Sensing apparatus and method

• US 20040134798A1
• Filed: 03/02/2004
• Published: 07/15/2004
• Est. Priority Date: 03/09/2001
• Status: Active Grant

• Current Assignee: DNAE Group Holdings Limited (Genting Bhd.)
• Original Assignee: DNA Electronics Limited (Genting Malaysia Berhad)
• Inventors: Toumazou, Christofer, Purushothaman, Sunil
• Granted Patent: US 7,686,929 B2
• Time in Patent Office: Days
• US Class Current: 205/793.5
• CPC Class Codes: C12Q 1/6825 Nucleic acid detection involving sensors
• CPC Class Codes: C12Q 2565/607 being a sensor, e.g. electrode
• CPC Class Codes: G01N 27/4145 specially adapted for biomolecules, e.g. gate electrode with immobilised receptors

Abstract

A sensing apparatus comprising an ion sensitive field effect transistor arranged to generate an electrical output signal in response to localised fluctuations of ionic charge at or adjacent the surface of the transistor, and means for detecting the electrical output signal from the ion sensitive field effect transistor, the localised fluctuations of ionic charge indicating events occurring during a chemical reaction.

Claims

1. A sensing apparatus comprising an ion sensitive field effect transistor arranged to generate an electrical output signal in response to localised fluctuations of ionic charge at or adjacent the surface of the transistor, and means for detecting the electrical output signal from the ion sensitive field effect transistor, the localised fluctuations of ionic charge indicating events occurring during a chemical reaction.

2. A sensing apparatus according to claim 1, wherein the ion sensitive field effect transistor is provided with a layer of silicon nitrite.

3. A sensing apparatus according to claim 1 or claim 2, wherein the ion sensitive field effect transistor is provided with an enzyme linked layer.

4. A sensing apparatus according to claim 2 and claim 3, wherein the enzyme linked layer is provided over the layer of silicon nitrite.

5. A sensing apparatus according to claim 4, wherein the enzyme linked layer comprises polymerase.

6. A sensing apparatus according to any preceding claim, wherein the ion sensitive field effect transistor is provided as part of an integrated circuit which is substantially covered by epoxy resin, and the field effect transistor is not covered by the epoxy resin.

7. A sensing apparatus according to any preceding claim, wherein the chemical reaction is DNA synthesis, and the localised fluctuations of ionic charge indicate the insertion of di-deoxynucleotide triphosphates (ddNTP) and deoxynucleotide triphosphates (dNTP).

8. A sensing apparatus according to claim 7, wherein the apparatus further comprises monitoring means is arranged to monitor the time at which the localised fluctuations occur and the magnitude of the localised fluctuations, to allow sequencing of DNA or mRNA.

9. A sensing apparatus according to claim 7 or claim 8, wherein the ion sensitive field effect transistor is configured to generate the electrical output signal in response to a pyrophosphate hydrolysis reaction.

10. A sensing apparatus according to claim 9, wherein the ion sensitive field effect transistor is located in a reagent mixture which has a pH of less than 7.

11. A sensing apparatus according to claim 10, wherein the ion sensitive field effect transistor is located in a reagent mixture which has a pH of 6.8.

12. A sensing apparatus according to claim 10 or claim 11, wherein the reagent mixture includes magnesium.

13. A sensing apparatus according to any preceding claim, wherein the apparatus comprises two ion sensitive field effect transistors, a first of the transistors being provided with an enzyme linked layer, and a second of the transistors being provided with a non-enzyme linked layer, and means for determining the difference between the electrical signals generated by the first and second transistors, to provide an electrical output signal.

14. A sensing apparatus according to claim 13, wherein the first and second transistors are connected to first and second operational amplifiers, and the outputs of the operational amplifiers are passed to a differential amplifier which provides the electrical output signal.

15. A sensing apparatus according to claim 14, wherein the electrical output signal is passed to an electrode located in the reagent mixture, to maintain voltages applied to the first and second transistors at a constant level.

16. A sensing apparatus according to claim 14 or claim 15, wherein the first and second transistors are arranged to form part of the first and second operational amplifiers respectively.

17. A sensing apparatus according to any preceding claim, wherein the apparatus includes at least one PMOS transistor arranged to operate in the weak inversion region.

18. A sensing apparatus according any preceding claim, wherein the apparatus includes at least one NMOS transistor arranged to operate in the weak inversion region.

19. A sensing apparatus according to any of claims 13 to 16, wherein the two ion sensitive field effect transistors are both PMOS transistors arranged to operate in the weak inversion region.

20. A sensing apparatus according to any of claims 13 to 16, wherein the two ion sensitive field effect transistors are both NMOS transistors arranged to operate in the weak inversion region.

21. A sensing apparatus according to claim 19 and claim 20, wherein the apparatus is provided with two ion sensitive field effect transistors are both PMOS transistors arranged to operate in the weak inversion region, and with two ion sensitive field effect transistors are both NMOS transistors arranged to operate in the weak inversion region.

22. A sensing apparatus according to any preceding claim, wherein the apparatus is configured to generate an electrical output signal in response to ion consumption or ion liberation.

23. A sensing apparatus according to any preceding claim, wherein the apparatus is configured to modify the electrical output signal at a speed that is sufficient to allow events of the chemical reaction to be monitored.

24. A sensing apparatus according to claim 23, wherein the apparatus is configured to modify the electrical output signal at a rate which is faster than 10 milliseconds.

25. A sensing apparatus according to claim 24, wherein the apparatus is configured to modify the electrical output signal at a rate which is faster than 3 milliseconds.

26. A sensing method comprising detecting an electrical signal output from an ion sensitive field effect transistor, and monitoring the detected electrical signal to discriminate localised fluctuations of ionic charge, the localised fluctuations of ionic charge occurring at or adjacent the surface of the field effect transistor indicating events occurring during a chemical reaction.

27. A sensing method according to claim 26, wherein the chemical reaction is DNA synthesis, and the fluctuations of ionic charge indicate the insertion of di-deoxynucleotide triphosphates (ddNTP) and deoxynucleotide triphosphates (dNTP).

28. A sensing method according to claim 27, wherein the time at which the fluctuations occur and the magnitude of the fluctuations is monitored to allow sequencing of DNA or mRNA.

29. A sensing method according to claim 27 or claim 28, wherein the method includes thermocycling.

30. A sensing method according to any of claims 26 to 29, wherein the method is repeated multiple times to improve signal to noise.