Abstract:
Provided are a magnetic particle separation assembly and method for separating a magnetically responsive complex from a non-magnetic test media in which the magnetically responsive complex is suspended. The assembly comprises an invertible rack for holding specimen containers and a magnetic support member for supporting the rack. The magnetic support member has a base and a planar member bisecting the base and extending upwardly therefrom. The planar vertical member has a plurality of magnets embedded therein. The magnets are disposed in a substantially horizontal orientation parallel to the base and spaced from the base. The invertible rack has a slot therethrough dimensioned to accept the planar vertical member of the magnetic support member. In one position, at least one container of a particular size is positioned within the rack so as to be adjacent to the magnetic support member in final assembly such that the magnetically responsive complex is separated from the non-magnetic media. In a second position in which the rack is inverted with respect to the support member, at least one other container of a different size is positioned within the rack in order to accomplish a similar separation result.

Description:
FIELD OF THE INVENTION 
     This invention relates, generally, to magnetic separation apparatus and methods in which magnetically responsive particles are used for isolating substances of interest from non-magnetic test media. 
     Particularly, the invention relates to a magnetic separation assembly having a magnetic support member and a removable invertible rack which can accommodate a variety of specimen container sizes. Moreover, the invention allows the user to efficiently manipulate multiple samples at any given time. 
     BACKGROUND OF THE INVENTION 
     Patient health care and biological research have made dramatic improvements in recent years, in part due to the utilization of assay techniques. Such assay techniques generally involve reacting a specimen to be assayed, usually a biological solution, e.g., blood, urine, tissue, cell, DNA, RNA, etc., with a magnetically responsive material, e.g., a magnetic containing material or a paramagnetic containing material, in a non-magnetic test media in a specimen container to produce a magnetically responsive complex. A magnetic field is applied or induced in or around the specimen container in order to isolate the magnetically responsive complex from the non-magnetic test media. Thereafter, either the magnetically responsive complex or the non-magnetic test media is withdrawn from the specimen container so that the magnetically responsive complex may be freed from the specimen material. The use of magnetic separation using solution and magnetic particles or complexes is well known in the art of diagnostic assay such as, but not limited to, immunoassay, genetic probe assay, ligand-receptor assay, protein-ligand assay, and hybridization-type assay. Apparatus and methods used to accomplish these types of assays vary from process to process and are well known in the art. The apparatus and methods can be of a non-automated type using a stationary magnet as disclosed in U.S. Pat. Nos. 3,985,649; 4,672,040; 4,695,392; 4,793,973; 4,935,147; 5,145,784; 5,279,936; 5,691,208; or of an automated or of a flow through type as disclosed in U.S. Pat. Nos. 3,970,518; 4,141,687; 4,375,407; 4,738,773; 4,910,148; 5,147,529; 5,318,914; 5,411,863; 5,536,475; 5,541,072; 5,602,042; 5,705,059; 5,711,871; 5,779,907; or of a type using a pin or magnetized means to dip into a container as disclosed in U.S. Pat. Nos. 4,272,510; 4,649,116; 4,751,053; 5,567,326; or of the stationary test tube rack magnetic separation type device with a magnetic member external to the container as disclosed in U.S. Pat. Nos. 5,571,481; 5,108,933; 4,988,618; 4,895,650; 4,438,068; Des. 280,130. The aforementioned U.S. patent disclosures are incorporated herein by reference so as to illustrate the background of the invention and are not, by their inclusion, necessarily conceded to be prior art. The assembly according to the present invention relates to a stationary test tube rack magnetic separation type device with a magnetic member external to specimen containers. 
     Known stationary test tube rack magnetic separation devices are generally inconveniently sized to accommodate only one size of specimen container (e.g., a vial or a test tube or any single volume container), thereby requiring the extra expense of purchasing additional devices to accommodate different sizes of specimen containers. 
     Another problem with prior stationary test tube rack magnetic separation type devices concerns decanting the non-magnetic test media from the specimen containers. Many of the prior devices have rows of specimen containers oriented in multi-column, multi-row arrays, thereby preventing removal of the non-magnetic test media by simply decanting the media. The proximity of the rows and columns provides opportunities for cross contamination of the material found within the specimen containers if a simple decanting operation is performed by tipping the devices. 
     Yet another problem exists in prior devices where the stationary test tube rack magnetic separation devices have a longitudinally slidable magnetic member which slides into and out of a longitudinal bore which is closed at one end (see e.g., U.S. Pat. No. 5,571,481). Should there be any dirt or debris within the bore, the longitudinal member may bind and the magnets in the magnetic member may not properly align with the test tube sidewalls, thereby reducing the accuracy of the assay. In addition, there may be longitudinal slippage or sliding of the device as the longitudinally slidable member is aligned with and longitudinally inserted into the longitudinal bore. The slippage may cause interference with the test tubes or the solutions therein. 
     Still other problems exist in prior devices where the magnets of the stationary test tube rack magnetic separation devices are snap-fitted into place. The action of snapping one or more magnets to the appropriate mechanism may lead to spillage of the samples thereby causing less than accurate results or undesirable contamination. Additionally, when installing one or more magnets in the separation device, it is possible to position the magnet(s) in the wrong orientation which may lead to a poor separation result. Moreover, considering the strength of the magnets typically used in these prior devices, a free or removable magnet may create a hazardous situation. Such magnets, when not properly handled or stored, may tend to attach themselves to undesired hosts thereby possibly causing a multitude of problems as can be appreciated by those skilled in the art. 
     Another problem with prior stationary test tube rack magnetic separation type devices is the lack of efficient handling of multiple samples during both the mixing and separating operations. 
     SUMMARY OF THE INVENTION 
     What is needed is a magnetic particle or complex separation assembly having a removable invertible rack which can accommodate a variety of specimen containers, which permits decanting of the contents of the specimen containers without cross contamination of the contents of the specimen containers, which utilizes a magnetic support member adapted to conveniently receive the removable invertible specimen rack, and which is safe, easy and inexpensive to use, as well as easy to clean. 
     The present invention relates broadly to magnetic separation apparatus and methods in which magnetically responsive particles or complexes are used for isolating substances of interest from non-magnetic test media. The invention relates specifically to a magnetic particle or complex separation assembly having a magnetic support member and a removable invertible rack which can accommodate a variety of specimen containers. 
     Briefly, in one aspect according to the present invention, the magnetic support member is provided with a base, a vertical member extending therefrom and a handle opposite the base. At least one magnet is embedded within the vertical member. The rack is provided with a pair of spaced apart plates supported by at least one vertical column extending between the plates. The plates each include at least one aperture having different sizes which are adapted to hold specimen containers of desired sizes. The rack further includes a slot extending therethrough dimensioned to receive the vertical member of the magnetic support member. In one position, the rack having at least one specimen container is positioned over the vertical member and rests upon the base of support member. The magnet located within the vertical member of the support member separates the magnetically responsive complexes from the non-magnetic material found within the container. In a second position, the rack is first slidably removed from the support member and inverted so as to accommodate at least one other container having a different size. The specimen rack is positioned onto the magnet support member in similar fashion as mentioned in relation to the first position so that the overall assembly can perform yet another magnetic complex separation. When assembled, the handle extends beyond the specimen rack and, since the specimen rack rests upon the base of the magnetic support member, the entire assembly is easily movable by way of the user grasping the handle. 
     Advantageously, the apparatus is of relatively simple construction and operation. Most advantageously, it is economical to utilize because it eliminates the need for redundant equipment to accommodate different sized specimen holders. Furthermore, because of its simple design and material selection, it is advantageously easy to clean. 
     Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings in which like numerals are used to designate like features. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view of a magnetic particle or complex separation assembly illustrating a magnetic support member and a removable invertible specimen rack according to the present invention. 
     FIG. 2 is an isometric view of the magnetic support member of FIG.  1 . 
     FIG. 3 is a cross-sectional side view of the magnetic support member of FIG. 2 taken along lines  3 — 3  of FIG. 4 illustrating a plurality of magnets embedded in the magnetic support member. 
     FIG. 4 is a front view of the magnetic support member of FIG. 2 with a front sheet removed further illustrating the plurality of magnets embedded in the magnetic support member. 
     FIG. 5 is an isometric view of the removable invertible specimen rack of FIG.  1 . 
     FIG. 6 is a top view of a portion of the removable invertible specimen rack of FIG.  5 . 
     FIG. 7 is a bottom view of a portion of the removable invertible specimen rack of FIG.  5 . 
     FIG. 8 is a side view of the removable invertible specimen rack of FIG.  5 . 
     FIG. 9 is an isometric view of the magnetic particle separation assembly according to the present invention with the removable specimen rack inverted and containing a sample of specimen holders illustrating the separation of magnetically responsive complexes from non-magnetic test media. 
    
    
     Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 and 9 depict a preferred embodiment of a magnetic complex separation assembly  10  according to the present invention. FIGS. 2-4 further illustrate a magnet support member  12  shown in FIGS. 1 and 9 according to the present invention. FIGS. 5-8 further illustrate a removable invertible specimen rack  14  also shown in FIGS. 1 and 9 according to the present invention. FIG. 1 shows the assembly  10  without any specimen containers. FIG. 9 shows the assembly  10  with the specimen rack  14  inverted from the orientation shown in FIG.  1  and holding a sample of a plurality of specimen containers  16 . FIGS. 2-4 show only the magnetic support member  12  of the assembly  10 , the specimen rack  14  having been removed. FIGS. 5-8 show only the specimen rack  14  of the assembly  10 , the magnetic support member  12  having been removed. 
     With reference to FIGS. 1-4, the magnetic support member  12  has a generally inverted “T” shape when viewed from the side (FIG.  3 ). The magnetic support member  12  includes a generally flat base  18 , a vertical planar member  20 , and a handle  22 . The base  18  is preferably rectangular in shape and includes a top portion  24 , bottom portion  26 , and sides  28 ,  30 ,  32  and  34 . The vertical member  20  is supported by base  18  and is preferably centered between sides  28  and  30  extending lengthwise between sides  32  and  34 . The vertical member  20  includes a body  36  having cavities therein, sides  38  and  40 , a top portion  42 , and a pair of outer sheets  44 . The handle  22  extends upward from the top portion  42  of vertical member  20 . Preferably, the handle  22  is a curved “T” shaped handle as shown. 
     Preferably, the base  18  is made of an elastomeric material, or a polyvinyl material, or a plastic material, or a polycarbonate material or any durable material capable of resisting periodic contact with water, ethanol, isopropyl alcohol, guanidine, hydrochloric acid, acetone and other common laboratory detergents, and is also capable of withstanding temperatures from about 4 degrees Celsius to about 130 degrees Celsius. Thermosetting and thermoplastic polymeric materials having the performance characteristics described are within the contemplation of the present invention. Although not shown, a rubber pad or the like is preferably attached to the bottom  26  of the base  18  in order to inhibit the assembly  10  from sliding or inadvertently moving when placed on a resting surface such as a countertop. 
     The body  36  of the vertical member  20  is preferably an injected molded magnetically permeable plastic material, but may be of any material appropriate for use according to the present invention. Even more preferably, the body  36  is of a waffle like structure providing for enhanced strength characteristics the purpose of which can be appreciated by those skilled in the art. 
     The outer sheets  44  are also preferably made of a magnetically permeable material such as, but not limited to, a polycarbonate material. The outer sheets  44  represent the boundary between the magnets  46  (FIGS. 3 and 4) and the specimen containers  16  (FIG.  9 ). In order to enhance the separation process, it is desirable to control the distance between the specimen containers  16  and the magnetic field generated by the magnets  46 . Therefore, in order to more accurately control the thickness of the sheets  44 , the sheets  44  are preferably punched out of a single flat sheet of polycarbonate material. A magnetically permeable material allows magnetic flux lines generated by a magnet to penetrate the material and emanate efficiently therefrom. As with the base material, the body and the sheet material should be compatible with the various chemical agents or solutions commonly used with the various assay techniques in accordance with the present invention. 
     The base  18 , the body  36  of the vertical member  20  and the handle  22  can be individual pieces assembled together according to known methods or the noted components can be of a single construction such as a single injected molded polycarbonate structure according to the various features set forth above. 
     As best shown in FIGS. 3 and 4, a plurality of magnets  46  are embedded in the cavities of the body  36  of vertical member  20 . The magnets  46  are preferably disposed in a horizontal orientation parallel to the base  18  and spaced from the base  18 . Preferably, no magnets are located in the base  18  itself. However, it is envisioned that magnets could be properly positioned within base  18  to repel the magnetized material away from the base  18  up and into the magnetic fields generated by the magnets  46 . Preferably, the magnets  46  are disposed in three evenly spaced horizontal rows in body  36  with four magnets  46  in each row. The magnets  46  are arranged in the rows such that the north pole “N” of one magnet is adjacent to the south pole “S” of the next positioned magnet, each row being commonly arranged. Pole orientation is generally through the horizontal axis. The significance of the number of magnets  46  and their respective location in the body  36  will be further explained below. The magnets are securely fixed within the rows of the body  36  by applying an adhesive material, such as an epoxy adhesive, to the sides of the magnets. The adhesive makes contact with portions of the body  36  and sets the magnets  46  in place. Prior to installing the magnets  46  into the magnetic support member  12 , the back outer sheet  44  may be attached to the body  36  with an adhesive such as an epoxy glue. Once the magnets  46  are set in place, the front outer sheet  44  may be attached to the body  36 . Alternatively, both of the sheets  44  may be attached to the body  36  after the magnets  46  are placed within the body  36 . The magnets  46  employed generally possess a strong magnetic field. In general, the stronger the magnetic field, the more effective the separation between the magnetically responsive particles or complexes and the non-magnetic material and the faster such separation occurs. The magnets  46  preferably have a magnetic strength of about 36 MegaGuass Oersted (MGO). The magnets  46  are preferably rare earth magnets. More preferably, the magnets are Neodymium/Iron/Boron magnets commercially available from numerous sources known to those in the art. 
     With reference to FIGS. 5-8, the specimen rack  14  includes a top plate  48 , a bottom plate  50 , and a pair of opposing vertical members  52  extending between the top  48  and bottom  50  plates. The plates  48  and  50  and vertical members  52  are arranged such that a large open area  53  exists between the top  48  and bottom  50  plates and vertical members  52 . The top  48  and bottom  50  plates respectively include slots  54  and  56  (see also FIGS.  6  and  7 ). The slots  54  and  56  are dimensioned such that the specimen rack  14  is positionable over and onto the magnetic support member  12  as shown in FIGS. 1 and 9. Moreover, the top  48  and bottom  50  plates and vertical members  52  are also dimensioned so that handle  22  extends beyond the top plate  48  of the specimen rack  14  as also shown in FIGS. 1 and 9. Two frame borders  58  extend around the top plate  48 , the vertical members  52  and the bottom plate  50  in order to assist in positioning and supporting the specimen rack  14  with respect to the magnetic support member  12 . There is no frictional or restrictive fit between the magnetic support member  12  and the specimen rack  14  which would prevent the specimen rack  14  from being freely removed from or positioned onto the magnetic support member  12 . 
     The top plate  48  and bottom plate  50  include a plurality of container holding apertures  60  and  62  (see also FIGS.  6  and  7 ), the purpose and function of which will be further described below. As shown, the apertures  60  in plate  48  are smaller in dimension than apertures  62  in plate  50 , the reason for which will be made clear below. In a preferred embodiment, there are three apertures  60  placed on one side of slot  54  and three apertures  60  placed on the other side of slot  54 , and there are three apertures  62  placed on one side of slot  56  and three apertures  62  placed on the other side of slot  56 . 
     The vertical members  52  are generally “I” shaped (FIG. 8) and integral with the top  48  and the bottom  50  plates. As shown, one member  52  is spaced from and substantially parallel to the other member  52 . Each member  52  includes a generally centrally located gripper portion  64  which extends outwardly from vertical members  52  and between the top  48  and the bottom  50  plates. The gripping portions  64  are suitably dimensioned to allow a user to easily raise and lower the specimen rack  14  over the magnetic support member  12 . Preferably, each of the gripping portions  64  is smooth and curved to prevent injury to the user. 
     As shown, plates  48  and  50  are generally flat plates designed to independently rest upon the generally flat base  18  of the magnetic support member  12  thereby providing stability to the overall assembly  10 . However, it is envisioned that the generally flat edges  66  (FIG. 8) of the vertical members  52  could extend beyond the plates  48  and  50  such that the appropriate edges  66  rest upon the generally flat base  18  of the magnetic support member  12  to provide the desired stability. Generally, the specimen rack  14  is capable of standing on its own apart from the magnetic support member  12  for decanting or pipetting processes, or for other processes associated with the present invention processes. 
     Preferably, the removable invertible specimen rack  14  is made of a plastic material such as an injected molded polycarbonate material which is resistant to periodic contact with water, ethanol, isopropyl alcohol, guanidine hydrochloride, acetone and common chemical detergents, which is also of sufficient durability to withstand normal handling abuse and mishaps, and which is also capable of withstanding temperatures of about 4 degrees Celsius to about 130 degrees Celsius. The rack  14  has no sharp edges and is safe for a user to handle. Preferably, the rack  14  is attractive being colored in DAY-GLO™ or neon colors for ease of visibility on a lab bench. The rack  14  also can be written on with conventional marking pens, such as SHARPIE™ magic markers. The specimen container apertures of the rack  14  are preferably labeled with numbers or letters to identify each individual tube held by the rack  14 . 
     The specimen rack  14  may be of a single construction such as an injected molded piece of polycarbonate material or the rack  14  may be of a plurality of pieces bound together to create the overall rack assembly  14  as shown. It is envisioned that the specimen rack  14  may consist of two substantially identical components or halves split down the middle of slots  54  and  56 . The vertical members  52  may include one or more male/female components such that the two halves fit together. The male/female connectors may be snap-fit connectors, press fit connectors or any number of known connector combinations. An adhesive such as an epoxy may also be used to secure the components or halves together. To further secure the components together such that the halves are not capable of separating from each other unless forced apart or broken, the halves may be welded together in any number of ways known to those skilled in the art depending on the type of material used to make up the halves of the rack  14 . 
     The specimen rack  14  of the assembly  10  is advantageously invertible having different sized receiving apertures  60  and  62  for holding containers  16  of different sizes. Although the top plate  48  and the bottom plate  50  are shown as having six substantially identically shaped respective apertures  60  and  62 , the rack  14  may be configured to accommodate any number of different shaped containers depending on the particular application. The preferred arrangement allows the user to observe every sample held by the rack  14 . Typically, in prior devices having multi-column, multi-row arrays, some samples are hidden from the user thereby preventing the user to observe the various operations such as the separation operations being performed in each specimen container. 
     With reference to FIG. 9, sample containers  16  are shown. Each container  16  should have an open top closed by a cap  68  and be preferably tubular in shape. The magnetic particle separation assembly  10  is used to separate or isolate magnetically responsive particles  70  from a non-magnetic test media  72 . The removable invertible rack  14  is slidably positioned upon the magnetic support member  12  such that the plate  48  or  50  having the desired sized apertures is positioned above and away from the base  18  closer to the handle  22 . An appropriately sized container is chosen so as to be properly positionable in the selected aperture. The container  16  suitably contains a specimen, such as a biological specimen, to be assayed. As is generally understood in the assay art, the specimen is suspended in a non-magnetic test media  72  found in the container  16  or, alternatively, the non-magnetic test media  72  is added to the specimen in the container  16 . A magnetically responsive material is added to the container  16  to form magnetically responsive complexes  70 . The magnetically responsive complexes  70  are attracted to the magnets  46  found within the magnetic support member  12  and adhere to the sidewalls of the containers  16  as shown in FIG.  9 . 
     In a preferred embodiment, in order to optimize the separation rate, it is desirable to properly manipulate the location of the specimen containers or tubes with respect to the appropriate magnetic field. With reference to FIGS. 4 and 9, the apertures  60  and  62  in the plates  48  and  50  of the specimen rack  14  are arranged such that the containers  16  positioned through the apertures  60  or  62  are centered over north-south pole dividing lines  74  found between adjacent magnets  46 . Thus, the front container  16  in FIG. 9 held by aperture  60  in plate  48  is centered over the north-south pole line  74  located furthest to the left as shown in FIG.  4 . Since the largest magnetic field is generated nearest the north-south pole line between two magnets, this arrangement will provide a substantially even magnetic field around the container  16  to enhance the magnetic separation and therefore reduce the separation time between the magnetically responsive complexes  70  and the non-magnetic material  72 . The preferred arrangement will pull the magnetically responsive material higher and faster in the specimen containers as compared to prior separation devices. 
     Once assembly  10  is completed, assembly  10  and any containers  16  including any contents therein may be conveniently carried by a user grasping the handle  22 . Because the specimen rack  14  rests on the base  18  of the support member  12 , the entire assembly  10  is easily movable. The non-magnetic test media  72  may be removed from the container by conventional decanting or aspirating techniques. The caps  68  on the containers  16  will prevent undesired cross contamination of the contents within the containers  16 . As should be appreciated, the specimen rack  14  is removed from the magnetic support member  12  by the user grasping the gripper portions  64  of the rack  14  and lifting the rack  14  upwards and away from the support member  12 . The containers  16  holding the magnetically responsive complexes  70  may undergo further processing so that the magnetically responsive complexes are freed according to known assay techniques. The assembly  10  is easily cleanable and conveniently usable. The assembly  10  may be cleaned, and/or chemically sterilized between uses according to methods well known in the art. Finally, it should be noted that the support member  12  does not need to be attached to the rack  14  by means of a clip, bead, detect, etc., as is commonly found in prior known devices. 
     The foregoing description of the present invention has been presented for purposes of illustration and description. Furthermore, the description is not intended to limit the invention in the form disclosed herein. Consequently, variations and modifications commensurate with the above teachings in skill or knowledge of the relevant art, are within the scope of the present invention. The embodiments described herein are further intended to explain the best modes known for practicing the invention and to enable others skilled in the art to utilize the invention as such, or other embodiments and with various modifications required by the particular applications or uses of the present invention. It is intended that the appended claims are to be construed to include alternative embodiments to the extent permitted by the prior art. 
     Various features of the invention are set forth in the following claims.