Abstract: A method for improving measurement precision in an optical biosensor assay for a ligand in a sample is described. The method involves referencing the assay with an artificially raised background level by the labelling of the optical waveguide with an appropriate reference reagent. Devices for use in such a method are also described.

Abstract: A method of assaying for a ligand in a sample involves incubating the sample in contact with a specific binding partner for the ligand carried on one surface of an optical structure, irradiating the structure at a suitable angle or range of angles to the normal such that the resonance and/or total internal reflection of the radiation occurs within the optical structure and/or the layer of specific binding partner, and analyzing the radiation in order to determine whether, and if desired the extent to which and/or rate at which the generated radiation and/or optical characteristics of the optical structure are altered by complex formation.

Abstract: The invention relates to a method of reducing scattering of light emerging from an optical edge of an optical waveguide. According to the invention, the optical edge is maintained in intimate contact with an index matching substance which itself also forms or intimately contacts a further optical component. The invention also relates to a disposable holder suitable for use in the method.

Abstract: The invention relates to a device for use in optical methods of assay. The device comprises an optical structure comprising a dielectric substrate (2) and a thin film waveguide (5), between which is interposed a buffer layer (4). The waveguide carries a layer (10) of reagent suitable for a desired assay. The invention also relates to methods of using the device in an assay.

Abstract: The invention relates to a device for use in methods of assay, for example those involving fluorescent moieties. The device possesses a cavity or cavities into which the sample liquid may be drawn by capillary action. Each cavity is formed from two transparent solid plates (35,36): one (36) is adapted to act as a waveguide and carries a suitable immobilized reagent on its surface within the cavity; the other (35) carries on its external surface and optionally also on part only of its internal surface a layer of light-absorbing material (37). The invention also relates to a method of manufacturing devices according to the invention, and to a method of assaying for a ligand in a sample using a device according to the invention.

Abstract: The vehicle comprises a sample receiving reservoir (15), a plurality of test stations each comprising an FCFD or other capillary fill sensor cell (3), and passage (22) for providing fluid communication between the reservoir and a conduit with which end portions of said cells communicated such that in use sample from the reservoir may be fed to the plurality of cells substantially simultaneously. The vehicle makes it easier to know time zero for each assay. Passage (22) providing fluid connection may comprise at least one pore in a wall of the reservoir, the or each pore being of a size such that surface tension of the liquid normally prevents escape of ligand. Rotation of the vehicle breaks surface tension and liquid is released into the conduit.

Abstract: The invention relates to a method of optical analysis which can advantageously be used in conjunction with optical assay techniques, particularly those wherein evanescent signals are to be analysed. The method makes use of the properties of an optical structure (described herein) which allows easy angular discrimination of optical signals emerging from a test object. The invention also relates to apparatus for use in said methods.