Abstract:
A method of loading a fluid sample into a capillary vessel, the method comprising: attaching one or more capillary vessels to a common carrier, each capillary vessel having an opening and an interior volume sized for loading the capillary vessel by capillary action; positioning the common carrier so that the capillary vessel openings face downward; and positioning the capillary vessel openings into contact with a fluid in a reservoir.

Description:
BACKGROUND  
       [0001]     When performing analytical procedures, it is often desirable to verify the quality of the sample that is being analyzed or otherwise processed. When sampling genetic material such as DNA or RNA for example, it is common perform an amplification process on a sample to increase the amount of genetic material. A small microliter portion of the amplified sample is then analyzed using a spectrophotometer to verify the amount or concentration of the genetic material in the sample.  
         [0002]     The samples are typically stored in the wells of a microtiter plate, interior volumes of Eppendorf tubes, or some similar laboratory container. Each sample from these laboratory containers is typically analyzed one at a time using a pipette or similar device to transfer a microliter volume of the sample to the analytical instrument or an individual sample holder that is inserted into the analytical instrument for analysis, although an alignment fixture can be used to aid in positioning a pipette at the opening of each corresponding sample holder. There are several problems with these techniques. For example, using pipettes to transfer micoliter volume samples commonly results inconsistent fill levels between vessels. Another problem is that bubbles can be transferred from the pipette tip into the sample holder or Cuvette. These inconsistencies cause undesirable results when the vessel is inserted into an analytical instrument for analysis.  
       SUMMARY  
       [0003]     In general terms, the present invention relates to simultaneously loading vessels using capillary action.  
         [0004]     One aspect of this invention is a method of loading a fluid sample into a capillary vessel. The method comprises attaching one or more capillary vessels to a common carrier, each capillary vessel having an opening and an interior volume sized for loading the capillary vessel by capillary action; positioning the common carrier so that the capillary vessel openings face downward; and positioning the capillary vessel openings into contact with a fluid in a reservoir.  
         [0005]     Another aspect of this invention is a method of loading a fluid sample. The method comprises attaching one or more Cuvettes to a common carrier, each Cuvette having an opening and an interior volume sized for loading the Cuvette by capillary action, the interior volume being about 2 μl or less; positioning the common carrier so that the Cuvette openings face downward; positioning the Cuvette openings into contact with a fluid in a reservoir; simultaneously loading fluid into the interior volume of the one or more Cuvettes by capillary action; and loading the common carrier into a spectrophotometer. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]     Further details are explained below with the help of the examples illustrated in the attached drawings in which:  
         [0007]      FIG. 1  is an axonometric projection of a common carrier loaded with two Cuvettes.  
         [0008]      FIG. 2  is an axonometric projection of the common carrier illustrated in  FIG. 1 , including three cuvette holder locations, with only one of them being loaded with a cuvette.  
         [0009]      FIG. 3  is an axonometric projection of a 96-well plate and the common carrier illustrated in  FIG. 1 .  
         [0010]      FIG. 4  is an axonometric projection of an area of detail of  FIG. 3 .  
         [0011]      FIG. 5  is an axonometric projection of the common carrier illustrated in  FIG. 1  and a clamping mechanism latched onto the common carrier. 
     
    
     DETAILED DESCRIPTION  
       [0012]     Various embodiments of the present invention will be described in detail with reference to the drawings, wherein like reference numerals represent like parts and assemblies throughout the several views. Reference to various embodiments does not limit the scope of the invention, which is limited only by the scope of the claims attached hereto. Additionally, any examples set forth in this specification are not intended to be limiting and merely set forth some of the many possible embodiments for the claimed invention.  
         [0013]     Referring to  FIGS. 1 and 2 , one possible embodiment of a common carrier  10  that provides a fixture for holding capillary vessels includes an elongated support member  12 , eight vessel holders or brackets  14   a - 14   h,  and a base  15 . The elongated support member  12  has oppositely disposed sides  36  and  38  extending along its length, and has an end portion  40 . The brackets  14   a - 14   h  are operatively connected to (e.g., either directly or indirectly linked to) and are structured to hold a capillary vessel such as a Cuvette  28  (shown mounted in brackets  14   a  and  14   h  in  FIG. 1  and in bracket  14   c  in  FIG. 2 ). Although the exemplary embodiment illustrates Cuvettes  28 , other embodiments of the common carrier  10  are configured to hold capillary vessels other than Cuvettes  28 .  
         [0014]     Bracket  14   d  has a top edge  18 , a bottom portion  19  attached to the elongated support member  12 , and two opposing and elongated bracket members  16   a  and  16   b  such as fingers, tines, or prongs. The two opposing bracket members  16   a  and  16   b  are separated by a gap  20 , which provides an aperture for an optical path when the common carrier  10  is used with a spectrophotometer or similar instrument so that light can pass through the Cuvette  28 . The width of the gap  20  can vary between embodiments to match the distance between the reservoirs (e.g., wells in a microtiter plate) from which samples are loaded.  
         [0015]     Bracket member  16   a  has a recess  22   a  formed by a concave surface  24   a  and a radial surface  25   a.  The recess  22   a  opens to the top edge  18  of the bracket  14   d  and extends toward the bottom portion  19  to the radial surface  25   a.  The concave surface  24   a  and the radial surface  25   a  are substantially orthogonal. Bracket member  14   b  has a recess  22   b  substantially similar to and opposing the recess  22   a.  The recess  22   b  is formed by a concave surface  24   b  and a radial surface (not shown). In one possible embodiment, as explained in more detail herein, the shape of the recesses  22   a  and  22   b  conform to the outer circumference of the laboratory vessel, which in the exemplary embodiment is a Cuvette  28  (shown mounted in brackets  14   a  and  14   h ).  
         [0016]     The recesses  22   a  and  22   b  form a receptacle for holding the Cuvette  28 . Additionally, the radial surface  25   a  of the elongated bracket member  16   a  and the radial surface (not shown) of the elongated bracket member  16   b  form a seat  26  against which the Cuvette  28  is positioned. Additionally, the distance between the seat  26  and the top edge  18  of the bracket  16   d  is smaller than the height of the Cuvette  28  so that when the Cuvette  28  is positioned against the seat  26 , the top edge  30  of the Cuvette  28  extends at least slightly beyond the top edge  18  of the bracket  14   d,  which assists capillary uptake of the sample. Additionally, the distances from the elongated support member  12  to the seat  26  and from the top edge  18  to the seat  26  are substantially consistent between each of the brackets  14   a - 14   h.    
         [0017]     The bottom portion  19  of the bracket  14   d  defines a break  32  that is open to the gap  20  and extends between the sides  36  and  38  of the elongated support member  12  and has a circular cross-section with a circumference slightly larger than the width of the gap  20 . The break provides a relief that makes it easier to spread the bracket members  16   a  and  16   b  so that a Cuvette  28  can be mounted in the recesses  22   a  and  228 . An alternative embodiment does not includes the break  32 , which makes the common carrier easier to mold when it is formed with a plastic, acrylic, or similar material. In this alternative embodiment the gap  20  terminates at the base portion of the bracket  14   d.  In another alternative embodiment, the gap  20 , with out without a break  32  terminates at a midpoint between the top edge  30  and the bottom portion  19  of the bracket  14   d.    
         [0018]     The common carrier  10  is formed with a resilient material so that the bracket members  16   a  and  16   b  of the bracket  14   d  can be spread and will naturally return to their original position. In this embodiment, the elongated bracket members  16   a  and  16   b  exert a spring force against the side of the Cuvette  28  and hold it in the receptacle formed by the recesses  22   a  and  22   b.  In one possible embodiment, the common carrier is a single piece and that is injection molded and formed with polycarbonate, acrylic, polysulphone, or another medical grade material that is resilient.  
         [0019]     Brackets  14   a - 14   c  and  14   e - 14   h  are substantially similar to the bracket  14   h.  In one possible embodiment, the distance d between adjacent brackets  14  is about 9 mm, which corresponds to a typical distance between wells in the column of a microtiter plate. This spacing allows Cuvettes  28  mounted in the brackets  14   a - 14   h  to be simultaneously dipped in the wells of a microtiter plate. In other possible embodiments, the distance d is a distance other then 9 mm and matches the distance between adjacent reservoirs from which samples are loaded into the Cuvettes  28 .  
         [0020]     In the exemplary embodiment, the Cuvette  28  has an internal cavity  24  with a depth of about 4 mm and cross-sectional dimensions of about 1 mm and about 1 mm to form a capacity volume of about 4 μl. Other embodiments use Cuvettes of different sizes so long as they are capable of being loaded by capillary action. Although a Cuvette of a particular size and structure is illustrated, other embodiments of the common carrier  10  can be used and configured for Cuvettes of other sizes and for other types of vessels that can be loaded with capillary action. For example, an alternative embodiment of a Cuvette has internal dimensions, of about 2 mm by about 1 mm by about 1 mm to form a capacity volume of about 2 μl. The range of dimensions and structures for the laboratory vessel that can be used with the common carrier  10  and still maintain the properties for capillary action depend on the internal dimensions of the laboratory vessel, the type of material that forms the laboratory vessel, and the type of fluid that is being loaded into the laboratory vessel.  
         [0021]     When the common carrier is used with a spectrophotometer, one possible embodiment of the Cuvette  28  or other capillary vessel has internal dimensions sized to be about the same size as or only slightly larger than the cross-sectional area of the light beam passed through the Cuvette  28 . Any sample loaded in the Cuvette that is not in the path of the light-beam is not analyzed by the spectrophotometer. This embodiment prevents unnecessary waste of the sample from the microtiter plate from which the Cuvette  28  is loaded.  
         [0022]     The end  40  of the elongated support member  12  has a grip  42 , which is formed with a first grip groove  44  defined in the first side  36  of the elongated support member  12 . The first grip groove  44  is linear and extends from and is orthogonal to the base  15 . A second grip recess (not shown) that mirrors the first recess  44  is formed on the opposite side  38  of the elongated support member  12 . The grip  42  provides a structure by which a clamping mechanism  46  for an automated spectrometer can grip or latch onto the common carrier  10  while the common carrier  10  is indexed through an a spectrophotometer or other analytical instrument for testing samples loaded in the Cuvettes  28 . The structure of the grip  42  can vary depending on the clamping mechanism  46  that grips or latches onto the common carrier  10 .  
         [0023]     Referring back to  FIGS. 1 and 2 , in one possible embodiment, the base  15  extends along the bottom portion of the elongated support member  12  and has a dovetail cross-section providing a width substantially wider than the elongated support member  12 . Sidewalls  50  and  52  slope downward from the sides  36  and  38 , respectively, of the elongated support member  12  to the bottom portion of the base  15 . The base  15  provides a structure that stabilizes the common carrier  10  when it is set on a lab bench or tabletop. It also provides a structure that a user can grab when loading the Cuvettes  28  as described herein.  
         [0024]     In one possible embodiment, the base  15  is configured to be slidably inserted into a track or guide  62  that and retains the common carrier in the automated spectrophotometer. The track  62  positions the common carrier in the automated spectrophotometer. In yet another possible embodiment, the base  15  includes indicia (not shown) indicating the location of each bracket on the common carrier  10 . Each of the indicia is a distinctive machine-readable marking that provides a positioning guide to locate and orient the Cuvettes  28  in the automated spectrophotometer. The automated spectrophotometer indexes the common carrier  10  by translating the clamping mechanism  46  to the correct position so that the desired Cuvette  28  within the optical path of the automated spectrophotometer.  
         [0025]     In use, referring to  FIGS. 3 and 4 , a microtiter plate  54  has a plurality of wells  56  organized into columns  58   a - 58   l  with eight wells  56   a - 56   h  in each column. Each of the wells contains a liquid sample  60 . For example, wells  56   a - 56   c  contain samples  60   a - 60   c,  respectively. Separate wells  56  may contain the same sample or different samples  60 .  
         [0026]     Cuvettes  28  are inserted into each of the brackets  16   a - 16   h  of the common carrier  10  and positioned so that the bottom of the Cuvette  28  rests against the seat  26 . The common carrier  10  is then inverted or turned upside down so that the openings of the Cuvettes  28  are facing downward. The inverted common carrier  10  is positioned over a column  58  of the microtiter plate  54  and lowered until each of the Cuvettes  28  enters a separate well  58   a - 58   h  in the column  58  of the microtiter plate  54 . The Cuvettes  28  are positioned so that the opening of each of the Cuvettes  28  is simultaneously in contact with the sample in the well  58   a - 58   h,  either touching the surface of the sample or positioned below the surface of the sample. The sample in each well  58   a - 58   h  then flows into its respective Cuvette  28  by capillary action.  
         [0027]     The common carrier  10  can be handled in a variety of ways when loading the Cuvettes  28  with samples and loading the common carrier  10  and Cuvettes  28  into a spectrophotometer. In one possible embodiment, for example, the Cuvettes  28  are manually loaded with sample and the common carrier  10  is manually inserted into the analytically instrument and secured to a carriage by the clamping mechanism  46 . In another possible embodiment, a robotic arm  46  is used to maneuver the common carrier when loading the Cuvettes  28  with sample, loading the common carrier  10  and Cuvettes  28  into the spectrophotometer, and or indexing the common carrier within the spectrophotometer. In yet another embodiment, the Cuvettes  28  are manually loaded with sample and then the common carrier  10  is automatically loaded into and indexed through the spectrophotometer using a robotic arm, conveyor system, or other automated mechanism.  
         [0028]     After the common carrier  10  and Cuvettes  28  are loaded in to the spectrophotometer, the common carrier  10  is indexed through the spectrophotometer so that each gap  20  and Cuvette  28  is sequentially aligned with the light source and optics of the spectrometer for analysis of the sample loaded in the Cuvette  28 . Although the common carrier  10  is disclosed as being used with a spectrophotometer, it can be used with other analytical instruments as well.  
         [0029]     Although the exemplary embodiment illustrates eight wells  56 A- 56   h  in a column of the microtiter plate  54  and eight brackets  16   a - 16   h  on the common carrier  10 , other embodiments are possible. In one possible embodiment, for example, the common carrier  10  has the same number of brackets  16  as the number of wells  56  of the microtiter plate  54  with which it is being used. In this embodiment, the number of brackets  16  and the number of wells  56  in a column  58  of the microtiter plate can  54  be eight, ten, twelve, sixteen, etc. In another embodiment, the number of brackets  16  on the common carrier  10  is less than and a factor of (i.e., evenly divisible into) the number of wells  56  in a column  58  of the microtiter plate  54 . For example, if there are four brackets  16  on the common carrier  10 , there are four, eight, or twelve, etc. wells  56  in a column  58  of the microtiter plate  54 .  
         [0030]     In another possible embodiment, Cuvettes  18  are loaded into only a portion of the brackets  16 . In yet another possible embodiment, Cuvettes  28  of different sizes (e.g., volume) are loaded into brackets  16  on a single common carrier  10 . When this embodiment is used, care is take to ensure that the opening of all of the Cuvettes  28  are placed in contact with or below the surface of the samples in microtiter plate wells  56 .  
         [0031]     After analysis of the samples loaded in the Cuvettes  28  is complete, the Cuvettes  28  are typically discarded. Alternately, the Cuvettes  28  can be cleaned. For example, the Cuvettes  28  can be rinsed with Isopropanol alcohol, then rinsed with water, and then dried with a nitrogen air gun. The common carrier  10  is also cleaned after use to prevent contamination of samples in later testing. In yet another possible embodiment, the Cuvettes  28  are discarded and the common carrier  10  is cleaned for reuse.  
       Experiment  
       [0032]     An experiment was conducted in which Cuvettes were loaded with sample using the common carrier described herein and using pipettes. Each column (eight wells) in a Falcon 96-well microtiter plate was filled with a total solution volume of 200 μl. The first column was filled with 200 μl of solution formed with water and food color, the second column was filled with 200 μl of solution formed with 30 μg/ml raffinose and food coloring, and the third column was filled 200 μl of solution formed with 100 μg/ml raffinose and food coloring. After loading the common carrier with Cuvettes, it was inverted and dipped into the first column in the microtiter plate. As the Cuvettes contacted the liquid, capillary action filling of the Cuvettes was observed. The common carrier was then turned to an upright position. This procedure was repeated for the second and third columns of the microtiter plate. After each repetition of the procedure, the Cuvettes and common carrier were rinsed with Isopropanol alcohol, rinsed with water, and then dried with a nitrogen air gun until it they were dry.  
         [0033]     The observed results for Cuvettes loaded using the common carrier were consistent for the water solution, the 30 μg/ml raffinose solution, and the 100 μg/ml raffinose solution, and included quick uptake of the solution into the Cuvettes, consistent fill levels between all eight Cuvettes held in the common carrier, and an absence of bubbles within the Cuvettes.  
         [0034]     The common method of filling Cuvettes by use of a pipette was also performed in the laboratory for the water solution, the 30 ml raffinose solution, and the 100 ml raffinose solution. Each Cuvette was filled with 4 μl of solution. Observed results included uneven filling and the transfer of bubbles from the pipette to the Cuvette. Further, difficulty was encountered in positioning the tip of the pipette into the Cuvette opening.  
         [0035]     The various embodiments described above are provided by way of illustration only and should not be construed to limit the invention. Those skilled in the art will readily recognize various modifications and changes that may be made to the present invention without following the example embodiments and applications illustrated and described herein, and without departing from the true spirit and scope of the present invention, which is set forth in the following claims.