IMPROVEMENTS IN OR RELATING TO SUPPORT MEANS

Abstract: The invention is concerned mainly with chemical analysis tests in which small plastics bodies [16], such as spheres, have an adsorbed coating of reagent which reacts with a component of a solution in which the spheres are immersed. A problem with such analysis methods is that a large number of tests must be made without any con­ fusion as to what spheres have been immersed in a given solution. A support means holding and identifying a plurality of spheres comprises a plate [10] having an array of holes [12] therein; and accessible through each hole a cage-like structure [14], of helical or basket form [104], in each of which a sphere [16] is supported with mini­ mal contact, so that maximum access of solution to the spheres is provided on immersion, and optimum drain­ ing on removal of the spheres from a solution. An important use is in bio-chemical and medical assay tests, for example, in screening of large numbers of diabetes suspects through blood tests.

Description: This invention relates to supports for small objects, more especially, although not exclusively, plastics forms, eg spheres, which are coated for example with material. to react in a process of analysis with biologi.cal fluids or solution thereof. Certain chemicals, for example the globulin fraction of antiserum against alpha-fetoprotein may be absorbed or covalently bonded to solid phases such as the plastic, polystyrene. This is made use of in the determination of, for example, the concentration of aipha-fet oprotein in human blood serum. It has been usual to bring the chemical and the riid phase ont wic it is co be absorbed or covalently bonded into contact witn each #her manuaJy Typically, two different types of manual procedures have been used; either a plastics solid form has been dipped or immersed in the appropriate coating solution, or the inside su.rface of a plastics tu'oe- like container has been coated by filling with the coating solution and then emptying. The coated forms may then be used. to determine the concentration of an analyte in a sample. Teach stage of this analysis has required a manual transfer whic is time consuming, leads to poor precision; causes problems in maintaining patient identity and is expensive. Plastics forms have been supported, in solution for coating, washing, or reaction in analysis, by stems which in turn have been supported from above. From the point of view of expense and convenience in manufacture and packing, and, at least, of convenience in use, it is preferable to do away with such supporting stems and use, for example, a plain sphere as the plastics form. It has been conventional in various industries, for coating, washing or draining of objects, to support them singly, or in numbers in a perforated container, However, the problems of chemical analysis to which, in particular, plastics forms are applied, requireE minimal contact of support with plastics form. This allows maximai circulation of fluid around the plastics form, and also maximal drainage on withdrawal from the fluid It is also highly desirable that the plastics form be able to move in relation to the support In medical work, in particular, maintenance of patient identity requires that each plastics form has its own indiidual support. The present invention meets these requirements to a very large extent and provides a means for supporting plastics forms so that they may easily be inserted into apparatus, used for analysis and then removed from the apparatus According to the invention, support means for supporting more than six objects comprises a substantially planar member having more than six siting means therein; and fixed thereto, one to each siting means, cage-like structures extending from said planar member substantially normal thereto, each cage-like structure being at least constricted at its end remote from said planar member; so that in use an obJect inserted in any one of said cage-like structures1 and allowed to fall therein, is retained at the end thereof remote from said planar member. The planar member may be a subatantially flat plate, each siting member then being a hole in said plate. Conveniently each cage-like structure is tapered in diameter away from the riaflar member and may have the end thereof remote from said planar member conforming substantially in snare to chat of a g lten object required to be supported in said cagewlike etruPtwes Each. cage-*like structure is preferably a filament formed in at least one helix fixed at one end in a respective siting means and constricted at the end thereof remote from said planar member. The filament may be a metal wire, for example stainless steel, and may further be covered with a layer Of inert material, for example polytetrafluoroethylene. The heJi: may be reinforced by an external shrunk-on or moulded sleeve. The planar member may conveniently be provided with locating holes of characteristically unsymmetrical cross section to mate, in use, with pegs of a complementary shape on a coacting abutment. Alternatively the planar member may have locating pegs of characteristically unsymmetrical cross section or arrangement to mate with holes of complementary shape in an abutment. In a modified construction, each cage-like structure is a basket comprising a plurality of filaments extending from said planar member substantially normal thereto, and shaped at the end of the structure remote from said planar member so that, in use, an object inserted in such basket, and allowed to fall therein, is retained at the end thereof remote from said planar member. Each filament may be a metal wire, such as stainless stew7, and can be coated with an inert material, for example polytetrafluoroethylene or a polyurethane varnish. The invention will be further described, bg way of example only, with reference to the accompanying drawings in which Fig. 1 is a trimetric geneatal view of a support means according to the invention. Fig 2 is a scrap view of part of the support means on a larger scale Fig. 3 is a scrap view of part of the support means showing locating means for locating the support means on an abutment. Fig, 4 illustrates one optional means for rendering a part of the support means less flexible by reinforcing itv Fig. 5 illustrates a cage-like structure in the form of a basket Fig. 6 illustrates a modified basket construction The support means comprises (Fig 1) a planar member in the form of a flat plate 10 in which are a number of holes 12, of which, in this embodiment there are twenty four, although up to a hundred or more such holes may be provided. In this embodiment each hole 12 has a female thread, and each is provided with a helix 14, of which thee only are shown in Fig 1, to avoid complication of the drawing. The remaining helices are indicated diagrammatically by their centre lines. - Each complete helix is shown supporting plastic solid foiat 16 of spherical shape. A form 16 is, in uset inserted shLe: hole 12 in the plate 10 and, (the plate being horizontal) falls to the end of the helix 14; that is to say the lower or remote end. Fig 2 indicates hod the plastics solid form 16 is prevented from dropping through the lower end of the helix. Substantially the last half turn at the lower end of the helix is constricted by being sh-ed, as indicated at 18, and turned inwards, slightly towards the axis of the helix Alternatively the last half turn may be bent in to a somewhat smaller radius or curvature than the remainder of the-helix In either case the plastics form 16 is permitted to rest loosely at the lower end of the-helix, having minimal contact therewith. In this embodiment of the invention, the filament from which the helices are made is basically stainless steel wire. In order to avoid reaction with fluids used in analysis, or in coating or washing the forms 16, the stainless steel ire is provided with an inert protective surface layer. For this purpose polyurethane varnish, and polytetrafluoroethylene have been found to be adequately effective. The protective layer may be provided as a thin-walled tube slid onto the wire and sealed at the lower end; or the wire may be prated with, or d¯pper1 ln, the invert material which is then allowed to harden or set. Alternatively a filament consistin wholly of suitably inert plastics material may be used. Especially in analysis for medical diagnostic purposes it may be very important to ensure patient identity between a particular plastics form 16, or set.of such forms, and a or a set of containers of fluid of given composition. Maintenance of identity can be assisted by making the plate 10 with locating holes (20 in Fig 3) of characterically unsymlnetrical cross section, to mate with pegs 22 of complementary shape on a coacting abutment. The abutment 24 may be part of an analysis apparatus. In an alternative construction, not separately illustrated, the peg 22 may be :part of the plate 10 and the hole 20 be part of the abutment 24. So that access of fluid to a plastics form 16 may be as free as possible, the filament of which the helices 14 are constructed should be of as small cross section as practicable. This may give a helix which is too flexible, and which responds too readily to, say, currents of washing fluid; even to the extent of releasing the form 16 from the helix. It has been found that a helix made from a small cross section filament can be rendered less flexible by enclosing part of the length of the helix in a shrunk-on sleeve of heat shlinkaLle membrane, usually a plastics material, as illustrated in Fig 4, at 26. The sleeve is confined to that part of the helix (about 2/3 to 3/4 of the length) lsear to the plate 10 and av= < y iusa the part occupied hy the plastics form 16, so that circulation of f:luit arou-l said form is not substantially hindered. The sleeve can be shrunk onto the helix by application of a hot air gun; but this can give rise to excessive shrinkage, constricting the helix and making it difficult or impossible to insert a plastic form. It has been found that more consistent results can be obtained by immersing the helix and sleeve in very hot water. Alternatively the sleeve may be moulded. It may be attached to the plate 10. As already described, the helix 14 may be fixed in the plate 10 by what, in use, is its upper end, as shown in Figs 1 and 2. Alternatively the helix may be fixed in the plate 10 at an intermediate location along its length, eg at the location 28 indicated in Fig 4. If desired, the sleeve 26 may be used in fixing the helix in the plate 10, and the sleeve may also be extended to the end 30 of the helix, for easier insertion of an object 14 in said helix. The sleeve need not then necessarily be shrunk on to the helix1 but merely enclose it, since being, in use, above plate 10 it cannot slip off the helix. A modified form of cage i ke structure may be erlployeÅa. Referring to Fig 5 the planar member in the form of a plate is indicated by 100 and one of a number of holes therethrough - up to a hundred or more - is indicated by 102. The cage or basket, indicated generally by 104, is elongated, and extends from the plate normal thereto, and, in use, in a downward direction therefrom, as illustrated. The basket comprises four filaments 106, substantially parallel with one another over the greater part of their length, and mutually joined at 108, thereby supporting a spherical 'plastics form 110. The filaments 106 are fixed in the plate 100 by being made a close fit in bores, indicated by 112, in plate 100. The filaments making up the cage 104 are made of a material which will not react with any liquid in which it is required, to support the plastics forms 110. This may be done by making the filaments of a solid inert material or by covering say a metal wire with an inert coating material. Fig 6 illustrates an alternative way of fixing the basket 104 in the plate 100. Here the ends of the filaments 106 adjacent the plate 100 have en outwardly bent shape with the portions 114 substantially at right angles to the rest of the basket, so that they engage the upper surfaces in use, of the plate 100, preventing the basket from passing through the plate This conssructioil has the advantage that, if required, a basket can readily be removed wrom the plate 1000 Use of the support meats is facil-tated by constructing the cage-like structures, whether of helix - or basket-form, so as to be tap@r@@@i@ diameter away from the planar member, at least in the,portior divectl adjacent said member. This facilitates the insertion of an array of cage- like structures into a corresponding array of containers, such as test tubes, without danger of one or more structurer becoming.fouled by an adjacent container Effective drainage of liquid from the support means, after immersion of a supported object, is desirable, in that it reduces contamination by one liquid of another in which the object may subsequently be immersed. It will usually be known what size and shape of object is to be held by the support means; a very common object being a spherical bead. Liquid tends to be retained between the object and the remote end of the cage-like structure, whether of helix - or basket-form. This retention is reduced by making said remote end conform substantially In shape, eg in radius of curvature, tithe shape of the object, so that minimal. gap exists between object and structure. Controlling the speed at which the supported objects are withdrawn from immersion can also assist in reducing retention of liquid by the cage-like structures. The optimal withdrawal speed is in the order of 5 to 10 mm/sec. Surface tension at the free surface of the liquid can be assisted to remove excess liquid by making the filament or filaments of the cage-like structures intersect the liquid surface at as steep an angle as possibles in the case of the helix-form, this involves using a steep helix angle, as steep as possible consistent with not permitting a supported object to escape laterally between turns of the helix Such lateral escape can be avoided, while achieving a steep helix angle, by making the cage-like structure of two or more coaxial helices of the same diameter.

Claims: CiIMs 1. Support means for supporting more than six objects; characterised by a substantially planar member (10) having more than six siting means (12) therein; and fixed thereto one to each siting means, cage-like structures (14) extending from said planar member substantially normal thereto, each cage-like structure (14) being at least constricted at its end (18) remote from said planar member; so that in use an object (16) inserted in any one of said cage-like structures, and allowed to fall therein, is retained at the end thereof remote from said planar member (10). 2. Support means according to claim 1 characterised in that the planar member '10) is a substantially flat plate, aild each siting means (12) is a hole in sad plate. 3. Support means according to crailu 1 or claim 2 characterised in that each cage-like structure (14) is tapered in diameter away from the planar member (10). 4. 51 port means according to any one of claims 1 to 3 characterised In that the end (18) of each cage-like structure (14) remote from the planar member (10) conforms substantially in shape to that of a given object required to be supported in said cage-like structure. 5. Support means according to any one of the preceeding claims characterised in that each cage-like structure t14) is at least one helix, formed from a filament, fixed at one end in a respective siting means (12) and constricted at the end thereof remote from said planar member. 6. Support means according to any one of claims 1 to 4 characterised in that each cage-like structure is a basket (104) comprising a plurality of filaments (106) extending from said planar member substantiallynormal thereto, and shaped at the end (108) of the structure remote from said planar member so that, in use, an object (110) inserted in such basket (104), and allowed to fall therein, is retained at the end thereof remote from said planar member. 7. Support means according to -claim 5 or claim 6 characterised in that each filament is a metal wire. 8. Support means according to claim 7 characterised in that the metal is stainless steel 9. Support means according to claim 7 or claim 8 characterised in that the metal wire is covered with a layer of inert material. 10. Support means according to any one of claims 5 and 7 to 10 characterised in that the helix (14) is reinforced by an external sleeve (26). 11. Support means according to any one of the preceeding claims characterised in that the planar member (10) has locating holes (20) of characteristically unsymmetrical cross section to mate, in use, with pegs (22) of complementary shape on a coacting abutment (24). 12. Support means according to any one of claims 1 to 11 characterised in that planar member (10) has locating pegs of characteristically unsymmetrical cross section or arrangement to mate with holes of a complementary shape in a coating abutment 13. Support means according to claim 1 substantially as hereinbefore described with reference to any one of the accompanying drawings.

Inventors: BUNCE, ROGER ABRAHAM, STUDER, ROLF OTTO
Applicants: SECRETARY OF STATE FOR SOCIAL SERVICES IN HER BRITANNIC MAJESTY'S GOVERNMENT OF THE UNITED KINGDOM OF GREAT BRITAIN AND
Application year: 1981
Main classification: G01N33
IPC codes: G01N33