APPARATUS FOR THERMALLY CYCLING SAMPLES OF BIOLOGICAL MATERIAL WITH SUBSTANTIAL TEMPERATURE UNIFORMITY

• US 20020030044A1
• Filed: 07/30/1999
• Published: 03/14/2002
• Est. Priority Date: 07/30/1999
• Status: Active Grant

• Current Assignee: Agilent Technologies, Inc.
• Original Assignee: Stratagene California
• Inventors: BROWN, LARRY R.
• Granted Patent: US 6,657,169 B2
• Time in Patent Office: Days
• US Class Current: 219/386
• CPC Class Codes: B01L 2200/147 Employing temperature sensors
• CPC Class Codes: B01L 2300/0829 Multi-well plates; Microtitration plates
• CPC Class Codes: B01L 2300/1805 Conductive heating, heat from thermostatted solids is conducted to receptacles, e.g. heating plates, blocks
• CPC Class Codes: B01L 2300/1822 using Peltier elements
• CPC Class Codes: B01L 7/52 with provision for submitting samples to a predetermined sequence of different temperatures, e.g. for treating nucleic acid samples amplification or hybridisation processes per se C12Q1/68; controlling sequential reactions for synthesis B01J19/0046
• CPC Class Codes: B01L 7/54 using spatial temperature gradients

Abstract

An apparatus for thermally cycling samples of a biological material. The apparatus in its preferred embodiment includes: a thermal block assembly including a plurality of sample holders for receiving samples of biological material; a heat sink thermally coupled to the thermal block assembly, the heat sink transferring heat away from the thermal block assembly to ambient air in contact with the heat sink; a first heat source thermally coupled to the thermal block assembly to provide heat to the thermal block assembly; and a second heat source thermally coupled to the first heat source and configured to provide heat to a portion of the first heat source. The arrangement of the heat sink, first heat source and second heat source can provide substantial temperature uniformity among the plurality of sample holders. The invention also includes a method for thermally cycling samples of biological material.

Claims

1. An apparatus for heating samples of biological material, comprising:

a thermal block assembly including a plurality of sample holders for receiving samples of biological material;

a heat sink thermally coupled to the thermal block assembly, said heat sink transferring heat away from the thermal block assembly to ambient air in contact with the heat sink;

a first heat source thermally coupled to the thermal block assembly to provide heat to the thermal block assembly; and

a second heat source thermally coupled to the first heat source and configured to provide heat to at least a portion of the first heat source,

wherein the arrangement of the heat sink, first heat source and second heat source can provide substantial temperature uniformity among the plurality of sample holders.

2. The apparatus of claim 1, wherein said second heat source is located on an outer surface of the heat sink in order to cause a temperature gradient across the heat sink.

3. The apparatus of claim 2, wherein said first heat source includes at least one thermoelectric heater utilizing the Peltier effect, said first heat source producing a temperature gradient as a function of the temperature gradient across the heat sink, said temperature gradient of the first heat source causing the thermal block assembly to be urged toward said substantial temperature uniformity by heating at least a portion adjacent the edges of the thermal block assembly.

4. The apparatus of claim 3, wherein said second heat source is located adjacent at least a portion of the heat sink radially outside of the portion on which the first heat source is located.

5. The apparatus of claim 4, wherein said second heat source includes at least one resistive element heater.

6. The apparatus of claim 1, said first heat source including a first side and a second side, said first side having a higher temperature at an outer periphery of the first heat source than at an inner periphery of the first heat source corresponding approximately to a temperature gradient across the heat sink.

7. The apparatus of claim 1, wherein said thermal block assembly further comprises a thermal block plate.

8. The apparatus of claim 7, wherein said plurality of sample holders comprise a plurality of sample wells.

9. The apparatus of claim 8, wherein said plurality of sample wells are coupled to a surface of the thermal block plate.

10. The apparatus of claim 9, wherein said plurality of sample wells are attached to the thermal block plate by a method selected from a group consisting of silver brazing, copper casting, and ultrasonic welding.

11. The apparatus of claim 9, wherein said plurality of sample wells and thermal block plate are both composed of a copper alloy.

12. The apparatus of claim 1, wherein said first heat source includes at least one thermoelectric heater utilizing the Peltier effect, said at least one thermoelectric heater including a first side and second side, said first side typically being at a higher temperature than said second side during a heating of the sample, said apparatus further comprising a first thermal interface element located between the thermal block assembly and the first side of the at least one thermoelectric heater to provide heat transfer to the thermal block assembly.

13. The apparatus of claim 12, further comprising a second thermal interface element located between the heat sink and a lower temperature side of the at least one thermoelectric heater to provide heat transfer between the heat sink and the lower temperature side of the at least one thermoelectric heater and to improve the cycle life of the thermoelectric heater.

14. The apparatus of claim 1, wherein said thermal block assembly further comprises a thermal block plate, said plurality of sample holders being located on a surface of the thermal block plate,

said apparatus further comprising:

a first cover of insulating material on the thermal block assembly; and

a plurality of longitudinal fasteners for imparting a compressive force across said first cover, said thermal block plate, said first heat source, and said heat sink.

15. The apparatus of claim 14, wherein each said longitudinal fastener includes a screw and an insulating screw cap on one end of the longitudinal fastener, said insulating screw cap being located on a bottom surface of the heat sink.

16. The apparatus of claim 15, wherein each longitudinal fastener further includes an insulating washer located between the end of each longitudinal fastener and the bottom surface of the heat sink.

17. The apparatus of claim 1, further comprising a spacer bracket, each said first heat source being positioned in an opening in the spacer bracket.

18. The apparatus of claim 17, wherein said spacer bracket is sized so that the thermal block assembly is placed in compression.

19. The apparatus of claim 1, further comprising:

a first cover of insulating material, said first cover tending to thermally insulate the sample holder of the thermal block assembly; and

a third heat source, said third heat source including a plate located above the thermal block assembly to provide heat to a plurality of sample tubes respectively located in the sample wells of the thermal block assembly, wherein said sample holders comprise sample wells.

20. The apparatus of claim 19, further comprising:

a second cover of insulating material, said second cover tending to thermally insulate the plurality of sample tubes respectively located in the sample wells of the thermal block assembly, said second cover comprising an assembly for holding the sample tubes in the thermal block by imparting a compressive load to improve the contact surface area between the respective heat sources and thermal block assembly, and a plate of insulating material for the thermal block assembly and first cover.

21. The apparatus of claim 20, wherein said holding assembly of the second cover includes a bracket with a clamping portion located adjacent the second cover for imparting said compressive load on the insulating plate.

22. The apparatus of claim 1, wherein said biological material includes a biological reaction mixture.

23. The apparatus of claim 22, wherein said apparatus is capable of thermally cycling said samples of biological reaction mixture.

25. The apparatus of claim 24, wherein each sample well extends for a substantial length of its respective cylindrical sample well opening in the first cover.

26. The apparatus of claim 24, wherein said thermal block assembly further comprises a thermal block plate, said plurality of sample wells being coupled to a surface of the thermal block plate.

27. The apparatus of claim 26, wherein the thermal block assembly further includes at least one sensor cup coupled to the surface of the thermal block plate, and wherein said first cover further includes at least one sensor cup opening corresponding to a respective sensor cup.

28. The apparatus of claim 26, further comprising:

a first heat source thermally coupled to the thermal block assembly, said first heat source providing heat to the thermal block assembly;

a second heat source located adjacent the first heat source, said second heat source providing heat to a portion of the first heat source; and

a third heat source, said third heat source including a plate located above the thermal block assembly to provide heat to a plurality of sample tubes respectively located in the sample wells of the thermal block assembly.

29. The apparatus of claim 28, wherein said first heat source is a thermoelectric heater utilizing the Peltier effect, said second and third heat sources are resistive element heaters, and said samples of biological material is a biological reaction mixture including DNA.

30. The apparatus of claim 24, further comprising a heat sink thermally coupled to the thermal block assembly, wherein said second heat source is located on an outer surface of the heat sink in order to cause a temperature gradient on the heat sink.

24. An apparatus for heating samples of a biological material, comprising:

a thermal block assembly including a plurality of sample wells for receiving samples of biological material; and

a first cover of insulating material, said first cover tending to thermally insulate the sample wells of the thermal block assembly, said first cover comprising a plate with a plurality of cylindrical sample well openings, each cylindrical sample well opening corresponding to a respective sample well, wherein the first cover surrounds the top and extends over at least a portion of the sides of the thermal block assembly.

31. An apparatus for thermally cycling samples of biological reaction mixture, comprising:

a thermal block assembly including a thermal block plate and a plurality of sample wells for receiving samples tubes containing biological reaction mixture;

a heat sink thermally coupled to the thermal block assembly, said heat sink transferring heat from the thermal block assembly to ambient air in contact with the heat sink;

at least one thermoelectric heater thermally coupled to the thermal block assembly, said at least one thermoelectric heater providing heat to the thermal block assembly;

thermal interface material between outer surfaces of the at least one thermoelectric heater and at least one of the thermal block assembly and heat sink, said thermal interface material providing heat transfer between the at least one thermoelectric heater and the at least one of the thermal block assembly and heat sink;

a first cover of insulating material for the sample wells of the thermal block assembly;

a first resistive element heater, said first resistive heater including a flat plate located above the thermal block assembly to provide heat to the thermal block assembly; and

a second resistive element heater located below the at least one thermoelectric heater for heating a bottom portion of said at least one thermoelectric heater.

32. The apparatus of claim 31, further comprising a second cover of insulating material including a holding assembly for holding the sample tubes in the sample wells by imparting a substantially uniform compressive load, and a plate of insulating material for the thermal block and first cover.

33. A method for thermally cycling samples of biological material in an apparatus with at least one sample holder located in a thermal block assembly, comprising the steps of:

inserting at least one sample of biological material into a sample holder of the apparatus;

measuring the temperature of the thermal block assembly at at least one location on the thermal block assembly;

calculating the desired temperature of the thermal block assembly;

comparing the desired temperature with the measured temperature, and if the measured temperature is less than the desired temperature, the method further comprises the steps of;

applying a first heat source, a portion of said heat from said first heat source being transferred to the thermal block assembly;

applying a second heat source, a portion of said heat from said second heat source being transferred to the first heater; and

applying a third heat source, a portion of said heat from said third heat source being transferred to the sample holders;

if the measured temperature is greater than the desired temperature, the method further comprises the step of cooling the thermal block assembly by imparting a cooling convection current on a heat sink which is thermally coupled to the thermal block assembly to provide heat transfer from the thermal block assembly to ambient air in contact with the heat sink; and

repeating the steps of measuring, calculating, and comparing until the predetermined thermal cycle for the samples of biological material is completed.

34. The method of claim 33, wherein the step of applying the second heat source includes applying said second heat source to the heat sink on which the second heat source is located, said heat sink then imparting a portion of the heat from the second heat source to the first heat source.

35. The method of claim 34, wherein the step of measuring the temperature of the thermal block assembly includes measuring the temperature at a plurality of locations on the thermal block assembly, and the step of applying the first heat source includes a plurality of first heat sources.

36. The method of claim 33, wherein the step of cooling the thermal block assembly includes using the first heat source to cool the thermal block assembly.

37. The method of claim 33, wherein the step of inserting at least one sample of biological material into a sample holder includes inserting a sample tube of biological reaction mixture into a sample well of the apparatus.