Test plates for chemical or biochemical analyses, or sample preparation and purification, which contain a plurality of individual wells or reaction chambers, are well-known laboratory tools. Such devices have been employed for a broad variety of purposes and assays, and are illustrated in U.S. Pat. Nos. 4,734,192 and 5,009,780, 5,141,719 for example. Microporous membrane filters and filtration devices containing the same have become particularly useful with many of the recently developed cell and tissue culture techniques and assays, especially in the fields of virology and immunology. Multiwell plates, used in assays, often utilize a vacuum applied to the underside of the membrane as the driving force to generate fluid flow through the membrane. Centrifugation also can be used as the driving force. The microplate format has been used as a convenient format for plate processing such as pipetting, washing, shaking, detecting, storing, etc.
Typically, a 96-well filtration plate is used to conduct multiple assays or purifications simultaneously. In the case of multiwell products, a membrane is placed on the bottom of each of the wells, or a single membrane extends across all of the wells. The membrane has specific properties selected to separate different molecules by filtration or to support biological or chemical reactions. High throughput applications, such as DNA sequencing, PCR product cleanup, plasmid preparation, drug screening and sample binding and elution require products that perform consistently and effectively.
One such filtration device commercially available from Millipore Corporation under the name “Multiscreen®” is a 96-well filter plate that can be loaded with adsorptive materials, filter materials or particles. The Multiscreen® underdrain has been processed in such a way in order to facilitate the release of droplets. More specifically, the MultiScreen® underdrain includes a spout for filtrate collection. This spout not only directs the droplets but also controls the size of the droplets. Without this underdrain system, very large drops form across the entire underside of the membrane and can cause contamination of individual wells. Access to the membrane can be had by removing the underdrain. However, the device is not compatible with automated robotics equipment such as liquid handlers, stackers, grippers and bar code readers.
The Society for Biomolecular Screening (SBS) has published certain dimensional guidelines for microplates in response to the non-uniformity of commercial products. Specifically, the dimensions of microplates produced by different vendors varied, causing numerous problems when microplates were to be used in automated laboratory instrumentation. The SBS guidelines address these variances by providing dimensional limits for microplates intended for automation.
In embodiments where the underdrain is removable, occasionally the underdrain can disengage from one or more wells, resulting in leakage. This is more likely to occur when the buffer dries in the underdrain spout and blocks the passage of the filtrate, as the resulting build-up of pressure ultimately can cause the underdrain to “pop-off” one or more wells. In addition, if the underdrain does not sit flat against the grid or other support surface used in a vacuum manifold, local disengagement can occur upon application of vacuum, again resulting in undesirable leakage between the underdrain and the plate.
The present invention provides an underdrain design for a multiwell device that when fixed to the device (either as an integral or removable component thereof), allows for adequate venting during filtration, minimizes or prevents air lock, and has improved structural integrity. The present invention also is directed to a laboratory device designed particularly for a multiplate format that includes a plate or tray having a plurality of wells, and an underdrain in fluid communication with each of the plurality of wells. The underdrain can be a separate, removable piece, or can be an integral unitary structure with the plate or tray forming a one-piece design. The design is preferably in compliance with SBS format.
According to a preferred embodiment of the present invention, there is provided a multiwell device including a multiwell plate or tray having a porous member such as a membrane for filtration, each respective well of the device being in fluid communication with an underdrain spout through the porous member which then directs fluid draining therefrom to a collection plate or the like. The device conforms to SBS guidelines. When positioned or stacked over a collection plate with corresponding wells that register with the wells of the multiwell plate, vents are defined which vent gases from the wells out of the device upon application of vacuum. In addition, a plurality of stand-off ribs associated with each respective well are provided to provide spacing between the underdrain and the collection plate. The multiwell plate (including the underdrain as an integral or removable piece) and collection plate can be placed in a stacked relationship on a vacuum manifold to carry out filtration. Fluid flows from the wells of the multiwell plate, through the membrane, into and out of the spouts of the underdrain, and into complementary wells of the collection plate.
Turning first to
Suitable materials of construction for the multiwell device base plate/filter plate of the present invention include polymers such as polycarbonates, polyesters, nylons, PTFE resins and other fluoropolymers, acrylic and methacrylic resins and copolymers, polysulphones, polyethersulphones, polyarylsulphones, polystyrenes, polyvinyl chlorides, chlorinated polyvinyl chlorides, ABS and its alloys and blends, polyolefins, preferably polyethylenes such as linear low density polyethylene, low density polyethylene, high density polyethylene, and ultrahigh molecular weight polyethylene and copolymers thereof, polypropylene and copolymers thereof and metallocene generated polyolefins. Preferred polymers are polyolefins, in particular polyethylenes and their copolymers, polystyrenes, polycarbonates and acrylic nitrile copolymers.
In the embodiment shown, the plate 10 includes a plurality of wells 12 having an open top and a bottom having a surface to which is sealed a substrate or support 50 (
The type of porous member or membrane suitable is not particularly limited, and can include nitrocellulose, cellulose acetate, polycarbonate, polypropylene and PVDF microporous membranes, PES or ultrafiltration membranes such as those made from polysulfone, PVDF, cellulose or the like. Other suitable separation materials include depth filter media (e.g., cellulosic or glass fiber based), loose or matrix-embedded chromatrographic media (e.g., beads, frits and other porous partially-fused vitreous substances, electrophoretic gels, etc.). These materials, as well as membranes, can further comprise or be coated with or otherwise include filter aids and like additives, or other materials which amplify, reduce, change or otherwise modify the separation characteristics and qualities of the base underlying material, such as the application of target specific binding sites onto a chromatographic bead. Each well contains or is associated with its own porous member that can be the same or different from the porous member associated with one or more of the other wells. Each such individual porous member is preferably coextensive with the bottom of its respective well and extends across the opening or drain in each well.
Turning now to
The underdrain 20 has a plurality of drains 23 formed therein, each preferably centrally located with respect to a well of the base plate 10 when fixed to the plate. The drain 23 allows fluid (usually filtrate) in the well to escape the well 12 (usually after passing through the membrane 50) and potentially be collected, such as in a complementary well of a collection plate 30. The drain 23 is in fluid communication with spout 24 of the underdrain, preferably centrally located with respect to the drain 23. Most preferably, the central axis of each drain 23 is co-linear with the central axis of a respective spout 24. The spout 24 is defined by an annular wall that extends vertically downward, in the direction of fluid flow during filtration. Preferably each spout 24 extends vertically downward a distance sufficient to extend beyond the plane of the opening of a respective well of a collection plate 30 when the base and underdrain are positioned over the collection plate 30 as shown in
As best seen in
Positioned radially outwardly (relative to spout 24) of the protecting member 25 are reinforcing members 28. Preferably the reinforcing members 28 associated with each spout 24 are equally spaced and symmetrically located about the respective protecting member 25 and spout 24. In the embodiment shown, there are four arc-shaped reinforcing members 28 associated with each spout 24, although more could be used and as few as one could be used without departing from the spirit of the invention. As best seen in
As best seen in
Turning again to
This application claims the benefit of Provisional U.S. Patent Application Ser. No. 60/511,396, filed Oct. 15, 2003.
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“Whatman: Not Just Another Pretty Multiwell Plate”, Whatman Corporation Product Brochure (Date of Publication: Cannot be determined). |
Number | Date | Country | |
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20050095175 A1 | May 2005 | US |
Number | Date | Country | |
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60511396 | Oct 2003 | US |