Assay Device & Method
There is disclosed a lateral flow assay device and method of producing the same. The device, which is for identifying carbohydrate antigens in a biological sample comprises a substrate having, a) a sample receiving zone, b) an extraction zone for receiving the sample from said sample receiving zone and which extraction zone comprises immobilised or otherwise absorbed therein at least one or more reactants and reagents which when combined react to form an extraction reagent for a desired antigen in said sample, said sample to be added to said sample receiving zone optionally comprising the remaining reactant required to form said extraction reagent if not present in said extraction zone, c) optionally a neutralising agent capable of bringing the pH of the resulting sample to within the operational pH range of the assay and, d) a detection zone for a labelled specific binding or capture reagent for said antigen to be detected.
1 . A lateral flow assay device for identifying carbohydrate antigens in a biological sample, said device comprising a substrate having
a) a sample receiving zone,
b) an extraction zone for receiving the sample from said sample receiving zone and which extraction zone comprises immobilised or otherwise absorbed therein at least one or more reactants and reagents which when combined react to form an extraction reagent for a desired antigen in said sample,
said sample to be added to said sample receiving zone optionally comprising the remaining reactant required to form said extraction reagent if not present in said extraction zone,
c) optionally a neutralising agent capable of bringing the pH of the resulting sample to within the operational pH range of the assay and,
d) a detection zone for a labelled specific binding or capture reagent for said antigen to be detected.
2 . A device according to claim 1 wherein said extraction zone comprises both said precursor reactants that when combined react to form said extraction reagent.
3 . A device according to claims 1 or 2 , wherein said antigen to be detected is a Streptococcal antigen.
4 . A device according to claim 3 , wherein said Streptococcal antigen is Streptococcal A antigen.
5 . A device according to any preceding claim wherein said extraction reagent is a nitrous acid, each of said precursor reactants being an acid and a nitrite and which when combined form the nitrous acid.
6 . A device according to claim 5 , wherein said acid is a sulfonic acid in the form of a resin and said nitrite is sodium nitrite.
7 . A device according to any preceding claim wherein said substrate comprises a lateral flow porous carrier.
8 . A device according to any of claims 1 to 6 wherein said substrate comprises microfluidic channels the dimensions of which are such as to allow a liquid sample move there through by means of capillary action.
9 . A device according to any preceding claims wherein said labelled specific binding reagent is immobilised at or upstream of said detection zone.
10 . A device according to any of claims 1 to 9 , wherein said labelled specific binding reagent is added to said substrate together with or after addition of said sample.
11 . A device according to any of claims 1 to 9 wherein said substrate comprises a mobilisable labelled specific capture reagent and provided at a position downstream from the optional neutralising agent.
12 . A device according to claim 11 , wherein the mobilisable capture reagent is provided on and/or in a separate porous carrier arranged so as to be in fluidic contact with and upstream from the porous carrier.
13 . A device according to claim 12 , wherein said separate porous carrier is macroporous and may be of a different material to that of the porous carrier.
14 . A device according to any preceding claim wherein said labelled specific binding reagent is labelled antibody.
15 . A device according to any preceding claim where said label is an enzyme label or a specific dye.
16 . A device according to any preceding claim, wherein said sample receiving zone comprises a sample receiving wick made of any bibulous, porous or fibrous material capable of absorbing liquid sample.
17 . A device according to any preceding claim, wherein the porous carrier is a nitrocellulose carrier.
18 . A device according to claim 17 , wherein said porous carrier is nitrocellulose and the macroporous carrier is selected from any of glass fibre of a synthetic polymeric material such as polypropylene.
19 . A device according to any preceding claim, wherein said substrate comprises an absorbent sink at the distal end thereof.
20 . A device according to any preceding claim further comprising a control zone at or downstream from the detection zone and which comprises a further immobilised capture reagent that is able to capture the labelled capture reagent.
21 . A kit for identifying carbohydrate antigens in a biological sample, which kit comprises a device according to any preceding claim and means for contacting said sample with said sample receiving area.
22 . A method of producing an assay device according to any of claims 1 to 20 , which method comprises immobilising in a lateral flow assay device having a sample receiving area, one or more reagents in an extraction zone of said device and which reagents when combined form an extraction reagent for any carbohydrate antigen in a sample added to said sample receiving zone, providing a neutralisation buffer downstream of said extraction zone to neutralise the pH of said extraction reagent subsequent to extraction of said antigen/analyte from said sample, and upstream from a capture/detection reagent immobilised in said assay device.
23 . A method according to claim 22 , wherein said method comprises pretreating said substrate with a surface active agent.
24 . A method for identifying carbohydrate antigens in a biological sample, which method comprises applying said biological sample to a sample receiving zone of a device according to any of claims 1 to 20 and monitoring for the presence of said antigen in said detection zone.