Chemistry: analytical and immunological testing – Including sample preparation – Volumetric liquid transfer
Patent
1995-08-25
1998-01-06
Alexander, Lyle A.
Chemistry: analytical and immunological testing
Including sample preparation
Volumetric liquid transfer
422 56, 422 58, 422 61, 436169, G01N 3122
Patent
active
057053979
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This application is the national filing of PCT/GB94/00356, filed Feb. 23, 1994.
The invention concerns analytical devices for use in assay procedures.
Simple self-contained devices for performing biochemical diagnostic assays in extra-laboratory conditions are being used in an ever widening range of applications. These devices are designed to avoid the need for complex manual procedures such that they can be reliably carried out by an unqualified user.
The analysis to be carried out in such assay procedures is generally in respect of an analyte in the form of an antigen within a body fluid sample, such as a sample of blood or urine. Generally, the antigen will first be specifically bound with antibody held at an analytical site. A first reagent, for example a labelling reagent, is then delivered to the analytical site, followed by a second reagent, for example a label detection reagent to provide a signal for the user. The signal may for example be a colorimetric change, the colour or intensity of colour produced providing information for the user.
Devices for realising an assay procedure of this kind are disclosed in patent application Ser. No. WO-90/11519, in which first and second liquid flow channels of porous materials end from a respective pair of channel ends to a common site, the channels being operable to transfer liquid by capillary flow to the common site in sequentially timed manner following simultaneous application of the liquid to the pair of channel ends. Document EP-A-0262328 describes a test strip for biochemical analysis, including an embodiment comprising multiple solvent transport pathways. One of the pathways may feature a convoluted flowpath formed by the incorporation of baffles in the device.
The first and second reagents are delivered to the analytical site by a liquid, such as a buffer solution. This solubilises and entrains the reagents to carry them onwards and thereby deliver them to the analytical site. The speed at which a reagent is carried is dependent on the length of the column of liquid, and a typical relationship may be represented as follows: width of channel, k and n are positive constants specific to the material of the device. For example, for Millipore AP25 filter paper, if T is in seconds and L is in min., k=0.016 and n=2.1.
Because the column of liquid carrying the first reagent through the analytical site is shorter than that subsequently carrying the second reagent through the analytical site, the first reagent travels considerably faster than the second (see the equation above). In sequential delivery analytical devices of this sort, whilst the second reagent is an enzymic reagent (which is often provided in excess), the first reagent is usually involved in an antibody/antigen reaction. For such a reaction it is most important that the time of contact between the reagents, or incubation period, is sufficient. With currently available devices this is not always the case and there is therefore a need to improve the effectiveness of this incubation stage.
The need to provide a sufficient incubation period is not of course restricted solely to sequential delivery analytical devices featuring two or more reagents, but can arise more generally with liquid transfer analytical devices.
SUMMARY OF THE INVENTION
It is an object of this invention to improve the situation described above and to this end there is provided an analytical device for use in assay procedures, comprising at least one liquid flow channel of porous material for capillary flow therealong, the channel leading from a channel end to an analytical site via a localised reagent site so as to provide a flow path to transport liquid from the channel end through the reagent site, wherein a permanent liquid-impermeable barrier is provided adjacent to the reagent site, the barrier intercepting said flow path to create a substantially stagnant zone whereby the distribution of the reagent is elongated as it is delivered from the reagent site to the analytical site by entrainment
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patent: 4810470 (1989-03-01), Burkhardt et al.
patent: 5177021 (1993-01-01), Kondo
patent: 5198193 (1993-03-01), Bunce et al.
patent: 5202268 (1993-04-01), Kuhn et al.
patent: 5354538 (1994-10-01), Bunce et al.
patent: 5516488 (1996-05-01), Bunce et al.
Alexander Lyle A.
British Technology Group Limited
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