when entering the evanescent field of the micro- sphere. This perturbation of the optical cavity leads to a red shift of a given resonance wavelength. (A) Light from a tunable laserdiode L (1.3 µm) is transmitted through a single mode optical fiber F. Two sil- ica microspheres S1 and S2 are evanescently coupled to the fiber. A photodetector P records the intensity at the other fiber end. Optical reso- nances from each sphere are identified as Lorentzian dips in the transmission spectrum. A hybridization event of a label-free oligonucleotide on sphere S1 is detected by an increase of the S1-specific resonance wavelength. (B) Micrograph of two spheres coupled to the same optical fiber running horizon- tally through the center of the image. The image shows res- onances of light orbitting inside each sphere. Sphere Multiplexing. (A) Transmis- sion spectrum for one (dotted line) and two (solid line) spheres coupled to the same optical fiber. Both spheres are modified with 27-mer oligonucle- otides. Shift of Resonances. (B) Shows the time trace of the two resonance posi- tions from S1 and S2. The arrows indi- cate when the two complementary DNA oligonucleotides were injected into the sample solution. Hybridization saturates within minutes and the reso- nance wavelength of the corresponding sphere increased about .038 nm each. Single nucleotide mismatch discrim- ination. (A) Time traces of resonance wavelengths in two spheres S1 and S2. S1 was modified with a 11-mer oligo- nucleotide (CTATCTCAGTC). The oligonucleotide immobilized on S2 differed by a single nucleotide (CTAT A TCAGTC). The arrow indi- cates when the oligonucleotide com- plementary to the sequence immobilized on sphere S1 was injected. In equilibrium, the wave- length shift for the perfect match sequence was approximately ten times as large as the shift for the mismatch sequence. (B) The difference signal allows one to identify a single nucle- otide mismatch with a high signal-to- noise of 54. References: “Protein detection by optical shift of a resonanc microcavity”, Applied Physics Letters 80 (21), 2002, 4057-4059 “Shift of Whispering Gallery Modes in Microspheres by Protein adsorption”, Optics Letters 28 (4), 2003, 272-274 2 3 1 4 5 6
Transcript of 1 DNA Detection by Differential Perturbation of two ...sphere S1 is detected by an increase of the...
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DNA Detection by Differential Perturbation of two Microsphere CavitiesFrank Vollmer1, Stephen Arnold2, Dieter Braun1, Iwao Teraoka2, Albert Libchaber1
1Center for Studies in Physics and Biology, The Rockefeller University, New York, NY 10021email: [email protected]
2Microparticle Photophysics Lab, Polytechnic University, Brooklyn, NY 11201www.poly.edu/microparticle
We report the detection of unlabeled DNA oligonucleotides on microsphereprobes from a response of their photonic resonance modes. Narrow linewidthresonant modes (called whispering-gallery-modes, WGMs) occur from a lightray orbitting inside the microsphere due to total internal reflection. The reso-nance wavelength increases when dielectric material such as nucleic acid isadded on the microparticles surface. Each microsphere is modified with anoligonucleotide probe of interest. The kinetics of an hybridization event isdetected with millisecond time resolution from an increase of a sphere spe-cific resonance wavelength. We demonstrate that the narrow, microspherespecific resonances are separated by several linewidths which allows multi-plexing of signals from two (or more) different microparticle probes coupledto the same waveguide. We show that the differential signal of two micro-spheres can be used to identify a single nucleotide mismatch in a label-free11-mer oligonucleotide. This approach to hybridization measurements is par-ticularly sensitive, with the typical differential signal for a single nucleotidemismatch at 54:1.
λ ... wavelength (1.3 µm)δλ ... wavelength shiftαex ... excess polarizability of the bound proteinσs ... surface density of the bound proteinn1, n2 ... refractive indices of the sphere and the buffer solution, respectivelyR ... orbital radiusε0 ... vacuum permittivity
FV is supported by a fellowship of the Boehringer Ingelheim Fonds, DB by a Fellowship of the Deutsche Fors-chungsgemeinschaft, research at the Polytechnic is supported by a National Science Foundation grant.
microsphere
eroded optical fiber
A light ray can be confined inside a dielectric sphere due to totalinternal reflection at the sphere surface. The long confinement time(high Q) allows the light to circumnavigate the sphere for manyorbits. If used for biosensing, such an optical resonance (WGM) enables thelight to interact with the same analyte molecule for several thousandtimes. The resonance thus improves the detection limit by orders ofmagnitude as compared to existing single pass techniques. The ulti-mate detection limit of an optical cavity has been estimated to be onthe order of a single, unlabeled macromolecule.
Resonances in glass microspheres can beexcited by the light transmitted through anoptical fiber. Coupling of light between fiber and sphereoccurs only for specific resonance wave-lengths. Experimentally, a resonance is detected as adip in the spectrum of the light intensitytransmitted through the fiber-sphere system.Detection of biomolecules is possible due tothe evanescent field which extends from themicrosphere surface. Dielectric material suchas DNA and protein molecules polarize whenentering the evanescent field of the micro-sphere. This perturbation of the optical cavityleads to a red shift of a given resonancewavelength.
(A) Light from a tunablelaserdiode L (1.3 µm) istransmitted through a singlemode optical fiber F. Two sil-ica microspheres S1 and S2are evanescently coupled tothe fiber. A photodetector Precords the intensity at theother fiber end. Optical reso-nances from each sphere areidentified as Lorentzian dipsin the transmission spectrum.A hybridization event of alabel-free oligonucleotide onsphere S1 is detected by anincrease of the S1-specificresonance wavelength.
(B) Micrograph of twospheres coupled to the sameoptical fiber running horizon-tally through the center of theimage. The image shows res-onances of light orbittinginside each sphere.
Sphere Multiplexing. (A) Transmis-sion spectrum for one (dotted line) andtwo (solid line) spheres coupled to thesame optical fiber. Both spheres aremodified with 27-mer oligonucle-otides.
Shift of Resonances. (B) Shows thetime trace of the two resonance posi-tions from S1 and S2. The arrows indi-cate when the two complementaryDNA oligonucleotides were injectedinto the sample solution. Hybridizationsaturates within minutes and the reso-nance wavelength of the correspondingsphere increased about .038 nm each.
Single nucleotide mismatch discrim-ination. (A) Time traces of resonancewavelengths in two spheres S1 and S2.S1 was modified with a 11-mer oligo-nucleotide (CTATCTCAGTC). Theoligonucleotide immobilized on S2differed by a single nucleotide(CTATATCAGTC). The arrow indi-cates when the oligonucleotide com-plementary to the sequenceimmobilized on sphere S1 wasinjected. In equilibrium, the wave-length shift for the perfect matchsequence was approximately ten timesas large as the shift for the mismatchsequence. (B) The difference signalallows one to identify a single nucle-otide mismatch with a high signal-to-noise of 54.
References:“Protein detection by optical shift of a resonanc microcavity”, Applied Physics Letters 80 (21), 2002,4057-4059“Shift of Whispering Gallery Modes in Microspheres by Protein adsorption”, Optics Letters 28 (4),2003, 272-274
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