Patent Publication Number: US-2015060278-A1

Title: Cylinder cam for gel electrophoresis

Description:
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/974,881 filed Apr. 3, 2014 and U.S. Provisional Patent Application Ser. No. 61/870,595 filed Aug. 27, 2013, both of which are hereby incorporated by reference in their entirety. 
    
    
     FIELD 
     The invention is related to the field of electrophoretic analysis of biological specimens, including the application of biological samples to an electrophoresis plate. More specifically, the present invention is directed to a cylindrical cam device and a method for facilitating electrophoretic analysis of biological samples utilizing the cylindrical cam device for in situ electrophoretic analysis of biological samples. 
     BACKGROUND 
     In clinical laboratory practice, various techniques, such as electrophoresis, are used to apply samples to substrates for separation and analysis. Electrophoresis in general is the voltage-driven migration of suspended and/or colloidal particles in a liquid or a gel, due to the effect of a potential difference across immersed electrodes. Electrophoresis is often used in the study of proteins and colloidal particles from biological samples, such as evaluation of lipoparticles and lipoproteins. In many devices that use electrophoresis, the strategy is to apply a sample just to the surface of a substrate, then apply a voltage to separate the components of the sample. This strategy is used in techniques like immunofixation-based electrophoresis and two-dimensional electrophoresis. 
     In immunofixation methods, such as described in U.S. Patent Application Publication No. 2012/0052594, which is hereby incorporated herein by reference in its entirety, a biological sample (e.g., serum) is applied to a substrate and the components are electrophoresed. Anti-sera containing labeled antibodies that target specific components of the blood are then applied to the substrate. The antibodies attach to their antigen targets, and the targets can be identified through some means of detecting the label. 
     IFE involves, as a first step, protein fraction resolution by electrophoresis. As a second step, the soluble antigen in each protein fraction is allowed to react with its antibody. The resultant antigen-antibody complexes will precipitate, at a rate dependent upon the proportion of the reactants, temperature, salt concentration, and pH. The antigen-antibody complexes are then visualized by staining. The IFE process is described in greater detail in U.S. Pat. No. 4,668,363, which is hereby incorporated by reference herein in its entirety. 
     Typically, a specimen from a single patient is diluted and then placed in multiple sample or application areas (also referred to as zones) on a single electrophoretic gel plate. The purpose of utilizing multiple sample areas is to enable detection separately of distinct analyte groups such as total serum protein, lipoprotein, or other proteins whose presence or absence may be of importance in medical diagnosis. Various antisera (i.e., fluid containing the antibody) such as IgG, IgM, etc., are deposited on the appropriate zones and permitted to react with the antigen in the sample. The term “incubation” refers to the time interval during which the antisera and antibody are in contact such that a reaction may occur. 
     In clinical applications, it is desirable to analyze many samples in parallel on the same substrate. This reduces the cost per sample analyzed and saves substantial time. High throughput instruments and devices, such as the SPIFE 3000 Assay instrument by Helena Laboratories, are made for this purpose. 
     High throughput instruments use an applicator comb to apply a series of samples in a single line on the substrate. Such an applicator comb, having a design using squared-off teeth, is described in U.S. Pat. No. 6,544,395, which is hereby incorporated by reference herein in its entirety. After the sample is applied in this technique, it is electrophoresed to separate the components of the sample. The result is a parallel series of channels of sample proteins or other biomolecules or biological particles in the gel. 
     After the electrophoretic separation step, the entire reaction zone is typically saturated with the antiserum since the antigen (e.g., the protein fraction, the lipoprotein fraction, etc.) resolution may have occurred virtually at any position along the reaction zone. The entire zone is typically covered because otherwise the antibody-antigen reaction may not occur. 
     Furthermore, a sufficient amount of antiserum is often deposited to ensure that the antigen will react with the antibody. Thus, it is conventional to apply excess amounts of antiserum. However, many prior art techniques and apparatus for applying the antiserum fail to properly control the flow of the antiserum. For example, in IFE, or any other procedure where various reagents are deposited on distinct zones of the same gel, the use of excess amounts of reagent can cause the reagent to “overflow” from one zone onto an adjacent zone. If the reagents in two adjacent zones each “overflow” their respective zones, the reagent which “overflows” one zone can contact the reagent which “overflows” from an adjacent zone, resulting in “cross-contamination” between zones or otherwise compromising the test results for one or more zones. 
     A method of applying antisera wherein a template mask is placed over the gel substrate and antisera is applied to the gel lanes is described in EPO Patent No. 1 048 949, which is hereby incorporated by reference herein in its entirety. This method can lead to substantial losses of antisera volume as sufficient liquid may be applied to the lanes to complete antisera flow along the entire length, though only a thin layer is required to interact with the separated biomolecules in the gel substrate. 
     Additional gel-based techniques for applying antisera are described in U.S. Pat. No. 7,989,215; U.S. Pat. No. 5,464,521; EPO Patent No. 1 335 201; and U.S. Pat. No. 4,668,363, all of which are incorporated herein by reference in their entirety. However, these techniques all include devices that require the reagent to be suspended above the entire length of the pattern during reagent absorption. Given the expense of reagents and antisera, these techniques are economically wasteful as large amounts of the reagent must be removed and discarded. 
     In techniques like immunofixation, the gel must be put in contact with antisera containing antibodies that target the sample components. Antisera is typically expensive and difficult to obtain. Thus, there is a desire in the market to use as little antisera as possible to produce acceptable results. 
     Methods have been proposed for preserving antisera volume, which include spreading a thin film on the surface of the electrophoresis gel. These methods, however, fail to save the antisera that is applied indiscriminately between lanes. Alternatively, individual lanes could be contacted with channels of antisera to conserve antisera volume. This method, however, is not scalable, requiring a skilled individual to apply liquid to multiple gel lanes. 
     The present invention is directed to overcoming these and other deficiencies in the art. 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention relates to a cylindrical cam device including an axle and a plurality of disk portions disposed about the axle. The plurality of disk portions define a plurality of interstitial regions disposed between the plurality of disk portions. Each of the plurality of disk portions comprises a radial edge. The radial edge of each of the plurality of disk portions comprises a material or structure capable of retaining a liquid and releasing at least a portion of the liquid onto a substrate. 
     Another aspect of the present invention relates to a method for facilitating electrophoretic analysis of biological samples comprising absorbing one or more liquids onto at least a portion of a radial edge of each of a plurality of disk portions disposed about an axle defining an axis. A portion of the radial edge of each of the plurality of disk portions is contacted to respective lanes of an electrophoretic gel substrate comprising one or more biological particles. The axle is rotated, thereby rotating the radial edge of each of the plurality of disk portions about the axis and along each of the respective lanes of the electrophoretic gel substrate. At least a portion of the one or more liquids is deposited from the radial edge of each of the plurality of disk portions along each of the respective lanes of the electrophoretic gel substrate. 
     This invention provides a number of advantages, including providing improved performance for deposition of a liquid onto an electrophoresis gel substrate. In particular, various embodiments of this invention offer improvements in deposition of a reagent, such as an antiserum, to various gel lanes on an electrophoresis gel plate in order to facilitate electrophoresis analysis of biological samples deposited on the plate; provide an accurate deposition to the individual gel lanes on the electrophoresis gel plate to provide improved preservation of antisera volume, while also providing a sufficient amount of antisera to obtain the desired results; allow for the simultaneous deposition along several distinct lanes to improve efficiency in high throughput laboratories; eliminate the need for complex and static rigid templates which can mechanically insult the gel; use smaller volumes of reagent leading to minimized leaking and contamination of adjacent areas; and offers more efficiencies, as there are no additional steps required remove and dispose unused reagent/antisera. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side perspective view of one embodiment of a cylindrical cam device of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention relates to a cylindrical cam device and a method for facilitating electrophoretic analysis of biological samples utilizing the cylindrical cam device. More specifically, the present invention herein is a cylinder cam for gel electrophoresis using parallel application of samples of a reagent, such as antisera, to an electrophoretic gel substrate. 
     One aspect of the present invention relates to a cylindrical cam device including an axle and a plurality of disk portions disposed about the axle. The plurality of disk portions define a plurality of interstitial regions disposed between the plurality of disk portions. Each of the plurality of disk portions comprises a radial edge. The radial edge of each of the plurality of disk portions comprises a material or structure capable of retaining a liquid and releasing at least a portion of the liquid onto a substrate. 
       FIG. 1  shows a side perspective view of one embodiment of a cylindrical cam device  10  of the present invention. Cylindrical cam device  10  may be utilized for the absorption and deposition of liquid samples on an electrophoresis gel plate. In particular, the cylindrical cam device  10  may be utilized for the absorption and deposition of a reagent, such as an antiserum by way of example, to individual gel lanes on an electrophoresis plate as described in EPO Patent No. 1,048,949, which is incorporated by reference herein. 
     Cylindrical cam device  10  includes an axle  12 , a plurality of disk portions  14 , a plurality of interstitial regions  16 , and a plurality of interstitial disk portions  17 , although cylindrical cam device  10  may include other elements in other configurations. Axle  12  is an elongate cylindrical rod that extends between a first end  18  and a second end  20 . Axle  12  is configured to support the plurality of disk portions  14  disposed thereon. First end  18  and second  20  of axle  12  allow for manipulation of the cylindrical cam device  10 . In one example, first end  18  and second end  20  of axle  12  extend beyond the plurality of disk portions  14 , such that the plurality of disk portions  14  may be rotated by rotating the axle  12  at either the first end  18  or the second end  20 , or both. Axle  12  may be rotated manually, although in other embodiments, axle  12  may be connected to and mechanically rotated by automated instrumentation. 
     The plurality of disk portions  14  are cylindrical disks disposed about the axle  12 . Each of the disk portions  14  includes a radial edge  22  around the circumference of the disk portion  14 . The radial edge  22  has a substantially concave shape which forms a recessed portion  24  in each of the plurality of disk portions  14 . The recessed portion  24  serves as aliquoting channels and are configured to receive and retain a liquid for deposition on a substrate, although the disk portions  14  may include other elements in other configurations to receive and retain a liquid therein. The diameter of each of the plurality of disk portions  14  is proportional to a volume of liquid to be retained and released from the disk portion  14 . The volume required may be modified through the use of appropriate excipients to complement surface tensions of the disk portions  14 , the reagent, and the gel utilized. In one embodiment, each of the disk portions  14  disposed along the axle  12  has the same diameter. 
     The plurality of disk portions  14  are disposed parallel to one another along the length of axle  12 . Although  FIG. 1  illustrates five disk portions  14  disposed on axle  12 , it is to be understood that other numbers of disk portions  14  may be utilized. In one example, axle  12  may include at least ten disk portions  14 . In another embodiment, axle  12  may include at least twenty disk portions  14 . In yet a further embodiment, axle  20  may include at least forty disk portions  14 . The plurality of disk portions  14  are equally spaced apart to correspond to parallel lanes on an electrophoretic gel substrate, although the disk portions  14  may be disposed in other configurations to be utilized with electrophoretic gel substrates known in the art. 
     Interstitial regions  16  are located, and define the space between, the plurality of disk portions  14 . The distance between adjacent disk portions  14  defined by the interstitial regions  16  is configured based on the width of the parallel lanes on the electrophoretic gel substrate as described further below. In one example, the interstitial regions  16  include interstitial disk portions  17  located therein. The interstitial disk portions  17  are cylindrical disks disposed about the axle  12 , which are located in the interstitial regions  16  between the disk portions  14 , although in another embodiment, the axle  12  may be exposed in the interstitial regions  16 . The interstitial disk portions  17  have a diameter that is smaller than the diameter of the two adjacent disk portions of the plurality of disk portions  14 . The interstitial portions  17  may be constructed of the same material as the disk portions  14 , although different materials may be utilized for the interstitial portions  17  and the plurality of disk portions  14 . 
     Another aspect of the present invention relates to a method for facilitating electrophoretic analysis of biological samples comprising absorbing one or more liquids onto at least a portion of a radial edge of each of a plurality of disk portions disposed about an axle defining an axis. A portion of the radial edge of each of the plurality of disk portions is contacted to respective lanes of an electrophoretic gel substrate comprising one or more biological particles. The axle is rotated, thereby rotating the radial edge of each of the plurality of disk portions about the axis and along each of the respective lanes of the electrophoretic gel substrate. At least a portion of the one or more liquids is deposited from the radial edge of each of the plurality of disk portions along each of the respective lanes of the electrophoretic gel substrate. 
     Referring again to  FIG. 1 , in operation, one or more liquids are loaded or absorbed onto recessed portions  24  of radial edges  22  of each of the plurality of disk portions  14 . The one or more liquids may include a reagent, such as an antiserum. In one example, the one or more liquids are antibodies bound to a signal producing molecule capable of producing a detectable signal when the one or more antibodies are bound to an antigen. The one or more liquids may be loaded onto the disk portions by pipetting the liquids onto recessed portions  24  of the radial edges  22 . Alternatively, the one or more liquids may be loaded onto disk portions  14  by contacting at least a portion of each radial edge  22  to a reservoir containing the one or more liquids. 
     Next, a portion of radial edge  22  of each of the plurality of disk portions  14  is contacted to a respective lane of an electrophoretic gel substrate defining a plurality of reaction zones. The plurality of lanes contain one or more biological particles, such as a patient fluid sample, the biological particles including one or more antigens recognizable by the antibodies in the one or more liquids loaded onto the disk portions  14  as described above. The biological particles may be deposited on the electrophoretic gel substrate as described in U.S. Patent Application Ser. No. 14/455,612, which is hereby incorporated herein by reference in its entirety. 
     The axle  12  of the cylindrical cam device  10  is then rotated to rotate radial edges  22  of each of the plurality of disk portions  14  along a respective lane of the electrophoretic gel substrate. The axle  12  may be manually rotated along the electrophoretic substrate, or automatically rotated utilizing a mechanical device coupled to the axle  12 . 
     As the axle  12  is rotated, such that radial edges  22  of the each of the plurality of disk portions  14  contact the reaction zone defined by the respective lane. In another embodiment, radial edge  22  maintains separation from the gel so that only the absorbed liquid is in contact with the gel. The one or more liquids, which are loaded onto the disk portions  14  as set forth above, are deposited from recessed portions  24  onto the respective lanes of the gel substrate. Recessed portions  24  expose a mobile “aliquot” of liquid, such as a reagent, to the reaction zones. The liquids are deposited from recessed portions  24  of the plurality of disk portions  14  to the reaction zones on the electrophoretic gel substrate, which facilitates a reaction between the antigens in the biological sample and the antibodies deposited by the cylindrical cam device  10 . In instances when the primary intended reagent is antisera, this mobile approach permits mixing, which maximizes antigen-antibody interaction. In one example, the liquids are deposited to cover substantially all of the reaction zones on the electrophoretic gel substrate. 
     Next, the antibodies from the liquids deposited on the substrate are allowed to incubate with corresponding antigens from the biological particles for a time interval. After the elapsed time interval, excess deposited liquid is washed away from the reaction zone using known methods. Antigens bound to the one or more antibodies may then be detected utilizing imaging techniques such as staining, fluorescent, radioactive or other techniques, to identify molecules and particles of interest within the biological particles on the gel substrate. 
     A further aspect of the present invention relates to a system comprising: (a) a cylindrical cam device as in  FIG. 1 , (b) an electrophoresis platform with means to support an electrophoretic gel, (c) an electrophoretic gel such as an agarose or polyacrylamide gel to rest on the platform, and (d) antisera solution for application to the gel by the cylindrical cam device. In combination, the cam device has antisera solution on its outer edges and contacts the electrophoretic gel, which is supported by a platform to disperse the antisera solution on the gel. In additional embodiments, the circumference of the cam outer edge is less than or equal to the length of the gel. The circumference of the cam outer edge may be about 100%, 95%, 90%, 85%, or 80% of the length of the gel to optimize application of antisera reagent to the gel surface. 
     The system may further comprise mechanical means to hold the cam such as a rail, frame, or mechanical arm. The mechanical means can hold the cam in a consistent position relative to the surface of the gel. It preferably allows the cam to be drawn across the surface of the gel at constant position relative to the surface of the gel. The mechanical means may have an automatic operation facility to move the cam across the gel without human intervention. 
     Although preferred embodiments have been depicted and described in detail herein, it will be apparent to those skilled in the relevant art that various modifications, additions, substitutions, and the like can be made without departing from the spirit of the invention and these are therefore considered to be within the scope of the invention as defined in the claims which follow.