Abstract:
An electrophoresis container apparatus having (1) a primary container tray made from a UV light transmitting materials, (2) a UV light transmitting gel contained in the primary container tray, and (3) a removable top sheet for covering the gel. The removable top sheet may also be UV light transmitting. The apparatus optionally comes with a handle having pincers for grasping the primary container and permitting easy movement of the apparatus from location to location. Because the apparatus transmits UV light, the gel can be used and analyzed while it is still in the tray. This eliminates the need to remove the gel before analysis and reduces the chances that the gel will be damaged during handling. Similarly, because the apparatus has an optional handle, the user can move the apparatus form location to location without touching the apparatus and exposing the user to dangerous chemicals, e.g., those often used in staining procedures.

Description:
This is a nonprovisional application claiming benefit of provisional application 60/074,790, filed on Feb. 16, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to apparatuses and methods for conducting gel electrophoresis. In particular, the present invention relates to ultraviolet light transparent apparatuses for holding electrophoresis gels and to methods for using such apparatuses to simply and safely process electrophoresis gels. 
     2. Background of the Invention 
     Gel electrophoresis is widely used in the molecular biology and biotechnology fields. Initially all laboratories made their own electrophoresis gels and apparatuses for containing such gels. Subsequently, as such gels became popular they were prefabricated and sold to laboratories in compact and easy to use apparatuses. However, prefabricated electrophoresis gels for are fragile and are subject to drying. Thus, these gels must be handled carefully. 
     Agarose gels has also been widely used in the molecular biology and biotechnology fields. Typical procedures include preparing the agarose gel, loading samples, running the electrophoresis, staining the samples with fluorescent dyes, and photographing the gels. The use of precast or prefabricated gels eliminates the time required for gel preparation and greatly minimizes potential human contact with highly toxic fluorescent dye stains. 
     One known electrophoresis gel container for packaging prefabricated electrophoresis gels or to be cast electrophoresis gels is shown in U.S. Pat. No. 5,443,704, entitled “Electrophoresis Gel Container Assemblies.” The device of the &#39;704 patent has a number of drawbacks. For example, it is not transparent to sufficient ultraviolet (“UV”) light to illuminate ethidium bromide-stained DNA bands. Therefore, visualization of stained bands of DNA fragments cannot be made with the &#39;704 device while the gel is still within the gel container. With the &#39;704 device, the user is required to remove the gel from the cassette and place the gel directly onto the ultraviolet light source (e.g., transilluminator) for viewing or photography (i.e., photographing to keep a record of the results). In contrast, according to one aspect of the invention discussed below, one can place the entire apparatus with the gel contained therein directly onto a transilluminator for direct viewing or photography. 
     The &#39;704 device also does not provide an immediate means of handling the gel without user contact with various solutions used in staining and destaining. In contrast, according to another aspect of the present invention as discussed below, handles are provided that allow the user to transfer the gel and container from place to place and from solution to solution without contacting the gel. This aspect of the invention minimizes the likelihood of contamination and prevents the user from contacting dangerous solutions commonly used in staining, e.g., ethidium bromide (a mutagen used in DNA and RNA staining). 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved disposable apparatus for holding electrophoresis gels. The apparatus, typically in the form of a tray, is constructed from UV light transparent materials and contains a UV light transparent pre-cast gel. The improved apparatus: (1) provides a method for conducting UV light analysis on the gel without removing the gel from the apparatus and (2) provides convenient and safe handling of gels by minimizing potential human contact with hazardous fluorescent dye stains. 
     According to one aspect of the invention, an electrophoresis container apparatus is provided which includes: a primary container having a bottom for supporting an electrophoresis gel and perimeter side walls extending from the bottom, the primary container being made from a UV light transmitting material; a removable top sheet adhered to the perimeter side walls of the primary container, optionally made from a UV light transmitting material; and an electrophoresis gel within the primary container, the gel being a UV light transmitting gel. 
     According to another aspect of the invention, a handle is provided that is configured to grasp opposite sides of the primary container. Preferably, the handle includes two opposing legs that are biased towards one another. 
     According to another aspect of the invention, a method of analyzing samples in an electrophoresis gel includes: a) providing an electrophoresis container apparatus, comprising: a primary container having a bottom for supporting an electrophoresis gel and perimeter side walls extending from the bottom, the primary container being made from a UV transmitting material; a removable top sheet adherable to the perimeter side walls of the primary container, optionally made from a UV light transmitting material; b) pre-casting a UV light transparent electrophoresis gel within the primary container; c) loading samples into the gel; d) carrying out electrophoresis on the samples; e) visualizing the samples in the gel with UV irradiation transmitted to the gel through the primary container. Optionally, the removable top sheet is completely removed before visualizing the samples in the gel or allowed to remain on the apparatus while visualizing the samples in the gel. If the removable top sheet is allowed to remain on the apparatus during visualization, it can be made of UV light transparent materials or, for analysis where visible light is emitted from the sample, from non-UV transparent materials. In gels where the stain is not included in the gel mixture, further steps of staining and rinsing the gel after carrying out the electrophoresis may be needed. 
     According to another aspect of the invention, the method also includes the step of grasping the primary container with the gel therein with a handle and transferring the container and gel to required locations during steps that require the apparatus to be moved, e.g., the visualization step requiring transfer to an illuminator or the optional staining and rinsing steps. 
     The above and other advantages, features and aspects of the present invention will be more readily perceived from the following description of the preferred embodiments thereof taken together with the accompanying drawings and claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given below and the accompanying drawings which are given by way of illustration only, and are not limiting of the present invention, and wherein: 
     FIG.  1 (A) is a schematic side view showing one embodiment with a gel container, a handle held by a user and a solution into which the gel container may be placed; 
     FIG.  1 (B) is a top view of a gel container showing the top sheet and the primary container thereunder in dashed lines; 
     FIG.  1 (C) is a side view of a handle according to one specific embodiment, showing a portion of the base partially cut-away; 
     FIG.  1 (D) is a cross-sectional view of the primary container taken along the line D—D shown in FIG.  1 (B); 
     FIG.  1 (E) is a side view of a section of a leg portion from the right side of FIG.  1 (C); 
     FIG.  2 (A) is a top and side view of a primary container according to one exemplary construction; 
     FIG.  2 (B) is a top and side view of a primary container and a comb therein according to one exemplary construction; and 
     FIG. 3 is a top and side view of gel dimensions according to one exemplary construction. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments of the present invention comprise a UV light transparent tray containing a UV light transparent electrophoresis gel or media covered by a removable top. The apparatus is in the form of a pre-cast and pre-packaged gel in a ready-to-use tray. The present invention is preferably designed for use in electrophoretic separations of polymeric biological materials, such as DNA, RNA and proteins. 
     According to the present invention, the gel contained in the tray may be stained or blotted in such a way as to allow transfer or visualization without removing the gel from the apparatus. The present invention is thus safer to use with dangerous solutions than present pre-cast apparatuses available in the marketplace. 
     In summary, as discussed below, preferred embodiments of the present invention show a gel tray apparatus wherein: 
     (a) the gel tray is transparent to UV light at useful wavelengths; 
     (b) the gel (gel with buffer incorporated in the gel) is transparent to UV light at useful wavelengths; and/or 
     (c) the gel tray has unique handles to facilitate use and safety. 
     FIGS.  1 (A)- 1 (D) show an exemplary preferred embodiment of the invention. A container  100 , FIG.  1 (A), includes a primary container  110 , FIG.  1 (D), and a top sheet  120 , FIG.  1 (B). The primary container  110 —or gel tray—serves as the primary holder of the gel material used for separations. The primary container  110  is preferably made from an ultraviolet (“UV”) light transparent plastic. In this manner, the primary container can be placed, e.g., directly onto a transilluminator for viewing, rather than a user having to remove the contained gel therefrom. 
     The UV transparent plastic is preferably either polymethylpentene UV transparent (“UVT”) acrylic. The preferred tray containing the gel is ultraviolet and visible light (“UV-VIS”) transparent. This enables visualization while the gel is within the container. For example, a convenient method of visualizing DNA in agarose gel includes using the fluorescent dye ethidium bromide, which is a highly toxic chemical. UV irradiation absorbed by the DNA at 260 nm and transmitted to the dye, or irradiation absorbed at 300 nm and 360 nm by the bound dye itself is emitted at 590 nm in the red-orange region of visible spectrum. 
     The material used for the primary container  110  and the top sheet  120  is preferably sufficiently UV transparent that enough UV light penetrates the primary container to strike the DNA bands in the gel to give substantial radiation in the visible wavelengths. Tests conducted with a variety of plastics indicate that only select materials such as polymethylpentene and UVT acrylic are sufficiently UV transparent to allow enough UV light to penetrate for good band visualization in, for example, observing DNA fragments with ethidium bromide staining. 
     The top sheet  120  is adhered to the primary container—e.g., with an adhesive—so as to form an envelope which holds the gel  200 , FIG.  1 (A), in a sufficiently rigid configuration as to be useable when desired. The primary container  110  preferably has an inner surface  111  that is adapted to provide good adherence of the gel  200  thereto. Pre-treatments for common plastic materials that allow good adherence of the gel to the plastic are desirable. For example, plastics with a rough (“buffed”) finish can allow good adherence of the gel to the plastic so as to avoid premature release of the gel from the cassette. 
     Preferably, the primary container  110  is also sufficiently sturdy to allow pressure to be imparted on opposite sides thereof, e.g., at side walls  112  and  113 , to allow the container  110  to be handled. The primary container  110  preferably has a sufficient strength to allow a user to lift the container with a pincer or a handle  300 , discussed below, without bending the container and damaging the gel contained therein. It can be important to provide the handles with sufficient inherent strength to grasp the primary container with the gel intact so as to allow handling without concern for damage or loss. It may also be important that the material used for the primary container  110  (and the top sheet  120  of the gel container) should also be rigid enough to support and maintain the integrity of the gel in transit to customers, even in transit to foreign countries, but flexible enough to allow easy removable. 
     The top sheet  120  of the container also preferably aids in maintaining a flat upper surface on the gel  200  and in protecting the gel  200  and the wells formed therein from being scratched or marred which would reduce the utility in the visualization of the bands. The top sheet  120  also protects the gel  200  from the evaporation of water in the buffer, The top sheet  120  is preferably made of plastic or, alternatively, of a water-impenetrable membrane of some sort. 
     As noted, the device preferably includes at least one handle  300 . Preferably, only one handle is provided, however, more than one handle can be provided. The handle  300  is preferably constructed to allow a user to move the primary container  110  and the gel  200  therein into, through, and from any solution (e.g., shown schematically in FIG.  1 (A) at  400 ) which could be dangerous were the user to come in contact with this solution. The handle  300  preferably allows the user to grasp, lift, and move the gel container  110  without directly contacting the gel container  110 , the gel  200 , or the solutions, e.g. 400, used in the gel&#39;s normal use and band visualization. 
     The handle is preferably be made of plastic, metal, and/or wood. The handle can also be made to have sufficient strength to be used to submerge the gel container completely in an electrophoresis, a staining, or a washing medium and to allow the user to move the container and gel about freely. In addition, the handle  300  is preferably attachable to and detachable from the primary container  110 . 
     According to one embodiment, the handle has a generally upside-down “U” shape. A base portion  310  of the “U” shape is preferably adapted to be grasped by a user&#39;s hand H, and the legs  320 ,  330  are preferably adapted to engage opposite sides  112 ,  113  of the primary container  110 . In order to facilitate engagement of the legs  320 ,  330  with the primary container  110 , the legs  320 ,  330  can include grooves  321 ,  331  cut into their grasping ends so as to allow an edge or flange  130  of the primary container  110  to nest neatly therein, to provide a sure and tight fit. The legs  320 ,  330  are preferably biased with a biasing means, such as a spring, towards one another so as to firmly engage the opposite sides of the primary container. As shown in FIG.  1 (C), one preferred embodiment of the biasing means includes a coil spring  340  which is fixedly connected to an upper side of both legs under tension therebetween. That is, the base of the “U” preferably has a spring-loaded device that draws the leg portions of the “U” together. Preferably, the spring-loaded device can release the gel container when pressure is applied by the user to create a bias opposite to that of the spring. 
     In the preferred embodiment shown in FIG.  1 (C), the base  310  is formed from a hollow tube  311 . The hollow tube  311  is fixedly attached to the upper end of the leg  320  with adhesives or the like. The leg  320  has a circular hole  322  formed therein that snugly receives a central hollow tube  350 . The tube  350  extends through the center of the hollow tube  311  and is fixedly attached at an opposite end thereof to the leg  330 . As a result, the tubes  350  and  311  are each fixed to respective ones of the legs and can be moved relative to one another in a telescoping manner. If desired, a plug member  312  can be fitted in the end of the tube  311  to provide a contact surface for the upper end of the leg  330  and to provide a snug opening therethough for the tube  350 . As shown, the plug member  312  has an inner portion  313  received in the end of the tube  311  and a central opening through which the tube  350  extends. The opposite end of the tube  350  extends out past the leg  320  such that it can be pressed in the direction R, FIG.  1 (A), to expand or separate the legs  320 ,  330 . The coil spring can be fixed, for example, to pins  351 ,  352  which are fixed to the legs  320 ,  330 , respectively. Preferably, a keyway is provided between the telescoping parts to prevent the legs  320 ,  330  from rotating relative to one another about the central axes of the tubes  311 ,  350 . In the illustrated embodiment, the pin  351  extends through upper and lower elongated slots  353  extending axially along the tube  350  such that the pin  351  is snugly received therein and passes therethrough. The length L of the slots  353  preferably limits outward movement of the leg portions, while the width of the slots limits rotational movement as discussed. Although this exemplary embodiment has been described in detail, it should be understood that the handle  300  can be modified in a variety of ways as would be understood by those in the art based on this disclosure. 
     FIG.  1 (E) shows a side view of the leg  320  from the right side in FIG.  1 (C). The leg  330  is preferably similar. The legs  320 ,  330  preferably have a width W that can extend along the sides  112  and  113  of the primary container to stably support the container when grasped. In one exemplary construction, the size of the width W relative to the length of the container  110  can be approximately as shown in FIGS.  1 (E) and  1 (B). 
     An important parameter of the preferred gel  200  is to have the gel transparent to UV light at useful wavelengths. Increased gel transparency can be obtained by the inclusion of certain modified polysaccharides (e.g., J.T. Baker&#39;s GelTwin and/or GelTwin II). 
     The gel  200  formed within the gel container is preferably made of agarose, an agarose + GelTwin II (J.T. Baker, catalog # 4370) combination, acrylamide, polyacrylamide, polyacrylamide analogues, natural polysaccharides, modified polysaccharides, or some combination thereof. The gel may contain a buffer and/or pre-staining agent or staining agent commonly used in the visualization of large polymers. The buffer is typically selected from any one of the commonly used buffers for DNA electrophoresis, such as TAE (Tris-Acetic Acid-EDTA), TBE (Tris-Boric Acid-EDTA) or TPE (Tris-Phosphoric Acid-EDTA) or protein electrophoresis, such as Tris-chloride or Tricine. The gel  200  is most preferably made of about 0.5-8% agarose. The gel  200  may have wells W shown in FIG. 3 pre-set therein so that it is ready for sample application and use upon removing the top sheet  120  of the two-part container. 
     FIGS.  2 (A) and  2 (B) illustrate dimensions of a container  110  according to one exemplary embodiment. FIG. 3 illustrates sizes of the gel  200  within the primary container according to one exemplary embodiment. In FIGS. 2-3, the reference numerals shown between arrows are also the sizes thereof in inches, except where the letters “cm” or “mm” are included, wherein such represent centimeters or millimeters, respectively. Dimensions described in the present disclosure fit a few of the more popular units, but are not necessarily ideal for all commercial submarine gel electrophoresis chambers. Those skilled in the art would recognize how to adapt the present invention to the particular application at hand based on this disclosure. 
     In the example shown in FIG.  1 (B), the primary container  110  (shown in dotted lines below the top sheet  120 ) has a square-shape or rectangular-shape base sheet of molded UV transparent plastic with four side walls  112 ,  113 ,  114  and  115 . The side walls preferably include a flange portion  130  having a generally flat upper surface for adhering the top sheet  120  thereto. Although the top sheet can be adhered to the primary container in a variety of ways, the preferred methods for adhering the top sheet include applying adhesives or glues or heat-sealing. Other methods can include, for example, applying a two-sided adhesive tape. 
     As noted, the top sheet  120  is preferably constructed of a UV transparent plastic but can be made from any material. The primary container  110  and the top sheet  120  together can form an envelope into which a gel-forming substance may be poured and allowed to solidify within the envelope. Alternatively, the gel may be poured in liquid form into the primary container  110  and at a later time, the top sheet  120  may be added. 
     When needed, the upper surface of the gel may be exposed by grasping a tab extension  121 , FIG.  1 (B), of the top sheet  120  and gently pulling the tab back so as to separate the top sheet  120  from the primary container  110  and from the upper gel surface to reveal the wells W of FIG. 3 previously formed by the teeth of a comb. The tab  121  can be formed, for example, by extending a portion of the top sheet  120  past an edge of the top sheet  120  adhered to the primary container. 
     The pre-formed wells W of FIG. 3 are preferably placed in a location in the gel allowing a good flow of electric current through the gel without interference from the walls of the primary container to distort any of the bands being electrophoresed through the gel. It can be important to place the wells designed to receive the user&#39;s samples at sufficient distances from the respective side walls of the primary container to avoid interference from these walls in the flow of electrons through the gel in a linear fashion. Based on tests conducted, the wells are preferably at a minimum of 1.0 cm from the nearest adjacent side wall, and preferably at least 1.5 cm in order to obtain bands of electrophoresed product of the highest integrity. Wells placed too close to the walls give skewed bands. 
     The gel container may be immersed into buffer in a submarine-style gel electrophoresis chamber commonly used in the art of submarine gel electrophoresis. Samples of the user&#39;s preference containing any of numerous natural or contrived polymeric molecules, either containing a pre-staining agent or without such an agent, and containing a non-ionic agent to increase the density of the solution such as to cause the sample to sink into the wells may then be applied to the wells. 
     The power supply may then be connected via the leads supplied by the manufacturer. The current can then be turned on for an extent and time sufficient for the migration of the molecules far enough in the gels to be satisfactory for the purposes of the user. In some situations, the bands may be viewed during electrophoresis as they progress through the gel medium by irradiating them with certain visible or ultraviolet light. 
     At an appropriate point, the current may be disconnected and the gel removed from the electrophoresis chamber and viewed directly, transferred to a visible or ultraviolet light illuminating table such as is commonly used in the visualization and/or photography of gels in the art of electrophoresis visualization and photography, or transferred with the aid of the handle to a solution containing a staining agent appropriate for the user&#39;s needs, such as ethidium bromide, for the visualization of DNA bands on the gel. Should the user choose to transfer the container to a staining solution, which typically will contain agents which the user would find dangerous, the handle  300  for the container will allow the user to avoid direct contact with the solution by using these handles for any grasping and moving necessary to place the container and gel combination into the solution or to remove it from the solution. Any desired agitation while in these solutions may be carried out by manual movement of the container via the handle or by placing the container of the solution and the container onto a platform which can be moved to cause agitation of the solution sufficient across the surface of the gel—e.g., to wash to and fro—but not vigorous enough to splash about freely and thus above the surface of the solution. At the conclusion of this staining period, the user may remove the container and gel via the handles without directly contacting the staining solution nor damaging the gel or its contents. The container and gel may then be placed in a washing solution in the same manner as in the staining process so as to remove excess staining solution or to further enhance the sensitivity of the staining process. The container and gel can then be placed onto an illumination table as described above for the purpose of visualization or photography. Visualization or photography may be carried out in a manner as known in the art of photography of electrophoresis gels. 
     At the conclusion of the visualization or the photography process, the gel container and the gel may be discarded according to normal laboratory practices. The gel can also be removed from the gel container, such as with a common laboratory spatula. In addition, the gel could be further treated—e.g., with a second staining agent—or dried or stored for later reference. 
     The invention being thus described, it will be apparent to those skilled in the art that the same may be varied in many ways without departing from the spirit and scope of the invention. Any and all such modifications are intended to be included within the scope of the following claims.