A process, means and devices for the quantitative determination, using electromagnetic radiation, of a component of a group including specifically bonding receptors and substances which can be specifically bonded by these receptors are based on a process comprising incubating one of the components, after it is immobilizing on the surface of a material having refractive index different from that of the components, with the other particular component and, optionally, further components, which can be labelled; irradiating the surface with electromagnetic radiation which is polarized parallel to the plane of incidence, the angle of incidence of the radiation being approximately equal to the angle .PHI. at which the intensity of the radiation reflected from the uncoated or precoated surface reaches a minimum; and ascertaining the intensity of the reflected radiation as a measure of the concentration to be determined.
A coherent light beam is made incident upon a cell via a polarizer. In the cell is contained a reaction liquid consisting of fine magnetic particles having an antibody coated thereon and a sample containing an antigen which is specifically reacted with the antibody on the particles. The particles are rotated in the reaction liquid by means of alternating magnetic fields having a frequency f.sub.0 and generated by coils arranged beside the cell. Light scattered by the particles is made incident upon a photodetector via a polarizer whose polarization plane is perpendicular to that of the analyzer. An output signal from the photodetector is synchronously detected by means of a reference signal having a frequency 2f.sub.0. Then a synchronously detected output signal represents an amount of the antigen contained in the sample.
A diffraction immunoassay method in which a diffraction grating design of non-light disturbing primary binding reagent on an insoluble surface is conjugated with analyte in a sample. If the primary binding reagent-analyte conjugate is light disturbing, a diffraction grating is formed. If the primary binding reagent-analyte conjugate is non-light disturbing, the analyte is further conjugated with a secondary binding reagent which is labeled with a light disturbing material to form a diffraction grating. Light from a narrow band light source is then applied to the surface, and the intensity of beams of diffracted light formed by the diffraction grating is determined. The diffraction immunoassay plate for the method comprises a smooth insoluble surface having on the surface thereof, a diffraction grating design of lines of the primary binding reagent. The diffraction immunoassay apparatus comprises a light source, a platform for supporting the diffraction immunoassay plates in the path of a beam of light from the light source, and at least one light detector positioned to detect light diffracted by the diffraction grating.
Apparatus and method for providing an optical detection of a binding reaction between a ligand and an antiligand, including, a pattern formed by a spatial array of microscopic dimensions of antiligand material, ligand material interacting with the antiligand material to produce a binding reaction between the ligand and the antiligand in the pattern, a source of optical radiation including energy at at least one wavelength directed to the pattern at a particular incidence angle to produce scattering of the energy from the pattern in accordance with the binding reaction and with a strong scattering intensity at one or more Bragg scattering angles, and at least one optical detector located relative to the pattern and aligned with a Bragg scattering angle to detect the strong scattering intensity at the Bragg scattering angle to produce a signal representative of the binding reaction.
A method of assaying for a ligand in a sample which includes incubating, simultaneously or in any desired sequence, a) the sample b) a reagent X and c) a reagent Y immobilised on the surface of an optical structure capable of exhibiting surface plasmon resonance, one of reagents X and Y is a specific binding partner to said ligand and the other of reagents X and Y is either a ligand analogue or a specific binding partner to said ligand, reagent X being such, that any formation of a direct or indirect complex between reagents X and Y results in an optical surface having an appreciably enhanced optical thickness as compared to the optical thickness of the optical surface which would prevail in the absence of reagent X, which method includes the step of determining whether and, if desired, the extent to which and/or rate at which the surface plasmon resonance effect exhibited by the optical structure is altered by said complex formation.
A new immunoassay system is provided for the detection of ligands or ligand binding partners in solution in a heterogeneous format. The invention relies upon the detection of back scattered light from an evanescent wave disturbed by the presence of a colloidal gold label brought to the interface by an immunological reaction. The evanescent wave existing at the interface in turn is the result of a totally internally reflected incident light wave. Placement of the detector at a back angle above the critical angle insures a superior signal-to-noise ratio. Apparatus and methods for scanning, detecting and manipulating light including a scattered total internal reflectance immunoassay system are provided.
