Patent Publication Number: US-2005136535-A1

Title: Cell culture device

Description:
BACKGROUND  
      The present invention relates to a cell culture device.  
      It is common, within the field of cell biology, to culture cells in order to harvest biologically active compounds produced by the cells, or indeed the cells themselves. Such cells are generally cultured on static plates which are enclosed in a bottle or flask. Flasks may generally be accessed through a neck portion, closed by means of a cap. When the flask is in use it is laid on its side so that the maximum possible surface area is horizontal. The cell cultivating medium covers the inner surface of this flask wall. Over time, the industry has developed a number of sizes of flask that are considered to be standard. One of these, known as the T-flask has four orthogonal walls (two major walls and two minor walls) and is configured so that the maximum surface area is available to the cells when the flask is laid on one of its major sides. These flasks are then stored in large automated storage systems consisting of a large number of recesses into which the flasks can be placed for storage or transport into, for example, an incubator. Cells are cultured within the flask within a cell culture medium that is isolated on the inner surface of the wall on which the flask rests. The flasks rest on a major wall in order to provide the maximum surface area.  
      It is well known within the field of cell biology that cell culture growth is optimised by providing the correct concentration of growing medium for the growing area that is defined by the major wall of the culture flask. However, it can be difficult to begin a cell culture in a standard T-flask as the concentrations may be too low as a result of the large surface area available. The industry is increasingly tending towards the use of smaller volumes and there is therefore a need to provide a smaller culture flask in which optimum growing conditions may be provided with a smaller quantity of growth medium. However, the problem arises as to how to store and transport these new smaller flasks as they do not fit conveniently in to pre-existing storage and incubation systems as these are configured to deal with standard flasks that have previously been developed by the industry, all of which are larger than the new generation of small flasks. However, the storage and incubation systems into which these flasks are usually placed are frequently large and complex devices that cannot easily or cheaply be replaced. The present invention therefore aims to provide a cell culture device that will enable a small growing area for cells to be isolated within a standard flask storage device.  
     SUMMARY OF THE INVENTION  
      According to the present invention there is provided a cell culture device comprising 
          a flask within which, in use, cells are cultured;     a structure connected to the flask and constructed to enable the flask to be held, in use, within a recess of a cell culture system;     wherein the volume of the envelope defined by the structure and the flask is greater than the volume of the flask.        

      The present invention therefore allows a small flask to be held securely within a pre-existing automated storage system provided with recesses considerably larger in size than the small flask to be stored. The principle is not limited to the storage of the small flasks but applies equally to any piece of automated laboratory equipment where flasks are held in position during a procedure, for example, during incubation in an incubator or low temperature storage in a freezer.  
      Preferably the flask is held within the envelope defined by the structure which may comprise a cuboid framework. This enables the structure to interface fully with the storage position within the automated storage system. This provides a greater level of security for the contents of the flask as the movement of the culture device within the storage device is reduced.  
      The structure may comprise a larger flask such as a T-flask or other industry standard flask. These flasks are readily available and are designed to fit within the automated lab systems and will therefore be exactly the right size. Furthermore, the enclosed space around the small flask in which the cells are cultured could be filled with a fluid or particulate solid in order to effect differing conditions from those in the surrounding flasks.  
      Alternatively, the larger flask may be empty so that, once the cell culture has reached its maximum population density within the small flask the contents may be transferred in to the larger flask using, for example, a pipette and culturing may continue within the larger flask. This allows any form of identification that has been applied to the flask to remain valid whilst the medium is cultured in firstly the smaller and latterly the larger flask.  
      The larger flask may further be provided with an opening that it arranged so as to permit access to the contents of the smaller flask. The neck portions of the smaller and larger flasks may be aligned to allow direct access using, for example, a pipette to extract the contents of the smaller flask. Alternatively, the small flask may be located off centre to a small degree provided that a pipette can still pass through the neck portion of the larger flask and access the contents of the smaller flask.  
      The smaller flask may further be provided with a closure member. Such a closure member maintains an enclosed environment within the smaller flask and ensures that, even if the flask is dropped, the contents remain safely within the smaller flask.  
      A spacing member may further be provided to separate the flask from the structure.  
      Alternatively, the small flask and the larger flask may share one wall. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Several examples of a cell culture device according to the present invention will now be described with reference to the accompanying drawings in which:  
       FIG. 1  shows a plan view of a first example of the present invention,  
       FIG. 2  shows a side view taken along the section A-A of  FIG. 1 ,  
       FIG. 3  shows an end view taken along the section B-B of  FIG. 1 ,  
       FIG. 4  shows a plan view of a second example of the present invention,  
       FIG. 5  shows a side view taken along the section A-A of  FIG. 4 ,  
       FIG. 6  shows an end view taken along the section B-B of  FIG. 4 ,  
       FIGS. 7A and 7B  show plan and side views of a pipette accessing the contents of the first example of the present invention, and  
       FIGS. 8A, 8B  and  8 C show plan, side and perspective view of a part of an automated storage system comprising a number of cell culture devices according to the present invention. 
    
    
     DETAIL DESCRIPTION  
       FIG. 1  shows a first example of a cell culture device  1  according to the present invention. Within the internal volume of the culture device  1  there is provided a smaller flask  10  in which cells may be cultured. The flask  10  consists of are four orthogonal walls  11 ,  12 ,  13  and  14  and a base  15 . There are two major walls  13  and  14  and two minor walls  11  and  12 . Above the four orthogonal walls  11  to  14  the walls of the flask  10  converge to meet at a neck portion  16 . The narrowing of the flask  10  at the neck portion  16  ensures that the contents of the flask  10  remain within the flask  10 . The neck  16  could screw threaded and may co-operate, in use, with a cap  17  to seal the contents of the flask from the ambient atmosphere and also from the contents of the cell culture device  1 . The use of a cap  17  to close the smaller flask  10  is only appropriate in some applications as a result of potential contamination of the sample held within the flask  10 . In order to overcome this problem a septum seal (not shown) may be used to close the smaller flask  10 . A septum seal is not removed but rather punctured to gain access to the contents of the inner flask  10  thereby reducing the danger of contamination of a sample.  
      Connected to the flask  10  is a structure  100  that forms the outer boundary of the culture device  1 . In one example of the present invention the structure takes the form of a flask  100  of rectangular cross-section having four orthogonal walls  111 ,  112 ,  113 , and  114  and a base  115  at one end. There are two major walls  113 ,  114  and two minor walls  111 ,  112 . At the other end of the flask  100  the four orthogonal walls  111  to  114  the walls converge to meet at a neck portion  116 . The neck  116  is screw threaded and co-operates in use, with a closure member, for example a cap  117  to seal the contents of the cell culture device  1  from the ambient atmosphere. The surface area of the major wall  11  of the small flask  10  is between 15% and 50% of the surface area of the major wall of the larger flask  100 .  
       FIG. 2  shows a side view of the first example of the culture device  1  according to the present invention. This shows the spacing member  18  which maintains the flask  10  in a stable position within the cell culture device  1 .  
       FIG. 3  shows an end view of the cell culture device  1 , partly in section. This shows that the neck portion  16  of the flask  10  and the neck portion  116  of the flask  100  are sufficiently aligned for access to be made to the flask  10  through the neck portion of the culture device  1 .  
      FIGS.  4  to  6  show a second example of a culture device  1  according to the present invention. Like reference numerals have been used throughout the description of these figures where appropriate. In this second example of a culture device  1  the flask  10  has exterior walls  11  and  14  and base portion  15  that also form part of the walls  111 ,  114  and base  115  of the cell culture device  1 .  FIG. 5  shows a side view of the cell culture device  1  and  FIG. 6  shows an end view.  
      In use a suspension comprising the cells to be cultured and culture medium is introduced into the flask  10  using a pipette  23  as shown in  FIG. 7 . The major wall  11  onto which the cells are to be cultured may be pre-treated with an agent that will assist the cells to adhere to the inner surface of the major wall  11  of the flask  10 . The cell culture device  1  is then held within the recess of an automated storage system. When the cell population has exhausted the cell culture medium in the smaller flask  10 , or when the population is sufficiently large that the area in which the cells are confined is sufficiently small to inhibit further population growth, the cells may be transferred into the larger flask  100  to continue growing. The transfer can be effected either by using a pipette  23  or by securing the cap  117  on the larger flask  100  and then inverting the cell culture device  1  to cause the cells to detach from the growing surface and move into the larger flask  100 . The cell culture device  1  is then returned to the automated cell storage device to allow the cells to continue to grow. Once the population density in the larger flask  100  is sufficiently high the cells can be removed from the flask  100 . During this operation it is preferable that none of the debris from the original incubation in the smaller flask  10  contaminates the contents of the larger flask. This operation is therefore preferably performed using a pipette  23  although it is possible, in some examples of the present invention, to rely on the tapering of the neck portion of the small flask to contain such debris.  
      Part of an automated cell storage device  30  is shown in  FIG. 8 . The storage unit  30  has a large number of recesses  31  each of which can hold a cell culture device  1  or a standard flask. The cell culture device  1  or flask is held in position by a number of retaining members  32 ,  33  that interface with the base  115  and minor walls  113 ,  144  of the cell culture device  1 . Depending on the type of system the temperature of the cells can be appropriately controlled to optimise the growth or to maintain the integrity of the culture for long term storage as appropriate.