The present application hereby claims priority under 35 U.S.C. §119 on German patent application numbers DE 10361399.4 filed Dec. 29, 2003, the entire contents of which is hereby incorporated herein by reference.
The invention generally relates to a method for dispensing liquids in a micro-grid pattern. In particular, it relates to a method for the simultaneous, parallel dispensing (spotting) of different quantities of liquid in the range of <<1 μl in a grid spacing of <1 mm. In addition, the invention also generally relates to the associated apparatus for carrying out the method.
Array technologies are increasingly being used in molecular diagnostics. Hitherto, the titer plate technology in which, for example 96 (8×12) miniaturized reaction vessels at a grid spacing of 9 mm and each having capacities of a few 100 μl are formed in a plastic plate of approx. 127×85×15 mm, has been in widespread use. Titer plates of 384 wells (4.5 mm grid spacing) and 1536 wells (2.25 mm grid spacing) are also known. The reaction vessels can be fed with reagents and analyte substances by the manufacturer or user, thereby allowing parallel analysis or diagnostics.
What are known as micro-arrays are likely to provide a further level of miniaturization, thereby increasing the capacity of parallel analysis or diagnostics. In these micro-arrays, the manufacturer or user applies reagents to a planar substrate, e.g. a glass specimen slide, at a grid spacing of 1 mm or below, and these reagents are then fed for simultaneous analysis.
The coating of the substrates, also known as spotting, can be carried out using various commercially available appliances, known as spotters. A number of methods are available for the spotting:
Working on this basis, it is an object of an embodiment of the invention to avoid at least one of the drawbacks of the above known methods and to propose a solution for a simple, inexpensive and reliable method. Preferably, the solution is gentle on the surface, for simultaneously discharging a plurality of spots, if appropriate of different substances, which is suitable for an industrial manufacturing process. In one embodiment, it is also intended to provide a suitable apparatus.
An object may be achieved with regard to an embodiment of the method Refinements of the method and the associated arrangement are provided throughout the disclosure.
The method according to an embodiment of the invention can allow for extremely small quantities of liquid to be transferred into the predetermined grid pattern. In the apparatus according to an embodiment of the invention, for this purpose there is at least one device having microcapillaries in a grid spacing of less than 1 mm, which may be realized either in 1-dimensional form (1-D) or in two-dimensional form (2-D). In the former case (1-D), the microcapillaries may be arranged in rows and columns, whereas in the latter case (2-D) the microcapillaries may be arranged in a row. In the apparatus according to an embodiment of the invention, there is at least one microelement for providing a defined geometric arrangement of the microcapillary tips, at least one device with macrocapillaries in a larger 1-D or 2-D grid spacing (e.g. 4.5 mm), at least one macroelement for providing a defined geometric arrangement of the macrocapillary tips and a macroelement for providing a defined geometric arrangement of the microcapillary inlet openings.
In an embodiment of the invention, the macrocapillaries may be advantageously coupled to the microcapillaries via a coupling mechanism that can be disconnected. In this arrangement, at least one pump device may be connected to each macrocapillary, and there may be a controller for controlling the flow of liquid. The overall arrangement has a robot-controlled device which allows the mobility and therefore accurate positioning of the system with the microcapillary tips separated in the x, y and z axes.
Further details and advantages of the invention will emerge from the following description of figures relating to exemplary embodiments with reference to the drawings in combination with the patent claims, in which:
a to 4g show a diagrammatically depicted dispensing sequence in individual substeps, and
For use in in-vitro diagnostics, an array of individual spots may be produced for a biochip. The individual spots are located on a substrate and include a capture device, on which the molecules can dock in accordance with the key/lock principle during the subsequent biochemical analysis. A suitable spotting solution may be used to produce the spot array. Furthermore, technical devices/methods for dispensing may be used to discharge the spots, for example at a micrometer spacing, onto the substrate.
For the latter purpose, a method may be provided for the simultaneous, parallel dispensing of different liquids in a micro-grid pattern, using an arrangement of macrocapillaries in a macro-grid pattern which are used to load the microcapillaries. This purpose may be served by the apparatus described below having microcapillaries which are held in the dispensing grid pattern by a microelement. The inlet openings of the microcapillaries and the outlet openings of the macrocapillaries may be held in a titer plate grid pattern by a macroelement. Two macroelements form the coupling location.
First of all, the problem to be overcome will be explained with reference to
Spots 101i, i.e. single spots 101n-1, 101n to 101n+m, are shown on the substrate 100 in
An important factor in the method described here is that the spotting is effected by simultaneous capillary/liquid/substrate contact but without capillary/substrate contact. For this purpose, the capillaries have to be automatically moved to the substrate in the μm range, for example to within {fraction (1/10)} μm, in order to allow accurate spotting.
Although spotting with capillary/liquid/substrate contact is known per se from the prior art cited in the introduction, in this prior art it is only possible to produce spots with a relatively large spacing, but not in a grid pattern with a grid spacing of <1 mm. To achieve this objective, in particular the capillaries 23i in the end region have to be guided parallel and form the two-dimensional micro-grid pattern with the capillary ends.
Individual working steps of the arrangement shown in
To advantageously realize the simultaneous, parallel dispensing, the following detailed procedure is adopted: the liquid is transferred from the macro-head 10 to the dispensing head, the dispensing head 20 being designed with at least one microcapillary 23 in such a way that it can work with a plurality of microcapillaries in parallel simultaneously. The microcapillary outlet openings are held in a defined dispensing grid pattern by way of a microelement, for example in the form of micro-openings which predetermine the dispensing grid pattern.
The dispensing grid pattern may, for example form a microarray 30 which is arranged with a two-dimensional grid spacing dimension of 400×400 μm. A microelement array 30 of this type has several tens of up to approx. 100 positions. The microelement openings have virtually the same (≧) diameter as the outer microcapillary diameter, which leads to the microcapillaries being held with micrometer accuracy in the dispensing grid pattern. The microcapillaries 23 are, for example, placed in the microelement in such a manner that the microcapillary outlet openings project a few millimeters (1 to 3 mm) out of the microelement and that there is a space for free drop formation for each of the individual microcapillaries 23i.
It is necessary to ensure that all the outlet openings of the microcapillaries 23i are arranged in one plane. The inlet openings of the microcapillaries 23i are simultaneously held in the titer plate grid spacing of, for example, 4.5 mm with the aid of the second macroelement 21.
As described, there is a macro-head 10 in the arrangement. The macro-head 10 is formed by the macrocapillaries 11i in a macro-grid pattern, each individual macrocapillary 11i being connected to the separate precision pump 15i. The overall arrangement including dispensing head 20 and macro-head 10 is realized in one axis, with at least one element of the dispensing head 20 or macro-head 10 being able to move freely in this axis. The macrocapillary outlet openings are held in a defined titer plate grid pattern by way of the first macroelement 12, for example in the form of openings which predetermine the titer plate grid pattern.
The titer plate grid pattern, may, for example, be in the form of an array which is provided with a two-dimensional grid spacing of 4.5×4.5 mm. The macroelement array 3 has the same number of positions as are to be realized in the dispensing head 20. The openings of the macroelements have a virtually identical (>=) diameter to the outer macrocapillary diameter, which leads to the macrocapillaries being held with macrometer accuracy in the titer plate grid pattern. The macrocapillaries 11i are, for example, positioned in such a manner in the first macroelement 21 that the macrocapillary outlet openings project a few millimeters (10 to 15 mm) out of the macroelement 21, so that each individual macrocapillary 11i can move freely into a titer plate opening.
It is necessary to ensure that all the macrocapillary outlet openings are arranged in one plane and that each individual macrocapillary can be sprung by way of a mechanism realized in the macroelement.
For practical implementation of the new dispensing method, the dispensing head 20/macro-head 10 structure is secured to a positioning mechanism with a plurality of robot axes, allowing mobility and accurate positioning. This system may, for example, have two horizontal axes, which are responsible for changing the position of the microcapillary outlet openings in the horizontal plane (x, y axes), and one vertical axis, which is designed to change the position of the microcapillary outlet openings in the vertical plane (z axis). To allow the macro-head to be disconnected from the dispensing head, a further vertical axis (z′ axis) is required, which together is oriented as a macro-head—z′ axis—dispensing head system with respect to the z axis.
Before commencing operation of the system, the macro-head 10 or the macrocapillaries 11i and pumps 15i has/have to be filled with system liquid, which performs the function of transporting and washing medium for the microcapillaries 23. The system liquid has to be introduced without any inclusions of gas so that it can be ensured that there is no undesirable compression of the system liquid in the closed system including pump 15—macrocapillary 11. This operation, i.e. the (system liquid filling) is repeated if appropriate if gas has unexpectedly formed in the system or if the system has been contaminated with the dispensing solution. The system liquid has to have a good solubility for the dispensing solution so that it can also be used as washing medium.
Then, a computer-controlled dispensing operation is realized. The dispensing operation is illustrated with reference to
By way of example, a 384-well titer plate is used (16×24 chambers at a grid spacing of 4.5 mm), and this plate is filled with various dispensing solutions in such a way that the dispensing solutions coincide with the macrocapillary pattern. The amount of solution introduced into one titer plate chamber may, for example, be 15 μl. The titer plate is placed onto a preprogrammed location.
In the disconnected state of the macro-head 10—dispensing head 20 system in accordance with
In a further step corresponding to
After this step, it is possible to move to a parked position corresponding to
This location 60 is filled with solvent in accordance with
In a drying station 70, in accordance with
Before dispensing onto an intended substrate, a feed location is moved to, which is used to cover the microcapillary outlet openings with uniform drops of the dispensing solution. This simulates a continuation of dispensing by the pumps 15i delivering an accurately defined volume of the dispensing solution (1 μl down to approx. 1 nl).
The drops formed on the microcapillary outlet openings are discharged onto the feed substrate at uniform time intervals by realizing contact with the feed substrate via the drops. This is effected by movement on the z axis. To ensure that it is impossible for liquid to be discharged onto the same location a number of times, the macro-head 10—dispensing head 20 system is moved using the x-y axes. This operation is repeated a number of times until uniform drops of the dispensing liquid have formed at all the microcapillaries.
The system is now ready for dispensing onto a final substrate in accordance with
The dispensing operation is carried out by the pumps delivering an accurately defined volume of the dispensing solution (1 μl to approx. 1 nl). The drops formed at the microcapillary outlet openings are discharged onto the feed substrate at uniform time intervals by realizing contact with the feed substrate via the drops, associated with a movement on the z axis. To allow a defined pattern to be realized, the macro-head—dispensing head system is moved using the x, z axes.
After the dispensing operation, the macro-head 10—dispensing head 20 system is washed in accordance with
This is followed by movement to the washing station for the macrocapillaries in accordance with
The program ends in a parked position and the system is ready for further use.
The method described and the associated apparatus can be used in particular to process spotting solutions, as are described in the German patent application bearing application number 103 61 395.1-52 “Verfahren und Spotting-Lösung zum Herstellen von Microarrays” [Method and spotting solution for producing microarrays], the entire contents of which are hereby incorporated herein by reference, and which has the same application priority, in particular for the production of biochips. Further, the entire contents of corresponding U.S. application entitled “PROCESS AND SPOTTING SOLUTION FOR PREPARING MICROARRAYS”, and filed on the same date as the present application, are also incorporated herein by reference.
Exemplary embodiments being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
Number | Date | Country | Kind |
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103 61 399.4 | Dec 2003 | DE | national |