WO2009107065A1

WO2009107065A1 - Reactor system

Info

Publication number: WO2009107065A1
Application number: PCT/IB2009/050745
Authority: WO
Inventors: Jeroen Looijen; Adrianus W. D. M. Van Den Bijgaart; Ronald C. De Gier; Sander C. Broers; Christoph Dobrusskin; Peter H. Bouma
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2008-02-29
Filing date: 2009-02-25
Publication date: 2009-09-03
Also published as: EP2100667A1

Abstract

A reactor system (100) for carrying out a reaction, comprising at least one reaction chamber (110) for holding reactants of the reaction; a thermal element (120) for heating or cooling the reactants of the reaction chamber (110); and an insulator (130), wherein the insulator (130) has a substantially high thermal resistance along a first axis (152) as compared to the thermal resistance along a second axis (154). The varying thermal resistance of the insulator (130) ensures a homogeneous temperature throughout the reaction chamber (110).

Description

REACTOR SYSTEM

FIELD OF THE INVENTION

The invention relates to a reactor system, particularly a reactor system for carrying out a polymerase chain reaction, more particularly a reactor system provided with an insulator.

BACKGROUND OF THE INVENTION

Since the initial invention of a polymerase chain reaction (PCR) process by Mullis in 1983, amplification using the PCR process has become a mainstream application, widely used in today's biochemical laboratories. The PCR process is used for the amplification of specific DNA fragments. Although the biochemical basics have been known since 1983, PCR was only adopted for routine use after the invention of automatic thermal cyclers.

Today's thermal cyclers allow running many polymerase chain reactions (PCR) in parallel. All reactions use the identical thermoprofϊle with the identical number of total cycles. The thermal cyclers do not apply completely independent PCR thermoprofϊles for each of the several PCR reactions in parallel - independent in terms of number of cycles, individual temperature settings and individual time steps. This fact limits the ability to simultaneously amplify different PCR reactions that require different temperature settings for optimal performance of each individual PCR reaction. US 5882903 -A relates to an assay system for conducting elevated temperature reactions in a fluid-tight manner within a reaction chamber, the assay system comprising: (a) a first assembly comprising the reaction chamber, and (b) a second assembly for temperature control, wherein the second assembly can be positioned adjacent to the reaction chamber. More particularly, the invention relates to an assay system comprising (a) a reaction chamber having a cover formed of a deformable material and (b) a mechanism for rapidly adjusting the temperature of the reaction chamber. Various embodiments disclosed to increase, decrease or maintain the temperature in the reaction chamber are very complicated. It requires two thermal blocks for heating or cooling the contents of the reaction chamber. OBJECT AND SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a reactor system that can carry out a reaction at a homogeneous temperature throughout the reaction chamber.

According to the invention, a reactor system for carrying out a reaction comprises at least one reaction chamber for holding reactants of the reaction; a thermal element for heating or cooling the reactants of the reaction chamber; and an insulator, wherein the insulator has a substantially high thermal resistance along a first axis as compared to the thermal resistance along a second axis.

As the thermal resistance varies along a first and a second axis, the heat transferred to the surroundings varies. The thermal resistance along the first axis is higher as compared to the thermal resistance along the second axis. This high thermal resistance minimizes heat loss to the surroundings. The thermal resistance along the second axis is lower than the thermal resistance along the first axis, or is of the same order of magnitude as the thermal resistance within the reactor system along the same axis. This equalizes the temperature within the reactor system. The lower thermal resistance along the second axis maximizes the heat transferred to cold zones of the reaction chamber and thus maintains a homogeneous temperature throughout the reaction chamber. The varying thermal resistance can also be obtained with an insulator comprising a combination of different materials having different thermal conductivities. In accordance with an embodiment of the invention, the higher thermal resistance along the first axis is achieved by a varying cross-section and/or material of the insulator.

In one embodiment, the invention relates to the insulator which comprises a first element having a first cross-section and being configured to make contact with the reaction chamber, a third element having a third cross-section and being configured to form a base of the insulator, and a second element having a second cross-section and being configured to couple the third element to the first element. An example of such an insulator having a varying cross-section is a T-shaped insulator with a base. The top horizontal portion of the T-shaped insulator is in close contact with the reaction chamber and ensures a homogeneous temperature along the horizontal direction by spreading the heat uniformly.

The vertical portion of the T-shaped insulator minimizes heat losses to the surroundings. The third element forms the base of the T-shaped insulator. In accordance with an embodiment of the invention, the first, second and third elements preferably have a circular cross-section, but square, rectangular or other cross- sections are not excluded.

In accordance with a further embodiment of the invention, the reaction chamber is provided with a first flexible foil on a side making contact with the insulator. The flexible foil, which forms a wall on at least one side of the reaction chamber, allows manipulation of inside pressure so as to enable transportation of the reactants into and out of the reaction chamber without having any additional components.

Furthermore, the first element of the insulator is provided with a second flexible foil. This flexible foil is in contact with the first flexible foil of the reaction chamber. A curvature in the first flexible foil leads to a non-uniform temperature in the reaction chamber. The insulator is therefore placed in such a way that the second flexible foil of the insulator makes perfect contact with the first flexible foil of the reaction chamber.

In accordance with another embodiment of the invention, the insulator is provided with a through-channel extending across the three elements of the insulator. The through-channel is connectable to external pressurized air and ensures a good thermal contact among the reaction chamber, the thermal elements and the insulator. During a thermal cycle, the volume of the reactants in the reaction chamber will expand and contract. For a good thermal contact with the thermal elements throughout the cycles, the expansion or contraction needs to be compensated by compensating the pressure on the outside of the reaction chamber. By connecting the through-channel to an external pressure-generating device, the air under the second foil can be pressurized. The second flexible foil of the insulator will deflect until the pressure inside the reaction chamber is the same as the external pressure.

In yet another embodiment, the invention relates to a through-channel which is configured to maintain a constant pressure, irrespective of a pressure of its surroundings. At high altitudes, the ambient pressure is low, and the boiling temperature may therefore be lower than the process temperature. Boiling may result in loss of water from a sample, thus affecting the concentration of the sample. The constant pressure is preferably at least atmospheric pressure. In a further embodiment of the invention, the reaction chamber is made of a material having a thermal conductivity in a range of 0.01 - 0.5 Wm ¹K^"1. In accordance with a further embodiment of the invention, the insulator is made of a material having a thermal conductivity in a range of 0.01 - 0.5 Wm ¹K^"1 along the first axis. The material may be polypropylene. In yet another embodiment of the invention, the reaction chambers have a surface-to-height ratio of at least 5. The reaction chambers may have any form, with the height of the chamber being smaller than its length. Examples of such chambers are flat chambers, but the invention is also applicable to other geometries such as convex, concave or conical shapes. The reaction chamber should be relatively thin and must be quantifiable by a ratio between height, H, and the hydraulic diameter. The hydraulic diameter, Dj₁, is based on the area, A, the cross-sectional area of the reaction chamber and is defined as D_n=4A/P, with P being the perimeter of the reaction chamber. (For a cylindrical chamber, Dj₁=D). The ratio HIDJ₁ may be maximally 1 :5, preferably 1 : 10 or smaller. In a preferred embodiment of the invention, the reaction is a polymerase chain reaction. Amplification of specific DNA fragments using the polymerase chain reaction (PCR) process is widely used in many biochemical labs. The polymerase chain reaction is used for in- vitro diagnostics and allows simultaneous measurement of multiple analytes from a single patient sample. The polymerase chain reaction provides optimized reproducible amplification conditions. Quick amplification allows rapid diagnostics. This reduces the turnaround time of the analytical instruments that require PCR amplification. Due to integration and possible automation, untrained personnel can operate these instruments. The PCR process can be used for diagnostics, for homeland security, and for research and forensic applications. In accordance with another embodiment of the invention, a reactor system for carrying out multiple reactions at a uniform temperature comprises: a. a central chamber for storing reactants required to carry out the reactions, wherein the central chamber is provided with at least one flexible wall; b. reaction chambers configured to receive the reactants from the central chamber and carry out the reaction, wherein the reaction chambers are provided with a flexible wall on a first side and a rigid wall on a second side; c. fluidic channels connecting the central chamber and the reaction chambers; d. a valve for opening and closing all fluidic channels simultaneously; e. a thermal element for heating or cooling reactants of the reaction, wherein the thermal element faces the second side of the reaction chamber; and f. an insulator facing the first side of each reaction chamber, wherein the insulator has a substantially high thermal resistance along a first axis as compared to the thermal resistance along a second axis. The invention provides a reactor system for executing several independent reactions, each with its own thermal settings, in physically separated reaction chambers. The flexible foil, which forms a wall on at least one side of the central chamber and on at least one side of the reaction chamber, allows manipulation of inside pressure so as to enable transportation of the reactants into and out of the reaction chambers without having any additional components. The reaction chambers thus do not have to be opened for filling or emptying. The valve closes the reaction chambers and prevents backing-mixing of the reactants during the reaction. The insulator with a geometry including varying cross-sectional areas ensures a uniform temperature in the reaction chamber. In accordance with a further embodiment of the invention, a method of carrying out a reaction comprising thermal cycling uses the above-mentioned reactor systems. If the reaction carried out is a polymerase chain reaction, many thermal cycles have to be applied to the reactants. During this thermal cycling, the reactants inside the reaction chamber may expand and contract. In order to ensure a good thermal contact between the reaction chamber and the thermal element throughout the thermal cycles, the expansion or contraction of the reactants needs to be compensated. The concept of compensation is based on the rigid, static side of the reaction chamber which is in contact with the thermal element.

BRIEF DESCRIPTION OF THE DRAWINGS These and other characteristics, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. This description is given by way of example only, without limiting the scope of the invention. The reference Figures hereinafter refer to the accompanying drawings. Fig. 1 shows a reactor system;

Fig. 2 is an exploded view of an insulator;

Fig.3 is a two-dimensional view of the reactor system shown in Fig.l; and

Fig. 4 shows a reactor system including multiple reaction chambers.

DESCRIPTION OF EMBODIMENTS

Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims and features of other dependent claims as appropriate and not merely as explicitly set out in the claims. As shown in Fig.l, a reactor system 100 includes a reaction chamber 110, a thermal element 120 and an insulator 130. The reaction chamber 110 is provided with a first flexible foil 112 on a side facing the insulator 130. Similarly, the insulator is provided with a second flexible foil 132 on a side adjacent to the reaction chamber 110. Fig.2 is an exploded view of the insulator 130. The insulator 130 has a varying cross-section along a longitudinal axis. The first element 134 has a first cross-section, while a third element 138 having a third cross-section forms a base of the insulator 130. The insulator comprises a second element 136 having a second cross-section which couples the third element 138 to the first element 134. The insulator is provided with a channel 140 extending across all of the three elements.

Fig.3 is a two-dimensional view of the reactor system 100. The reactor system 100 includes the reaction chamber 110, the thermal element 120 and the insulator 130. The reaction chamber 110 is provided with the first flexible foil 112 on a side facing the insulator 130. Similarly, the insulator is provided with the second flexible foil 132 on a side adjacent to the reaction chamber 110. The insulator 130 comprises the first element 134, the second element 136 and the third element 138. The insulator 130 is provided with a channel 140.

Fig.4 shows a reactor system 200 including multiple reaction chambers, only two reaction chambers 220 of which are shown. The reactor system 200 is provided with a central chamber 210. The central chamber 210 has at least one flexible wall 212. The reaction chambers 220 have a flexible wall on a first side and a rigid wall on a second side (not shown). Fluidic channels 230 connect the central chamber 210 and the reaction chambers 220. A valve 240 is provided for opening and closing all fluidic channels 230 simultaneously. A thermal element 250 per reaction chamber 220 faces a second side of the reaction chamber 220. An insulator 260 per reaction chamber 220 faces the first side of each reaction chamber 220. The insulator 260 is provided with a channel 265.

The reaction chamber 110 shown in Fig.l is loaded with reactants required to carry out a reaction. The reaction chamber 110 is held between the thermal element 120 and the insulator 130. In the course of the reaction, the volume of the reactants inside the reaction chamber 110 will expand and contract. In order to ensure a good thermal contact throughout, the channel 140 of the insulator 130 is connected to externally pressurized air. This will pressurize the air below the second flexible foil 132. The second flexible foil 132 will deflect until the pressure inside the reaction chamber 110 is the same as the pressurized air. This ensures that the reaction will always be performed under identical conditions, irrespective of ambient conditions. Boiling of the reactants is prevented by maintaining at least the ambient pressure at sea level. At high altitudes, the ambient pressure is low and, consequently, the reactants have a low boiling temperature. Especially for a PCR, the process requires a temperature of about 95⁰C, which exceeds the boiling temperature at high altitudes. Boiling may result in loss of water from a sample to be analyzed, which adversely affects the concentration of the sample. Boiling may deteriorate the PCR performance. It is clear from Fig.l that there is only one thermal element 120 on one side, with the insulator 130 on the other side. There are no multiple thermal elements per reaction chamber. In this way, the thermal element 120 can be integrated on the reaction chamber 110 as a passive element or, alternatively, may be positioned as an external heater which is actively addressed. The insulator 130 shown in Fig.2 has a varying cross-section along a longitudinal axis. The first element 134 having a first cross-section makes contact with the reaction chamber 110. The insulator 130 comprises a third element 138 having a third cross- section which forms a base of the insulator 130. The insulator comprises a second element 136 having a second cross-section which couples the third element 138 to the first element 134. The insulator is provided with a channel 140 extending across all of the three elements.

„, , ■ _{Λ c}- _{Λ T},

Thermal resistance is defined as R =

wherein R is the thermal resistance;

L is the length of the insulator; k is the thermal conductivity of the insulator; and

A is the cross-sectional area of the insulator.

When the cross-section and/or the material vary, the resistance and hence the heat transfer change. The insulator has such a cross-sectional area that the thermal resistance along the first axis 152 is high enough to insulate the reaction system from its surroundings, whereas the thermal resistance in the second axis 154 is low enough to equalize the temperature within the reaction chamber. This ensures that the heat transferred to the surroundings is minimized, whereas the heat transferred to cold parts of the reaction chamber 110 is maximized. This maintains a homogeneous temperature in the reaction chamber 110.

In the reactor system 200, shown in Fig.4, the insulator 260 is brought upwards by applying a force F until the reaction chamber 220 is clamped between the thermal element 250 and the insulator 260. The thermal element 250 heats the reactants of the reaction chamber 220 to a desired temperature. The insulator 260 ensures that the heat is not lost to the atmosphere. This further ensures a uniform temperature throughout the reaction chamber without any hot or cold spots. The central chamber 210 can be pre-fϊlled with the reactants. The valve 240 is opened and a pressure is applied on the flexible top foil 212 of the central chamber 210. As a result, the reactants are pressed into the reaction chamber 220 via the fluidic channels 230. Each reaction chamber 220 has one fluidic channel 230. In order to keep the insulator 260 in place, the upward force F on the insulator 260 needs to be larger than the projected reactant volume of the reaction chamber 220 multiplied by the pressure exerted by the reactants in the reaction chamber 220. The valve 240 is closed after all reaction chambers 220 have been filled. The volume of the reaction chamber 220 is determined by its geometry.

The reaction takes place after the reaction chamber 220 has been filled with the reactants. The upward force F is still present. This maintains a controlled pressure on the reactants and keeps the reaction chamber 220 pressed to the thermal element 250. Connecting externally pressurized air via the channel 265 in the insulator 260 can pressurize the air under the second flexible foil. The air under the second flexible foil provides compliance to the reaction chamber 220 and ensures a good contact with the thermal element 250. During the reaction, expansion of the reactants is compensated by the air buffer under the second flexible foil. If the reaction carried out is a polymerase chain reaction, many thermal cycles have to be applied to the reactants. During this thermal cycling, the reactants inside the reaction chamber 220 may expand and contract. For a good thermal contact between the reaction chamber 220 and the thermal element 250 throughout the thermal cycles, the expansion or contraction of the reactants needs to be compensated. The concept of compensation is based on the rigid, static side of the reaction chamber 220 which is in contact with the thermal element 250. The reaction chamber 220 is pressed upwards to the thermal element 250 by a force F. This force is exerted by a spring or pressure-loaded support element (not shown). Every reaction chamber 220 has its own supporting element in order to ensure a good thermal contact of all individual reaction chambers 220 and the thermal element 250. Any play between them is eliminated. Since the reaction chambers 220 are closed by the first flexible foil on at least one side, expansion or contraction of the reactants can take place. The supporting elements of the first flexible foil, which are also flexible, allow the resulting motion of the flexible foil without losing preload of the reaction chamber 220 to the thermal element 250. The present invention has been described by way of non- limiting example with reference to particular embodiments and the drawings. Any reference signs in the claims shall not be construed as limiting the scope. The drawings described are only schematic and non- limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. Use of the verb "comprise" and its conjugations in the present description and claims does not exclude other elements or steps. Use of the indefinite or definite article "a", "an" or "the" referring to a singular noun includes a plural of this noun, unless specifically stated otherwise.

Furthermore, the terms first, second, third and the like in the description and claims are used to distinguish between similar elements and not necessarily to describe a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described hereinbefore are capable of operation in sequences other than those herein described or illustrated. Moreover, the terms top, bottom, over, under and the like in the description and claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described hereinbefore are capable of operation in orientations other than those herein described or illustrated. The term "reaction" in the context of the invention may refer to an interaction between elements to form a new substance, a physical change of state of a substance, an amplification reaction or a chemical reaction.

The term "homogeneous temperature" in the context of the invention refers to a temperature at which 90% of the reactants are preferably within +/- I⁰C of a set temperature.

Although preferred embodiments, specific constructions and configurations have been described hereinbefore for the device according to the present invention, it will be evident to those skilled in the art that various changes or modifications of form and detail may be made without departing from the scope and spirit of the invention.

Claims

CLAIMS:

1. A reactor system (100) for carrying out a reaction, comprising at least one reaction chamber (110) for holding reactants of the reaction; a thermal element (120) for heating or cooling the reactants of the reaction chamber (110); and an insulator (130), wherein the insulator (130) has a substantially high thermal resistance along a first axis (152) as compared to the thermal resistance along a second axis (154).

2. The reactor system (100) of claim 1, wherein the high thermal resistance along the first axis (152) as compared to the thermal resistance along the second axis (154) is achieved by a varying cross-section and/or material of the insulator (130).

3. The reactor system (100) of claim 2, wherein the insulator comprises a first element (134) having a first cross-section and being configured to make contact with the reaction chamber (110), a third element (138) having a third cross-section and being configured to form a base of the insulator (130), and a second element (136) having a second cross-section and being configured to couple the third element (138) to the first element (134).

4. The reactor system (100) of claim 3, wherein the first, second and third elements have a circular cross-section.

5. The reactor system (100) of claim 1, wherein the reaction chamber (110) is provided with a first flexible foil (112) on a side making contact with the insulator (130).

6. The reactor system (100) of claim 3, wherein the first element (134) is provided with a second flexible foil (132).

7. The reactor system (100) of claim 3, wherein the insulator (130) is provided with a through-channel (140) extending across the three elements.

8. The reactor system (100) of claim 7, wherein the through-channel (140) is configured to maintain a constant pressure, irrespective of a pressure of its surroundings.

9. The reactor system (100) of claim 8, wherein the constant pressure is at least atmospheric pressure.

10. The reactor system (100) of claim 1, wherein the reaction chamber comprises a material having a thermal conductivity in a range of 0.01 - 0.5 Wm ¹K^"1

11. The reactor system (100) of claim 1 , wherein the insulator (130) comprises a material having a thermal conductivity in a range of 0.01 - 0.5 Wm ¹K^"1 along the first axis.

12. The reactor system (100) of claim 11, wherein the material is polypropylene.

13. The reactor system (100) of claim 1, wherein the reaction chambers have a surface-to-height ratio of at least 5.

14. The reactor system (100) of claim 1, wherein the reaction is a polymerase chain reaction.

15. A reactor system (200) for carrying out multiple reactions at a homogeneous temperature, comprising: a. a central chamber (210) for storing reactants required to carry out the reactions, wherein the central chamber (210) is provided with at least one flexible wall (212); b. reaction chambers (220) configured to receive the reactants from the central chamber (210) and carry out the reaction, wherein the reaction chambers (220) are provided with a flexible wall on a first side and a rigid wall on a second side; c. fluidic channels (230) connecting the central chamber (210) and the reaction chambers (220); d. a valve (240) for opening and closing all fluidic channels (230) simultaneously; e. a thermal element (250) for heating or cooling reactants of the reaction, wherein the thermal element (250) faces the second side of the reaction chamber (220); and f. an insulator (260) facing the first side of each reaction chamber (220), wherein the insulator (260) has a substantially high thermal resistance along a first axis (152) as compared to the thermal resistance along a second axis (154).

16. A method of carrying out a reaction comprising thermal cycling, wherein use is made of the reactor system of claim 1.