Abstract:
A method for transferring a liquid using a device having a waste chamber, a pipette tip parking chamber and at least one process chamber is disclosed. The liquid may be transferred between process chambers, or from one process chamber to the waste chamber, or from a primary sample tube external to the device to one process chamber, or from one process chamber to a specimen container external to said device, and wherein said transfer of the liquid is effected by means of pipetting operations carried out with said pipette tip. The method is particularly suitable for contamination-free processing of biological samples.

Description:
This is a divisional of application Ser. No. 09/093,776 filed on Jun. 9, 1998, U.S. Pat. No. 6,063,341. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to a disposable device for carrying out a process in which a biological sample is processed with one or more reagents. 
     The invention relates in particular to a disposable device which is suitable for carrying out a process for obtaining a purified nucleic acid sample from a biological sample. 
     The invention further relates to use of such a device for processing a fluid biological sample with one or more reagents in order to obtain a purified nucleic acid sample. 
     Known methods for obtaining a purified nucleic acid sample suitable to be amplified, by, for example, a polymerase chain reaction (PCR) are usually carried out manually and involve a number of steps and in particular a plurality of pipetting operations. Since contamination of the purified sample to be obtained has to be reduced as far as possible, the manual process has to be carried out with great care and is therefore a time consuming task. 
     Known apparatus for automatically carrying out pipetting operations in analyzer systems have been found inadequate for methods aiming to obtain purified nucleic acid samples suitable to be amplified, such as by a polymerase chain reaction (PCR), because contamination of the sample is likely to occur during pipetting operations. 
     SUMMARY OF THE INVENTION 
     A main object of the invention, therefore, is to provide a device to ensure a contamination-free automatic processing of samples and reagents to a degree which is sufficient to comply with the requirements of nucleic acid purification methods which provide nucleic acid samples having a high degree of purity and being thereby suitable to be amplified. 
     According to a first aspect of the invention, this problem is solved by a disposable process device which comprises an array of chambers integrally connected to each other, a cover insert removably connected to the array of chambers, and a disposable pipetting tip. 
     The integrally built array of chambers comprises an upper part shaped as an elongated tray and having an interior delimited by a bottom wall and a side wall which extends perpendicular to and along the perimeter of the bottom wall; a first process chamber having an open top end and a closed bottom end connected by a tubular wall which extends substantially perpendicular to the bottom wall of said upper part and downwardly from a first opening in said bottom wall, said first opening forming the open top end of the first process chamber; and a waste chamber for receiving waste liquids, said waste chamber having an open top end and a closed bottom end connected by a side wall which extends substantially perpendicular to the bottom wall of said upper part and downwardly from a second opening in said bottom wall, said second opening forming the open top end of the waste chamber. 
     The cover insert is configured and dimensioned to be inserted in the chamber array and the cover insert comprises an elongated cover having openings providing access to the process chamber and the waste chamber respectively when said cover insert is inserted in said chamber array; and a parking chamber for parking therein said disposable pipetting tip, said parking chamber having an open top end and a closed bottom end connected by a tubular wall which extends substantially perpendicular to the cover and downwardly from an opening in the cover. 
     The disposable pipetting tip is configured and dimensioned to be at least partially inserted in the interior of the parking chamber. 
     According to a second aspect of the invention, the contamination-free automated processing of samples and reagents is attained by using a device according to the invention for carrying out a process wherein a fluid biological sample is processed with one or more reagents. This process comprises steps of automatic transfer of liquids from a process chamber to the waste chamber, or from a primary sample tube external to the device to the first process chamber, or from a process chamber to a specimen container external to the device, and wherein said transfer of liquids is effected by means of pipetting operations carried out exclusively with the disposable pipette tip which is part of the device. 
     The main advantage of the device and of the process according to the invention is that they make possible a contamination-free automatic processing of samples and reagents to a degree which is sufficient to comply with the requirements of nucleic acid purification methods which provide nucleic acid samples having a high degree of purity and being thereby suitable to be amplified, such as by a polymerase chain reaction (PCR). 
     A further advantage of the device according to the invention is that a plurality of these devices can be used simultaneously in an automatic apparatus to obtain a corresponding plurality of purified nucleic acid samples from respective biological samples. 
     A specific advantage of an embodiment of the device according to the invention comprising only one process chamber is that it is cheaper than a device comprising more than one process chamber, and that the small size of the device contributes to less waste material which must be disposed of after use of the device, and it reduces the cost of packaging material therefor. 
     A preferred embodiment of the device according to the invention is characterized in that the cover comprises a first channel which provides access to the interior of the process chamber for dispensing a liquid into this chamber. This dispensing is typically effected with a pipetting cannula other than the disposable pipetting tip. The advantage of this embodiment is that the channel mentioned ensures that during the pipetting operation the tip of the pipetting cannula is located within a substantially closed environment which prevents accidental contamination during the transfer of liquid from the pipetting cannula to the process chamber. 
     A further preferred embodiment of the device according to the invention is characterized in that a substantial part of the parking chamber is located within the waste chamber when said cover insert is inserted into said array of chambers. This configuration advantageously reduces the space occupied by the device, because no additional space is necessary for the parking chamber. 
     In another preferred embodiment of the device according to the invention, the process chamber depends freely downwardly from the bottom wall of said upper part of chamber array. This configuration offers the advantage that the lower part of the process chamber is accessible to external means, e.g. magnets, used to obtain separation of magnetic particles in suspension in a liquid contained in the process chamber. 
     A further preferred embodiment of the device according to the invention is characterized in that the integrally built array of chambers further comprises a second process chamber having an open top end and a closed bottom end connected by a tubular wall which extends substantially perpendicular to the bottom wall of said upper part and downwardly from a third opening in said bottom wall. The third opening forms the open top end of the second process chamber. The advantage of this embodiment is that it offers more flexibility with regard to the sequence of process steps for carrying out a particular method. This flexibility is increased e.g. by maintaining the process chambers at different temperatures, e.g. one at 60° C. and the other at 37° C., or by using one of the process chambers for provisional storage of a reagent before it is transferred to the other process chamber. 
     A preferred embodiment of the device according to the invention and comprising two process chambers is characterized in that the bottom wall of said upper part comprises a second channel which provides access to the interior of the second process chamber for dispensing a liquid into this chamber. This dispensing is typically effected with a pipetting cannula other than the disposable pipetting tip. The advantage of this embodiment is that the second channel ensures that during the pipetting operation the tip of the pipetting cannula is located within a substantially closed environment which prevents accidental contamination during the transfer of liquid from the pipetting cannula to the second process chamber. 
     Another preferred embodiment of the device according to the invention and comprising two process chambers is characterized in that the first process chamber, the waste chamber and the second process chamber are arranged in a row. This linear configuration advantageously simplifies the arrangement of a plurality of devices according to the invention in an automatic processing apparatus and also the transport means used for moving the disposable pipetting tip and the pipetting cannula to their pipetting positions with respect to the various chambers of the device. 
     Another preferred embodiment of the device according to the invention and comprising two process chambers is characterized in that the waste chamber is located between the first process chamber and the second process chamber. This configuration advantageously reduces the motion paths of the disposable pipetting tip and the pipetting cannula necessary to bring these to their pipetting positions with respect to the various chambers of the device. 
     A further preferred embodiment of the device according to the invention and comprising two process chambers is characterized in that the second process chamber depends freely downwardly from the bottom wall of said upper part of chamber array. This configuration offers the advantage that the lower part of the second process chamber is accessible to external means, e.g. magnets, used to obtain separation of magnetic particles in suspension in a liquid contained in the second process chamber. 
     Preferred embodiments of the device according to the invention are characterized in that the array of chambers of the device according to the invention is a single piece of plastic material. 
     Preferred embodiments of the device according to the invention are characterized in that said cover insert of the device according to the invention is a single piece of plastic material. 
     These preferred embodiments make it possible to reduce the manufacture price of the device. 
     A preferred use of the device according to the invention is for carrying out a process characterized in that it comprises steps of dispensing a liquid reagent from a reagent container external to the device into the process chamber, said dispensing being effected with a pipetting cannula other than the disposable tip which is part of the device. 
     A preferred use of the device according to the invention and comprising two process chambers is a process which comprises the steps of automatic transfer of liquids from the first process chamber into the second process chamber or vice versa, or from the first or the second process chamber to the waste chamber, or from a primary sample tube external to the device to the first or the second process chamber, or from the first or the second process chamber to a specimen container external to the device, and wherein said transfer of liquids is effected by means of pipetting operations carried out exclusively with the disposable tip which is part of the device. 
     A further preferred use of the device according to the invention and comprising two process chambers is a process which comprises the steps of dispensing a liquid reagent from a reagent container external to the device into the first process chamber or the second process chamber, said dispensing being effected with a pipetting cannula other than the disposable tip which is part of the device. 
     A preferred use of the device according to the invention is a process for isolating a nucleic acid contained in a biological sample. 
    
    
     Preferred embodiments of the invention are described below, by way of example, with reference to the accompanying drawings wherein: 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a first embodiment of device according to the invention. 
     FIG. 2 is a view of a cross-section on line II—II in FIG. 1 
     FIG. 3 is a top plan view of the device according to FIG.  1 . 
     FIG. 4 is a perspective view of a second embodiment of device according to the invention. 
     FIG. 5 is a view of a cross-section on line V—V in FIG. 4 
     FIG. 6 is a top plan view of the device according to FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 to  3  show a first embodiment of a device  11  according to the invention. This first embodiment comprises an integrally built array of chambers  19 , an integrally built cover insert  12  and a disposable pipetting tip  18 . Array of chambers  19  and cover insert  12  are assembled together by inserting cover insert  12  into the upper part of array of chambers  19 . FIGS. 1 and 2 show this assembly. 
     Array of chambers  19  comprises an upper part which is shaped as an elongated tray and which has an interior delimited by a bottom wall  39  and a side wall  38  which extends perpendicular to and along the perimeter of bottom wall  39 ; a process chamber  26 ; and a waste chamber  25  for receiving waste liquids. 
     Process chamber  26  has an open top end and a closed bottom end connected by a tubular wall  16  which extends substantially perpendicular to bottom wall  39  of the upper part of array of chambers  19  and downwardly from a first opening in bottom wall  39 . This first opening forms the open top end of first process chamber  26 . Process chamber  26  depends freely downwardly from the bottom wall  39  of the upper part of chamber array  19 . 
     Waste chamber  25  has an open top end and a closed bottom end connected by a side wall  15  which extends substantially perpendicular to bottom wall  39  of the upper part of array of chambers  19  and downwardly from a second opening in bottom wall  39 . This second opening forms the open top end of waste chamber  25 . 
     Cover insert  12  is configured and dimensioned to be inserted in chamber array  19 . Cover insert  12  comprises an elongated cover  13  having openings  36  and  35  providing access to process chamber  26  and to waste chamber  25  respectively when cover insert  12  is inserted in chamber array  19 ; and a parking chamber  24  for parking therein the disposable pipetting tip  18 . 
     In a preferred embodiment cover  13  includes a jet deflector  23  which has the position shown in particular by FIG.  2  and which serves for deflecting a jet of liquid pipetted into waste chamber  25 . Jet deflector  23  prevents such a jet from impinging directly onto the free surface of liquid already contained in waste chamber  25 . Such impact is undesirable, because in some cases it may cause splashing and expel some droplets out of waste chamber  25  through opening  35 . 
     Parking chamber  24  has an open top end and a closed bottom end connected by a tubular wall  14  which extends substantially perpendicular to cover  13  and downwardly from an opening  34  in cover  13 . In a preferred embodiment the top end of tubular wall  14  of parking chamber  24  lies above cover  13 . 
     Disposable pipetting tip  18  is configured and dimensioned to be at least partially inserted in the interior of parking chamber  24 . Disposable pipetting tip  18  has a tubular wall part of which snugly fits into the interior of parking chamber  24 . The lower end of pipetting tip is desirably kept at some distance from the bottom and from the side walls of parking chamber  24 . 
     The upper part of disposable pipetting tip  18  is so configured and dimensioned that it can be gripped and held by a suitable pipetting tip-gripper (not shown) which is part of pipetting tip transport means of an automatic apparatus (not shown) so that pipetting tip  18  can be moved by the pipetting tip-gripper to different pipetting positions within the apparatus. Preferably the pipetting tip-gripper is such that when it grips tip  18  it fluidically connects this tip with a dosing pipettor (not shown) included in the automatic apparatus. 
     In the preferred embodiment shown by FIG. 2 a filter  31  is located within the upper part of pipetting tip  18 . Filter  31  serves to prevent contamination by carry-over of gas or liquid during pipetting operations. 
     In the preferred embodiment shown by FIGS. 1 to  3  pipetting tip  18  is so configured and dimensioned that it can also be used as closure of the waste chamber  25  when the lower part of pipetting tip  18  is inserted through opening  35  into the waste chamber  25 . 
     The shape of cover insert  12  is such that it can be gripped and held by a suitable gripper (not shown) which is part of transport means of an automatic apparatus (not shown) so that cover insert  12  and thereby the entire device  11  can be moved by the gripper to different positions within the apparatus, e.g. from a parking position, where an array of devices  11  is positioned side by side, to an incubator position. 
     In the preferred embodiment shown by FIGS. 1 to  3  cover insert  12  has an array of four tangs  21 ,  22 ,  28 ,  29  arranged as shown by the figures. 
     In a preferred embodiment the configuration and dimensions of this array of tangs and the configuration and dimensions of the upper part of disposable pipetting tip  18  are so chosen that the top of the pipetting tip  18  or a couple of tangs, e.g.  21  and  22  or  28  and  29  can be gripped with the same gripper. 
     Cover  13  comprises a first channel  32  which provides access to the interior of the first process chamber  26  for pipetting into this chamber a reagent from a reagent container located outside device  11 . This pipetting operation is effected with a pipetting cannula (not shown in the figures) other than disposable pipetting tip  18 . 
     As shown by FIGS. 1 and 2 a substantial part of parking chamber  24  is located within waste chamber  25  when cover insert  12  is inserted into array of chambers  19 . 
     FIGS. 4 to  6  show a second embodiment of a device  41  according to the invention. This second embodiment comprises an integrally built array of chambers  49 , an integrally built cover insert  42  and a disposable pipetting tip  48 . Array of chambers  49  and cover insert  42  are assembled together by inserting cover insert  42  into the upper part of array of chambers  49 . FIGS. 4 and 5 show this assembly. 
     Array of chambers  49  comprises an upper part which is shaped as an elongated tray and which has an interior delimited by a bottom wall  69  and a side wall  68  which extends perpendicular to and along the perimeter of bottom wall  69 ; a first process chamber  56 ; a second process chamber  57 ; and a waste chamber  55  for receiving waste liquids. 
     Process chamber  56  has an open top end and a closed bottom end connected by a tubular wall  46  which extends substantially perpendicular to bottom wall  69  of the upper part of array of chambers  49  and downwardly from a first opening  66  in bottom wall  69 . This first opening forms the open top end of first process chamber  56 . 
     Process chamber  57  has an open top end and a closed bottom end connected by a tubular wall  47  which extends substantially perpendicular to bottom wall  69  of the upper part of array of chambers  49  and downwardly from a first opening in bottom wall  69 . This first opening forms the open top end of process chamber  57 . 
     Process chamber  56  and process chamber  57  depend freely downwardly from the bottom wall  69  of the upper part of chamber array  49 . 
     Waste chamber  55  has an open top end and a closed bottom end connected by a side wall  45  which extends substantially perpendicular to bottom wall  69  of the upper part of array of chambers  49  and downwardly from a second opening in bottom wall  69 . This second opening forms the open top end of waste chamber  55 . 
     Cover insert  42  is configured and dimensioned to be inserted in chamber array  49 . Cover insert  42  comprises an elongated cover  43  having openings  66 ,  65  and  67  providing access to process chamber  56 , to waste chamber  55 , and to process chamber  57  respectively when cover insert  42  is inserted in chamber array  49 ; and a parking chamber  54  for parking therein the disposable pipetting tip  48 . 
     In a preferred embodiment cover  43  includes a jet deflector  53  which has the position shown in particular by FIG.  5  and which serves for deflecting a jet of liquid pipetted into waste chamber  55 . Jet deflector  53  prevents such a jet from impinging directly onto the free surface of liquid already contained in waste chamber  55 . Such impact is undesirable, because in some cases it may cause splashing and expel some droplets out of waste chamber  55  through opening  65 . 
     Parking chamber  54  has an open top end and a closed bottom end connected by a tubular wall  44  which extends substantially perpendicular to cover  43  and downwardly from an opening  64  in cover  43 . In a preferred embodiment the top end of tubular wall  44  of parking chamber  54  lies above cover  43 . 
     Disposable pipetting tip  48  is configured and dimensioned to be at least partially inserted in the interior of parking chamber  54 . Disposable pipetting tip  48  has a tubular wall part of which snugly fits into the interior of parking chamber  54 . The lower end of pipetting tip is desirably kept at some distance from the bottom and from the side walls of parking chamber  54 . 
     The upper part of disposable pipetting tip  48  is so configured and dimensioned that it can be gripped and held by a suitable pipetting tip-gripper (not shown) which is part of pipetting tip transport means of an automatic apparatus (not shown) so that pipetting tip  48  can be moved by the pipetting tip-gripper to different pipetting positions within the apparatus. Preferably the pipetting tip-gripper is such that when it grips tip  48  it fluidically connects this tip with a dosing pipettor (not shown) included in the automatic apparatus. In the preferred embodiment shown by FIG. 5 a filter  61  is located within the upper part of pipetting tip  48 . Filter  61  serves to prevent contamination by carry-over of gas or liquid during pipetting operations. 
     In the preferred embodiment shown by FIGS. 4 to  6  pipetting tip  48  is so configured and dimensioned that it can also be used as closure of the waste chamber  55  when the lower part of pipetting tip  48  is inserted through opening  65  into the waste chamber  55 . 
     The shape of cover insert  42  is such that it can be gripped and held by a suitable gripper (not shown) which is part of transport means of an automatic apparatus (not shown) so that cover insert  42  and thereby the entire device  41  can be moved by the gripper to different positions within the apparatus, e.g. from a parking position, where an array of devices  41  is positioned side by side, to an incubator position. 
     In the preferred embodiment shown by FIGS. 4 to  6  cover insert  42  has an array of four tangs  51 ,  52 ,  58 ,  59  arranged as shown by the figures. 
     In a preferred embodiment the configuration and dimensions of this array of tangs and the configuration and dimensions of the upper part of disposable pipetting tip  48  are so chosen that the top of the pipetting tip  48  or a couple of tangs, e.g.  51  and  52  or  58  and  59 , can be gripped with the same gripper. 
     Cover  43  comprises a first channel  62  which provides access to the interior of the first process chamber  56  for pipetting into this chamber a reagent from a reagent container located outside device  41 . Cover  43  further comprises a second channel  63  which provides access to the interior of the second process chamber  57  for pipetting into this chamber a reagent from a reagent container located outside device  41 . These pipetting operations are effected with a pipetting cannula (not shown in the figures) other than disposable pipetting tip  48 . 
     As shown by FIGS. 4 and 5 a substantial part of parking chamber  54  is located within waste chamber  55  when cover insert  42  is inserted into array of chambers  49 . 
     In a preferred embodiment the first process chamber  56 , the waste chamber  55  and the second process chamber  57  are linearly arranged in a row. 
     In a further preferred embodiment the waste chamber  55  is located between the first process chamber  56  and the second process chamber  57 . 
     In preferred embodiments of a device according to the invention the array of chambers  19  and  49 , respectively are a single piece of a suitable plastic material, e.g. a polypropylene. In preferred embodiments, the cover insert  12  and  42 , respectively, is a single piece of a suitable plastic material, e.g. a polypropylene. 
     When device  11  described above with reference to FIGS. 1-3 is used for processing a fluid biological sample with one or more reagents in process chamber  26 , such a process comprises steps of automatic transfer of liquids from the process chamber  26  to the waste chamber  25 , or from a primary sample tube external to the device to the process chamber  26 , or from the first process chamber  26  to a specimen container external to the device. According to the invention these transfers of liquids are effected by means of pipetting operations carried out exclusively with the disposable tip  18  which is part of the device  11 , whereas steps of dispensing a liquid reagent from a reagent container external to the device into the first process chamber  26  are effected with a pipetting cannula other than the disposable tip  18  which is part of the device  11 . 
     When device  41  described above with reference to FIGS. 4-6 is used for processing a fluid biological sample with one or more reagents in process chambers, such a process comprises steps of automatic transfer of liquids from the first process chamber  56  into the second process chamber  57  or vice versa, or from the first or the second process chamber  56 ,  57  to the waste chamber  55 , or from a primary sample tube external to the device to the first or the second process chamber  56 ,  57 , or from the first or the second process chamber  56 ,  57  to a specimen container external to the device. According to the invention these transfers of liquids are effected by means of pipetting operations carried out exclusively with the disposable tip  48  which is part of the device  41 , whereas steps of dispensing a liquid reagent from a reagent container external to the device into the first process chamber  56  or the second process chamber  57  are effected with a pipetting cannula other than the disposable tip  48  which is part of the device  41 . 
     A preferred use of device  41  according to the invention is for carrying out a process for isolating a nucleic acid contained in a biological sample. Such a process comprises for instance the following steps: 
     A) Device  41  is transferred by gripper of transport mechanism of an automatic apparatus from a storage position to an incubating position in an incubator. 
     B) A lysis solution from an external container is pipetted into process chamber  56  by means of a pipetting cannula of an automatic pipetting device. 
     C) A predetermined volume of a fluid biological sample from an external container is pipetted into process chamber  56  by means of disposable tip  48  of device  41 . 
     D) An internal quality standard solution from an external container is pipetted into process chamber  56  by means of a pipetting cannula of an automatic pipetting device. 
     E) A probe solution from an external container is pipetted into process chamber  57  by means of a pipetting cannula of an automatic pipetting device. 
     F) The mixture contained in process chamber  56  is incubated at 60°. 
     G) The entire liquid mixture contained in process chamber  56  is pipetted into process chamber  57  by means of pipetting tip  48 . 
     H) The mixture contained in process chamber  57  is incubated at 37°. 
     I) A bead (solid phase) solution from an external container is pipetted into process chamber  57  by means of a pipetting cannula of an automatic pipetting device. 
     J) The mixture contained in process chamber  57  is incubated at 37°. 
     K) Device  41  is transferred by gripper of transport mechanism of an automatic apparatus from the incubating position in an incubator to a processing position in a separation and washing station of the automatic apparatus. 
     L) At the separation and washing station several washing steps of the beads contained in process chamber  57  are carried out and waste liquid is transferred from this chamber to waste chamber  55  means of disposable tip  48 . 
     M) Target solution remaining in process chamber  57  and containing isolated nucleic acid is pipetted into an external specimen container by means of disposable tip  48 .