WO2003008100A1

WO2003008100A1 - Device for simultaneous processing of discrete quantities of flowable material

Info

Publication number: WO2003008100A1
Application number: PCT/GB2002/003222
Authority: WO
Inventors: Christopher Richard Biddell; Stefan Fischer-Fruhholz; Colin Kalman Lanyi
Original assignee: Vivascience Ag
Priority date: 2001-07-17
Filing date: 2002-07-12
Publication date: 2003-01-30
Also published as: GB2377990B; GB0117394D0; GB2377990A

Abstract

A device, in the form of a multi-well plate, for simultaneous processing of discrete quantities of flowable material for the purpose of, for example, purification, concentration or extraction of target substances comprises an injection-moulded body (10) with a plurality of receptacles (12) each having an entry end opening (12a) for introduction of an individual charge of the flowable material and an exit opening (12b) for outflow of at least part of the material. A single membrane (16), for example an ion exchange or a filtration membrane, is fixed to the body (10) by bonding to close the exit openings (12b) of the receptacles and form an external face of the device. The membrane (16) is formed with individual effective zones (16a) each closing the exit opening (12b) of a respective one of the receptacles and each separated in terms of flow from the outer zones. The zones (16a) can be defined by cuts (17) extending entirely through the membrane.

Description

DEVICE FOR SIMULTANEOUS PROCESSING OF DISCRETE QUANTITIES OF FLOWABLE MATERIAL

The present invention relates to a device for simultaneous processing of discrete quantities of flowable material, especially for separating components of the material.

Separation of components of materials in liquid phase is carried out for many purposes and in many fields, including processing of very small material quantities for the purpose of purification, concentration, extraction of target substances and isolation of substances for analysis and classification. Microfiltration and other such techniques frequently involve processing large numbers of individual charges of materials of the same or different composition and the time required for carrying out such processing is an important factor in economic utilisation of industrial or laboratory equipment and skilled personnel. In the case of component separation by way of membranes with properties for ion exchange chromatography, one effective method of isolating charged compounds entails loading a small-volume receptacle or column with a quantity of liquid in which the compounds are present, spinning the column to drive the material through an ion exchange membrane at an outlet end of the column by centrifugal force and subsequently eluting compounds which have been bound in the membrane by ion exchange. If processing of multiple quantities in this manner is required, it is necessary to fill single columns individually and to individually fit the columns to and subsequently remove the columns from a centrifuge, which represents a time-consuming and repetitive task.

In order to simplify processing of multiple quantities, it is established practice to use units in the form of multi-well plates which have a number of receptacles or wells with open outlet ends covered by an ion exchange membrane. Such a unit accelerates the processing of multiple quantities of flowable materials to be purified or concentrated, but unconstrained flow of material within the membrane and consequent communication of the individual quantities with each other imposes limitations on the scope of use of the unit. The unit is unusable for processing very small amounts of material for analytical or other purposes, as losses can occur within the membrane. Communicating flow within the membrane also removes any possibility of determining the origin from the different charges of material. In the field of filtration, this difficulty is addressed by multi-well filtration units with separately produced membranes individually fixed within each well, for example as described in United States patent specification 5 116 496, but the advantages in terms of improved utility are offset by higher production cost and complication in manufacture and assembly. Production cost considerations are of particular significance in the context of mass-produced, low-value articles used in large numbers and, due to membrane contamination, discarded after single use or use for only a few separation cycles.

An advance over the use of individual membranes for the wells is represented by a multi- well plate currently on the market and utilising a single microfiltration membrane sandwiched between a first moulded body defining wells and a second moulded body defining corresponding openings. The two bodies have integral sharp-edged ridges which encircle the well outlets and corresponding openings and which under the action of ultrasound and pressure penetrate the membrane material and are fused together so as to secure the bodies to each other with the membrane clamped between. The production cost of the plate is, however, increased by the need for a second moulded body and an associated mould and the integrally moulded ridges constitute potential points of leakage if, due to a moulding fault such as gas inclusions in mould grooves defining the ridges, the ridges are improperly formed and fail to correctly mate. Location of the membrane by clamping also necessitates support, against possible displacement by fluid pressure, of the membrane zones within the fused-together ridges by support cages moulded in the openings of the second body. These cages add to production cost and increase the vulnerability of the second body to damage during mould removal and assembly.

The principal object of the present invention is therefore the provision of a device of simple and economic construction for processing discrete quantities of flowable material simultaneously, but without the risk of partial intermixing of the quantities during processing. Other objects and advantages of the invention will be apparent from the following description.

According to a first aspect of the present invention there is provided a device for simultaneous processing of discrete quantities of flowable material, comprising a body defining a plurality of receptacles each having an entry end opening for introduction of an individual charge of the flowable material and an exit end opening for outflow of at least part of the material of the introduced charge and a single membrane permanently fixed to the body to close the exit end openings of the receptacles and to form an external face of the device and acting on the material to permit throughflow of one component thereof, but to restrain throughflow of another component thereof, the membrane being formed with individual effective zones each closing the exit end opening of a respective one of the receptacles and each separated in terms of flow from the or each other effective zone.

Such a device embodies the advantages of allowing simultaneous processing of multiple charges of material by way of an economic construction with a single membrane for all the charge receptacles, with secure location of the membrane and with a minimum number of components, but overcomes the disadvantages associated with communicating flow within the membrane. In the case of processing of, for example, attomole and femtomole amounts of liquid to isolate target substances, the dispersal of substances separated from each processed charge can be confined to a small membrane zone exclusive to that charge, so that subsequent elution of the substances from the membrane may be able to be performed with a greater degree of success.

In one convenient embodiment of the device, the membrane zones are separated by cuts extending entirely through the thickness of the membrane. In production, the cuts can be applied simultaneously so that a single work step is sufficient to divide the membrane into the individual zones. The separation of the zones in terms of flow is thus provided by flow barriers resulting from, for example, excision of strip portions of the membrane by way of the cuts. The amount of membrane material removed by the cuts, i.e. width of the barriers, can be determined in dependence on the cutting technique, porosity or permeability of the membrane and other factors. Equally, however, a flow barrier can be provided by, for example, slitting the membrane material and simultaneously heat sealing the slit edges.

Preferably, each of the cuts follows the outline of the exit end opening of a respective one of the receptacles, so that each zone substantially corresponds in shape with the shape, which is preferably circular, of that opening. Each cut is preferably disposed at a predetermined spacing outwardly of the outline of that end opening, the spacing being such that attachment to the body of the portion of membrane material defining the respective zone is not compromised, but that the overall area of the zone is no larger than desired. The cuts could equally well, however, be applied in a grid arrangement.

Although cutting of the membrane represents a particularly simple method of forming the zones, other methods of separating the zones in terms of flow are possible, including treatment of rectilinear or curvilinear portions of the membrane to be substantially non- porous or non-permeable. This can be carried out by infusion of the membrane with a non-porous or impermeable substance, such as adhesive or other fluid-impermeable sealant, along tracks bounding the zones.

Depending on the shape of the exit end openings of the receptacles, the proximity of these openings to each other and the desired areas of the membrane zones, the zones can additionally be separated in terms of flow from portions of the membrane disposed between the zones.

The membrane is preferably fixed to the body by bonding, which in one advantageous embodiment can be achieved by directly moulding the body onto the membrane. This results in an intimate connection between the. materials of the body and the membrane. Alternatively, the membrane can be bonded to the body by, for example, thermal welding or by means of an adhesive.

The membrane itself can be constructed for separation of components differing with respect to at least one of composition and electrical charge, in which case the membrane can be, for example, an ion exchange, a reverse phase or an affinity membrane. Additionally or alternatively, the membrane can be constructed for separation of components differing with respect to at least one of volume and mass. Such a membrane can be a filter, including a microfilter or an ultrafilter. The membrane can have, for example, a porous or non-porous, but fluid-permeable, construction as desired.

In order to facilitate introduction of the charges of flowable material into the individual receptacles, but to minimise, if this is required, the areas of the effective zones of the membrane, the cross-sectional area of the exit end opening of each receptacle can be greater than that of the entry end opening. This can be achieved by, for example, suitably shaping each receptacle such as by providing a step or inward taper at the exit end. Utilisation of the area available within the body can be optimised by arranging the receptacles adjacent to one another in rows, the receptacles preferably having a cylindrical form to assist flow of material therethrough.

If so desired the device can include a support member secured to the body and supporting the membrane at a side thereof remote from the body, such support enabling the membrane to better withstand, for example, increased throughflow pressure resulting from subjecting the device in use to higher levels of centrifugal force. The support member can be, for example, a plate or grid structure provided with openings respectively coincident with the receptacle end openings of the body and thus with the effective zones of the membrane and can be fixed to the body by any suitable means, such as adhesive, ultrasonic welding, interference fit or mechanical fasteners.

According to a second aspect of the invention there is provided a method of producing a device in accordance with the first aspect of the invention, the method comprising the steps of producing a body defining a plurality of receptacles each having an entry end opening for introduction of an individual charge of the flowable material and an exit end opening for outflow of at least part of the material, permanently fixing a single membrane to the body to close the exit end openings of the receptacles and form an external face of the device and dividing the membrane into individual effective zones each closing the exit end opening of a respective one of the receptacles and each separated in terms of flow from the or each other effective zone.

The step of dividing preferably comprises cutting the membrane, for which purpose use of a laser cutter advantageously allows execution of precisely defined and accurately located cuts. The steps of producing the body and fixing the membrane can be conveniently carried out simultaneously by injection-moulding the body on the membrane.

An embodiment of the device and an example of the method of the present invention will now be more particularly described with reference to the accompanying drawings, in which:

Fig. 1 is a schematic perspective view from above of a device embodying the invention;

Fig. 2 is a cross-section, to an enlarged scale in relation to Fig. 1 and along the line ll-ll of Fig. 3, of part of the device, with components shown in exaggerated thicknesses for the sake of clarity;

Fig. 3 is a plan view, in the direction of arrow 111 in Fig. 2, of the part of the device shown in Fig. 2; and

Fig. 4 is an inverted plan view, in the direction of arrow IV in Fig. 2, of a part of the device similar to that shown in Fig. 3. Referring now to the drawings there is shown a device in the form of a multi-well plate for simultaneous processing of discrete quantities of flowable material, in this instance for isolating charged compounds from liquid samples by an ion exchange procedure as described further below. This represents merely one form of material processing for component separation and, depending on the particular' plate construction adopted, the device can be employed for a wide variety of tasks connected with inter alia extraction, purification and concentration.

The plate consists of an injection-moulded plate-shaped integral body 10 of a thermoplastics material, for example polypropylene or polystyrene, which is intrinsically rigid, light, low in cost, inert to organic solutions and resistant to corrosive or chemical attack by the media intended to be processed. Lightness and rigidity are provided not only by the choice of material, but also by the body design, which can combine minimum use of material in conjunction with recognised reinforcing and bracing techniques. The body 10 thus comprises a hollow frame 11 of rectangular plan surrounding a plurality of thin-walled cylindrical receptacles 12 of identical volumetric capacity appropriate to the quantity of material each receptacle is to receive for processing. Each receptacle 12 has an open entry end 12a at the top and open exit end 12b at the bottom. The cross-sectional area of the exit end 12b is preferably less than that of the entry end 12a, so as to allow restricted outflow of the material to be processed, but relatively unrestricted inflow. The reduction in cross-sectional area, which is not depicted in the illustrated simplified embodiment, can be achieved by, for example, provision of a step at the exit end.

The receptacles 12 are arranged adjacent to one another in rows to form an array of, for example, eight-by-twelve receptacles, thus a total of ninety-six. The receptacles can, however, be present in any desired number and pattern. The receptacles are connected together firstly by vertical webs 13 attached to the circumferential wall of each receptacle at four equidistantly spaced points and secondly by horizontal webs 14 which together define a planar base surface 15 interrupted by the receptacle exit ends 12b. The webs 13 and 14 additionally connect the receptacles 12 to the frame 11.

The exit ends 12b of the receptacles 12 are closed by a single rectangular membrane 16 which is permanently fixed, in particular bonded, to the body 10 at the base surface 15 so as to define an external face of the plate and which consists of, for example, a sheet of regenerated cellulose with a reinforcing weave of polyester. The cellulose sheet defines a matrix in which positively or negatively charged functional groups such as sulphonic acid or quaternary ammonium have been covalently bound to provide an anion exchanger or a cation exchanger for binding, by electrostatic interaction, oppositely charged components of materials processed by the device, i.e. flowable materials introduced into the receptacles 12. This form of membrane is merely one of various possibilities for component separation, but it is common to all membranes that each of the material quantities to be processed has to flow at least partially into the membrane, with at least one component of the material passing entirely through the membrane and at least one component restrained from passing through by retention within the membrane (as in ion exchange) or by being checked at the inflow or upstream surface of the membrane. In the case of a single membrane closing the exit ends of all receptacles, the difficulty arises that communicating flow of material from the different receptacles is possible within the membrane, with the result that components from the individual material charges are intermixed. This precludes accurate assessment of the origin of subsequently eluted isolated components. Moreover, the diffusion of isolated components within the membrane can render recovery problematic or impossible in the case of extremely small component sizes, i.e. the components remain bound in the membrane matrix. This difficulty is avoided by forming the membrane 16 with individual effective zones 16a each associated with the exit end 12b of a respective one of the receptacles 12 and each separated in terms of flow from the other effective zones. The zones 16a are each defined by a circular cut 17, for example of a width of about 0.25 millimetres, passing entirely through the membrane 16 and following a circular path around, but at a small spacing outwardly of, the exit end 12b of the respective receptacle. The width of the cut 17, by which a narrow strip portion of the membrane material is excised, is sufficient to form a flow barrier at the perimeter of each zone 16a and thus prevent an undesired communicating flow to other zones or, as in the case of the illustrated example, the residual membrane material between the zones. The spacing of the cut 17 from the boundary of the exit end 12b of the associated receptacle is kept to a minimum, but remains sufficient to ensure adhesion of the membrane material defining the zone to the base surface 15 of the body 10 at least for the expected service life of the device.

Production of the device can be undertaken in particularly economic manner by injection moulding the plate body 10 directly onto the membrane 16, for which purpose the latter can be placed on a support surface in a mould defining the shape of the plate and the constituent thermoplastic material for the body 10 then injected into the mould to enter into intimate connection with the membrane 16 by penetration into the pores of the membrane matrix. Laser cutting of the membrane, i.e. thermal destruction of the membrane material along the track of a laser beam, to define the cuts 17 and thus form the zones 16a can be carried out in an automated process with computer-controlled guidance of the beam. Cutting in this manner results in particularly accurately dimensioned zones. The width of the cuts can be determined by setting the focus of the beam, which is preferably a low- power beam. The zones can, however, be separated from one another by other methods, such as application of adhesive penetrating into and sealing the membrane matrix along paths corresponding to the cuts. A device of this construction has a minimum number of components, i.e. moulded body and membrane, and thus can be produced at low cost compatible with a product intended for single use or use only a small number of times before discard.

In use of the device, by way of example, for charged compound separation from liquid samples, for example isolation of proteinaceous compounds for analysis and classification, the receptacles 12 are charged with the samples and sealed at their open ends 12a. The plate 10 is spun in a centrifuge at appropriate speed and for a given time to drive the material of the samples through the membrane zones 16a and into a collector communicating with the membrane at its face remote from the receptacles. Depending on the choice of membrane, in particular binding capacity and charged functional group, the target compounds are retained in the membrane matrix by anion or cation exchange and can subsequently be recovered by elution with a suitable eluting solution. The detailed procedures for such an ion exchange procedure, including sample prefiltration, equilibration of the membrane and washing, are well-known and do not require further description. The division of the membrane 16 into discrete effective zones 16a individually associated with the receptacles allows simultaneous processing of as many samples as receptacles are provided - 96 in the present example - but without risk of intermixture of separated compounds originating from different samples and without losses due to escape of compounds within the membrane matrix into regions incapable of sufficient interaction with the eluting agent.

Claims

1. A device for simultaneous processing of discrete quantities of flowable material, comprising a body defining a plurality of receptacles each having an entry end opening for introduction of an individual charge of the flowable material and an exit end opening for outflow of at least part of the material of the introduced charge and a single membrane closing the exit end openings of the receptacles and acting on the material to permit throughflow of one component thereof, but to restrain throughflow of another component thereof, the membrane being formed with individual effective zones each closing the exit end opening of a respective one of the receptacles and each separated in terms of flow from the or each other effective zone.

2. A device as claimed in claim 1 , wherein the zones are separated by cuts extending entirely through the thickness of the membrane.

3. A device as claimed in claim 2, wherein the cuts are of such a width as to excise strip portions of the membrane.

4. A device as claimed in claim 2 or claim 3, wherein each of the cuts follows the outline of the exit end opening of a respective one of the receptacles.

5. A device as claimed in claim 4, wherein each of the cuts is disposed at a predetermined spacing outwardly of the outline of the exit end opening of the respective receptacle.

6. A device as claimed in claim 1, wherein the zones are separated by linear portions of the membrane treated to be substantially non-porous or non-permeable.

7. A device as claimed in claim 6, wherein the treated linear portions are produced by infusion of those portions with a non-porous or impermeable substance.

8. A device as claimed in claim 7, wherein the substance is an adhesive.

9. A device as claimed in any one of the preceding claims, wherein the zones are additionally separated in terms of flow from portions of the membrane disposed between the zones.

10. A device as claimed in any one of the preceding claims, wherein the membrane is bonded to the body.

11. A device as claimed in claim 10, wherein the membrane is bonded to the body by moulding of the body on the membrane.

12. A device as claimed in claim 10, wherein the membrane is bonded to the body by thermal welding.

13. A device as claimed in claim 10, wherein the membrane is bonded to the body by means of adhesive.

14. A device as claimed in any one of the preceding claims, wherein the membrane is constructed for separation of components differing with respect to at least one of composition and electrical charge.

15. A device as claimed in claim 14, wherein the membrane is an ion exchange or reverse phase membrane.

16. A device as claimed in any one of the preceding claims, wherein the membrane is constructed for separation of components differing with respect to at least one of volume and mass.

17. A device as claimed in claim 16, wherein the membrane is a filter.

18. A device as claimed in any one of the preceding claims, wherein the cross- sectional area of the exit end opening of each receptacle is greater than that of the entry end opening of that receptacle.

19. A device as claimed in any one of the preceding claims, wherein the receptacles are arranged adjacent to one another in rows.

20. A device as claimed in any one of the preceding claims, wherein the receptacles are cylindrical.

21. A device as claimed in any one of the preceding claims, comprising a support member secured to the body and supporting the membrane at side thereof remote from the body.

22. A method of producing a device as claimed in claim 1, comprising the steps of producing a body defining a plurality of receptacles each having an entry end opening for introduction of an individual charge of the flowable material and an exit end opening for outflow of at least part of the material, permanently fixing a single membrane to the body to close the exit end openings of the receptacles form an external face of the device and dividing the membrane into individual effective zones each closing the exit end opening of a respective one of the receptacles and each separated in terms of flow from the or each other effective zone.

23. A method as claimed in claim 22, wherein the step of dividing comprises cutting the membrane.

24. A method as claimed in claim 23, wherein the cutting of the membrane is carried out by a laser cutter.

25. A method as claimed in any one of claims 22 to 24, wherein the steps of producing and fixing are carried out simultaneously by injection-moulding the body on the membrane.