Test plate apparatus

Abstract: A test plate apparatus is provided having at least one set of wells comprising two essentially parallel rows of wells and a central area between the wells. Each well has a first volume for housing means for effecting a fluid interaction process such as for cell growth and a second volume which permits addition or removal of liquid from the wells without disturbing the fluid interaction process.

Description: BACKGROUND OF THE INVENTION This invention relates to an apparatus suitable for promoting fluid interactions such as by growing cells in a nutrient liquid within a multiplicity of wells in a test plate. More particularly, this invention relates to such an apparatus which permits adding or removing liquid from wells in the test plate without disturbing the material such as cells within the wells. In addition, this invention also relates to a test plate for use in such apparatus. At the present time, multi-well test plates are provided wherein the wells have a circular shape and size which permits the introduction therein of a tubular member having a membrane upon which cell attachment, growth and differentiation occurs. The microporous member allows free diffusion of ions and macromolecules between cells and their apical and basolateral surfaces through a liquid medium which surrounds the tubular member and which permeates the membrane. The test plates containing the wells are rectangular and having a standard size of about 82.55 mm (3.25 inches) by 127 mm (5 inches) in order to accommodate standard analytical apparatus. Since the plate size is defined and since it is desired to avoid corners in the wells to avoid liquid stagnation areas, the wells are circular. In addition, the clearance between the interior well wall and the outside wall of the tubular member insert is minimized. The member insert is generally as large as possible to maximize the cell growth-area which leads to a lower error in the data gathering. However, a balance exists in that the basal and apical fluid volumes should be as close to equal for easy pipeting, to minimize fluid pressure between inner and outer wells and as large as possible to reduce the frequency of pipetting. This space requirement renders it difficult to insert pipetting means into the well to remove or add liquid while the tubular member is positioned within the well. The periodic removal of liquid to remove cell waste and additions of liquid to provide cell nutrients is required to maintain cell viability. In addition, cell based assay protocols require fluid manipulation. In addition, automatically controlled pipetting means cannot be used since the tubular member position is random and the probability that the pipetting means would damage the cells and pierce the membrane is high. Thus, it is presently necessary to pipette manually in order to avoid cell damage by the pipetting apparatus. This procedure is time-consuming, since it generally requires individual well treatment and is undesirable, since it may cause cell damage. Accordingly, it would be desirable to provide a test plate arrangement which permits removing or adding liquid from or to wells in the cell plate which permits the use of standard automatic pipetting means. SUMMARY OF THE INVENTION According to the present invention there is provided an apparatus for growing cells comprising a test plate having at least one set of wells, each of said set of wells comprising two essentially parallel rows of wells, each of said wells comprising a first volume and a second volume communicating with each other, hollow members having an open end and a closed end covered by a porous membrane, each member being positioned with its membrane within each well, means being provided for maintaining said member within said first volume of the well, said second volume having a shape which permits introduction of pipetting means for adding or removing liquid from said second volume. Additionally, there is also provided a test plate for use in such apparatus and comprising the features of claim 5. Preferred embodiments of the apparatus for growing cells and of the test plate for use in such apparatus are defined in the subclaims. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a top view of a test plate of the invention. Figure 2 is a cross-sectional view of the plate of Figure 1 taken along line 2-2. Figure 3 is a top view of a strip of a plurality of cell retention devices useful in the present invention. Figure 4 is a side view of the strip of Figure 3. Figure 5 is a top view of the test plate of Figure 1 with the strip of Figure 3 in place. Figure 6 is a cross-sectional view of the device of Figure 5 taken along line 6-6. Figure 7 is a cross-sectional view of a single cell retention device useful in the present invention. Figure 8 is a partial top view of the cell retention device of Figure 7 in place within a well of the plate of Figure 1. Figure 9 is a top view of cluster of wells useful in the present invention. Figure 10 is a cross-sectional view of the cluster of Figure 9 taken along line 10-10 without showing the wells. Figure 11 is a top view of various well designs useful in the present invention while accommodating the strip of Figure 3. Figure 12 is a top view of well having an extension from the well wall to restrict movement of a tubular member. Figure 13 is a side view of the well of Figure 12. Figure 14 is a top view of a well having an extension from the well floor to restrict movement of a tubular member. Figure 15 is a side view of the well of Figure 14. DESCRIPTION OF SPECIFIC EMBODIMENTS This invention is based upon the concept of providing a test plate containing a plurality of wells shaped to accommodate means for retaining cells and for allowing cell growth while permitting automatically controlled manipulation procedures to promote cell growth without adversely affecting cell growth. In addition, means are provided to maintain the means for retaining cells within a first volume of the well while permitting access to a second volume of the well with means for promoting cell growth without disturbing the growing cells. The means for positioning the cell retaining means can comprise the well shape or can comprise complementary ridge and slot means forming part of the cell retaining means and the plate. Referring to Figure 1, a plate 10 is shown for illustration purposes which includes a plurality of wells 12. The wells have a tear-drop shape comprising a circular portion cross section 14 and a triangular section 16 formed from the two converging legs 18 and 20. The tear-drop shaped wells 12 comprise a preferred form of the wells of this invention since the well is free of sharp corners where liquid can stagnate. A set of two rows of wells such as the row of six wells 22 and the row of six wells 24 are positioned so that the triangular sections such as sections 26 and 28 extend into a central portion 30 positioned between the circular portion cross section 32 and 34 of wells 12. Slots 36 are provided in the solid portions of the plate 10 between wells 12 for reasons which will be explained below. A shelf 38 can be provided in order to support a cover over the wells 12 if desired. Furthermore, an additional number of wells can be provided in area 40 if desired. Figures 3 and 4 show a unitary strip 42, including a plurality of tubular members 44 having open ends 46 and a bottom which is rendered closed by having a membrane 48 sealed thereto. The strip 42 includes a segmented ridge 50 which fits into slots 36 when the strip 42 is positioned within a row of wells 12 in plate 10 (see Figures 1 and 5). The strip 42 is provided with end ridges 52 and 54 which contact an inner surface of a well 12 at the ends of each row of wells. The slots 36, ridge 50 and end ridges 52 and 54 serve to maintain the tubular members in place within the circular portion 14 of wells 12 (see Figure 5). As shown in Figure 5, the strip 42 is positioned so that the tubular member 44 having open end 46 fits within the circular portion 14 of wells 12. Even if the ridge 50 becomes dislodged from the slots 36, the tubular members 44 cannot enter the entire triangular portion 16 of well 12 because the width of the triangular portion 16 becomes less than the outer diameter of the tubular member 44. Thus, at least a portion of the triangular section remains open and free of the tubular member 44 so that pipetting can be effected within the triangular section 12 without disturbing cells on membrane 48 within the circular portion 14. The strip 42 can be provided with a handle 56 to promote ease of positioning the tubular members 44. Alternatively, additional wells 12 can be provided in plate 10 in the area occupied by the handles 56. Referring to Figures 7 and 8, an individual tubular member 47 is shown having an open end 58 and a closed end 60. The closed end 60 comprises a membrane 55 useful for growing cells such as is disclosed in U.S. Patent 4,917,793. The membrane 55 is sealed over the entire periphery of end 60. It is preferred that the tubular member 44 (47) be transparent in order to enhance viewing of cell growth within membrane 55. In use, the closed end 60 is immersed into an aqueous growth medium in well 12 and then viable cells are introduced onto membrane 55. Spaced apart protrusions 62 are provided to space membrane 55 apart from the bottom surface of well 12 so that both the top and bottom surfaces of the cells contact the growth medium. The growth medium outside of the tubular members 44 (47) is periodically replaced with fresh growth medium by means of a pipette, which extends into triangular section 16 of well 12 without disturbing the cells or membrane 55 within tubular member 44. The media inside the tubular members 44 (47) need only be changed after the cells have attached and formed a monolayer by pipetting from inside the tubular member 44 (47). An alternative means for including a plurality of tubular members on an unitary device is shown in Figures 9 and 10. The tubular member 44 and sealed membrane 55 are arranged as a cluster of four on a common central support 64 and arms 66. The tubular members 44 fit into four adjacently-positioned wells 12. The arms 66 can be provided with a notch 68 to permit easy breakage of the tubular member 44 from the arm 66. The means shown in Figures 9 and 10 can be expanded to include additional wells, e.g. 8, 12, 16, etc., if desired. Referring to Figure 11, a plurality of differently-shaped wells are shown which are useful in the present invention. The sets of complementary wells 68, 70, 72 and 74 do not require ridges in the strips 76, 78, 80 and 82 which complement slots in the plate 10 as explained above, since the outer diameter of the tubular member 44 in these wells is less than the width of the smaller portion of these wells. The tubular portions in wells 84 and 88 do not have areas with a diameter smaller than the outside diameter of the tubular member 44. Therefore, ridges 50 in the strips 90 and 92 are provided to maintain the members 44 in a portion of the wells 84 and 88 when a pipette is not inserted. Thus the means for retaining the tubular members 44 within a given portion of the wells in plate 10 can comprise a complementary set of ridges and slots or, preferably, shaping the wells to have a portion of the wells with a diameter smaller than the outer diameter of the tubular members 44 or 47. Referring to Figs. 12 and 13, the well shape for retaining the tubular member 47 can comprise an extension 94 extending from wall 96 of well 98. The distance between the end 99 of extension 94 and the opposing portion of wall 96 in less than the outer diameter of tubular member 47 so that tubular member 47 cnnot by-pass extension 94. Referring to Figs. 14 and 15, the well shape for retaining the tubular member 47 comprises an extension extending from the floor 93 of well 95. The distance between the extension 91 and the wall 97 is less than the outer diameter of tubular member 47 so that the tubular member 47 is retained within the area shown.

Claims: Apparatus for growing cells comprising a test plate (10) having at least one set of wells (12, 68, 70, 72, 74, 84, 88, 95, 98), each of said set of wells (12, 68, 70, 72, 74, 84, 88, 95, 98) comprising two essentially parallel rows (22, 24) of wells, each of said wells (12, 68, 70, 72, 74, 84, 88, 95, 98) comprising a first volume (14) and a second volume (16) communicating with each other, hollow members (44, 47) having an open end (46, 58) and a closed end (60) covered by a porous membrane (48, 55), each member (44, 47) being positioned with its membrane (48, 55) within each well (12, 68, 70, 72, 74, 84, 88, 95, 98), means (36, 50, 52, 54, 91, 94) being provided for maintaining said member (44, 47) within said first volume (14) of the well (12, 68, 70, 72, 74, 84, 88, 95, 98), said second volume (16) having a shape which permits introduction of pipetting means for adding or removing liquid from said second volume (16). Apparatus for growing cells according to claim 1, wherein said members (44) within a row of said test plate being molded integrally. Apparatus for growing cells according to claim 1, wherein a set of said members (44) being formed integrally for positioning within adjacent wells (12, 68, 70, 72, 74, 84, 88, 95, 98) of the adjacent rows (22, 24) of wells. Apparatus for growing cells according to any of claims 1 to 3, wherein said hollow members (44, 47) are tubular. A test plate having at least one set of wells for use in the apparatus according to claim 1, 2, 3 or 4, each of said set of wells (12, 68, 70, 72, 74, 84, 88, 95, 98) comprising two essentially parallel rows of wells, each of said wells (12, 68, 70, 72, 74, 84, 88, 95, 98) comprising a first volume (14) for housing hollow members (44, 47) for effecting a fluid interaction process and a second volume (16) communicating with said first volume (14) and being formed so as to not allow entering of said hollow members (44, 47) into said second volume (16), said second volume (16) having a shape which permits introduction of pipetting means for adding or removing liquid from said second volume (16). The test plate according to claim 5, wherein said wells (12) have a tear-drop shape comprising a circular portion cross section for said first volume (14) and a triangular-like cross section (26, 28) for said second volume (16) formed from two converging legs (18, 20). The test plate according to claim 6, wherein a first well (12) from a first row in each set has a first leg positioned essentially parallel to a second leg of a second well (12) in a second row along substantially the entire length of said first leg and said second leg within a central area between said parallel rows. The test plate according to claim 5 wherein, said wells (68, 72, 74) are L-shaped having a base section and a leg section wherein said leg sections extend into a central area between said parallel rows. The test plate according to claim 5, including an extension means (94) extending from a wall (96) of each of said wells (98) to prevent said hollow members (47) from entering said second volume (16). The test plate according to claim 5, including an extension means (91) extending from a floor (93) of each of said wells (95) to prevent said hollow members (47) from entering said second volume (16).

Inventors: CLARK PHILIP, CLARK, PHILIP
Applicants: MILLIPORE CORP, MILLIPORE CORPORATION
Application year: 1991
Main classification: B01L3
IPC codes: C12M1, C12M3, B01L3