U.S. patent application number 09/966917 was filed with the patent office on 2002-07-04 for heat sealing septum for storage plates.
Invention is credited to Audino, Deborah C., Martin, Gregory R..
Application Number | 20020083686 09/966917 |
Document ID | / |
Family ID | 26929852 |
Filed Date | 2002-07-04 |
United States Patent
Application |
20020083686 |
Kind Code |
A1 |
Audino, Deborah C. ; et
al. |
July 4, 2002 |
Heat sealing septum for storage plates
Abstract
An apparatus for sealing fluid containing vessels comprising a
sheet of elastomer forming a sealing member having a top and bottom
surface, and disposed on a plate containing a plurality of wells
for storing fluids. A product that can seal the wells of a
multiwell plate, and has the aspects of being vapor resistant, heat
sealable, and able to be manipulated by automated analytical
equipment. The sealing material is constituted of an elastomer made
of synthetic rubber and a layer, comprising a polymer film or a
foil attached to one side of the elastomer to form a vapor barrier.
The combination of these elements produces a sealing mat that
couples the barrier properties of the polymer film or foil with the
sealing properties of the elastomer septum.
Inventors: |
Audino, Deborah C.;
(Portsmouth, NH) ; Martin, Gregory R.; (Acton,
ME) |
Correspondence
Address: |
CORNING INCORPORATED
SP-TI-3-1
CORNING
NY
14831
|
Family ID: |
26929852 |
Appl. No.: |
09/966917 |
Filed: |
September 28, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60236512 |
Sep 29, 2000 |
|
|
|
Current U.S.
Class: |
53/478 ;
53/329.2 |
Current CPC
Class: |
B01L 3/50853 20130101;
B01L 3/50851 20130101; B65B 11/50 20130101 |
Class at
Publication: |
53/478 ;
53/329.2 |
International
Class: |
B65B 051/10 |
Claims
We claim:
1. An apparatus for sealing fluid containing vessels comprising: a
sheet of elastomer forming a sealing member having a top and bottom
surface, disposed on a plate containing a plurality of wells for
storing fluids, and said sealing member is thermally bonded to said
plate, wherein said elastomer has a propensity to reseal after
being punctured.
2. An apparatus for sealing fluid containing vessels of claim 1,
wherein said elastomer is made of a thermoplastic polymer
material.
3. An apparatus for sealing fluid containing vessels of claim 1,
wherein said bottom surface of said elastomer is made of a
thermosetting polymer having a chemical affinity to said plate's
chemical composition.
4. An apparatus for sealing fluid containing vessels of claim 1,
wherein said elastomer is joined to a film that is compatible to
said plate's composition.
5. An apparatus for sealing fluid containing vessels comprising: a)
a film of elastomer having a top and bottom surface, bonded to b) a
metallic foil on at least one of said surfaces, and c) said foil is
thermally sealable to a multiwell test plate, wherein said
elastomer and foil together make a vapor resistant barrier.
6. An apparatus for sealing fluid containing vessels of claim 5,
wherein said elastomer is thermally sealed to said test plate by
means of heat bonding a compatible polymer between said metallic
foil and said test plate.
7. An apparatus for sealing fluid containing vessels comprising: a)
a film of elastomer having a top and bottom surface, bonded to b) a
polymer film on at least one of said surfaces, and c) said polymer
film is thermally sealed to a multiwell test plate, wherein said
elastomer and polymer film together make a vapor resistant
barrier.
8. An apparatus for sealing fluid containing vessels of anyone of
claims 1, 4, or 5, wherein said elastomer is made of a
thermoplastic polymeric compound chosen from the group consisting
of: an elastic material that is made from polypropylene blended
with ethylene-propylene diene methylene (EPDM) rubber particles,
styrene-butadiene, poly(ester-block-ether), or
nylon-block-polyether.
9. An apparatus for sealing fluid containing vessels of anyone of
claims 1, 3, 4, 5 or 7, wherein said elastomer is made of a
cross-linked polymeric compound chosen from the group consisting
of: polybutadiene, cross-linked epoxidized polybutadiene,
ethylene-propylene diene methylene (EPDM), polyisobutylene,
polychloroprene (neoprene), cis-1,4-polyisoprene, polyurethane,
nitrile rubber (Buna-N), epichlorohydrin rubber, silicone block
copolymers or silicone.
10. An apparatus for sealing fluid containing vessels of anyone of
claims 1, 3, 4, 5 or 7, wherein said elastomer is hydrophobic.
11. An apparatus for sealing fluid containing vessels of anyone of
claims 1, 3, 4, 5 or 7, wherein said elastomer's lower surface has
a chemical composition that is totally compatible to form a bond
with said plate's chemical composition, thereby creating a
non-releasable seal.
12. An apparatus for sealing fluid containing vessels of anyone of
claims 1, 3, 4, 5 or 7, wherein said elastomer's lower surface has
a chemical composition that is partially compatible to form a bond
with said plate's chemical composition, thereby creating a
releasable seal.
13. An apparatus for sealing fluid containing vessels of anyone of
claims 3 4, or 5, wherein said compatible polymer is of a
chemically similar composition as that of said test plate.
14. An apparatus for sealing fluid containing vessels of anyone of
claims 3, 4, or 5, wherein said compatible polymer is
poly(ethylene-co-maleic anhydride).
15. An apparatus for sealing fluid containing vessels of claim 1 or
5, wherein said elastomer is made of a polypropylene blended with
EPDM rubber particles.
16. An apparatus for sealing fluid containing vessels of anyone of
claims 3, 4, or 5, wherein said test plate is made from
polypropylene.
17. An apparatus for sealing fluid containing vessels of anyone of
claims 3, 4, or 5, wherein said test plate is made from
polystyrene.
18. An apparatus for sealing fluid containing vessels of anyone of
claims 3, 4, or 5, wherein said compatible polymer melts at a lower
temperature than a temperature at which said test plate begins to
deform.
19. An apparatus for sealing fluid containing vessels of claim 18,
wherein said lower temperature is at or lower than 165.degree.
C.
20. A method of sealing a fluid container comprising the following
steps: a) providing a roll of film made of an elastomer having a
top and bottom surface, the bottom surface is bonded to a layer
comprising a metallic foil or a thermoplastic film that is
compatible with a polymer material of a microtiter test plate, and
said test plate having a plurality of wells located in its top
surface; b) cutting an unrolled roll of said film, wherein each cut
piece of film corresponds with the length and width dimensions of
said top surface of said test plate, whereby each well in said test
plate is covered by said film;. c) disposing planarly said cut
piece of film onto said top surface of said test plate; d) affixing
said cut piece of film to said top surface of said test plate,
whereby each well in said test plate is covered by said film; e)
applying heat to said cut piece of film to thereby
thermo-chemically bond said cut piece of film to said top surface
of test plate.
21. An apparatus for sealing fluid containing vessels comprising:
a) a planar sealing member composed of elastic material and
disposed on a plate having a plurality of fluid receiving wells; b)
a metallic foil laminated to said planar sealing member; c) a rigid
lid defined by a peripheral skirt and a top and bottom surface
having a predetermined matrix of openings extending through, and
said openings correspond to said wells in said plate; d) wherein
said sealing member and metallic foil laminate is either molded or
welded to said bottom surface, with said sealing member in direct
contact with said bottom surface and said metallic foil exposed
toward said open wells in said plate, and said metallic foil is
heat sealed to said plate.
22. An apparatus for sealing fluid containing vessels of claim 21,
wherein a polymer, that is compatible with said plate's chemical
composition, adheres said metallic foil to said plate by thermally
bonding.
23. An apparatus for sealing fluid containing vessels of claim 21,
wherein said matrix of openings is 96 holes.
24. An apparatus for sealing fluid containing vessels of claim 21,
wherein said matrix of openings is 384 holes.
25. An apparatus for sealing fluid containing vessels of claim 21,
wherein said matrix of openings is 1536 holes.
26. An apparatus for sealing fluid containing vessels of claim 21,
wherein said lid has a single large rectangular opening.
27. A microtiter plate having a plurality of fluid receiving wells
comprising a planar sealing member composed of an elastomer
material and disposed on said plate; a metallic foil laminated to
said planar sealing member; a thermoplastic film; a rigid lid
defined by a peripheral skirt and a top and bottom surface having a
predetermined matrix of openings extending through, and said
openings correspond to said wells in said plate; wherein said
sealing member and metallic foil laminate is either molded or
welded to said bottom surface, with said sealing member in direct
contact with said bottom surface and said metallic foil exposed
toward said open wells in said plate, and said metallic foil is
heat sealed to said plate.
28. The microtiter plate of claim 27, wherein a polymer, that is
compatible with said plate's chemical composition, adheres said
metallic foil to said plate by thermally bonding.
29. The microtiter plate of claim 27, wherein said matrix of
openings is 96 holes.
30. The microtiter plate of claim 21, wherein said matrix of
openings is 384 holes to-1536 holes.
31. The microtiter plate of claim 27, wherein said lid has a single
large rectangular opening.
Description
CLAIM OF PRIORITY
[0001] The present Application claims priority to U.S. Provisional
Application No. 60/236,512, filed on Sep. 29, 2000, in the names of
Deborah C. Audino and Gregory R. Martin. The content of the
Provisional Application is incorporated herein in its entirety.
FIELD OF INVENTION
[0002] The invention relates to a septum for sealing liquid
containing vessels. In particular, the invention relates to an
elastomer sheet used to thermally seal wells of a microtiter test
plate used in biological or chemical assays.
BACKGROUND
[0003] Today, the reacting and testing of large numbers of
biological samples constitutes a fundamental technique of analysis
in modem biological or medical diagnostic science. Specific
examples include polymerase chain reaction (PCR) techniques,
radio-immune assay (RIA), enzyme linked immune-sorbent assay
(ELISA), enzyme immune assay (EIA), enzyme assays, including
receptor binding assays, membrane capture assays, cell washing, and
others similar tests. The physical equipment used to perform these
large numbers of required tests efficiently, accurately, and
safely, has been for many years the microtiter plates or
"microplates," also known as multiwell plates. Multiwell plates
come in various sizes, from 6 to over 1536 wells. The most typical
multiwell plates contain ninety-six (96) molded plastic wells in an
8.times.12 array with a typical volume capacity of about 200
microliters.
[0004] In the striving for ever increasing efficiency and to reduce
manually repetitive tasks performed by laboratory technicians, many
multi-sample plates have been adapted for use in automated handling
systems. Such systems employ multiwell plates for storing, reacting
and/or analyzing liquid samples, and typically includes a liquid
handling device, which transfers fluid between selected containers
and/or wells, and an automated plate handling apparatus to
manipulate multiwell plates that contain the samples.
[0005] Usually, multiwell plates possess a lid designed to prevent
dust or other contaminants from entering the wells, as well as to
reduce the rate of evaporation. These lids generally are sturdy
enough to withstand handling by the variety of automated scientific
instruments and robotic means used to remove and replace the lids
on the multiwell plates.
[0006] Nevertheless, in several ways the design of the standard
multiwell plate still has some shortcomings. Many multiwell plate
lids fit loosely and are not designed to seal the tops of the open
wells. Samples of test compounds being stored in plates need to
avoid adsorption of water from the surrounding atmosphere. Samples
handled in an automated system may need to be heated and/or
agitated at various points during the processing cycle. Such
operations normally require the wells containing the samples to be
sealed. Liquids can spill out of the wells or aerosols can form
during fluid transfers. Liquids escaping from the wells, however
minute in quantity, can contaminate the analysis being performed,
and may also create a hazard if the testing involves infectious
materials. Moreover, condensation tends to form from the wells
since the lids do not create a tight seal. Over time, this
condensation can spread along the lid and drip from one well into
neighboring wells, creating cross-contamination between the samples
in the wells. Thus, the seals typically need to be fluid-tight to
prevent loss of sample fluid, especially when the contents of a
well is heated, creating a positive pressure in the well. Often
after the heating and/or agitation step, the plates need to be
uncovered in order to add other reagents, or to extract reacted
samples. A case illustrative from the realm of molecular biology--a
typical PCR involves cycling liquid samples, contained within
individual wells of a test plate, 30 times between temperatures of
about 50.degree. C. to about 94-95.degree. C. During this cycling
process, liquid may evaporate, contributing excessively to
cross-talk between the wells. Compounds being stored in hygroscopic
solvents need to avoid adsorption of water so as avoid unintended
dilution or hydrolysis during storage.
[0007] To minimize such evaporation, adsorption, or cross talk,
manufactures in the microplate industry have developed a variety of
sealing devices for multiwell plates. Products in the form of tapes
and sealing mats are available on the market to cover the wells of
a multiwell plate. For example, tapes are typically made of
polyester, polypropylene, or a fluoropolymer, and sold by a variety
of suppliers including Hybaid, Rainin, MJ Research, Techne, Top
Flight, and Corning Costar. Sealing mats are typically made from
synthetic rubber, polypropylene, or silicone and have a matrix of
sealing plugs situated on one surface of the mat for use in
plugging individual wells.
[0008] In the past elastomer mats have depended on either a
pressure system or a friction fit to mechanically seal the
multiwell plates. Examples, such as U.S. Pat. Nos. 5,056,427 (the
`427 patent), 5,604,130 (the `130 patent), and 5,853.586 (the `586
patent), describe sealing mechanisms that are held to the plate by
either a pressure plate or a pressure differential. The `427 patent
claims a tight sealing structure for use with a reagent tray that
suppresses evaporation of fluids during thermal reactions. A
planar, elastic, sealing member is placed on top of the tray to
cover the openings, and is secured to the reagent tray by a
pressure plate. Likewise, the `130 patent discloses a sealing cover
for a multiwell, microtitration plate that uses another pressure
apparatus. The cover contains a pad, fashioned from a flexible
polymer sheet, and a plurality of resiliently compressible ridges
formed on the sheet. The ridges deform when pressure is applied to
the cover, which effectively forms a fluid-tight seal between the
pad and well openings in the plate. When the pressure is released,
the ridges rebound sufficiently to their original form to break the
seal. In the `586 patent, a flexible sealing member collapses, in
the direction of a filtration vacuum, into each individual well of
a multiwell plate.
[0009] Although useful in preventing liquid content loss by
evaporation or cross-talk, the tapes and mats are not designed for
used in automated assay processes. The materials from which these
products are made are too thin to be efficiently worked by most
automated instruments. The polypropylene mats need significant
pressure to place and remove them, while the silicone mats are too
flimsy for a machine to handle them, requiring a lab worker to
manually fit and remove them. Additionally, silicone has too large
a free volume and, thus permits free diffusion of water or solvent
vapors as well other gases through the seal. Hence, there is a need
for a cover capable of effectively sealing the wells of a multiwell
plate in an automated system. The seal should prevent the loss of
well contents during heating or agitation processes, yet be usable
without the need to apply unnecessary force or unduly complex
systems.
SUMMARY OF INVENTION
[0010] The present invention comprises a product that can seal the
wells of a multiwell plate, has the aspects of being vapor
resistant, heat sealable, and is able to be manipulated by
automated analytical equipment. The sealing material is constituted
of an elastomer made of synthetic rubber and a layer, comprising a
polymer film or a foil attached to one side of the elastomer to
form a vapor barrier. Alternatively, the sealing layer of the
invention comprises a cross-linked elastomer that is laminated to a
thermoplastic film. The combination of these elements produces a
sealing mat that couples the barrier properties of the polymer film
or foil with the sealing properties of the elastomer septum.
[0011] The invention comprises also a microtiter well plate having
such a sealing material. The bottom surface of the elastomer is
sealed thermally to the top surface of the microtiter well plate,
in a manner that it covers the entire plate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a perspective view of one embodiment of the
present invention showing an elastomer sheet adhered to a multiwell
test plate of a standard configuration.
[0013] FIG. 2 is an embodiment of a septum with a laminated
structure in which a metal foil with a polymer coating on both
sides of the foil is attached to an elastomer sheet.
[0014] FIG. 3 is a top-down sequence of the layers of another
laminate embodiment comprises: an elastomer sheet, a polymer
binder, a metallic foil, and another polymer layer.
[0015] FIG. 4 is a cross-linked elastomer, having a thickness that
is laminated to a thermoplastic film.
[0016] FIG. 5 is an apparatus that alternatively embodies the
invention wherein an elastomer material of a sealing member is set
in a lid designed to fittingly engage a multiwell plate.
[0017] FIGS. 5A and 5B are two variations of a partial
cross-sectional view of an elastomer sealing sheet under a
micro-titer plate lid placed over the micro-titer well plate.
[0018] FIG. 6 is an exploded view showing one embodiment of the
invention with a micro-titer plate lid having a plurality of holes,
which extend through the material of the lid, and an elastomer
sealing sheet arranged below it, ready to be welded to the
underside or inner surface of the lid.
[0019] FIG. 6A is a cross-sectional view of part of the lid of a
micro-titer plate.
DETAILED DESCRIPTION OF THE INVENTION
[0020] The invention comprises certain elastomers used either alone
or as part of a laminated structure for sealing liquid containers,
in particular, for multiwell plates employed in the biological
research or pharmaceutical industries. The invention also includes
microtiter plate devices having such an elastomer-sealing
structure. As currently conceived in the most simplistic form, an
elastomer film 10 welds to the upper surface 12 of a multiwell
plate 14 to produce an integral seal of each well 16, as shown in
FIG. 1. This is achieved by selecting a material of a similar
chemical composition, or at least of a compatible composition, as
that of the plate's upper surface. Thermoplastic elastomers (TPEs)
can be welded to polymers that are similar or compatible to one of
the TPE's phases. The affinity of similar chemical materials
increases the strength of the bond between the elastomer septum and
the plate to which it is sealed.
[0021] At the present time, a large number of storage or multiwell
test plates are molded out of polypropylene (PP). A compatible TPE
such as santoprene.RTM., an elastic material that is made from
polypropylene blended with ethylene-propylene dienemethylene (EPDM)
rubber particles is well suited for sealing polypropylene plates.
Thus, a santoprene.RTM. elastomer sheet, for example, can be cut to
size and welded thermally quite easily and securely to the
polypropylene substrate. Similarly, styrene-butadiene rubber could
weld to styrene made objects. Other TPEs are
poly(ester-block-ether) and nylon-block-polyether. These TPE's, as
well as thermoset elastomers, can be joined or laminated to a film
compatible with the polymer of the plate being sealed. Silicone
materials, although usable, are not as favored as they are highly
permeable for certain applications.
[0022] Elastomers in general have low durometer hardness. By
selectively choosing materials with the appropriately low durometer
hardness and high elasticity, any perforation that is made in the
elastomer film by piercing with a syringe needle, a pipette tip, or
any other insertion will close-up again once the insertion is
removed. An elastomer material that has a durometer value of about
30-70 shore A, such as santoprene.RTM. is illustrative. A more
preferred hardness is within the range of between about 35-60 shore
A. Available from Advanced Elastomer Systems, santoprene.RTM.
deforms to accommodate the insertion, then rapidly recovers its
original shape to close the puncture, preventing either air from
outside from seeping in or vapors from within each well from
leaking out. In an embodiment of the invention, a santoprene.RTM.
sheet having a durometer value of about 55 shore A was used and
found to work well. The elastomer sheet in a relaxed,
non-compressed state will have on average a thickness of about
0.020 to about 0.130 of an inch. Certain sections of an elastomer
sheet, however, may be slightly thinner or thicker, contingent on
the type of use and the corresponding part or section of a test
plate that the sheet will cover and seal. For instance, those parts
of the elastomer sheet which engage the tops of inter-well walls of
a multiwell plate may be slightly thicker, so as to better bind
with the plate, while the parts of the sheet that are immediately
over a well opening may be thinner, to permit ease of penetration
by a syringe needle or pipette tip. This description is in no way
limiting to the invention, since the reverse may also be applicable
and a viable embodiment.
[0023] Another embodiment of the septum includes a laminated
structure in which a metal foil 18 with a polymer coating 20a, 20b
on both top and bottom sides of the foil is attached to an
elastomer sheet 10, as illustrated in FIG. 2. Some problems at this
time with existing sealing mechanisms have partly motivated our
decision to combine a polymer with a metallic foil. Previously,
seals such as sealing tapes often contaminated the samples in wells
because solvent splashing onto the under surface of pressure
sensitive adhesive leached contaminants into samples. A polymeric
material combined with a metal foil is better because it is not
extractable and can not be affected by solvents leaching. The metal
foil also acts as an effective vapor barrier to avoid gas diffusion
into or out of the well. For example of the designed function, the
properties of the elastomer-foil laminate can keep dimethyl
sulfoxide (DMSO) solvent in the wells of a multiwell plate, while
keeping water, oxygen or other gases out to prevent hydrolysis or
oxidation.
[0024] In another embodiment, a laminate of multiple layers
comprises, from top to bottom: an elastomer sheet 10, a first
polymer binder 21, a metallic foil 18, and a second polymer layer
22. This embodiment is illustrated schematically in FIG. 3. The
first polymer coating bonds the metal foil to the elastomer, while
the second polymer layer is welded to seal the laminated structure
to a storage or test plate, which is the final substrate. A heating
block, such as a platten, can be used to supply heat through the
elastomer to the surface of the well-plate so as to melt the second
polymer layer against the interface of the plate. For instance, a
santoprene.RTM. elastomer will bind to a polypropylene coating on
one side of the foil, while the same or another type of polymer
applied on the other side of the foil is left free to adhere to the
surface of the plate. So as not to deform or damage the underlying
test plate, the adhesive polymer that is selected will ideally
soften and melt at a temperature lower than that for polypropylene
compounds. Typically, a polypropylene test plate melts between
about 160.degree. C. to about 189.degree. C. Consequently, the
adhesive polymer will ideally soften or melt at a temperature at or
below about 157.degree. C. Other adhesive polymers that can be used
include any grade of polypropylene with a lower melting
temperature. Test plates made from polystyrene, which melts between
about 240-250.degree. C., can better tolerate slightly higher
temperatures.
[0025] When using a tie layer between an elastomer and test plate
surface, most ideally the tie layer will melt first, before the
test plate material starts to soften. First, the best seal is
achieved when both faces melt just enough to have physical
entanglements of the polymers. But desiring to minimize heat
exposure heat history to working biological samples contained
within, a second type of seal can be achieved when we use materials
that melt at a lower temperature to avoid plate deformation. These
kinds of materials, nonetheless, still have good sealing
properties.
[0026] A co-polymer such as Plexar.TM. may be employed to make a
hot-melt adhesive with good adhesion properties between the metal
foil and the plate. Plexar.TM. is poly(ethylene-co-maleic
anhydride), and commercially available from Equistar. The polar
maleic anhydride functionalizes the polymer to make it stick to
metal. Plexar.TM. film is mentioned specifically, as it will stick
to both metals and santoprene.RTM.. Other co-polymers that may work
to stick metal foils to the plate include materials that contain
vinyl acetate and the like. This composite structure will enhance
the sealing properties of the elastomer with the barrier properties
of the metal foil. Any monomer that has highly polar groups can
produce good adhesion.
[0027] It is envisioned that elastomer materials or polymer films
having chemical compositions that are only partially compatible
with the material of a multiwell test plate will permit us to
create releasable seals. That is, once a elastomer sheet adheres to
the test plate material, any incompatibility of the polymer film
will allow release when force is applied to pull the sheet off.
Generally, the less compatible the sheet is with the plate or lid
material the less likely the sheet will bond securely with the
plate or lid. Therefore, up to a certain point, by selectively
employing partially compatible polymers, we can more likely make
peelable seals.
[0028] In an alternative embodiment, the layers of the laminate can
comprise: an elastomer sheet, a metal foil and another polymer
layer. The polymer coating between the elastomer sheet and metal
foil can be omitted when direct lamination of the foil to elastomer
is achieved. Also, if a cross-linked elastomer is used, then the
lower layer of a laminate would need to be a thermoplastic polymer
that is compatible with or the same as the material of the
underlying microplate (such as either polypropylene or
polystyrene), since the cross-linked elastomer itself can't be
melted to form a seal. Examples of cross-linked elastomer materials
suitable for use with the invention include butyl rubbers, that
have low permeability to air, neoprene, that imparts good chemical
resistance, and other like materials, including Buna-N or better
termed as nitrile rubber (i.e.,
poly(acrylonitrile-co-1,3-butadiene)). As mentioned before,
silicone also can be used but it is least desirable. As illustrated
in FIG. 4, a cross-linked elastomer 24 having a thickness of about
0.20-0.130 inches is laminated to a thermoplastic film 26 having a
thickness that is as thin as possible, possibly about 0.001-0.004
inches. A metalic foil layer 18 could also be sandwiched between
the elastomer and thermoplastic layers to provide possibly a better
vapor barrier. Another option is to omit the foil layer entirely.
It is believed that these cross-linked variations of the present
invention can be important since these designs for a sealing septum
may be much more commercially practical. Preferred embodiments may
include, for example, the following. For sealing polypropylene (PP)
plates, a polypropylene film or compatible material is corona
treated on one side. This side is coated with a layer of partially
epoxydized polybutadiene (PolyBD 605E resin from Sartomer) with a
dissolved (1-4% prefered) cationic photoinitiator (SarCat K185 from
Sartomer). The polybutadiene then polymerizes to form a
cross-linked elastomer (like a thermoset) that is bonded to the
thermoplastic film. For sealing polystyrene plates, like that for
PP, above, except that the thermoplastic film that is corona
treated would be a polystyrene film or compatible material.
[0029] The invention is embodied by an apparatus for sealing fluid
containing vessels. In its broadest iteration, the apparatus
comprises a sheet of elastomer forming a sealing member having a
top and bottom surface, disposed on a plate containing a plurality
of wells for storing fluids, and the sealing member is
thermo-chemically bonded to the plate, wherein the elastomer has a
propensity to reseal after being punctured. The elastomer is made
of a thermoplastic polymer material. Alternatively, the elastomer
can be made of a thermosetting polymer joined or laminated to a
film having a chemical affinity to the plate's chemical
composition.
[0030] An apparatus that alternatively embodies the invention
comprises setting an elastomer material of the sealing member in a
lid 30 designed to fittingly engage a multiwell plate 14. FIGS. 5
shows a perspective view of such an apparatus. The lid 30 has
several openings 32 that conform to the arrangement of micro-titer
wells. FIGS. 5A and 5B show two variations of a partial
cross-sectional view of a micro-titer plate with a cover 34 and
elastomer seal 36 configured over one well 38. In FIG. 5A, the lid
is open 39 over the well, like as shown in FIGS. 6 and 6A. In FIG.
5B the lid is one solid piece without any holes extending through
the lid material. In FIG. 5A, the well underneath the elastomer
seal may be accessed through the elastomer with, for instance, a
syringe or pipette tip. The elastomer self-seals once the intrusion
is removed.
[0031] FIG. 6 shows an exploded, perspective view of a microtiter
plate cover or lid 30 having a top surface 40 and a descending
skirt 42 or sidewall with a plurality of holes 44, extending
through the lid material, arranged in the format of a 96-well
plate. An elastomer sealing film 10 of an embodiment described
herein is located under the lid 30. FIG. 6A is a partial cut-away
view of the lid shown in FIG. 6.
[0032] An elastomer could be either molded as part of a
polypropylene lid or welded in a secondary operation to the lid. No
glue or other polymer adhesive is employed to engage or adhere the
elastomer sheet to the lid. Rather an elastomer, like
santoprene.RTM., directly welds with the polypropylene material of
the underside of the lid or top surface of the plate. Melting at
the interface between the lid or plate and the thermoplastic
elastomer achieves the seal. Other ways of attaching the septum can
include insert molding the seal by injecting the elastomer material
onto the plate for lids that that have access openings. Variations
in the type of elastomer used are also possible so long as these
materials can directly bond with the material of the plate or
lid.
[0033] The lid is in the form of a substantially rectangular rigid
frame that has a top and bottom surface and is surrounded by a
peripheral skirt. FIG. 6 is an exploded view of another embodiment
of the present invention. The bottom of the lid holds an elastomer
sheet, which is sized to fit within the confines of the peripheral
skirt, flush against the top of a multiwell plate.
[0034] The dimensions of the lid are preferably sized such that the
outer skirt section of the frame will fit over an industry standard
96 well plate. The skirt section preferably extends perpendicularly
from the outer frame periphery. This skirt section helps to center
the frame over a multiwell plate and preferably extends
approximately 0.4 cm from the frame's top surface. Furthermore, the
skirt section serves as a suitable region for a clamping device
from an automated robotic extension to attach in order to secure
the lid to a plate, or conversely, to remove the lid from a
plate.
[0035] The size of the lid frame should be compatible with plates
that fit into PCR equipment that are currently available such as
the GENE AMP 9600 manufactured by Perkin Elmer, or the DNA ENGINE
PTC 200 made by MJ Research. Preferably, the outer dimensions of
the frame are approximately 8.5 cm.times.12.5 cm. But, not
withstanding this preference, the framed seal does not have to be
limited to use for PCR plates, rather its dimensions can be changed
to fit any multiwell plate.
[0036] The top surface of the lid has a matrix of holes extending
through it. The holes permit access to individual wells through the
elastomer sheet by means of a needle, pipette tip, or other
penetrating device. The holes in the lid are designed to correspond
to the number of wells in a corresponding microplate, i.e., 48, 96,
384, 1536, etc. Preferably the holes are arranged in a matrix of
mutually perpendicular 8 and 12 holerows for use with a 96 well
plate.
[0037] Therefore to recapitulate, our invention is an apparatus for
sealing fluid containing vessels comprising a sheet of elastomer
forming a sealing member having a top and bottom surface, and
disposed on a plate containing a plurality of wells for storing
fluids. The sealing member is thermally bonded to the plate,
wherein the elastomer has a propensity to reseal after being
punctured. In one variation, the elastomer is made of a
thermoplastic polymer material. Another way of characterizing the
elastomer is that it is made of a thermosetting polymer laminated
to a film having an affinity to the plate's chemical composition or
is laminated to a film that is compatible to said plate's
composition. In one version, the apparatus also has a film of
elastomer having a top and bottom surface, bonded to a metallic
foil on at least one of said surfaces. The foil is thermally
sealable to a multiwell test plate, wherein the elastomer and foil
together make a vapor resistant barrier. The elastomer is thermally
sealed to said test plate by means of heat bonding a compatible
polymer between said metallic foil and said test plate. Another
iteration of the invention, is an apparatus comprising a film of
elastomer having a top and bottom surface, bonded to a polymer film
on at least one of said surfaces, and the polymer film is likewise,
thermally sealed to a multiwell test plate. The elastomer and
polymer film together also make a vapor resistant barrier.
[0038] In an alternative embodiment, our invention is an apparatus
comprising a planar sealing member composed of elastic material and
disposed on a test plate having a plurality of fluid receiving
wells. A metallic foil or polymer film is adhered to the planar
sealing member. A rigid lid defined by a peripheral skirt and a top
and bottom surface having a predetermined matrix of openings with
extending through, is attached to the test plate and the openings
correspond to the wells in the plate. Alternatively, the lid has a
single large rectangular opening. The sealing member and metallic
foil or polymer film is either molded or welded to said bottom
surface, with the sealing member in direct contact with the bottom
surface, and the metallic foil or polymer film as a barrier layer
exposed toward the open wells in the test plate. The polymer film
or metallic foil is heat sealed to the plate. A polymer, that is
compatible with the plate's chemical composition, adheres the
metallic foil to the plate by thermally bonding.
[0039] The apparatus is can also be characterized by having an
elastomer made of a thermoplastic polymeric compound chosen from
the group consisting of: an elastic material that is made from
polypropylene blended with ethylene-propylene diene methylene
(EPDM) rubber particles, styrene-butadiene,
poly(ester-block-ether), or nylon-block-polyether. Alternatively,
the elastomer is made of a cross-linked polymeric compound chosen
from the group consisting of: polybutadiene, cross-linked
epoxidized polybutadiene, ethylene-propylene diene methylene
(EPDM), polyisobutylene, polychloroprene (neoprene),
cis-1,4-polyisoprene, polyurethane, nitrile rubber (Buna-N),
epichlorohydrin rubber, silicone block copolymers or silicone. More
particularly, the elastomer can be made of a polypropylene blended
with EPDM rubber particles. The elastomer can be hydrophobic. The
elastomer's lower surface has a chemical composition that is
totally compatible to form a bond with said plate's chemical
composition, thereby creating a non-releasable seal; or, the
elastomer's lower surface has a chemical composition that is
partially compatible to form a bond with said plate's chemical
composition, thereby creating a releasable seal.
[0040] The apparatus can have a base test plate made from
polypropylene or polystyrene. The compatible polymer is of a
chemically similar composition as that of said test plate. More
particularly, a specific embodiment uses a compatible polymer that
is poly(ethylene-co-maleic anhydride). The compatible polymer melts
at a lower temperature than a temperature at which said test plate
begins to deform. Hence, the heating temperature is at or below
about 165-160.degree. C., preferably about 157.degree. C. or
below.
[0041] Our invention also incorporates a method of sealing a fluid
container comprising the following steps:
[0042] a) providing a roll of film made of an elastomer having a
top and bottom surface, the bottom surface is bonded to a layer
comprising a metallic foil or a thermoplastic film that is
compatible with the polymer material of a microtiter test plate,
and a test plate having a plurality of wells located in a top
surface of said test plate; b) cutting an unrolled roll of said
elastomer film, wherein each cut piece of film corresponds with the
length and width dimensions of said top surface of said test plate,
whereby each well in said test plate is covered by said elastomer
film; c) disposing planarly said cut piece of film onto said top
surface of said test plate; d) affixing said cut piece of film to
said top surface of said test plate, whereby each well in said test
plate is covered by said elastomer film; e) applying heat to said
cut piece of film to thereby thermo-chemically bond said cut piece
of film to said top surface of test plate.
[0043] Although a preferred embodiment of the invention has been
disclosed in detail for the purpose of illustration, those skilled
in the art can appreciate that variations or modifications may be
made thereof and other embodiments may be perceived without
departing from the scope of the invention, as defined by the
appended claims and their equivalents.
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