Method for removing a fluid from a a vessel comprising a penetrable cap

0001The present invention relates to a method for removing a fluid substance from a closed system.

0002In this method use is made of caps for use in combination with fluid-holding vessels, such as those designated to receive and retain biological specimens for clinical analysis, patient monitoring or diagnosis. In particular, the cap is penetrable by a fluid transfer device used to transfer fluids to or from a fluid-holding vessel, where the vessel and cap remain physically and sealably associated during a fluid transfer.

0003Collection devices are a type of cap and vessel combination commonly used for receiving and storing biological specimens for delivery to clinical laboratories, where the specimens may be analyzed to determine the existence or state of particular condition or the presence of a particular infectious agent, such as a virus or bacterial micoorganism. Types of biological specimens commonly collected and delivered to clinical laboratories for analysis include blond, urine, sputum, saliva, pus, mucous and cerebrospinal fluid. Since these specimen-type may contain pathogenic organisms, it is important to ensure that collection devices are constructed to be substantially leak-proof during transport from the site of collection to the site of analysis. This feature of collection devices is especially important when the clinical laboratory and the collection facility are remote from one another, increasing the likelihood that the collection device will be inverted or severely jostled during transport and potentially subjected to substantial temperature and pressure fluctuations.

0004To prevent specimen leakage, and possible contamination of the surrounding environment, collection device caps are typically designed to be screwed, snapped or otherwise frictionally fitted or welded onto the vessel component, thereby forming a substantially leak-proof seal between the cap and the vessel. In addition to preventing fluid specimen from leaking, a substantially leak-proof seal formed between the cap and the vessel components of a collection device may also aid in ameliorating exposure of the specimen to potentially contaminating influences from the immediate environment. This aspect of a leak-proof seal is important for preventing the introduction of contaminants into the collection device that could alter the qualitative or quantitative results of an assay.

0005While a leak-proof seal should prevent specimen seepage during transport, the actual removal of the cap from the vessel prior to specimen analysis presents another potential opportunity for contamination. When removing the cap, specimen which may have collected on the underside of the cap during transport could come into contact with a clinician, possibly exposing the clinician to a harmful pathogen present in the fluid sample. And if the specimen is proteinaceous or mucoid in nature, or if the transport medium contains detergents or surfactants, then a film or bubbles could form around the mouth of the vessel during transport which could burst when the cap is removed from the vessel, thereby disseminating specimen into the testing environment. Another risk associated with cap removal is the potential for creating a contaminating aerosol which may lead to false positives or exaggerated results in other specimens being simultaneously or subsequently assayed in the same general work area through cross-contamination. It is also possible that specimen residue from one collection device, which may have been inadvertently transferred to a gloved hand of a clinician, will come into contact with specimen from another collection device through routine or careless removal of caps and handling of the collection devices.

0006Concerns with cross-contamination are especially acute when the assay being performed involves nucleic acid detection and includes an amplification procedure such as the well known polymerase chain reaction (PCR), or a transcription-based amplification system such as transcription-mediated amplification (TMA). (A review of several amplification procedures currently in use, including PCR and TMA, is provided in <nplcit id="ncit0001" npl-type="s"><text>HELEN H. LEE ET AL., NUCLEIC ACID AMPLIFICATION TECHNOLOGIES (1997</text></nplcit>).) Since amplification is intended to enhance assay sensitivity by increasing the quantity of targeted nucleic acid sequences present in a specimen, transferring even a minute amount of pathogen-bearing specimen from one vessel, or target nucleic acid from a positive control sample, to another vessel containing an otherwise negative specimen could result in a false-positive result.

0007To minimize the potential for creating contaminating specimen aerosols, and to limit direct contact between specimens and humans or the environment, it is desirable to have a collection device cap which can be penetrated by a fluid transfer device (e.g., a pipette tip which can be used with an air displacement pipette) while the cap remains physically and sealably associated with the vessel. The material and construction of the penetrable aspect of the cap should facilitate the venting of air displaced from the interior space of the collection device to ensure accurate fluid transfers and to prevent a rapid release of aerosols as the fluid transfer device is being inserted into or withdrawn from the collection device. And, because air is vented from the interior space of the collection device after the cap has been penetrated, it would be particularly helpful if means were included for minimizing aerosol release through the cap once it was penetrated by the fluid transfer device. Also, to limit the amount of potentially contaminating fluid present on the exterior of the fluid transfer device after it is has been withdrawn from the collection device, it would be advantageous if the cap also included means for wiping or absorbing fluid present on the outside of the fluid transfer device as it is being withdrawn from the collection device. To prevent damage to the fluid transfer device which could affect its ability to predictably and reliably dispense or draw fluids, and to facilitate its use in manual pipetting applications, the cap should also be designed to limit the forces necessary for the fluid transfer device to penetrate the cap. Ideally, the collection device could be used in both manual and automated formats and would be suitable for use with disposable pipette tips made of a plastic material.

0008Collection device caps which can be penetrated by a fluid transfer device will have other advantages, as well, including the time-savings insulting from clinicians not having to manually remove caps from vessels before retrieving sample aliquots from the collection devices for assaying. Anther advantage of penetrable collection device caps would be the reduction in repetitive motion injuries suffered by clinicians from repeatedly unscrewing caps.

0009Caps capable of being penetrated by fluid transfer devices are known from <patcit id="pcit0001" dnum="WO0069389A"><text>WO 00/69389</text></patcit>, <patcit id="pcit0002" dnum="EP0330883A1"><text>EP 0330883 A1</text></patcit>, <patcit id="pcit0003" dnum="US5202093A"><text>US 5,202,093</text></patcit> and <patcit id="pcit0004" dnum="EP0999146A2"><text>EP 099914 6 A2</text></patcit>.

0010An object of the present invention is to improve a method for removing a fluid substance from a closed system of prior art as mentioned above in order to avoid any potential contamination.

0011This is achieved by the features in claim 1. Further preferred embodiments are claimed in the dependent claims.

0012Potential contamination problems associated with conventional collection devices are solved by providing a penetrable cap for use with a vessel component of a collection device which includes: (i) a closed side wall having an inner surface, an outer surface, a top surface and a bottom surface; (ii) attachment means for fixing the cap to an open end of the vessel in sealing engagement, (iii) a ledge which extends in a radial and inward direction from an inner surface of the side wall of the cap and has an end surface which defines an aperture sized to receive a fluid transfer device, where the inner surface of the side wall of the cap and a top surface of the ledge define a first bore; (iv) a frangible seal for preventing the passage of a fluid from an interior space of the vessel into the first bore when the cap is fixed to the vessel in sealing engagement, where the seal is affixed to either the top surface or a bottom surface of the ledge; (v) filtering means for impeding or preventing the release of an aerosol or bubbles from the interior spate of the vessel to the atmosphere, where the filtering means is positioned substantially within the first bore; and (vi) retaining means for containing the filtering means within the first bore. (A "closed side wall" is one which lacks fully exposed end surfaces.) The retaining means is preferably affixed to a top wall of the cap. The side wall, the flange and the ledge of the cap are molded from a plastic material and preferably form a unitary piece.

0013The penetrable cap includes a skirt which depends from the bottom surface of the ledge, where an inner surface of the skirt defies a second bore having a diameter or width smaller than that of the first bore. The skirt may be included <i>inter alia</i> to further prevent a fluid from leaking from the interior of the vessel when the cap is fixed to the vessel in sealing engagement. (By "sealing engagement" is meant touching contact between solid surfaces which is intended to prevent or impede the passage of a fluid.) An outer surface of the skirt preferably includes a seal bead which is in frictional contact with an inner surface of the vessel. With this embodiment, the frangible seal may be affixed to either the top surface of the ledge or to a bottom surface of the skirt. The side wall, the flange, the ledge and the skirt of the cap of this embodiment are molded from a plastic material and preferably form a unitary piece.

0014The retaining means is a second frangible seal. The second frangible seal may comprise the same or a different material than the frangible seal affixed to the top or bottom surface of the ledge, or to the bottom surface of the skirt. Both seals are penetrable by a fluid transfer device with the application of moderate manual force and each seal comprises a foil.

0015In an embodiment not suitable for the method of the present invention, the retaining means comprises a foil ring having a centrally located hole which is sized to receive a fluid transfer device and which is substantially axially aligned with the first bore and the second bore, if present. The diameter or width of this hole is smallerthan the diameter or width of a filter contained within the first bore so that the foil ring can function to contain the filter within the cap. The foil ring of this embodiment may be affixed to the top wall of the cap by means of an adhesive or by means of a plastic liner which has been applied to the foil ring and which can be welded to the surface of the top wall of the cap.

0016In another embodiment not suitable for the method of the present invention, the retaining means includes a plastic disc having a hole formed therein which is sized to receive a fluid transfer device and which is substantially axially aligned with the first bore and the second bore, if present. The retaining means of this embodiment functions to contain a filter within the first bore. The disc may be affixed to the top wall of the cap or the top wall may be adapted to include a seat for receiving the disc in, for example, a frictional or snap fit.

0017In a further embodiment not suitable for the method of the invention the retaining means comprises a removable seal which is designed to limit exposure of a filter to environmental contaminants and may include a tab for easy removal prior to penetrating the cap. Because this seal may be removed prior to penetration of the cap, it is not a requirement that this particular retaining means be comprised of a frangible material which can be pierced by a fluid transfer device applying moderate manual force. Since the removable seal can function to protect the filter against external contaminants during shipping, the removable seal may be applied, for example, to the fixed disc described above for retaining the filter within the first bore.

0018The cap is provided as part of a collection device which includes a vessel for containing fluids. When provided as a part of a collection device, the cap preferably includes the skirt feature described above, which is positioned adjacent to an inner surface of an open end of the vessel to impede the passage of a fluid from the interior space of the vessel to the environment outside of the collection device. Including a seal bead on an outer surface of the skirt further facilitates this objective by increasing the pressure which is exerted by the skirt on the inner surface of the vessel. The collection device may contain, for example, a dry powder, pellets of chemical reagents, buffers, stabilizers, or a transport medium for preserving a specimen while it is being shipped from a collection location to a site for analysis. The collection device may also be provided in packaged combination with a specimen retrieval device (<i>e.g.</i>, a swab) for obtaining a specimen from a human, animal, water, environmental, industrial, food or other source. Instructional materials may additionally be included with the collection device which detail proper use of the collection device when obtaining or transporting a specimen or appropriate techniques for retrieving a fluid sample from the collection device at the site of analysis. When in packaged combination, the recited items are provided in the same container (e.g., a mail or delivery container for shipping), but do not need to be <i>per se</i> physically associated with one another in the container or combined in the same wrapper or vessel within the container.

0019The cap is used in a method for retrieving a fluid substance from the vessel component of a collection device with a plastic pipette tip for use with an air displacement pipette. When the cap is penetrated by the pipette tip, air passageways are formed between the pipette tip and the frangible seals of the cap, thereby facilitating the venting of air from within the vessel. After fluid is removed from the collection device, at least some portion of the fluid sample may be exposed to amplification reagents and conditions permitting a targeted nucleic acid sequence which may be present in the fluid sample to be amplified. Various amplification procedures, and their associated reagents and conditions, are well known to those skilled in the art of nucleic acid diagnostics.

0020A method is provided for removing a fluid substance contained in a closed system comprising a cap and a fluid-holding vessel. In addition to the cap and vessel components, the phrase "closed system" is used herein to refer to a cap that is fixed to a vessel in sealing engagement to prevent the fluid contents of the system from escaping into the surrounding environment. The method includes penetrating first and second frangible seals affixed to the cap with a fluid transfer device, where the first seal is axially aligned below the second seal. Penetration of the first and second seals by the fluid transfer device results in the formation of air passageways between the seals and the fluid transfer device which aid in venting air from the interior space of the system. The fluid transfer device is a plastic pipette tip for use with an air displacement pipette. In a preferred mode, the method further includes passing the fluid transfer device through a filter contained within the cap and interposed between the first and second seals.

0021Once fluid has been removed from the system in this method, some or all of the fluid sample may be exposed to amplification reagents and conditions permitting a targeted nucleic acid sequence which may be present in the fluid sample to be amplified. As noted above, a variety of amplification procedures are well known to those skilled in the art of nucleic acid diagnostics, and appropriate reagents and conditions for use with any of these amplification procedures could be determined without engaging in undue experimentation.

0022The methods of the presently claimed invention may be performed manually or adapted for use with a semi-automated or fully automated instrument. Examples of instrument systems which could be readily adapted for use with the collection devices or other closed systems include those sold under the trade names of DTS 400 (detection only) and DTS 1600 (amplification and detection) by Gen-Probe Incorporated of San Diego, California, which represent embodiments of instrument systems disclosed by Acosta <i>et al.,</i> "Assay Work Station," <patcit id="pcit0005" dnum="US6254826B"><text>U.S. Patent No. 6,254,826</text></patcit>, and those disclosed by Ammann <i>et al.,</i> "Automated Process for Isolating and Amplifying a Target Nucleic Acid Sequence," <patcit id="pcit0006" dnum="US6335166B"><text>U.S. Patent No. 6,335,166</text></patcit>, both of which enjoy common ownership herewith.

0023These and other features, aspects, and advantages of the present invention will become apparent to those skilled in the art after considering the following detailed description, appended claims and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

0024<ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">FIG. 1</figref> is an exploded perspective view of the cap and vessel components of a preferred collection device used in the present invention.</li><li><figref idref="f0002">FIG. 2</figref> is an enlarged top plan view of the core cap of <figref idref="f0001">FIG. 1</figref>.</li><li><figref idref="f0002">FIG. 3</figref> is an enlarged bottom view of the core cap of <figref idref="f0001">FIG. 1</figref>.</li><li><figref idref="f0003">FIG. 4</figref> is an enlarged partial section side view of the collection device of <figref idref="f0001 f0002">Figs. 1-3</figref> (showing core cap only), taken along the 4-4 line thereof.</li><li><figref idref="f0004">FIG. 5</figref> is an enlarged partial section side view of another collection device used in the present invention.</li><li><figref idref="f0005">FIG. 6</figref> is an enlarged section side view of the cap of <figref idref="f0001">FIG. 1</figref>.</li><li><figref idref="f0005">FIG. 7</figref> is an enlarged section side view of another cap used in the present invention.</li><li><figref idref="f0006">FIG. 8</figref> is an enlarged section side view of a frangible seal used in the present invention.</li><li><figref idref="f0006">FIG. 9</figref> is an enlarged section side view of another frangible seal used in the present invention.</li><li><figref idref="f0007">FIG. 10</figref> is an enlarged top plan view of the core cap and filter of <figref idref="f0001">FIG. 1</figref>.</li><li><figref idref="f0008">FIG. 11</figref> is a top plan view of the cap of <figref idref="f0005">Figs. 6 and 7</figref> showing perforations in the frangible seal.</li><li><figref idref="f0008">FIG. 12</figref> is an enlarged top plan view of a further cap</li><li><figref idref="f0009">FIG. 13</figref> is an enlarged section side view of yet another cap.</li><li><figref idref="f0009">FIG. 14</figref> is a top plan view of the cap of <figref idref="f0009">FIG. 13</figref>. <figref idref="f0010">FIG. 15</figref> is an enlarged section side view of still another cap.</li><li><figref idref="f0010">FIG. 16</figref> is a top plan view of the cap of <figref idref="f0010">FIG. 15</figref>:</li><li><figref idref="f0011">FIG. 17</figref> is a partial section side view of the collection device of <figref idref="f0001">FIG. 1</figref>, after it has been penetrated by a fluid transfer device.</li><li><figref idref="f0012">FIG. 18</figref> is a top plan view of the cap and fluid transfer device of <figref idref="f0011">FIG. 17</figref>.</li></ul>

DETAILED DESCRIPTION OF THE INVENTION

0025While the present invention may be embodied in a variety of forms, the following description and accompanying drawings are merely intended to disclose some of these forms as specific examples of the present invention. Accordingly, the present invention is not intended to be limited to the forms or embodiments so described and illustrated. Instead, the full scope of the present invention is set forth in the appended claims.

0026With reference to the figures, preferred caps 30A-B for use in methods of the present invention are shown alone or in combination with a vessel 20 which can be used for receiving and storing fluid specimens for subsequent analysis, including analysis with nucleic acid-based assays or immunoassays diagnostic for a particular pathogenic organism. When the desired specimen is a biological fluid, the specimen can be, for example, blood, urine, saliva, sputum, mucous or other bodily secretion, pus, amniotic fluid, cerebrospinal fluid or seminal fluid. However, the present invention also contemplates materials other than these specific biological fluids, including, but not limited to, water, chemicals and assay reagents, as well as solid substances which can be dissolved in whole or in part in a fluid milieu (e.g., tissue specimens, stool, environmental samples, food products, powders, particles and granules). The vessel 20 is preferably capable of forming a substantially leak-proof seal with the cap 30A-E and can be of any shape or composition, provided the vessel is shaped to receive and retain the material of interest (e.g., fluid specimen or assay reagents). Where the vessel 20 contains a specimen to be assayed, it is important that the composition of the vessel be essentially inert so that it does not significantly interfere with the performance or results of an assay. A preferred vessel 20 is formed of polypropylene and has a generally cylindrical shape which measures approximately 13 mm x 82 mm.

0027As illustrated in the figures, particularly preferred caps 30A-B for use in methods of the present invention include an integrally molded core structure 31 A (referred to herein as the "core cap") which comprises: (i) a generally cylindrical side wall 35; (ii) a flange 36 depending from a bottom surface 37 of the side wall and having an inner surface 38 adapted to grip an outer surface 21 of a generally cylindrical side wall 22 of an open-ended vessel 20; (iii) a ledge 39 extending radially inwardly from an inner surface 40 of the side wall 35 above the flange 36; and (iv) a generally cylindrical skirt 41 depending from a bottom surface 42 of the ledge in a substantially parallel orientation to the flange. The inner surface 40 of the side wall 35 and a top surface 43 of the ledge 39 define a first bore 44, as shown in <figref idref="f0003">FIG. 4</figref>, which is sized to receive a filter 33, as shown in <figref idref="f0005">Figs. 6 and 7</figref>, that may be frictionally fitted or otherwise immobilized within the first bore. In a preferred embodiment, the ledge 39 aids in retaining the filter 33 within the first bore 44 during penetration of the cap 30A-E by a fluid transfer device. The ledge 39 can also function as a surface for affixing a frangible seal 32, as depicted in <figref idref="f0005">FIG. 6</figref>. An inner surface 45 of the skirt 41 beneath the top surface 43 of the ledge 39 defines a second bore 46 which is smaller in diameter than the first bore 44 and is sized to permit movement therethrough of a fluid transfer device. (The proximal portion of the skirt 41, where the top surface 43 of the ledge 39 meets the inner surface 45 of the skirt, may be chamfered to deflect a misaligned fluid transfer device during penetration of the cap 30A-E, provided sufficient surface area remains on the top surface of the ledge for affixing the frangible seal 32 thereto.) As shown in <figref idref="f0005">FIG. 7</figref>, the skirt 41 includes a bottom surface 47 which may serve as an alternate location for affixing the frangible seal 32.

0028In an alternative core cap 31B embodiment shown in <figref idref="f0004">FIG. 5</figref>, the skirt 41 is eliminated from the core cap 31A structure shown in <figref idref="f0003">FIG. 4</figref>. In this embodiment, the frangible seal 32 may be affixed to either the bottom surface 42 or the top surface 43 of the ledge 39. However, since the skirt 41 aids in preventing fluids from leaking from a collection device 10, it may be desirable to include an alternative fluid retainer for this core cap 31B embodiment, such as a neoprene O-ring (not shown) fitted between the bottom surface 37 of the side wall 35 and an annular top surface 23 of the vessel 20.

0029While the ledge 39 of the core cap 31B shown in <figref idref="f0004">FIG. 5</figref> forms a flange structure having bottom and top surfaces 42, 43, this embodiment may be modified so that the inner surface 40 of the side wall 35 is extended radially inward until an end surface 62 of the ledge and the inner surface of the side wall are co-extensive. In this modified form of the core cap 31B (not shown), the ledge 39 is defined by the bottom surface 37 of the side wall 35, since the top surface 43 of the ledge is eliminated. Because the bore 44 of this embodiment is defined solely by the inner surface 40 of the side wall 35, the frangible seal 32 must be affixed to the bottom (or sole) surface 42 of the ledge 39.

0030A similar modification may be made to the preferred core cap 31A, whereby the inner surface 40 of the side wall 35 is extended radially inward until the inner surface 45 of the skirt 41 is co-extensive with the inner surface of the side wall. This modified form of the core cap 31A (not shown) eliminates the ledge 39, transforms the first and second bores 44, 46 into a single bore, and requires that the frangible seal 32 be affixed to the bottom surface 47 of the skirt 41. The disadvantage of these modified forms of the core caps 31A, 31B is that the alteration or elimination of the ledge 39 makes it is more difficult to maintain the filter 33 within the cap 30A-E when the cap is penetrated by a fluid transfer device. This problem may be overcome by adhering the filter 33 to the side wall 35 of the cap 30A-E, the frangible seal 32 or the retaining means 34A-C, for example.

0031The core cap 31A-B may be integrally molded from a number of different polymer and heteropolymer resins, including, but not limited to, polyolefins (e.g., high density polyethylene ("HDPE"), low density polyethylene ("LDPE"), a mixture af HDPE and LDPE, or polypropylene), polystyrene, high impact polystyrene and polycarbonate. A currently preferred material for forming the core cap 31A-B is an HDPE material sold under the tradename Alathon M5370 by GE Polymerland of Huntersville, North Carolina. Skilled artisans will readily appreciate that the range of acceptable cap resins will, in part, depend upon the nature of the resin used to form the vessel, since the properties of the resins used to form these two components will affect how well the cap 30A-E and vessel 20 components of a collection device 10 can form a leak proof seal and the ease with which the cap can be securely screwed onto the vessel. As with the vessel 20 component, the material of the core cap 31A-B should be essentially inert with respect to a fluid substance (including assay reagents) contained in the collection device 10 so that the material of the core cap does not significantly interfere with the performance or results of an assay.

0032The core cap 31A-B is injection molded as a unitary piece using procedures well-known to those skilled in the art of injection molding. After the core cap 31A-B has been formed and cured for a sufficient period of time, the following components are added to the core cap in the indicated manner and in any practicable order: <ol id="ol0001" compact="compact"><li>(i) the frangible seal 32 to the top surface 43 of the ledge 39 of either core cap 31A-B, to the bottom surface 42 of the ledge of the alternative core cap 31B, or to the bottom surface 47 of the skirt 41 of the preferred core cap 31A;</li><li>(ii) a filter 33 within the first bore 44; and (iii) a retainer 34A-D to the annular top wall 48.</li></ol>

0033The frangible seal 32 is included to provide a substantially leak-proof barrier between the fluid contents of a collection device 10 and the filter 33 contained in the first bore 44. For this reason, it is not critical whether the frangible seal 32 is affixed to a surface 42, 43 of the ledge 39 or to the bottom surface 47 of the skirt 41. According to a preferred embodiment of the present invention, the width of the annular top surface 43 of the ledge 39 is about 0.08 inches (2.03 mm), the thickness of the ledge (the distance between the top and bottom surfaces 43, 42 of the ledge) is about 0.038 inches (0.97 mm), the combined width of the annular bottom surface 42 of the ledge and the exposed bottom surface 37 of the side wall 35 is about 0.115 inches (2.92 mm), and the width of the annular bottom surface 47 of the skirt 41 is about 0.025 inches (0.635 mm). The dimensions of these features of the core cap 31A-B may vary, of course, provided sufficient surface area exists for affixing the frangible seal 32 to the core cap in a substantially leak-proof manner.

0034The frangible seal 32 is made of a foil (<i>e.g</i>., aluminum foil or other foil exhibiting low water vapor transmission), which can be affixed to a surface 42, 43 of the ledge 39 or to the bottom surface 47 of the skirt 41 by means well known to those skilled in the art, including adhesives. The frangible seal 32 is not an integral component of the core cap 31A-B. The frangible seal 32 may further include a compatibilizer, such as a thin veneer of plastic applied to one or both surfaces of the foil, which will promote a substantially leak-proof attachment of the frangible seal to a surface of the core cap 31A-B with the application of thermal energy. A heat sealer or heat induction sealer may be used to generate the requisite thermal energy. (To avoid the potentially deleterious effects of corrosion, it is recommended that all portions of a metallic frangible seal 32 which might become exposed to the fluid contents of a collection device 10 during routine handling be coated with a plastic liner.) A TOSS Machine heatsealer (Packworld USA; Nazareth, Pennsylvania; Model No. RS242) is preferred for attaching the frangible seal 32 to a surface 42, 43 of the ledge 39 or to the bottom surface 47 of the skirt 41. Ultrasonic and radio frequency welding procedures known to those skilled in the art may also be used to affix-the frangible seal 32 to the core cap 31A-B.

0035To further promote attachment of the frangible seal 32 to the core cap 31A-B, a surface 42, 43 of the ledge 39 or the bottom surface 47 of the skirt 41 may be modified during injection molding of the core cap to include an energy director, such as an annular ring or series of protuberances. By limiting contact between the frangible seal 32 and a plastic surface of the ledge 39 or skirt 41, an energy director allows the frangible seal 32 to be affixed to the ledge or skirt in less time and using less energy than would be required in its absence when an ultrasonic welding procedure is followed. This is because the smaller surface area of the protruding energy director melts and forms a weld with the plastic material of the frangible seal 32 more quickly than is possible with a flat, unmodified plastic surface. An energy director is preferably acontinuous surface ring which is triangular in cross-section.

0036In order to facilitate the venting of air from within a collection device 10, the frangible seal 32 is constructed so that it tears when the seal is penetrated by a fluid transfer device, thereby forming air passageways 70 between the seal and the fluid transfer device, as described in detail <i>infra.</i> To achieve this tearing, the seal 32 preferably includes a brittle layer comprised of a hard plastic material, such as a polyester. (<i>See</i><nplcit id="ncit0002" npl-type="b"><text>CHARLES A. HARPER, HANDBOOK OF PLASTICS, ELASTOMERS, AND COMPOSITES § 1.7.13 (1997 3d ed</text></nplcit>.) for a discussion of the properties of polyesters.) As shown in <figref idref="f0006">FIG. 8</figref>, the preferred seal 32 of the present invention is a co-laminate that includes a foil layer, a heat seal layer and an intervening brittle layer (Unipac; Ontario, Canada; Product No. SG-75M (excluding the pulp board and wax layers typically included with this product)). With this preferred seal 32, the foil layer is an aluminum foil having a thickness of about 0.001 inches (0.0254 mm), the heat seal layer is a polyethylene film having a thickness of about 0.0015 inches (0.0381 mm), and the brittle layer is a polyester having a thickness of about 0,0005 inches (0.0127 mm). Because this particular seal 32 design would have a metallic surface exposed to the contents of a collection device 10 after sealing - if applied to the bottom surface 42 of the ledge 39 or to the bottom surface 47 of the skirt 41 -- it is preferred that this seal 32 be applied to the top surface 43 of the ledge, as shown in <figref idref="f0005">Figs, 6</figref>, <figref idref="f0009">13</figref>, <figref idref="f0010">15</figref> and <figref idref="f0011">17</figref>. In this way, the cap 30A, C, D and E of these embodiments will have no metallic surfaces exposed to the fluid contents of an associated vessel 20. While the diameter of the seal 32 will depend upon the dimensions of the cap 30A-E, the presently preferred seal has a diameter of about 0.5 inches (12.70 mm).

0037An alternative frangible seal 32 embodiment is depicted in <figref idref="f0006">FIG. 9</figref>, which shows a top foil layer with a lower combined brittle/heat seal layer comprised of an epoxy resin. The epoxy resin is selected for its mechanical strength, which will promote formation of the desired air passageways 70 discussed above when the material is penetrated by a fluid transfer device. And, so that this seal 32 can be affixed to a plastic surface using a commonly practiced thermoplastic welding procedure, the epoxy layer further includes a compatibilizer dispersed within the epoxy resin, as shown in <figref idref="f0006">FIG. 9</figref>. A preferred compatibilizer of this seal 32 embodiment is a polyethylene.

0038As illustrated in the figures, the filter 33 is positioned within the first bore 44 above the ledge 39 and is incorporated to retard or block the movement of an escaping aerosol or bubbles after the seal has been pierced by a fluid transfer device. The filter 33 can also be constructed to perform a wiping action on the outside of a fluid transfer device as the fluid transfer device is being removed from a collection device 10. In a preferred mode, the filter 33 functions to draw fluids away from the outside of a fluid transfer device by means of capillary action. As used herein, however, the term "filter" refers generally to a material which performs a wiping function to remove fluids present on the outside of a fluid transfer device and/or an absorbing function to hold or otherwise sequester fluids removed from the outside of a fluid transfer device. For reasons discussed below, the filters 33 of the present invention are composed of a material or combination of materials having pores or interstices which admit the passage of a gas. Examples of filter 33 materials which may be used with the cap 30A-E of the present invention include, but are not limited to, pile fabrics, sponges, foams (with or without a surface skin), felts, sliver knits, Gore-Tex®, Lycra®, and other materials and blends, both natural and synthetic. These materials may also be mechanically or chemically treated to further improve the intended functions of the filter 33. For example, napping may be used to increase the surface area and, therefore, the fluid holding capacity of a filter 33. The material of the filter 33 may also be pre-treated with a wetting agent, such as a surfactant, to lower the surface tension of a fluid present on an outer surface of a fluid transfer device. An acrylic binder might be used, for example, to actually bind the wetting agent to the filter 33 material. Additionally, the filter 33 may include a super-absorbent polymer, (<i>see, e.g.,</i> Sackmann <i>et al.,</i> "Pre-Formed Super Absorbers with High Swelling Capacity," <patcit id="pcit0007" dnum="US6156848A"><text>U.S. Patent No. 6,156,848</text></patcit>), to prevent a fluid from escaping from a penetrated collection device 10.

0039To limit the unobstructed passage of air from within a collection device 10 to the environment, the filter 33 is preferably made of a resilient material whose original shape is restored, or substantially restored, as a fluid transfer device is being removed from the collection device. This characteristic of the filter 33 is especially important when the fluid transfer device has a non-uniform diameter, as is the case with most pipette tips used with standard air displacement pipettes. Thus, materials such as pile fabric, sponges, foams and Lycra are preferred because they tend to quickly restore their original shape after exposure to compressive forces. Pile fabric is a particularly preferred filter 33. An example of a preferred pile fabric is an acrylic material having a thickness of about 0.375 inches (9.53 mm) which is available from Roller Fabrics of Milwaukee, Wisconsin as Part No. ASW 112. Examples of other acceptable pile fabrics include those made of acrylic and polyester materials and which range in size from about 0.25 inches (6.35 mm) to about 0.3125 inches (7.94 mm). Such pile fabrics are available from Mount Vernon Mills, Inc. of LaFrance, South Carolina as Part Nos. 0446, 0439 and 0433. The filter 33 material is preferably inert with respect to a fluid substance contained within the vessel 20.

0040Because the filter 33 is intended to remove fluid from the exterior of a fluid transfer device and to capture fluid in the form of an aerosol or bubbles, it is best if the material and dimensions of the filter material are chosen so that the filter does not become saturated with fluid during use. If the filter 33 does become saturated, fluid may not be adequately wiped from the exterior of the fluid transfer device and bubbles may be produced as the fluid transfer device passes through the filter or as air is displaced from within the collection device 10. Thus, it is important to adapt the size and adsorptive properties of the filter 33 in order to achieve adequate wiping and aerosol or bubble containment. Considerations when selecting a filter 33 will include the cap configuration, the shape and size of the fluid transfer device and the nature and amount of fluid substance contained in the vessel 20, especially in view of the number of anticipated fluid transfers for a given collection device 10. As the amount of fluid a filter 33 is likely to be exposed to increases, the volume of the filter material or its absorptive properties may need to be adjusted so that the filter does not become saturated during use.

0041It is also important that the filter 33 be constructed and arranged in the cap 30A-E so that the flow of air out of the collection device 10 remains relatively unimpeded as the cap is being penetrated by a fluid transfer device. In other words, the material of the filter 33 and its arrangement within the cap 30A-E should facilitate the venting of air displaced from within the collection device 10. Of course, this venting property of the filter 33 needs to be balanced with the requirement that the filter material have sufficient density to trap an escaping aerosol or bubbles. Consequently, those skilled in the art will appreciate the need to select or design filter 33 materials having matrices that are capable of trapping an aerosol or bubbles, while simultaneously permitting air to be vented from within the collection device 10 once the underlying seal 32 has been pierced by a fluid transfer device.

0042As the figures show, the filter 33 is preferably sized to fit within the first bore 44 beneath the horizontal plane of the annular top wall 48. In a preferred cap 30A-E of the present invention, the filter 33 also rests substantially or completely above the ledge 39, even though the seal 32 may be affixed to the bottom surface 47 of the skirt 41, as illustrated in <figref idref="f0005">FIG. 7</figref>. To better ensure that the filter 33 is not substantially moved from its position within the first bore 44 by frictional contact with a fluid transfer device penetrating or being removed from the cap 30A-E, the filter may be bound to the top surface 43 of the ledge 39 or to the inner surface 40 of the side wall 35 using an inert adhesive. Notwithstanding, the filter 33 is preferably a pile fabric which is snugly fitted in the first bore 44 and retained there by means of the seal 32 and the retainer 34A-D, without the use of an adhesive. In preferred cap 30A-E embodiments, the first bore 44 is about 0.50 inches (12.70 mm) in diameter and has a height of about 0.31 inches (7.87 mm).

0043The material and configuration of the filter 33 should be such that it creates minimal frictional interference with a fluid transfer device as it is being inserted into or withdrawn from the collection device 10. In the case of a sponge or foam, for example, this may require boring a hole or creating one or more slits in the center of the filter 33 (not shown) which are sized to minimize frictional interference between the filter and a fluid transfer device, while at the same time providing enough interference so that aerosol or bubble transmission is limited and the wiping action is performed by the filter material. If a pile fabric is employed as the filter 33, the pile fabric is preferably arranged in the manner shown in <figref idref="f0007">FIG. 10</figref>, such that the free ends of individual fibers (shown as squiggles, but not specifically identified with a reference number) are oriented radially inwardly toward the longitudinal axis 80 of the cap 30A-E and away from the pile fabric backing 49 which is in touching or fixed contact with the inner surface 40 of the side wall 35. When rolling the pile fabric for insertion into the first bore 44, care should be taken not to wind the pile fabric so tightly that it will create excessive frictional interference with a fluid transfer device penetrating the cap 30A-E, thereby substantially impeding movement of the fluid transfer device. A particularly preferred pile fabric is available from Mount Vernon Mills, Inc. as Part No. 0446, which has a thickness of about 0.25 inches (6.35 mm) and is cut to have a length of about 1.44 inches (36.58 mm) and a width of about 0.25 inches (6.35 mm).

0044To immobilize the filter 33 within the first bore 44, the caps 30A-E include a retainer 34A-D positioned above the filter, preferably on the annular top wall 48. In a preferred embodiment shown in <figref idref="f0005">Figs. 6 and 7</figref>, the retainer 34A is a solid, generally circular frangible seal which may be of the same or a different material than the frangible seal 32 positioned beneath the filter 33. Preferably, the retainer 34A includes the same materials as the preferred seal 32 described above, which comprises an aluminum foil layer, a polyester brittle layer, and a polyethylene heat seal layer (Unipac; Ontario, Canada; Product No. SG-75M (excluding the pulp board and wax layers typically included with this product)). This retainer 34A can be applied to the annular top wall 48 with a heat sealer or heat induction sealer in the same manner that the seal 32 is applied to a surface 42, 43 of the ledge 39 or to the bottom surface 47 of the skirt 41. Like the preferred seal 32, the preferred retainer 34A has a foil layer thickness of about 0.001 inches (0.0254 mm), a brittle layer thickness of about 0.0005 inches (0.0127 mm), and a heat seal layer thickness of about 0.0015 inches (0.0381 mm). The diameter of the preferred retainer is about 0.625 inches (15.88 mm). Of course, the diameter of this preferred retainer 34A may vary and will depend upon the dimensions of the annular top wall 48.

0045As illustrated in <figref idref="f0008">FIG. 11</figref>, the retainer 34A may be adapted to facilitate penetration by including one or more series of perforations 50 which extend radially outwardly from a center point 51 of the retainer. The center point 51 of these radiating perforations 50 is preferably positioned to coincide with the expected entry point of a fluid transfer device. Also contemplated by the present invention are other types of adaptations that would reduce the tensile strength of the retainer 34A, including creases, score lines or other mechanical impressions applied to the material of the retainer. The same adaptations may also be made to the seal 32, provided the seal will continue to exhibit low water vapor transmission characteristics after the collection device 10 is exposed to normal shipping and storage conditions.

0046Besides providing a means for keeping the filter 33 fixed within the first bore 44 prior to and during a fluid transfer, a seal retainer 34A can protect the underlying filter from external contaminants prior to penetration of the cap 30A. Moreover, a cap 30A designed to completely seal the filter 33 within the first bore 44 may be sterilized prior to use by, for example, gamma irradiation. Additionally, the retainer 34 of such a cap 30A could be wiped with a disinfectant or the entire collection device 10 could be irradiated with ultraviolet light prior to penetration to facilitate a sterile fluid transfer.

0047Although not suitable for use in a method of the invention, in those instances where the potential presence of contaminants on the filter would not be of significant concern, the retainer may comprise a foil ring, for example, which includes a centrally located hole which is sized to receive a fluid transfer device. As illustrated in <figref idref="f0008">FIG. 12</figref>, a cap 30C having a retainer 34B with a centrally located hole 52 could aid in retaining the filter 33 within the first bore 44, while at the same time limiting the number of surfaces that a fluid transfer device would have to pierce in order to fully penetrate the cap. To retain the filter 33 within the first bore 44, the diameter of the hole 52 would have to be smaller than the diameter of the filter when the hole and the filter are substantially axially aligned.

0048Another cap 30D embodiment not suitable for use in a method of the invention is illustrated in <figref idref="f0009">Figs. 13 and 14</figref>. The retainer 34C of this cap 30D is a plastic disc which includes a centrally located hole 53 sized to receive a fluid transfer device. The disc 34C may be affixed to the annular top wall 48 by means of an adhesive or welded by heat, ultrasound or other appropriate welding method known to skilled artisans. Alternatively, the annular top wall 48 may be modified to include a seat 54 which is sized to receive the disc 34C in, for example, a frictional or snap fit. While this particular cap 30D embodiment does not provide the filter 33 with a completely sealed environment, the disc retainer 34C can nevertheless function to contain the filter 33 within the first bore 44 during transport of the collection device 10, as well as during a fluid transfer. If it is important to protect the filter 33 from potential contaminants prior to use, then the cap 30D of this embodiment could further include a seal, such as the frangible seal 34A described <i>supra,</i> affixed to a top 55 or a bottom surface 56 of the disc 34C so that the hole 53 is fully and sealably covered. As illustrated in <figref idref="f0010">Figs. 15 and 16</figref>, one such seal 34D could include a. tab 57 for easy removal. With this design, the seal 34D of a cap 30E could be removed just before penetration of the cap with a fluid transfer device, allowing the filter 33 to be protected from external contaminants immediately prior to use. An advantage of this cap 30E over, for example, the cap 30A-B embodiments shown in <figref idref="f0005">Figs. 6 and 7</figref> is that penetration of the cap will require less force since there is only one seal 32, as opposed to the two seals 32, 34A of those embodiments, that the fluid transfer device needs to pierce.

0049When a cap 30A-B for use in methods of the present invention is pierced by a fluid transfer device 90 which is used to retrieve at least a portion of a fluid sample 100 contained in a collection device 10, as shown in <figref idref="f0011">FIG. 17</figref>, one or more tears are formed in the frangible seal 32 and the retainer 34A. As <figref idref="f0012">FIG. 18</figref> illustrates, these tears in the frangible seal form air passageways 70 which facilitate the venting of air displaced from within a collection device 10 as the fluid transfer device 90 enters the interior space 11 (defined as the space below the cap 30A-E and within inner surfaces 24, 25 of the side wall 22 and a bottom wall 26 of the vessel 20) of the collection device 10. By providing means for venting air displaced from within a collection device 10, the volume accuracy of fluid transfers (<i>e.g.</i>, pipetting) will likely be improved. While a variety of conventional plastic pipette tips having beveled or flat tips can be used with the present invention, a preferred fluid transfer device is the Genesis series 1000 µl Tecan-Tip (with filter), available fromEppendorf-Netherler-Hinz GmbH of Hamburg, Germany as Part No. <patcit id="pcit0008" dnum="DE612513"><text>612-513</text></patcit>. Fluid transfer devices of the present invention are preferably able to penetrate the frangible seal 32 with the application of less than about 3 pounds force (13.34 N), more preferably less than about 2 pounds force (8.90 N), even more preferably less than about 1 pound force (4.45 N), and most preferably less than about 0.5 pounds force (2.22 N).

0050The insertion force, which is the total or additive force required to pierce all penetrable surfaces of a cap 30A-E according to the present invention (i.e., the frangible seal 32, the filter 33 and, optionally, the retainer 34A) with a fluid transfer device, is preferably less than about 8 pounds force (35.59 N), more preferably less than about 6.5 pounds force (28.91 N), even more preferably less than about 5 pounds force (22.24 N), and most preferably less than about 4.5 pounds force (20.02 N). The withdrawal force, which is the force required to completely withdraw a fluid transfer device from the collection device 10 after the cap 30A-E has been completely penetrated, is preferably less than about 4 pounds force (17.79 N), more preferably less than about 3 pounds force (13.34 N), even more preferably less than about 2 pounds force (8.90 N), and most preferably less than about 1 pound force (4.45 N). The forces exerted on the fluid transfer device as it is being withdrawn from a collection device 10 should be minimized to avoid stripping the fluid transfer device from, for example, the mounting probe of a vacuum pipette. Insertion and withdrawal forces can be determined using conventional force measurement instruments, such as a motorized test stand (Model No. TCD 200) and digital force gauge (Model No. DFGS-50) available from John Chatillon &amp; Sons, Inc. of Greensboro, North Carolina.

0051A cap 30A-E is generally provided in combination with a fluid-holding vessel 20 as components .of a collection device 10. The cap 30A-E and vessel 20 of the collection device 10 can be joined by means of mated threads which allow the cap to be screwed, snapped or otherwise frictionally fitted onto an outer surface 21 of the side wall 22 at the open end of the vessel. When the cap 30A-E is frictionally fitted onto the vessel 20, the bottom surface 37 of the side wall 35 of the cap is preferably in contact with the annular top surface 23 of the vessel to provide an interference fit, thereby facilitating the essentially leak-proof seal discussed above. The cap 30A-E can be modified to further improve resistance of the collection device 10 to leaking by providing an annular seal bead 58 to an outer surface 59 of the skirt 41, as shown in <figref idref="f0003">FIG. 4</figref>. If the seal bead 58 is included, it should be sized so that it will be in frictional contact with the inner surface 24 of the side wall 22 of the vessel 20 but will not substantially interfere with joining of the cap 30A-E and vessel. The annular center 60 of the preferred seal bead 58 is about 0.071 inches (1.80 mm) from the bottom surface 37 of the side wall 35 and extends radially outwardly about 0.0085 inches (0.216 mm) from the outer surface 59 of the skirt 41, where the thickness of the skirt 41 above the seal bead 58 is about 0.052 inches (1.32 mm). The skirt 41 preferably includes a beveled base 61 below the seal bead 58 to facilitate joining of the cap 30A-E and vessel 20. In a preferred embodiment, the skirt 41 extends downward a vertical distance of about 0.109 inches (2.77 mm) from the annular center 60 of the seal bead 58 to the bottom surface 47 of the skirt and uniformly decreases in thickness from about 0.0605 inches (1.54 mm) to about 0.025 inches (0.635 mm) between the annular center of the seal bead and the bottom surface of the skirt. The second bore 46 of this preferred embodiment has a diameter of about 0.340 inches (8.64 mm) and a height of about 0.218 inches (5.54 mm).

0052When provided as a component of a kit, the collection device 10 preferably includes a specimen retrieval device for obtaining a sample to be analyzed, where the specimen retrieval device has preferably been sized to fit within the interior space 11 of the collection device after the cap 30A-E and vessel 20 have been joined. A preferred specimen retrieval device is a swab, such as the swab disclosed by Pestes <i>et al.,</i> "Cell Collection Swab," <patcit id="pcit0009" dnum="US5623942A"><text>U.S. Patent No. 5,623,942</text></patcit>. This particular swab is preferred because it is manufactured to include a score line which is positioned on the stem of the swab, allowing the swab to be manually snapped in two after a specimen has been obtained, leaving the lower, specimen-bearing portion of the swab entirely inside the vessel 20 component of the collection device 10. When the specimen is being transported to a clinical laboratory, the collection device 10 also preferably includes a transport medium for preserving the sample prior to analysis. Transport mediums are well known in the art and will vary depending upon the sample type and whether cell lysis prior to analysis is necessary.

0053Additionally, a kit may include instructions recorded in a tangible form (<i>e.g.</i>, contained on paper or an electronic medium) which explain how the components of the collection device 10 are to be manipulated when obtaining a fluid sample or how the cap 30A-E is to be secured onto the vessel 20 prior to transporting the collection device to a clinical laboratory. Alternatively, or in addition to, the instructions may detail proper pipetting techniques for retrieving at least a portion of the sample from the collection device 10 prior to analysis. These instructions may include information about types of fluid transfer devices that can be used to penetrate the cap 30A-E, positioning of a fluid transfer device for penetrating the cap and/or the amount of force needed to penetrate the cap. The instructional materials may also detail proper use of the collection device when the sample is to be exposed to reagents and conditions useful for amplifying a nucleic acid sequence targeted for detection.

0054Amplification prior to detection is particularly desirable in diagnostic assays where the initial population of targeted nucleic acid sequences in a sample is expected to be relatively small, making detection of the targeted nucleic acid sequences more difficult. There are many procedures for amplifying nucleic acids which are well known in the art, including, but not limited to, the polymerase chain reaction (PCR), (<i>see, e.g.,</i> Mullis, "Process for Amplifying, Detecting, and/or Cloning Nucleic Acid Sequences," <patcit id="pcit0010" dnum="US4683195A"><text>U.S. Patent No. 4,683,195</text></patcit>), transcription-mediated amplification (TMA), (<i>see, e.g.</i>, Kacian <i>et al.,</i> "Nucleic Acid Sequence Amplification Methods," <patcit id="pcit0011" dnum="US5399491A"><text>U.S. Patent No. 5,399,491</text></patcit>), ligase chain reaction (LCR), (<i>see, e.g.,</i> Birkenmeyer, "Amplification of Target Nucleic Acids Using Gap Filling Ligase Chain Reaction," <patcit id="pcit0012" dnum="US5427930A"><text>U.S. Patent No. 5,427,930</text></patcit>), and strand displacement amplification (SDA), (<i>see, e.g.</i>, Walker, "Strand Displacement Amplification," <patcit id="pcit0013" dnum="US5455166A"><text>U.S. Patent No. 5,455,166</text></patcit>). The particular reagents (<i>e.g.,</i> enzymes and primers) and conditions selected by practitioners will vary depending upon the particular nucleic acid sequence being targeted for detection and the specific amplification procedure to be followed. Those skilled in the art of nucleic acid diagnostics, however, will be able to select appropriate reagents and conditions for amplifying a specific targeted nucleic acid sequence following a particular amplification procedure without having to engage in undue experimentation.