Rapid diagnostic test using colorimetric LAMP
Kits and methods are provided for performing multiplex Loop-Mediated Isothermal Amplification (LAMP) reactions. These kits and methods are directed to specific and sensitive methods of target nucleic acid detection and more specifically pathogen diagnostics such as detection of Coronavirus. The kits and methods utilize a plurality of sets of oligonucleotide primers for targeting the viral nucleic acid target.
1. A method for determining whether a target nucleic acid is present in a saliva sample from a subject, comprising:
(a) obtaining the saliva sample in a saliva collection container;
(b) incubating the saliva sample with a reducing agent at a temperature in the range of 65° C.-95° C.;
(c) directly combining an aliquot of the product of step (b) with a reaction mix in a reaction container containing one or more sets of oligonucleotide primers for amplifying a target nucleic acid by Loop-Mediated Isothermal Amplification (LAMP), and a mastermix comprising a strand-displacing DNA polymerase and nucleoside triphosphates;
(d) incubating the reaction mix under conditions suitable for LAMP; and
(e) detecting an amplification product in the reaction mix, corresponding to the presence of the target nucleic acid in the saliva sample.
2. The method according to claim 1 , wherein the reaction mix of (c) further comprises an indicator and step (e) comprises detecting the target nucleic acid in the saliva sample by a change in the indicator.
3. The method according to claim 1 , further comprising: detecting the change in the indicator through the walls of the reaction container.
4. The method according to claim 2 , wherein the indicator is selected from the group consisting of a metallochromic dye, a pH sensitive color dye, an intercalating dye and a fluorescent reporter indicator.
5. The method according to claim 1 , wherein the incubation of (b) is for one hour or less.
6. The method according to claim 1 , wherein (b) comprises incubating the saliva sample with the reducing agent and a detergent.
7. The method according to claim 1 , wherein the reaction mix of (c) further comprises a guanidinium salt.
8. The method according to claim 1 , wherein (b) comprises incubating the saliva sample with the reducing agent and an RNase inhibitor.
9. The method according to claim 1 , wherein (b) comprises incubating the saliva sample with the reducing agent and a proteinase.
10. The method according to claim 1 , wherein the target nucleic acid is a viral RNA and the mastermix further comprises a reverse transcriptase and ribonucleoside triphosphates.
11. The method according to claim 10 , wherein the viral RNA is a Coronavirus RNA.
12. The method according to claim 2 , wherein a change in the indicator indicates that the aliquot of the sample used in step (c) comprises at least 20 copies of the target nucleic acid.
13. The method according to claim 1 , wherein the reaction mix of (c) comprises two or more sets of oligonucleotide primers that hybridize to a single target nucleic acid.
14. The method according to claim 1 , wherein the saliva collection container is a tube that holds a volume of at least 900 μl.
15. A kit, comprising:
(a) a saliva collection container comprising a reducing agent in a buffer;
(b) a mastermix comprising a strand displacing polymerase, a reverse transcriptase, reversible inhibitors of the strand displacing polymerase and the reverse transcriptase and ribonucleoside triphosphates, wherein the mastermix is in a second container that has walls that are transparent to visible light and/or fluorescence; and
(c) an indicator selected from a metallochromic dye, a pH sensitive color dye, an intercalating dye and a fluorescent reporter, wherein the indicator is the second container or in a third container.
16. The kit according to claim 15 , further comprising (d) one or more sets of oligonucleotide primers for hybridizing to the target nucleic acid.
17. The kit according to claim 15 , further comprising uracil DNA glycosylase.
18. The kit according to claim 15 , wherein the master mix and/or the indicator is lyophilized.
19. The kit according to claim 15 , wherein the saliva collection container is a tube capable of holding a volume of 900 μl.