Assay device
An assay device ( 1 ) for determining the presence and/or amount of an analyte present or potentially present in a liquid sample comprises: (i) a capillary tube ( 2 ) having an upstream region ( 3 ) into which the sample to be assayed is introduced for transfer by capillary action along the capillary tube to a downstream region thereof; (ii) a collection of first binding partners ( 5 ) immobilized within the capillary tube ( 2 ), said first binding partners ( 5 ) being capable of specifically binding to the analyte; (iii) a collection of second binding partners ( 6 ) displaceabley bound to a fraction of said first binding partners ( 5 ) whereby there are free first binding partners ( 5 ) immobilized within the capillary tube, said second binding partners ( 6 ) having a label and being displaceable from the first binding partners ( 5 ) by the analyte to be detected; and (iv) a detection region ( 4 ) for sample that has transferred to said downstream region of said capillary tube, said detection region being adapted to generate a detectable signal from the label on displaced second binding partners ( 6 ) that have transferred to the downstream region.
1. A method of assaying a liquid sample for determining the presence and/or amount of a target nucleic acid analyte present or potentially present in the sample, the method comprising the steps of:
(a) providing a capillary tube having immobilised therein a collection of first binding partners which comprise nucleic acid sequences capable of specifically binding to the analyte, said capillary tube further incorporating a collection of second binding partners which comprise nucleic acid sequences displaceably bound to a fraction of said first binding partners wherein 10-90% by mole of said first binding partners have said second binding partners bound thereto whereby there are free first binding partners immobilised within the capillary tube, said second binding partners having a label and being displaceable from the first binding partners by the analyte to be detected;
(b) causing the liquid sample to flow from an upstream end of the capillary tube to a downstream end thereof; and
(c) detecting for the presence of the label at the downstream end of the capillary tube.
2. A method as claimed in claim 1 wherein 50-70% by mole of said first binding partners have said second binding partners bound thereto.
3. A method as claimed in claim 1 wherein the first binding partners are covalently immobilised within the capillary tube.
4. A method as claimed in claim 1 wherein the nucleic acid sequences of the first binding partners and the nucleic acid sequences of the second binding partners comprise DNA, mRNA, RNA or PNA sequences.
5. A method of assaying a liquid sample for determining the presence and/or amount of an analyte present or potentially present in the sample, the method comprising the steps of:
(a) providing a capillary tube having immobilised therein a collection of first binding partners which comprise a polysaccharide capable of specifically binding to the analyte, said capillary tube further incorporating a collection of second binding partners which comprise a lectin displaceabley hybridised to a fraction of said first binding partners wherein 10-90% by mole of said first binding partners have said second binding partners bound thereto whereby there are free first binding partners immobilised within the capillary tube, said second binding partners having a label and being displaceable from the first binding partners by the analyte to be detected;
(b) causing the liquid sample to flow from an upstream end of the capillary tube to a downstream end thereof; and
(c) detecting for the presence of the label at the downstream end of the capillary tube.
6. A method as claimed in claim 5 for the detection of an organism having surface lectins capable of displacing the labelled, lectin second binding partner.
7. A method as claimed in claim 5 wherein 50-70% by mole of said first binding partners have said second binding partners bound thereto.
8. A method as claimed in claim 5 wherein the first binding partners are covalently immobilised within the capillary tube.