Lateral flow assays with time delayed components
View Patent ↗A lateral flow device may include one or more enhancement elements, where the enhancement elements bind to the analyte sandwich to increase a detection signal in the test zone. In preferred embodiments, some or all of the enhancement elements are encapsulated.
1. A lateral flow device for detecting an analyte comprising:
a test strip comprising a sample application zone and a test zone;
a first conjugate comprising a first binding partner for the analyte and a label;
a second binding partner for the analyte capable of being immobilized in the test zone; and
at least one encapsulated enhancement element;
wherein the analyte, the conjugate, and the second binding partner form a sandwich which is immobilized in the test zone when the analyte is present; and
wherein the encapsulated enhancement element binds to the sandwich after being released from encapsulation to increase a detection signal in the test zone.
2. The lateral flow device of claim 1 , wherein the label comprises colloidal gold and the enhancement element comprises at least one silver salt.
3. The lateral flow device of claim 1 , wherein the enhancement element comprises an antigen and the first conjugate further comprises a third binding partner for the antigen.
4. The lateral flow device of claim 3 , wherein the enhancement element further comprises a label.
5. The lateral flow device of claim 1 , wherein the test zone comprises no molecule which specifically binds the analyte.
6. The lateral flow device of claim 1 , wherein the second binding partner comprises a tag and the test zone comprises an immobilized binding partner of the tag.
7. The lateral flow device of claim 1 , wherein:
the first binding partner for the analyte comprises a mixture of the first binding partner for the analyte conjugated to a tag and the first binding partner for the analyte without the tag;
the second binding partner for the analyte is immobilized in the test zone; and
wherein the enhancement element comprises a second conjugate comprising a label and a binding partner for the first binding partner for the analyte.
8. The lateral flow device of claim 7 , wherein approximately 1-10% of the first binding partner for the analyte is conjugated to a tag.
9. The lateral flow device of claim 8 , further comprising a tag binding partner with a detectable label, wherein when the tag binding partner is added to the test at the test zone, it increases a detection signal in the presence of analyte.
10. The lateral flow device of claim 1 , wherein the enhancement element comprises an enzyme.
11. The lateral flow device of claim 1 , wherein the enhancement element is encapsulated in a structure of a type selected from the group consisting of: a) capsules; b) pearls; c) microbeads; d) spheres; e) crystals; f) particles; and g) any combination of a) through f).
12. The lateral flow device of claim 1 , wherein the enhancement element is encapsulated in a material selected from the group consisting of cellulose and silica.
13. A method of enhancing a signal on a lateral flow device comprising a test strip comprising a sample application zone and a test zone, a conjugate comprising a first binding partner for an analyte in a sample and a label, a second binding partner for the analyte; and an encapsulated enhancement element, comprising the steps of:
a) immobilizing a sandwich formed between the analyte, if present in the sample, the conjugate, and the second binding partner in a test zone of the lateral flow device;
b) delaying release of the enhancement element due to encapsulation; and
c) binding the enhancement element to the sandwich after being released from encapsulation such that the enhancement element increases a detection signal in the test zone.
14. The method of claim 13 , wherein the enhancement element is in a volatile liquid.
15. The method of claim 13 , wherein the conjugate further comprises colloidal gold and the enhancement element comprises at least one silver salt.
16. The method of claim 13 , wherein the enhancement element comprises
an antigen and the conjugate further comprises a third binding partner for the antigen.
17. The method of claim 13 , wherein the enhancement element further comprises a label.
18. The method of claim 13 , wherein the test zone comprises no molecule which specifically binds the analyte.
19. The method of claim 13 , wherein the enhancement element is encapsulated in a capsule of a type selected from the group consisting of: a) capsules; b) pearls; c) microbeads; d) spheres; e) crystals; f) particles; and g) any combination of a) through f).
20. The method of claim 13 , wherein the enhancement element is encapsulated in a material selected from the group consisting of cellulose and silica.
21. The method of claim 13 , further comprising, before step a), the step of encapsulating the enhancement element.