Abstract:
This invention discloses an improved process of distributing liquid physiological specimens over a surface, i.e. the filming process in a laboratory, during which a liquid sample is distributed over a specimen-display surface like a conventional laboratory slide. The invention relates to the utilisation of the centrifugal force in a rotating device. By placing the surface that is to be filmed by the sample, in such a way that it is pointed towards the axis of rotation, the influence of the centrifugal force will distribute the sample over the whole surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is entitled to the benefit of and incorporates by reference essential subject matter disclosed in International Application No. PCT/DK03/00209 filed on Mar. 27, 2003 and Danish Patent Application No. PA 2002 00514 filed on Apr. 9, 2002. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates to a process for centrifugal distribution of liquid physiological specimens over a surface with an array of assays, the array being placed in a rotating device and the liquid physiological specimens being distributed on the surface by the dynamic forces of the rotation, the surface pointing towards the axis of rotation, the liquid physiological specimens being forced towards the surface under the influence of the dynamic forces of the rotation.  
       BACKGROUND OF THE INVENTION  
       [0003]     Centrifugal distribution of liquids physiological specimens over a surface with an array of assays is often referred to as “filming” by those working in medical laboratories, and the liquid physiological specimens are often called “samples”.  
         [0004]     In this connection, the term “a liquid physiological specimen” is to be understood in a very broad manner, covering, of course, physiological specimens like blood and spittle, but also pre-treated DNA extracts are comprised by the term.  
         [0005]     As an example, applying a drop of blood to a slide, where the surface of the slide contains an array of assays, takes place in a DNA-testing process. When the drop of blood is distributed over the surface of the slide, the elements in the blood will react or connect to the assays where they fit, and analysing the slide afterwards will give the result of the DNA-testing.  
         [0006]     To achieve the contact between the elements of the sample and the assays, the elements have to diffuse from the sample to the assays, and obviously the duration of this diffusion will increase with the thickness of the sample layer on the surface of the slide. This will reduce the duration of the process, if the thickness of the layer is reduced, and therefore reducing the thickness of the layer is desirable.  
         [0007]     When filming, the main problem to solve is to equally distribute and re-circulate the sample over the whole of the surface, the sample being distributed to all the assays in the array. One way of solving this problem is to place the array of assays flat in a rotating device, the surface being in the same plane as the rotational movement. This will force, or rather throw, the sample along the surface, due to the dynamic reaction to the rotation. In the following, this dynamic reaction will be referred to as the centrifugal force, and must be understood as the act of a particle moving away from the centre of a rotating movement.  
         [0008]     When distributing a sample by throwing it across the surface of the array of assays, the sample applied to the surface does not distribute equally over the whole surface, reproduction of the result being hard to obtain. A single drop of the sample is not likely to distribute over the whole surface, and therefore does not necessarily reach all assays in the array. Therefore, a number of extra drops is applied to the surface, which will increase the duration of each test and the used amount of the sample, which is often expensive. Also, each specimen in the sample will be forced along the surface, contact between the specimens and all the assays in the array being hard to obtain, which also influences the reproduction ability of the test.  
         [0009]     Another known method of overcoming the problems of the filming process is to force the sample through micro channels, in which the array of assays is contained. This method will reduce the duration of the process, but is very sensitive to pollution, the size of the elements in the sample, and the production of the micro channels.  
         [0010]     It is an object of this invention to overcome the difficulties of reproducing test results. It is a further object of this invention to reduce the duration of each test, and to reduce the used amount of the sample for each test. Yet another object of the invention is to reduce the sensitivity with regard to pollution and to the size of the elements in the sample.  
       SUMMARY OF THE INVENTION  
       [0011]     The object of this invention is achieved in that the liquid physiological specimens are applied as drops to an area of the surface opposite a drain end, and in that the distribution of the liquid physiological specimens is controlled by adjusting the position of the surface relative to the axis of rotating, in such a way that a thin film of the liquid physiological specimens will be formed over the whole surface before drops are forced over the edge in the drain end of the surface. Hereby it is achieved that the elements in the sample are forced in the direction of the assays, and a drop of the sample will be completely filmed by the dynamic forces. Further, it is achieved that all assays in the array are in contact with the sample, and that the elements in the sample will have equal and best conditions for diffusion to the assays. Yet further, it is achieved that it is possible to control the direction of the distribution, and the rate at which the sample distributes over the surface.  
         [0012]     It is an advantage that the array of assays itself further rotates around another axis than that of the rotating device, meaning that the elements in the sample will be distributed to all, or nearly all, assays in the array.  
         [0013]     It is particularly preferred that the surface, to which the sample is applied, is formed as a hollow in a material part, where the hollow forms a closed container when the material part is covered with a lid, and where the sample is applied to the surface before the lid covers the hollow. The sample is contained in a closed container, and can be re-circulated over the surface without having any disturbing and/or damaging contact with the surroundings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     In the following, the invention will be described in detail with references to the drawings, showing:  
         [0015]     FIGS.  1 A-G illustrate a slide having a number of assays, and show the progression of a liquid sample under centrifugal force.  
         [0016]      FIG. 2  is a partly in section perspective view of the rotating device of the present invention.  
         [0017]      FIG. 3  is a partly in section perspective view of a portion of the rotating device of  FIG. 2 .  
         [0018]      FIG. 4  shows an embodiment of an array of assays, placed in a hollow.  
         [0019]      FIG. 5  is a perspective view of a device containing two arrays of assays, placed in a hollow.  
         [0020]      FIG. 6  schematically illustrates a rotating array of assays in accordance with the invention.  
         [0021]     FIGS.  7 A-E are functional views showing the process or re-circulation in accordance with  FIG. 6 .  
         [0022]      FIG. 8  schematically illustrates a embodiment of a rotating device.  
         [0023]      FIG. 9  schematically illustrates a embodiment of a rotating device. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]      FIG. 1A  shows a sectional view of a slide  1 , having a surface  2  with an array of assays  3 . Such slides are widely used in laboratories, e.g. for microscopic analyses of blood specimens. The slide of  FIG. 1A  has a frame part  4  along three of the sides, which will be understood from the sectional view in  FIG. 1B . The fourth side  5  is formed and works as a drain part, where the specimens can flow away from the surface  2 .  
         [0025]     The slide  1  is placed in a rotating device  9  of  FIG. 2 , said device comprising several sections  13 .  FIG. 3  shows one of the sections  13  in a sectional view, and with the slide  1  placed in the holder  14 . As the rotating device is rotating, centrifugal forces will act from the centre of rotation, and at right angle, towards the circumference  12  of the rotating device  9 . The plunger part  11  of  FIG. 2  will be forced towards the part  16  of  FIG. 3 , due to the dynamic forces, and under this pressure liquid sample contained behind part  16  will be dosed as drops by a capillary part  17 , and led through the pipe  18  to the slide  1 . The mouth of the pipe ends at the end of the slide where the holder is placed, and at a certain distance from the slide. The slide itself is placed in an upright position along the circumference  12  of the rotating device  9 , the centrifugal force acting substantially parallel to a normal axis of the surface of the slide. The surface of the slide  1  is therefore substantially parallel to the rotating axis of the rotating device.  
         [0026]     The drop  6  in  FIGS. 1A and 1B  is a drop, which has just left the pipe  18 , and as the drop hits the surface of the slide, it will be distributed over the surface by the centrifugal force. This is indicated by arrows in  FIGS. 1C  to  1 F, and the frame  4  on the three sides of the slide  1  will force the distribution towards the drain part  5  of the slide  1 , from where drops  7  will be thrown of the slide. The centrifugal force has now distributed a thin layer of the sample over the whole surface, and every assay  3  in the array has got in contact with the sample.  
         [0027]     The velocity with which the sample is distributed towards the drain part  5  can be controlled by controlling the angular position of the slide, and by controlling the rotational speed of the rotating device. As the distribution over the surface is controllable, only a very small amount of sample liquid is needed for each slide. As a consequence of the dynamic forces, surface tensions will only have limited effect.  
         [0028]     In some test application it is important that the used amount of sample liquid is reduced to a minimum, and that the applied sample liquid is maintained on the surface of the slide, and not thrown away over a drain part as previously described. This is known as re-circulation of the sample along the surface.  FIG. 4  shows a structure  19 , placed in a hollow, which has a surface  2  with an array of assays  3 , and is supplied with small pockets  20  placed along the circumference of the structure. This structure is formed as a hollow  19  in a material part  21 , shown in  FIG. 5 , with a lid  22  on top of it. When the lid is placed on top of the material part  21 , each of the two hollows  19  and  19   a  forms a small test volume, and the assembled material part with lid forms a slide  26 .  
         [0029]      FIG. 6  shows the slide  26  placed in a rotating device with an axis of rotation  10 , the rotation direction being indicated by an arrow  24 . The slide  26  is placed at a centre line  23  that is placed at an angle Y relative to the rotating axis  10 , and at a distance X from the rotating axis  10 , the centrifugal force acting on the surface as previously described with a normal portion. In addition, the dynamic forces will act upon the surface with a tangential portion, the sample being forced across the surface. The slide  26  is rotated around the centre line  23 , indicated by the arrow  25 . The effect of this additional rotation  25  will be described with reference to  FIG. 7 .  
         [0030]      FIG. 7A  shows a drop of a liquid sample applied to the test volume in the container, and the lid is then placed on top of the container. Subsequently, the slide  26  is placed in the rotating device, the centrifugal force acting upon the surface and filming the sample on the array of assays. Some of the sample will be distributed into the small pockets, and as the slide  26  rotates around an axis, the liquid sample will flow from one pocket to the array of assays, and along the circumference to the next pockets, indicated in  FIG. 7B . The shape of the pockets will, however, distribute liquid sample over the whole array of assays, as the slide  26  is rotated, indicated in  FIGS. 7C  to  7 E. Each pocket then acts as a collecting area, from where liquid sample once again is distributed to the array of assays, and re-circulation occurs.  
         [0031]     Re-circulation as described in  FIG. 7  has basically the effect known from a washing machine. The sample is again and again washed across the array of assays, whereby reproduction of the testing is obtained.  
         [0032]      FIG. 8  shows another embodiment of a rotating slide in a rotating device. The slide  28  is now formed as a cylinder part, which rotates around its own axis  27 . The axis  27  is more or less parallel to the rotation axis  10  of the rotating device, and the centrifugal force will thus act upon the surface of the slide  28 . The array of assays is placed on the inner surface of the slide  28 , and on the top and on the bottom the slide has a frame part  4 , extending from the inner surface of the cylinder towards the axis of rotation  27 . As a drop of the liquid sample is applied inside the slide  28 , it will be distributed as a column along the inner surface, and the column will be placed where the distance from the axis of rotation  10  is largest. As the slide is rotated around the axis  27 , the column will wash the whole of the inner surface, and hereby re-circulation will occur.  
         [0033]      FIG. 9  shows a third embodiment of a rotating slide in a rotating device. Here the slide is formed as a cone part  30 , which rotates around its own axis  29 . The axis  29  is placed at an angle relative to the rotation axis  10  of the rotating device, a part of the inner surface of the cone shaped slide being more or less parallel to the rotation axis  10  of the rotating device, and the centrifugal force will thus act upon this part of the inner surface of the cone shaped slide  30 . Due to the centrifugal force, a column of liquid sample  31  will be formed on the inner part of the cone shaped slide, which is more or less parallel to the axis of rotation  10 . As the cone shaped slide is rotated around its own axis  29 , liquid sample will wash the whole inner surface, and hereby re-circulation will occur.  
         [0034]     As mentioned in the beginning of the application, the invention can be utilised in laboratories for DNA-testing. However, this application does not in any way limit the invention. A slide can contain similar assays for reaction with specific elements or different assays for reaction with a group of elements. The invented process can be utilised for distribution of a sample over any surface of a slide, and the application will then depend on the slide used in the process.  
         [0035]     Thus, a portable apparatus for testing purposes on location is a possibility. This could be an apparatus testing for diseases when consulting a doctor, or an apparatus testing for cultures of bacteria in watercourses. Only the slide used in the process defines the application for a given apparatus.