Optics: measuring and testing – Of light reflection
Patent
1994-07-08
1996-02-13
Rosenberger, Richard A.
Optics: measuring and testing
Of light reflection
356128, G01N 2155
Patent
active
054915562
DESCRIPTION:
BRIEF SUMMARY
This invention relates to sensors, especially those termed biosensors, ie devices for the analysis of biologically active species such as antigens and antibodies in samples of biological origin. In particular, the invention relates to biosensors based on resonant optical phenomena, eg surface plasmon resonance or resonant attenuated or frustrated total internal reflection.
Many devices for the automatic determination of biochemical analytes in solution have been proposed in recent years. Typically, such devices (biosensors) include a sensitised coating layer which is located in the evanescent region of a resonant field. Detection of the analyte typically utilizes optical techniques such as, for example, surface plasmon resonance (SPR), and is based on changes in the thickness and/or refractive index of the coating layer resulting from interaction of that layer with the analyte. This causes a change, eg in the angular position of the resonance.
Other optical biosensors include a waveguide in which a beam of light is propagated. The optical characteristics of the device are influenced by changes occurring at the surface of the waveguide. One form of optical biosensor is based on frustrated total reflection. The principles of frustrated total reflection (FTR) are well-known; the technique is described, for example, by Bosacchi and Oehrle [Applied Optics (1982), 21, 2167-2173]. An FTR device for use in immunoassay is disclosed in European Patent Application No 0205236A and comprises a cavity layer bounded on one side by the sample under investigation and on the other side by a spacer layer which in turn is mounted on a substrate. The substrate-spacer layer interface is irradiated with monochromatic radiation such that total reflection occurs, the associated evanescent field penetrating through the spacer layer. If the thickness of the spacer layer is correct and the incident parallel wave vector matches one of the resonant mode propagation constants, the total reflection is frustrated and radiation is coupled into the cavity layer. The cavity layer must be composed of material which has a higher refractive index than the spacer layer and which is transparent at the wavelength of the incident radiation.
In devices of this kind, the position of resonance is monitored by varying the angle at which light is incident on the sensor. The scanning of angle may be performed either sequentially or simultaneously ie by varying the angle of incidence of a parallel beam of light or by simultaneously irradiating over a range of angles using a fan-shaped beam of light as described (in connection with SPR) in European Patent Application No 0305109A. In the former case, prior proposals have involved a single-channel detector which is mechanically scanned over a range of angles; this necessitates synchronisation of the movement of the light source and the detector. In the latter case, in which a range of angles is irradiated simultaneously, it is generally necessary to use a multi-channel detector having angular resolution. This leads to relatively high manufacturing costs.
There has now been devised an apparatus involving the use of a resonant optical sensor for the determination of a chemical or biochemical species, which overcomes or substantially mitigates some or all of the disadvantages of the prior art arrangements described above.
According to the invention, there is provided apparatus for the determination of a chemical or biochemical species, comprising a resonant optical biosensor disposed in a light path between a pivotally-mounted source of monochromatic light and a stationary detector adapted to monitor some characteristic of the light, there being provided means for causing pivotal motion of the light source so as to vary the angle of incidence of the light on the sensor and means for monitoring the instantaneous angle of incidence.
The apparatus according to the invention is advantageous primarily in that it is of relatively simple construction and uses only a single-channel detector. Also, the means for monitor
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patent: 4142797 (1979-03-01), Astheimer
patent: 4877747 (1989-10-01), Stewart
patent: 5023053 (1991-06-01), Finlan
Patent Abstracts of Japan, vol. 12, No. 88, 23 Mar. 1988.
Maule Colin H.
Molloy James O.
Stewart Douglas A.
Fisons plc
Rosenberger Richard A.
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