Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reissue Patent
2000-02-03
2001-12-18
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C356S329000, C422S068100, C250S559400
Reissue Patent
active
RE037473
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to the field of optical sensing and, more particularly, to a method and apparatus for assaying chemical and biological materials.
BACKGROUND OF THE INVENTION
Recently, extremely sensitive optical sensors have been constructed by exploiting an effect known as surface plasmon resonance (SPR). These sensors are capable of detecting the presence of a wide variety of materials in concentrations as low as picomoles per liter. SPR sensors have been constructed to detect many biomolecules including dinitrophenyl, keyhole limpet hemocyanin, &agr;-Feto protein, IgE, IgG, bovine and human serum albumin, glucose, urea, avidin, lectin, DNA, RNA, hapten, HIV antibodies, human transferrin, and chymotrypsinogen. Additionally, SPR sensors have been built which detect chemicals such as polyazulene and various gases including halothane, tricloroethane and carbon tetrachloride.
An SPR sensor is constructed by sensitizing a surface of a substrate to a specific substance. Typically, the surface of the substrate is coated with a thin film of metal such as silver, gold or aluminum. Next a sensitizing layer, such as a monomolecular layer of complementary antigens, is covalently bonded to the surface of the thin film. In this manner, the thin film is capable of interacting with a predetermined chemical, biochemical or biological substance. When an SPR sensor is exposed to a sample that includes the targeted substance, the substance attaches to the sensitizing layer and changes the effective index of refraction at the surface of the sensor. Detection of the targeted substance is accomplished by observing the optical properties of the surface of the SPR sensor.
The most common SPR sensor involves exposing the surface of the sensor to a light beam through a glass prism. At a specific angle of incidence, known as the resonance angle, a component of the light beam's wavevector in the plane of the sensor surface matches a wavevector of a surface plasmon in the thin film, resulting in very efficient energy transfer and excitation of the surface plasmon in the thin film. As a result, at the resonance angle the reflected light from the surface of the sensor exhibits a sharp dip that is readily detected. When the targeted substance attaches to the surface of the sensor, a shift in the resonance angle occurs due to the change in the refractive index at the surface of the sensor. A quantitative measure of the concentration of the targeted substance can be calculated according to the magnitude of shift in the resonance angle.
SPR sensors have also been constructed using metallized diffraction gratings instead of prisms. For SPR grating sensors, resonance occurs when a component of the incident light polarization is perpendicular to the groove direction of the grating and the angle of incidence is appropriate for energy transfer and excitation of the thin metal film. As with prism-based sensors, a change in the amount of light reflected is observed when the angle of incidence equals the resonance angle. Previous SPR grating sensors have incorporated square-wave or sinusoidal groove profiles.
SPR grating sensors offer many benefits over SPR sensors having glass prisms including a thicker, more robust metal film. Furthermore, the grating period for an SPR grating sensor can be adjusted for any desired resonance angle. Despite these benefits, both current SPR grating sensors and prism-based sensors are susceptible to degradation due to oxidation of the metal film and its continuous exposure to the sample. For this reason, the thin metal film is usually constructed with a metal that tarnishes slowly, such as gold, rather than a highly sensitive metal which tarnishes more quickly, such as silver. Another disadvantage of current SPR sensors is that the metal film causes many biological substances to denature, thus leading to erroneous readings. For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon understanding the present invention, there is a need in the art for an optical sensor having improved sensitivity and less susceptibility to degradation.
SUMMARY OF THE INVENTION
In one aspect, the invention is a sensor for assaying a substance in a sample. The sensor comprises a substrate having a plurality of grooves in a surface. The grooves are formed in a substantially periodic profile such as sinusoidal, trapezoidal or any other suitable formation. A metal layer is formed outwardly from the surface of the substrate. In this manner, the metal layer substantially conforms to the grooved profile of the surface of the substrate. A dielectric layer is formed outwardly from the metal layer and is selected so as to suppress the zero-order reflectance of light polarized parallel to the grooves of the surface for at least one angle of incidence. It is preferable that the dielectric layer has a thickness of at least 50 nm or, more preferably, at least 130 nm.
The sensor may include a sensitizing layer formed outwardly from the dielectric layer. The sensitizing layer is capable of interacting with the substance in the sample and thereby changes the angle of incidence at which the sensor suppresses the zero-order reflectance of incident light. In one embodiment the sensitizing layer comprises a layer of antigens. In another embodiment, the dielectric layer is capable of interacting with the substance in the sample.
In yet another embodiment, the invention is a sensor for assaying a plurality of substances in a sample. The sensor includes a substrate having a surface formed in a substantially periodic grooved profile and a metal layer is formed outwardly from the surface of the substrate. A plurality of substantially non-overlapping dielectric layers are formed outwardly from the metal layer. Each of the dielectric layers is capable of suppressing the zero-order reflectance of incident light for at least one corresponding angle of incidence and polarization. This embodiment facilitates the sensing of a plurality of substances in a sample or the reuse of a single sensor for multiple samples having various substances.
In one aspect, the invention is a method for assaying a substance in a sample using a sensor having a grooved diffraction grating surface coated with a dielectric layer. The sensor is exposed over a plurality of incident angles by a light beam polarized parallel to the grooves in the diffraction grating surface. A controller detects a first diffraction anomaly angle at which zero-order reflectance of a component of the incident light having a polarization parallel to the grooves of the sensor is a minimum. After interacting the sensor with the sample, the sensor is exposed a second time with a light beam over the plurality of incident angles and a second diffraction anomaly angle is detected. A measure of the substance in the sample is determined as a function of the first diffraction anomaly angle and the second diffraction anomaly angle.
REFERENCES:
patent: 4828387 (1989-05-01), Sawyers
patent: 4877747 (1989-10-01), Stewart
patent: 4882288 (1989-11-01), North
patent: 4931384 (1990-06-01), Layton
patent: 4992385 (1991-02-01), Godfrey
patent: 5071248 (1991-12-01), Tiefenthaler
patent: 5118608 (1992-06-01), Layton
patent: 5310686 (1994-05-01), Sawyers
patent: 5365067 (1994-11-01), Cole et al.
patent: 5478755 (1995-12-01), Attridge
patent: 5479260 (1995-12-01), Fattinger
patent: 5492840 (1996-02-01), Malmqvist
patent: 5583643 (1996-12-01), Gass
patent: 5598267 (1997-01-01), Sambles et al.
patent: 5907436 (1999-05-01), Perry et al.
patent: 0 321 523 (1992-02-01), None
patent: 0 517 930 (1992-12-01), None
patent: 0677734 (1995-10-01), None
patent: WO92/04617 (1992-03-01), None
patent: WO97/09608 (1997-03-01), None
“A Compact Surface Plasmon Resonance Sensor for Measurement of Water in Process”, Applied Spectroscopy, R. Matsubara, vol. 42, No. 8, 1998, pp. 1375-1379.*
“A Direct Surface Plasmon-Polariton Immunosensor: Preliminary Investigation of the Non-specific Adsorption of Serum Components to
Imation Corp.
Le Que T.
Levinson Eric D.
LandOfFree
Diffraction anomaly sensor having grating coated with... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Diffraction anomaly sensor having grating coated with..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Diffraction anomaly sensor having grating coated with... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2583660