Assay device and methods

Abstract

The present invention relates to the use of amphipathic polymers to enhance lateral flow and reagent mixing on assay devices. More specifically, the invention relates to use of an amphipathic polymer in assay methods including a device for determining the concentration of lipids in blood serum or plasma.

Description

FIELD OF THE INVENTION[0001]The present invention relates to the use of amphipathic polymers to enhance lateral flow and reagent mixing on assay devices. More specifically, the invention relates to use of an amphipathic polymer in assay methods including a device for determining the concentration of lipids in blood serum or plasma.BACKGROUND TO THE INVENTION[0002]Lateral flow assay devices and methods are known in the art. Previously, such devices have been developed to test samples that are easily available in large quantities. However, when the test sample is blood or a component of blood, the collection of a large sample is not always possible, particularly at a point of care such as a doctor's surgery.[0003]Generally these devices comprise a lateral flow matrix, for example, nitrocellulose membranes and the like. A sample applied to the matrix flows along the matrix, and one or more analytes within the sample react with one or more reagents within the lateral flow matrix. Typica...

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Benefits of technology

[0016]The Applicants have made the surprising discovery that by use of amphipathic polymers in an assay system, considerable gains in both the efficiency and / or speed of the assay can be achieved. The Applicant's methods are also applicable to rapidly combining hydrophobic reagents and compounds such as luminophores with analytes, for example lipoproteins, in aqueous solution(s) / suspension(s) without direct application of organic solvents. This method enables the lipoprotein contents of blood, foodstuffs, and the like to be easily quantified by measurement of fluorescence. The use of such methods has also enabled the development of a rapid and inexpensive point of care cholesterol assay system.

[0021]Surprisingly it has been found that the amphipathic polymers may be used to coat the surface of, for example, plastics or glass to enhance fluid flow to move and / or mix aqueous solutions, for example with ‘dry’ components combined within or as layers above or below the coating of amphipathic polymers. The use of amphipathic polymers also has the advantage that lateral flow of fluids is improved, for example, over the traditional ‘wicking’ with porous materials such as is disclosed in U.S. Pat. No. 6,485,982. Wicking methods of the prior art rely on the use of a support vehicle such as paper or a membrane through which liquid is drawn by capillary action. The use of amphipathic polymers removes the need for a support vehicle which relies solely on capillary action and has the surprising effect that liquids may travel greater distances or at greater speeds, for example, along microtubes or surfaces than in porous materials by capillary action alone.

[0026]Thus, an amphipathic polymer may be used to coat a surface such as the inside of a tube, capillary, channel, well, membrane or the like. It will be apparent that the amphipathic polymer may also be used as a coating for membranes used in ‘standard’ lateral flow assays to speed up and / or provide greater control over the fluid flow.

[0070]Advantageously, the apparatus may be used to carry out quick and easy assays that can be conducted simultaneously, in parallel, to determine the presence / absence or concentration of an analyte from the biological fluid. For example, the use of an amphipathic polymer reduces the time an assay takes from several hours or even days to around as little as one minute.

Problems solved by technology

However, when the test sample is blood or a component of blood, the collection of a large sample is not always possible, particularly at a point of care such as a doctor's surgery.

Unfortunately, variations associated with sample transfer and diffusion of the sample to the membrane result in a flow that is largely uncontrolled and uneven before reaching a test area.

Such a reliance on capillary action may have an adverse affect on the accuracy of the device because the amount of analyte and / or label captured across a test area is not consistent.

The use of capillary action alone also means that assays are slow because of unreliable fluid wicking.

The assays are also unsuitable for small fluid samples, such as in nucleic acid detection, where the membrane may dry before the assay is completed or there may be insufficient fluid to travel the length of the test device.

It is well known that the concentration of various lipoproteins in the blood is correlated with the risk of an individual developing atherosclerosis.

Thus, if the levels of HDL cholesterol are determined to be low, an individual may have an increased risk of developing atherosclerosis.

Each of these methods suffers from a number of drawbacks.

For example, ultracentrifugation requires the use of specialised laboratory equipment and may take several days to complete.

Fractional precipitation and electrophoretic separation are both time-consuming and again require the use of specialised equipment.

Thus, the equation provides an indirect estimation based on three independent lipid analyses each of which provides a potential source of error.

As a result of these drawbacks, the results of cholesterol assays are not available for several hours or even days and cannot be performed in smaller laboratories or by doctors in their surgeries.

Such interactions may also be thermodynamically unfavourable.

However, such methods suffer from the drawback that the organic solvent is often toxic or can interfere with enzymatic reactions or fluorescence measurement.

Such methods are generally also not suitable for point of care use such as in a Doctor's surgery or clinic.

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