METHOD FOR MULTIPLYING DNA, ROTATION DEVICE AND SYSTEM FOR MULTIPLYING DNA

Abstract

A method for multiplying DNA includes using a rotation device to rotate a sample carrier about an axis of rotation. The sample carrier has at least one cavity in which a sample liquid containing DNA is received. The cavity is heated to a high temperature value only on a heat input side lying in a rotation plane by using a heating device. As a result of the heating, a convection current is created in the sample liquid in the cavity, the convection current having substantial current components directed perpendicularly to the rotation plane. A circulation time of a liquid particle along a current path of the convection current is predetermined by the speed of the rotation. A rotation device for multiplying DNA and a system for multiplying DNA, are also provided.

Claims

1. A method for multiplying DNA, the method comprising: using a rotation device to rotate a sample carrier about a rotation axis, the sample carrier having at least one cavity in which a sample liquid containing DNA has been accommodated; using a heating device to heat the cavity to a high temperature value only on a heat input side of the cavity lying in a rotation plane; carrying out the heating to generate a convection current of the sample liquid inside the cavity, the convection current having substantial current components directed perpendicularly to the rotation plane; and using a speed of rotation of the sample carrier to specify a circulation time of a liquid particle along a current path of the convection current.

2. The method according to claim 1, which further comprises cooling the cavity on a heat output side of the cavity to a temperature value lower than the temperature value on the heat input side, the heat output side being opposite the heat input side.

3. The method according to claim 2, which further comprises at least one of carrying out the heating by applying a constant temperature value to the heat input side or carrying out the cooling by applying a constant temperature value to the heat output side.

4. The method according to claim 2, which further comprises carrying out the cooling by applying a stream of cooling air.

5. The method according to claim 1, which further comprises carrying out the heating with the heating device spanning at least a base of the cavity disposed on the heat input side.

6. The method according to claim 5, which further comprises integrating the heating device into a sample holder of the rotation device supporting the sample carrier.

7. The method according to claim 1, which further comprises guiding the convection current inside the cavity by a flow resistance assigned to the cavity.

8. The method according to claim 7, which further comprises carrying out the guiding of the convection current by the flow resistance in such a way that: a part of a current path directed from the heat input side to the heat output side runs on a side of the cavity nearest to the rotation axis, and a part of the current path directed from the heat output side to the heat input side runs on a side of the cavity remote from the rotation axis.

9. The method according to claim 1, which further comprises providing the sample carrier with a plurality of cavities for parallel multiplication of DNA.

10. A rotation device for multiplying DNA, the rotation device comprising: a process chamber; a sample holder disposed in said process chamber for holding at least one sample carrier having at least one cavity for accommodating a DNA-containing sample liquid, said sample holder having a rotation plane, and the at least one cavity having a heat input side lying in said rotation plane; a rotational drive configured to rotate the sample holder about a rotation axis during intended operation; a heating device configured to heat the heat input side to a high temperature value during the intended operation; and a controller control-linked to said rotational drive and to said heating device, said controller configured to carry out the method for multiplying DNA according to claim 1.

11. The rotation device according to claim 10, wherein said heating device at least one of includes a Peltier element or is integrated into said sample holder.

12. The rotation device according to claim 10, which further comprises a cooling device configured to cool a heat output side of the cavity to a low temperature value, the heat output side disposed opposite to the heat input side.

13. The rotation device according to claim 12, wherein said cooling device includes a fan causing cooling air to flow through said process chamber.

14. A system for multiplying DNA, the system comprising: the rotation device according to claim 10; and the sample carrier.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0044] FIG. 1 is a diagrammatic, side-elevational view of a system for multiplying DNA, including a rotation device and a sample carrier;

[0045] FIG. 2 is a sectional view of a detail of the sample carrier and a sample holder of the rotation device;

[0046] FIG. 3 is a view similar to FIG. 2 of an alternative exemplary embodiment of the sample carrier;

[0047] FIG. 4 is a top-plan view of the sample carrier of FIG. 3;

[0048] FIG. 5 is a view similar to FIG. 4 of a further exemplary embodiment of the sample carrier; and

[0049] FIG. 6 is a flow chart of a method for multiplying DNA.

DETAILED DESCRIPTION OF THE INVENTION

[0050] Referring now in detail to the figures of the drawings, in which parts corresponding to one another are always provided with the same reference signs, and first, particularly, to FIG. 1 thereof, there is seen a system 1 for multiplying DNA. The system 1 includes a rotation device 2 and a sample carrier 4. What is carried out by using the system 1 is a method for multiplying DNA that will be described in greater detail below on the basis of FIG. 6.

[0051] The rotation device 2 includes a housing 6 which surrounds a housing interior, referred to hereinafter as “process chamber 8.” Furthermore, the rotation device 2 includes a sample holder 10. Mounted thereon is the sample carrier 4 when the method is carried out (i.e., during intended operation). The sample holder 10 is rotatable about a rotation axis 14 by using a rotational drive 12. The sample holder 10 is therefore a rotary plate. Furthermore, the rotation device 2 includes a fan 16 as a cooling device, through the use of which a stream of cooling air flows through the process chamber 8 during intended operation. In addition, the rotation device 2 includes a fluorescence detector 18.

[0052] The sample carrier 4 has at least one cavity 20 (see FIG. 2) for accommodating a DNA-containing sample liquid. In a preferred exemplary embodiment, the sample carrier 4 has two or more of the cavities 20. The cavity 20 has a cuboid shape having, for example, dimensions of about 5×3×1.2 mm.sup.3 and is delimited by a bottom wall 22 and a top wall 24 in relation to the bottom side (hereinafter: “heat input side 26”) and the top side (hereinafter: “heat output side 28”), respectively, and by lateral walls in relation to the remaining sides, which lateral wall are not depicted in greater detail. The walls of the sample carrier 4 are made of plastic, specifically a cyclic olefin copolymer (COC). During intended operation, the heat input side 26 of the sample carrier 4 is positioned on the sample holder 10.

[0053] The rotation device 2 includes a heating device 30. It in turn includes a Peltier element which extends planarly over the top side of the sample holder 10 that faces the heat input side 26, optionally multiple Peltier elements positioned side-by-side for planar heat emission. The heating device 30 is integrated into the sample holder 10. In an exemplary embodiment not depicted in greater detail, an aluminum plate for homogenous temperature distribution is disposed between the Peltier element and the sample holder 10.

[0054] A controller 11 of the rotation device 2 for controlling the rotational drive 12, the heating device 30 and the fan 16 is present.

[0055] In order to multiply DNA, the sample carrier 4 and the DNA-containing sample liquid is provided in a first method step S1 (see FIG. 6). The sample liquid contains not only the DNA to be multiplied, but also primer molecules, structural building blocks for forming new DNA strands, and polymerase. In a second method step S2, the cavities 20 are filled with the sample liquid.

[0056] In a third method step S3, the sample carrier 4 is kept constant at a high temperature value of about 95° C. on the heat input side 26 by using the heating device 30. In parallel, the rotational drive 12 drives the sample holder 10 for rotation about the rotation axis 14, and so each cavity 20 is rotated about the rotation axis 14. By using the fan 16, a stream of cooling air (of preferably 40° C.) is blown over the sample carrier 4, and so the heat output side 28 thereof is kept constant at this low temperature value.

[0057] Due to the bottom-sided heating and the top-sided cooling, what are formed inside the cavity 20 are a warm region 32 and a cold region 34 (indicated by dotted lines), i.e., a temperature gradient which runs parallel to the rotation axis 14. In the cold region 34, the sample liquid has a temperature value of about 60° C. In the warm region 32, the temperature value of the sample liquid lies above the melting temperature of the DNA, specifically above 90° C.

[0058] Due to the bottom-sided heating and the top-sided cooling, what is established is a buoyancy-driven convection current, based on the temperature-related density differences of the sample liquid. The convection current is basically annular (namely approximately in the form of an oval, cf. semicircular arrows in FIG. 2) and oriented with current components approximately perpendicular to the rotation plane of the sample holder 10. Due to the centrifugal forces of the rotation (directed to the right in FIG. 2) and to the Coriolis force likewise present due to the rotation, what however also occurs is (homogeneous) mixing of the sample liquid transversely to the basic current path of the convection current. The speed of the convection current increases as the speed of rotation increases.

[0059] In the course of the convection current, the sample liquid thus passes (approximately parallel to the rotation plane) through the warm region 32, in which the temperature causes denaturation of the DNA. Therefore, the warm region 32 is also referred to as the “denaturation zone.” After flowing to the heat output side 28 in a direction approximately perpendicular to the rotation plane, the sample liquid passes (again approximately parallel to the rotation plane) through the cold region 34, in which primer hybridization and then extension of the DNA strands take place. The cold region 34 is therefore also referred to as the annealing or extension zone. After passage through the cold region 34, the sample liquid flows (approximately perpendicularly to the rotation plane) back to the warm region 32.

[0060] The method step S3 is maintained until the fluorescence detector 18 determines a sufficiently high conversion of the structural building blocks, etc., intended for the multiplication. To this end, what is specifically carried out is a threshold comparison between a value of the measured fluorescence and a threshold specified (e.g., empirically determined) for a sufficiently high conversion. If the threshold is exceeded, the rotation of the sample holder 10 and the heating by using the heating device 30 are stopped, and the sample liquid is removed from the respective cavity 20, in a fourth method step S4.

[0061] Alternatively, the method step S3 is terminated after a specified time. The time plot of the fluorescence is optionally used to estimate the concentration of the DNA in the original sample.

[0062] The method steps S1 to S3 in particular can also be at least partially simultaneously carried out. In particular, the sample holder 10 need not stand still during the filling of the cavities 20. Similarly, the heating device 30 can also be already heating the heat input side 26.

[0063] FIGS. 3 and 4 depict an alternative exemplary embodiment of the sample carrier 4 having a modified structure of the respective cavity 20. Disposed inside the cavity 20 is a flow resistance 36 in the form of a beam or cuboid extending parallel to the rotation plane through the cavity 20. The flow resistance 36 is disposed in such a way that a radially inner (directed to the rotation axis 14) first flow channel 38 and a radially outer flow channel 40 are kept clear, and the current path of the convection current runs through the channels. Therefore, the flow resistance 36 separates the warm region 32 from the cold region 34, with the exception of the flow channels 38 and 40.

[0064] In the exemplary embodiment depicted, the flow channels 38 and 40 have the same channel cross section. In addition, the warm and cold regions 32 and 34 have the same dimensions.

[0065] In an optional exemplary embodiment (not depicted in greater detail), the flow resistance 36 is disposed in such a way that a larger partial volume of the cavity 20 is assigned to the cold region 34 than to the warm region 32. This achieves a higher extension time (residence time in the cold region 34, i.e., the extension zone).

[0066] Further optionally, the flow channels 38 and 40 have different channel cross sections.

[0067] FIG. 5 depicts a further exemplary embodiment of the cavity 20. The flow resistance 36 divides the respective flow channels 38 and 40 into subchannels 44 by using further webs 42. The subchannels 44 respectively assigned to the flow channels 38 and 40 can again have different cross sections.

[0068] The subject matter of the invention is not restricted to the above-described exemplary embodiments. Rather, further embodiments of the invention can be derived from the above description by a person skilled in the art. In particular, the individual features of the invention described on the basis of the various exemplary embodiments and their structural variants can also be combined with one another in another way.

[0069] The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention.

TABLE-US-00001 List of Reference Signs: 1 System 2 Rotation device 4 Sample carrier 6 Housing 8 Process chamber 10 Sample holder 12 Rotational drive 14 Rotation axis 16 Fan 18 Fluorescence detector 20 Cavity 22 Bottom wall 24 Top wall 26 Heat input side 28 Heat output side 30 Heating device 32 Region 34 Region 36 Flow resistance 38 Flow channel 40 Flow channel 42 Web 44 Subchannel S1 Method step S2 Method step S3 Method step S4 Method step S5 Method step