MICROSCOPE SLIDE AND SLIDE ASSEMBLY

Abstract: Two rectangular slides having front and rear faces are held with front faces (112, 132) facing each other. Raised end portions (122, 142) on one or both front faces abut and space the front faces by a distance (e.g., 100 to 250 µm) conductive for reversible capillary action between the slides. Raised island portions (125, 145) on one or both front faces are located at corners opposite the raised end portions. The raised island portions serve to maintain spacing between the front faces, particularly as the ends of the slides opposite to the raised end portions contact an absorbent material. An opening between the raised island portions permits liquid to enter and leave the gap (140) between the front faces.

Description: Microscope slides are typically rectangular glass objects having front and back faces or surfaces of a length (height) such as 75 mm or 3" (76.2 mm) and a width such as 25 mm or 1" (25.4 mm). Such slides are made in a variety of thicknesses such as 0.9, 1.0 or 1.2 mm. It is common to frost part or all of the front face of the slide for a variety of purposes such as enabling the user to write sample identifying information on the slide. For such frosting or other reasons, a portion of the front face may be roughened or carved into. Other portions of the front face of the slide may remain sufficiently flat to be optically clear. A partially coated slide described in US Patents Nos 4 481 246, 4 624 882 and 4 697 914 and typically sold under the SUPERFROST registered trademark has a polymeric coating of thickness under 20 microns (20 µm) at an end on the surface of the slide (e.g. the end 10 mm). In DE-A-3 630 866, there are described modified microscope slides used in a method involving capillary action. Two microscope slides are arranged with front faces or surfaces opposite and held with such faces separated by a capillary gap (e.g. of about 50 to 500 µm thickness). Such a gap is defined in some disclosed embodiments by a shim (tape or cover slip) fastened or held between the top portions of the apposite front faces. In another disclosed embodiment, the gap is defined by a coating on one of the slides. In the course of further developing slide pairs and slides for capillary action, methods based upon the invention of DE-A-3 630 866, upon which are based the prior art portions of claims 1 and 8, a problem has been recognised and overcome involving the stability of the capillary gap. The solution, as defined in claims 1 and 8, has involved a coating on one or both front slide faces near a common end (typically the top end) and island coatings on the corners of the opposite end (typically the bottom left and bottom right corners) of one or both slides of the slide pair. The total thickness of end coatings should be a thickness desirable for reversible capillary action (e.g. about 50 - 500 µm), but the total thickness of the island coatings can be either smaller, larger or (preferably) in the same range. Brief Description of the Figures Figure 1 is a front elevational view of a slide according to a first embodiment of the present invention; Figure 2 is a side elevational view of a slide assembly consisting of two slides according to the first embodiment; Figure 3A is a side elevational view of liquid being drawn into a capillary gap; Figure 3B is a side elevational view of liquid being drawn out of a capillary gap; Figure 4A is an enlarged front elevational view of a corner of a slide according to a second embodiment of the present invention; Figure 4B is a view similar to that of Figure 4A of a slide according to a third embodiment of the present invention; Figure 4C is a view similar to that of Figure 4B of a slide according to a fourth embodiment of the present invention; Figure 5 is an enlarged side elevational view of a slide pair consisting of two slides according to a fifth embodiment of the present invention. Detailed Description In Figure 1, a microscope slide 110 according to a first embodiment of the present invention is shown. The front face 112 of the slide 110 has a tissue specimen 20 centered from left to right and placed on the lower one-third of the slide 110. A top coating 122 covers a portion of the front face of the slide (e.g., the top 31.8 mm out of a total height of 76.2 mm). Small triangular coating portions or raised islands 125 cover the bottom left and right corners of the front face of slide 110. Each of these coatings are one-half the thickness of the desired gap of a slide assembly as illustrated in Figure 2 (e.g., each coating being 80 um thick to form a 160 um thick gap). The sample 20 of tissue is positioned on slide 110 below coating 122, but above both the raised islands 125 and lower edge 114 of slide 110. Representative dimensions for coating 122 are 31.8 mm high h , 25.4 mm wide w (the full width of slide 110) and 0.08 mm (80 um) thick t . Significant variations in height h and width w are permissable and, as described below, the thickness t can be 25 - 250 um. Representative dimensions for triangular coating portions 125 (raised islands) are 4 mm maximum height (along the outer left and right edges of slide 110), 4 mm maximum width (along the bottom edge 114) and 80 um thickness. Substantial variations in the height and general shape of the raised islands 125 are permissable (as described more fully below in connection with Figures 4A, 4B and 4C); nevertheless it is preferred that each raised island extend from each corner inwardly along bottom edge 114 and upwardly along a side edge of slide 110. Figure 2 is a side view of two identical slides 110 and 130 in a slide holder. Slides 110 and 130 together form a slide assembly when held together as shown in Figure 2. Top coating 122 on slide 110 abuts against identical top coating 142 on slide 130. Bottom corner coating 125 on slide 110 abuts against bottom corner coating 145 in slide 130. Slides 110 and 130 are pressed together by clips 161 and 162 which are, respectively, above and below the midpoint of coatings 122 and 142. The tops of slides 110 and 130 are received within a slot 158 of alignment strip 156 of a slide holder described in U.S. patent application U.S.S.N. 032,874 of Brigati and Cuomo, filed March 31, 1987. That slide holder provides for each row of slide pairs two alignment strips with multiple slots (e.g., ten slots in each of two alignment strips for a row of ten slide pairs) positioned to engage the two top corners of each slide pair within a slot. Divider brackets of the slide holder extend downwardly on either side of each row of slide pairs. Clips on the divider brackets (illustrated as one top clip and one bottom clip on each divider bracket, or forty clips total for a row of ten slide pairs) hold the slides in a slide pair against each other and maintain the slide pairs in parallel alignment. Referring again to Figure 2, the horizontally-extending surface of the slot 158 mantains precise vertical alignment between slides 110 and 130. For the holder described in application 032,874, slots are provided near each of the two top corners of slides 110 and 130 and side walls are provided to maintain horizontal alignment between slides 110 and 130 in a direction into the page in the view of Figure 2. In such slide holder, each alignment strip has mutliple slots (illustrated as ten) so that multiple (ten) slide pairs can be held in a fixed array. Because each of coatings 122, 125, 142 and 145 is about 80 micrometers thick, the 160 micrometer thick gap 140 is maintained, but flares out at a 45 degree angle alpha from a width wl of 17.4 mm at the lower edge to a width w of 25.40 mm at a height of 40 mm above such lower edge (see Figure 1). In use, up to thirty slide pairs (with samples on one or both slide of each pair) are inserted into the holder. The holder is then lowered onto a series of liquids, typically liquid reagents. Each liquid may be in the form of a bath or sheet, in the form of individual round droplets supported on a droplet holder (see Figure 7 of GB 2,180,647) or in the form of laterally-extending aliquots on a modified droplet holder (see Figures 3A, 3B and 3C of an application of Brigati, U.S.S.N. 032,875, filed March 31, 1987). Liquid raises by capillary action into the gap 140 between each first slide 110 and the adjacent second or facing slide 130. See Figure 3A hereof. After the appropriate time of liquid contacting sample on one or both slides, the slide assembly is then lowered on a flat blotter 72. Liquid is then drawn by capillary action into the blotter 72 so as to evacuate each capillary gap 140, as shown in Figure 3B hereof. If a droplet holder is used for the particular step, then the process can be individualized so as to treat different slide pairs with different liquids (e.g., different primary antibodies, nucleic acid probes, enzymes or chromogens). After evacuation, the slide assembly can then be contacted by another reagent in the form of droplets, laterally-extending aliquots or a sheet or bath of liquid. Looking at Figure 3A, a liquid droplet is in hole 66 through elastomeric member 64 on rigid base 62. The lower edges 114 and 134 of slides 110 and 130, respectively, contact the top of the droplet so that the lower edge 142 of gap 140 also contacts the droplet. A rising column of liquid 70 is drawn upward into the gap 140 by capillary action as described more fully in GB 2,180,647A. Looking at Figure 3B, the lower edges 114 and 134 of slides 110 and 130 contact, at the end of a treating or washing step, a blotter 72 of absorbent material. The liquid is then drawn by capillary action out of gap 140 through its lower edge 42 into blotter 72, where it forms a downwardly and outwardly spreading liquid front 74, causing the column 70 of liquid in gap 140 to fall. In the course of multiple treatment steps, the pair of slides 110 and 130 is repeatedly contacted with sources of treating liquids (some of which may be discrete droplets as in hole 66) and blotters such as blotter 72. Looking at Figures 2 and 3B, it should be appreciated that coatings 122 and 142, coupled with the rigidity of slides 110 and 130, will usually, but not always, suffice to maintain the thickness of the gap 140 between lower edges 114 and 134 constant. In particular, when lower edges 114 and 134 are pressed down into a blotter 72, the blotter 72 will tend to press edges 114 and 134 of slides 110 and 130 together. Such pressure is likely to occur when the resistance of edges 114 and 134 against blotter 72 is relied upon to stop the downward motion of the array slides as is the case with current models of Fisher Scientific Company's HISTOMATIC slide stainer, CODE-ON version, which employs a solenoid mechanism to stop downward movement when the slide array encounters a resistance. By providing raised islands 125 and 145 (as seen in Figure 2), edges 114 and 134 are prevented from coming together to close lower edge 42 of gap 140. The triangular shape of islands 125 and 145 is ideal for maintaining the spacing between lower edges 114 and 134 without islands 125 and 145 themselves sealing off any appreciable portion of gap 140 (i.e., only the outer 4 mm on each side of a 25.4 mm gap, leaving the central 17.4 mm open). During filling of the gap (as shown in Figure 2A) the rising column 70 easily broadens from the smaller width wl at lower edge 42 (17.4 mm) to the full width w (25.4 mm) at the top of islands 125 and 145 (4 mm above lower edges 114, 42 and 134). During evacuation of the gap (as shown in Figure 3B), the falling column 70 easily narrows from the full width w (25.4 mm) at the top of islands 125 and 145 to the narrower width wl (17.4 mm) at lower edge 42. The angled edge 127 of islands 125 and 145 (forming an acute angle alpha of 45 degrees with the lower edges 114 and 134, respectively) does not hold up residual liquid at the end of the evacuation step. Figure 4A illustrates a modified slide according to a second embodiment of the present invention, looking at the bottom left corner (the bottom right corner would be a mirror image). Raised island 225 is at the bottom left corner of slide 210, with its lower edge extending from the corner along lower edge 214 of slide 210. Because raised island 225 is square in shape (e.g., 4 mm by 4 mm), its bottom right side 226 forms a 90 degree angle 225a with lower edge 214, its upper left side 227 forms a 90 degree angle 225b with the left edge 211 of slide 210 and its side 227 forms another 90 degree angle 225c with side 226. When two modified slides 210 are maintained in face-to-face alignment (as with slides 110 and 130 in Figures 2, 3A and 3B), the slide pair can be used to draw in treating liquid and evacuate treating liquid into a blotter as described above. The facing islands 225 will prevent the lower end of the gap from closing and will not interfere at all with the rising column of liquid during the drawing of liquid into the gap. During evacuation, substantially all of the liquid will be evacuated from the gap (except of course that liquid which is absorbed into or adsorbed onto the sample), but some small amount of liquid may remain on top of each raised island 225 (i.e., on top of the horizontal edge 227 between angles 225b and 225c). The bottom left corner of a microscope slide 310 according to a third embodiment of the present invention is illustrated in Figure 4B. Raised island 325 extends upwardly from the lower edge 314 of slide 310. Raised island 325 has the shape (profile) of a quarter circle, with a curved edge 327 extending between point 325b on the left edge of slide 310 and point 325a on the lower edge 314 of slide 310. The convex shape of this curved portion 327 (and of the corresponding portion of the mirror-image island on the bottom right of the front face of slide 310) should enable two slides 310, when held in face-to-face alignment, to be evacuated more completely than two slides 210 (as shown in Figure 4A) when held in similar face-to-face alignment, and to be evacuated as completely, or almost as completely, as slides 110 and 130, as shown in Figures 2, 3A and 3B. Figure 4C illustrates the bottom left corner of a slide 410 according to a fourth embodiment of the present invention. The generally convex shape of the portion of raised island 425 between points 425b and 425a should facilitate complete evacuation of the gap between two face-to-face slides 410. Figure 5 illustrates, in side view, two face-to-face slides 510 and 530. The front face 512 of slide 510 extends from the top edge 518 to the bottom edge 514, with about the to 40% of front face 512 being coated by raised portion 522 (e.g., of thickness 80 um). The facing front face 532 of slide 530 extends from top edge 538 to bottom edge 534, with the top one-third of front face 532 being coated with a raised portion 542 (e.g., of thickness 80 um). Instead of having raised islands on the bottom corners of both slide 510 and slide 530, a single pair of raised islands 525 (only one of which is visible in this side view) is formed at and above the bottom edge 514 of slide 510. A gap 540 of uniform thickness g of approximately 160 um between faces 512 and 532 can be maintained by forming raised islands 525 with a thickness of 160 um rather than 80 um. It is entirely suitable, however, for raised islands 525 to be of a different thickness than the sum of the thicknesses of raised portions 522 and 542. It is also entirely suitable to have raised portion 522, raised portion 542 and raised islands 525 each be of a different thickness (such as 75 um, 100 um and 150 um, respectively) in order to facilitate the fabrication of slides 510 and 530 without materially altering the thickness g of the gap 540. In each of the various embodiments, the sum of the thicknesses of the abutting raised end portions (top coatings) may range generally between about 50 to about 500 um, but is preferably between about 75 and about 250 um, more preferably between about 100 and about 250 um and most preferably between about 100 and about 200 um. In certain cases, the preferred range is about 75 to about 200 um, especially about 75 to about 150 um, when particularly smooth glass is used and longer evacuation times are acceptable. The same ranges apply to individual slides which are to be used in conjunction with slides without raised end portions (e.g., conventional flat microscope slides). It is preferred, however, to have raised end portions on both slides in a facing pair, whose thicknesses may be the same or different. For the most common case in which facing slides have raised end portions of identical thicknesses (as would be the case if the slides were in all respects identical), the raised end portion on each slide could be about 25 to about 250 um thick, but would preferably be about 38 to about 125 um thick, more preferably about 50 to about 125 um thick and most preferably about 50 to about 100 thick. It is not necessary, however, for each raised end portion (top coating) to be of uniform thickness, with the above thickness applying to the thickest portion of the top coating on a slide, provided that it would abut the top coating, if any of the facing slide. Such thickest portion would normally comprise the majority of the area of the top coating in those cases where the top coating is not of uniform thickness. As a general rule, too much thickness produces a gap too thick to draw liquid in efficiently, while too little thickness produces a gap too thin for liquid to be easily drawn out by capillary action. The various preferred thicknesses of raised portions of individual slides and of slide assemblies are designed with this feature in mind. From a fabrication standpoint, it is easiest to form a raised portion on an individual slide of 10 to 125 um. Corresponding preferred, more preferred and most preferred ranges apply to the island portions of each slide and of the slide pair. It is suitable, however, for the facing island portions to contain less than 50 um total thickness, although this is not preferred. In general the sum of the thickness of the island portions of a slide pair should be reasonably proportioned relative to the sum of the thicknesses of the raised end portions of the same slide pair (e.g., between 66 % and 150 % of such sum) in order not to form a capillary gap that slants excessively from top to bottom. As pointed out by Figure 5, however, that reasonable proportioning of the two sums does not preclude the island portions on an individual slide being much thicker than the raised end portions on the same slide. A variety of techniques are contemplated to form both the raised portions (122, 142, 222, 322, 422 and 522 in various Figures) and the raised islands (125, 145, 225, 325, 425 and 525 in various figures) on slides. The base slide material is normally optical quality glass, but clear plastic may also be used. Optically opaque surfaces such as plastic, metal or elastomers can be used in certain applications. In the event that the raised portions and raised islands are to be formed by coating, various thermoplastic, thermosetting or resinous materials may be used and applied in the form of a paint, melt or ink. In the event that a coating process is used, one or more layers may be applied. In some forms, colors are selected for individual layers that will assist in identifying either particular slides or the front or back faces of particular slides. Thus, for example, all slides associated with a particular test could have blue and white coating layers, but the control slides could have white corner spots and the sample slides have blue corner spots. Furthermore, the frontmost coating layer that forms raised portion 122 could be blue, while the rearmost layer could be white. It is also suitable to coat the surfaces of the slides which are in contact with the capillary gap with coatings such as gelatin, albumin or serum in order to increase the rate of capillary action during both filling and evacuation of the gap.

Claims: A microscope slide assembly comprising a first substantially rectangular slide (110) having front (112) and back faces and a second substantially rectangular slide (130) having front (132) and back faces, the first and second slides (110,130) being arranged substantially in parallel in the slide assembly with the front face (112) of the first slide being adjacent to and facing the front face (132) of the second slide and with the four corners of the first slide each being adjacent to and facing a corresponding corner of the second slide (130), an end portion of one or both said slides (110,130) having a raised portion (122) such as to provide a thickness 50 to 500 pm separating the front faces (112,132) of the first and second slides (110,130), characterised in that a pair of raised islands (125) are disposed at the two pairs of facing corners of the first and second slides distal from the end portion where the raised portion is provided, each raised island (125) being separated and spaced from the raised portion (122) and from the other raised island (125). A microscope slide assembly according to claim 1, wherein the raised islands (125) are of right triangular shape and have edges substantially aligned with the edges of the first and second slides (110,130). A microscope slide assembly according to claim 1 or 2, wherein the raised portion (122) and raised islands (125) are each formed on the first slide (110). A microscope slide assembly according to claim 1 or 2, wherein each of the first and second slides (110,130) have raised portions (122,142) and islands (125,145) thereon of substantially equal thickness. A microscope slide assembly according to claim 4, wherein the thickness of the raised portions and islands on each of the first and second slides lies in the range of 38 to 125 µm. A microscope slide assembly according to any preceding claim, including means (161,162) for holding the first and second slides (110,130) in front-front facing relationship. A microscope slide assembly according to any preceding claim, wherein the raised portions and islands have a thickness to provide a separation between the slides in the range of 75 to 250 µm. A substantially rectangular microscope slide (130) having a front face (112) provided near one end thereof with a raised portion (122) having a thickness of not more than 500 µm, characterised in that a pair of raised island portions (125) are provided on the corners of the front face (112) distal from the one end, each of the raised island portions (125) being separated and spaced from the raised portion (122) and the other raised island portion (125), the raised portion (122) and the raised island (125) portions having a thickness in the range of 10 to 500 µm. A microscope slide according to claim 8, wherein the raised (122) and island (125) portions have a thickness in the range of 25 to 500 µm. A microscope slide according to claim 9, wherein the thickness is in the range of 50 to 125 µm. A microscope slide according to claim 8, wherein the raised portion (122) and the raised island (125) portions have a thickness in the range of 10 to 250 µm. A microscope slide according to claim 11, wherein the thickness is in the range of 25 to 125 µm. A microscope slide according to claim 12, wherein the thickenss is in the range of 38 to 100 µm. A microscope slide according to any one of claims 8 to 13, wherein the raised island portions each have a thickness of about 66% to about 150% of the thickness of the raised portion near one end of the slide. A microscope slide according to any one of claims 8 to 14, wherein the raised islands are of right triangular shape and have edges substantially aligned with edges of the slide.

Inventors: BABBITT, THOMAS JOHN, BRIGATI, DAVID JOHN
Applicants: ERIE SCIENTIFIC COMPANY (A DELAWARE CORPORATION), FISHER SCIENTIFIC COMPANY
Application year: 1988
Main classification: G02B21
IPC codes: G01N1, G02B21