An assay plate system to assay a cell culture model

Abstract

An assay plate system for assaying a cell culture model comprises (a) an assay plate comprising an upper surface and at least one row of wells, each well formed by a recess in the upper surface having an open top flush with the upper surface, a sidewall, and a closed transparent base, and (b) a gasket comprising a plate having a top surface, a bottom surface, and at least one elongated recesses formed in the bottom surface that together with the upper surface of the assay plate defines a fluidic conduit for the at least one row of wells when the upper surface of the assay plate and bottom surface of the gasket plate abut. The elongated recess comprises at least one projection that projects into one of the wells when the upper surface of the assay plate and bottom surface of the gasket plate abut, to modify fluid flow conditions in the well. The projection and the well are configured to provide a fluid flow path in the well all around the projection when the upper surface of the assay plate and bottom surface of the gasket plate abut.

Description

[0001] An assay plate system to assay a cell culture model

[0002] Field of the Invention

[0003] The present invention relates to an assay plate system to assay a cell culture model and especially a 3-D cell culture model such as an organoid or microtissue. Also contemplated is a method of assaying a cell culture model that employs an assay plate system of the invention.

[0004] Background to the Invention

[0005] During the process of drug discovery, test drugs need to be tested on cells to determine how they work and the effects of the drug on the cells. To date, the pharmaceutical industry has relied primarily on animal models and human cell line cultures that bear little resemblance to normal or disease human tissue, resulting in only one in every ten drugs making it through clinical testing. This high failure rate in clinical trials of drugs that make it through pre-clinical testing adds greatly to the cost of drug development.

[0006] Microtissues or organoids are tiny, self-organized three-dimensional tissue cultures that are derived from stem cells and other cell types such as primary cells. Such cultures can be crafted to replicate much of the complexity of an organ, or to express selected aspects of it like producing only certain types of cells. Organoids / microtissues may be grown from a variety of precursor cell types including stem cells — cells that can divide indefinitely and produce different types of cells as part of their progeny. Scientists have learned how to create the right environment for the precursor cells so they can follow their own genetic instructions to self-organize, forming tiny structures that resemble miniature organs composed of many cell types. Organoids / microtissues can range in size from less than the width of a hair to 5 mm. Many scientists believe that microtissues have the capacity to be more accurate and physiologically relevant models than existing animal models and that using organoids in pre-clinical testing of drugs will reduce the failure rate of drugs that enter clinical trials. These models will allow drug and vaccine manufacturers to bring products to market in a more timely and efficient manner. There is therefore a need for a technology to facilitate high throughput organoid screening that reproduces physiological conditions (e.g., temperature, CO2 and nutrients), facilitates fluid flow to the organoids, and allows organoids to be imaged.

[0007] WO 2024 / 013301 describes an assay plate system suitable for assaying in real-time cell culture models, especially 3-D cell culture models such as organoids, microtissues and spheroids, generally in a high-throughput manner. The system comprises a disposable assay plate containing one or more fluidic conduits, each having at least two or three wells, a fluid inlet conduit and a fluid outlet conduit. The wells are formed in an upper surface of an assay plate and have transparent bases allowing well contents to be imaged, and the conduits are defined by the upper surface of the assay plate, and a gasket that overlies the plate to form conduits in the plate comprising rows or columns of wells. Bringing drugs / dyes and / or cells into contact with microtissues in wells of a plate is challenging at the microfluidic level. The microtissues may move in fluid flow conditions and be lost from the region under investigation.

[0008] US2021 / 246405 describes a system for growing cell culture spheroids comprising a plate with wells, and a cover plate with protrusions that distance the cover plate from the top of the plate. The purpose is to provide a channel between the plate and cover plate which allows culture medium flow between the wells but prevents cell culture spheroids passing of the wells. The protrusions are disposed above the wells (to contact a surface of the assay plate) or are disposed between the wells.

[0009] EP3283 discloses a system for propagating cells comprising a cell growth plate with wells, and a cover plate configured to engage the cell growth plate to seal the wells. This system is a static system and is not suitable for high throughput organoid screening that reproduces physiological flow conditions. US2018 / 0142195 describes a method of creating a miniature multicellular biological construct comprises depositing cells into a pillar-microwell, exposing the pillarmicrowell to growth media, and incubating the cells. The system may include a perfusion channel chip (Fig. 7) that engages with the pillar-microwell plate to provide perfusion channels for the pillar-microwells. The microwells are disposed at the top of micropillars, and do not have a transparent base, which necessitates that the microwell plate and perfusion channel chip have to be separated to allow the biological construct to be imaged. Moreover, even if the microwells were provided with a transparent base, their position on top of micropillars would make imaging the wells from underneath extremely challenging.

[0010] It is an objective of the invention to overcome at least one of the above-referenced problems.

[0011] Summary of the Invention

[0012] The Applicant has addressed the problem of the assay plate-plus-gasket system of W02024 / 013301 by providing the gasket plate with projections configured to be received in wells of the plate when the gasket and plate are assembled together. The projections are dimensioned to be received within the wells of the plate leaving a fluid flow gap between the projection and the walls of the well to manipulate the fluid flow conditions local to the microtissue to provide flow conditions in the wells that are more physiologically relevant and, ideally, prevent movement or loss of microtissues within the wells.

[0013] Described herein is an assay plate system for assaying a cell culture model, the assay plate system comprising: an assay plate comprising an upper surface and at least one row of wells, each well comprising a recess formed in the upper surface having an open top, a sidewall, and a closed transparent base; and a gasket comprising a plate having a top surface, a bottom surface, and at least one elongated recesses formed in the bottom surface that together with the upper surface of the assay plate defines a fluidic conduit for at least one row of wells when the upper surface of the assay plate and bottom surface of the gasket plate abut, characterised in that the elongated recess comprises at least one projection configured to project into one of the wells when the upper surface of the assay plate and bottom surface of the gasket plate abut.

[0014] Typically, the open top of the well is flush with the upper surface of the assay plate.

[0015] The projection is generally dimensioned to modify fluid flow conditions in the well.

[0016] In any embodiment, the projection and the well are dimensioned to provide a fluid flow path in the well all around the projection when the upper surface of the assay plate and bottom surface of the gasket plate abut.

[0017] In any embodiment, a fluid flow gap defined between the projection and the sidewall and base of the well is about 100-3000, 500 to 1500, 700 to 1000 or 800-800 microns. The gap between the projection and the well may be the same all around the well or may differ at different positions around the well, but any differences will be within the 100-3000 micron range to ensure that the desired fluid flow conditions are obtained.

[0018] In any embodiment, the projection is centered in the well when the upper surface of the assay plate and bottom surface of the gasket plate abut.

[0019] In any embodiment, the well has an upper part and a lower part, in which the upper part has a curved conical recess shape. Typically, the lower part has a concave rounded recess shape.

[0020] In any embodiment, the projection has a proximal stem part and a distal head part.

[0021] In any embodiment, the distal head part is dimensioned to nest within the well in a spaced-apart relationship to the sidewall and base of the well. In any embodiment, the distal head part has a curved conical section.

[0022] In any embodiment, the distal head part has a distal rounded tip.

[0023] In any embodiment, the distal head part comprises a proximal flange section, wherein the system is configured such that when the when the assay plate and gasket abut, the proximal flange section is flush with and spaced-apart from the upper surface of the assay plate.

[0024] In any embodiment, a shape and curvature of the curved conical section and the distal rounded tip section match the curvature of the sidewall and base of the well.

[0025] In any embodiment, the projection is configured to reduce the effective volume of the well by at least 40%, 50% or 60% (v / v). The “effective volume” refers to the space in the well that can receive fluid when the assay plate and gasket plate are assembled.

[0026] In any embodiment, the assay plate comprises a grid array of the wells including at least three rows of wells, and the gasket plate a grid array of projections corresponding to the grid array of wells.

[0027] In any embodiment, the well has an upper part and a lower part, in which the upper part has a curved conical recess shape.

[0028] In any embodiment, the lower part has a concave rounded (ideally hemi-spherical) recess shape.

[0029] In any embodiment, the upper part of the well has a maximum width of about 1-7mm

[0030] In any embodiment, the lower part of the well has a maximum width of about 0.5 to 4mm.

[0031] The assay plate system typically comprises a cover plate configured to abut the top part of the gasket upon assembly of the assay plate system. In any embodiment, the gasket is formed from PTFE (Teflon). The use of PTFE forthe gasket has been found to be advantageous as it can be machined to allow for more accurate manufacture, it does not interact with or adsorb molecules in the plate, and it is a stiffer material that silicone allow the gasket to be more easily handled.

[0032] In any embodiment, the assay plate system comprises a second gasket configured for replacement of the (first) gasket in the assembled assay plate system, the second gasket comprising a plate having a top surface, a bottom surface, and a plurality of elongated recesses formed in the bottom surface that together with the upper surface of the assay plate define a fluidic conduit for each column of wells providing fluidic communication between the column of wells.

[0033] The provision of an assay plate system having a modular first and second gaskets allows the system to be first assembled to provide fluidic conduits on the top of the assay plate containing columns of wells before the assay plate is reassembled with the second gasket to provide fluidic conduits on the top of the assay plate containing rows of wells. As explained in further detail below, this allows the assay plate to be assembled in a cell growth / maturation configuration and then reassembled in a microtissue assay configuration.

[0034] In any embodiment, the top wall of the recesses (which form the top wall of the conduits when the system is assembled) are gas permeable and ideally liquid impermeable. The top of the recess typically has a thickness of 0.5 to 2 mm, 1 .4 to 1 .8 mm, or about 1.6 mm. When the gasket is formed from PFTE, a wall thickness of about 1 .6 mm is sufficiently thin to allow gas diffusion through the wall.

[0035] In any embodiment, the sidewalls of the recesses (which form the sides of the conduits when the system is assembled) have a height of 1 to 3 mm, 1 .5 to 2.5 mm, or about 2.0 mm.

[0036] In any embodiment, the assay plate comprises: a fluid inlet conduit for each column of wells having a first fluid inlet aperture disposed on the upper surface at a first end of each column of wells; and a fluid outlet conduit for each column of wells having a first fluid outlet aperture disposed on the upper surface at a second end of each column of wells.

[0037] The provision of a fluid inlet and outlet conduits at each end of a column of wells allows fluid to be directed along the columns of wells (for example, when growing cells into organoids).

[0038] In any embodiment, the fluid inlet conduit for each row or column of wells comprises a second fluid inlet aperture disposed on a lower surface of the assay plate at the first end of each row or column of wells.

[0039] In any embodiment, the fluid outlet conduit for each row or column of wells comprise a second fluid outlet aperture disposed on a lower surface of the assay plate at the second end of each row or column of wells.

[0040] The arrangement of the fluid inlet and outlet conduits allows assay fluids to be provided to the columns or rows of wells from underneath the plate.

[0041] In any embodiment, the assay plate system comprises a base plate comprising a central through aperture comprising a recessed shoulder that extends around a periphery of the central through aperture, in which the recessed shoulder is dimensioned to receive the assay plate. This provides an effective base for receiving the assay plate and gasket plate and retaining them in position during the assay.

[0042] In any embodiment, an upper surface of the base plate is configured for coupling to the cover plate such that when the base plate and cover plate are coupled together with the assay plate and gasket sandwiched between the base plate and cover plate, the cover plate abuts the top of the gasket plate.

[0043] In any embodiment, the recessed shoulder of the base plate is configured to allow the assay plate and gasket nest within the base plate. In any embodiment, the assay plate comprises at least 2, 3, 4, 5, 6, 7 or 8 rows of wells.

[0044] In any embodiment, the assay plate comprises at least 2, 3, 4, 5, 6, 7 or 8 columns of wells.

[0045] In another aspect, the invention provides a method of assaying a cell culture model (for example a 3-D cell culture model such as an organoid) that employs an assay plate system of the invention, comprising the steps of: placing a first cell culture model in a first well of a first assay well system; delivering a fluid comprising a test molecule to the fluidic conduit of the first assay well system so that the test molecule is incubated with the first cell culture model; and imaging the first cell culture model through the transparent base of the first well with an imaging device.

[0046] In another aspect, there is provided a method of assaying a microtissue that employs an assay plate system of the invention, comprising the steps of: placing a first microtissue sample in a first well of a first row of wells; placing a second microtissue sample in a second well of the first row of wells; optionally, placing a third microtissue sample in a third well of the first row of wells; delivering a first fluid to the fluid inlet conduit of the first row of wells so that the first fluid is incubated with each microtissue sample in the first row of wells; and imaging the wells through the transparent base of each well with an imaging device.

[0047] In any embodiment, the method comprises the steps of: delivering a second fluid to the fluid inlet conduit of the second row of wells so that the second fluid is incubated with each microtissue sample in the second row of wells; and imaging the wells of the second row of wells through the transparent base of each well with an imaging device.

[0048] In any embodiment, the method comprises the step of recirculating fluid across the wells or each row of wells.

[0049] In any embodiment, the first fluid comprises a first concentration of a first test molecule and the second fluid comprises a second concentration of the first test molecule.

[0050] Other aspects and preferred embodiments of the invention are defined and described in the other claims set out below.

[0051] Brief Description of the Figures

[0052] FIG. 1 is a perspective view of an assay plate forming part of one embodiment of an assay plate system of the invention.

[0053] FIG. 2 is a perspective view of an underside of a gasket plate forming part of one embodiment of an assay plate system of the invention.

[0054] FIG. 3A is a side elevational view of an assembled assay plate system of the invention with the top surface of the assay plate of Figure 1 abutting the underside of the gasket plate of Figure 2.

[0055] FIG. 3B is a sectional view taken along the lines A-A of Figure 3A.

[0056] FIG. 3C is a detailed view of part of the sectional view of the assay plate system of Figure 3B. Detailed Description of the Invention

[0057] All publications, patents, patent applications and other references mentioned herein are hereby incorporated by reference in their entireties for all purposes as if each individual publication, patent or patent application were specifically and individually indicated to be incorporated by reference and the content thereof recited in full.

[0058] Where used herein and unless specifically indicated otherwise, the following terms are intended to have the following meanings in addition to any broader (or narrower) meanings the terms might enjoy in the art:

[0059] Unless otherwise required by context, the use herein of the singular is to be read to include the plural and vice versa. The term "a" or "an" used in relation to an entity is to be read to refer to one or more of that entity. As such, the terms "a" (or "an"), "one or more," and "at least one" are used interchangeably herein.

[0060] As used herein, the term "comprise," or variations thereof such as "comprises" or "comprising," are to be read to indicate the inclusion of any recited integer (e.g. a feature, element, characteristic, property, method / process step or limitation) or group of integers (e.g. features, element, characteristics, properties, method / process steps or limitations) but not the exclusion of any other integer or group of integers. Thus, as used herein the term "comprising" is inclusive or open-ended and does not exclude additional, unrecited integers or method / process steps.

[0061] The cell culture model may be a 2-D or 3-D cell culture model. As used herein, the term “3-D cell culture model” refers to a miniaturized and simplified version of an organ produced in vitro in three dimensions that shows realistic micro-anatomy. Examples include organoids, microtissues and spheroids. Organoids / microtissues are derived from one or a few cells from a tissue, embryonic stem cells or induced pluripotent stem cells, which can self-organize in three-dimensional culture owing to their self-renewal and differentiation capacities. Such 3-D cell culture models typically have a maximum dimension of 50-1500 pm. Examples of 3-D cell culture model include liver, hepatic, pancreatic, epithelial, kidney, cardiac, retinal, blastoid, glioblastoma, thyroid and testicular organoids.

[0062] As used herein, the term “3-D cell culture model precursor” or “precursor” refers to a cell or composition of cells capable of being cultured to form a 3-D cell culture model. The precursor may be a cell from a specific tissue, a cell line, a patient cell or tissue sample, an embryonic stem cell, or an induced pluripotent stem cell. The assay plate system of the invention may be used to assay cell culture models such as organoids and to grow 2-D or 3-D cell culture model from precursor cells. Growth generally comprises placing a suitable precursor cell type(s) into a well, adding assay fluid (which may be cell culture fluid containing agents to promote the growth of the desired 2-D or 3-D cell culture model), and recirculation of the assay fluid to the well or wells.

[0063] As used herein, the term “assay plate system” refers to an assay plate body having assay wells suitable for assaying a 2-D or 3-D cell culture model such as an organoid. The plate generally has at least two rows of wells each row comprising at least two or three assay wells and generally a fluid inlet conduit and fluid outlet conduit. The plate includes a gasket plate to form conduits containing rows or columns of wells providing fluidic connection between the fluid inlet conduit, the wells, and the fluid outlet conduit in series, for example a PTFE gasket) This allows an assay liquid to be supplied to the each well. The plate is generally planar and the wells are generally formed in the top of the plate. The wells of the assay plate body generally have a base formed of a light transparent material that allows the wells to be imaged with an imaging system disposed under the plate. The wells are generally U-bottom wells.

[0064] The assay plate and spacer / gasket of the system of the invention are generally disposable, whereas the other parts of the system may be re-usable.

[0065] As used herein, the term “light transparent material” refers to a material that is transparent. The base of the wells is generally formed from a light transparent material allow the organoids / microtissue in the wells to be imaged with an imaging device from below the second plate. The light transparent material is generally a polymeric material suitable for melting and casting. The light transparent material may be PM MA, cyclic olefin copolymer (COC), perfluoropolyethers (PFPEs), polyurethane, Flexdym, polylactic acid (PLA) or PDMS.

[0066] As used herein, the term “well imaging system” refers to an imaging device configured to image the wells of the plate assembly, generally from a position beneath the plate assembly. Examples of imaging devices include microscopes that can undertake white light and fluorescent imaging.

[0067] As used herein, the term “Teflon” refers to polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene, however similar polymers that are liquid impermeable, gas permeable, and machinable, for example, fluorinated ethylene propylene, polychlorotrifluoroethylene, Perfluoroalkoxy alkane (PFA) and Fluorinated ethylene propylene (FEP) can be used in its place. The term “machining” has its art- recognised meaning, e.g. to reduce or finish an article by turning, shaping, planing, or milling by machine-operated tools.

[0068] Exemplification

[0069] The invention will now be described with reference to specific Examples. These are merely exemplary and for illustrative purposes only: they are not intended to be limiting in any way to the scope of the monopoly claimed or to the invention described. These examples constitute the best mode currently contemplated for practicing the invention.

[0070] Referring to the Figures, and initially to Figure 1 , an assay plate 1 forming part of an assay plate system of the invention, is illustrated. The assay plate 1 comprises a rectangular planar plate with an upper surface 2, lower surface 3, and a peripheral sidewall 4 that extends around the upper surface 2 of the plate to define a recess 5. The plate is machined from acrylic but may also be may also be made by injection moulding using polystyrene, polypropylene or cyclo-olefins. The upper surface 2 has forty wells (6) arranged as a 4x10 grid array of wells comprising ten rows of four wells each. A fluid inlet conduit 7 is disposed at a first end of each row of wells, and a fluid outlet conduit 8 is disposed at a second end of each row of wells. These conduits are flu idically connected to a fluidic system for moving fluid across the wells during use.

[0071] Referring to Figure 2, the gasket plate (or spacer plate) 10 comprises a rectangular planar plate having an underside 11 with ten elongated recesses 12. Each recess includes four projections 13 that are equally spaced-apart along the recess. The plate 10 is dimensioned to nest snugly within the recess 5 of the assay plate with each recess 12 overlying a row of four wells 6. Thus, when the gasket plate 10 nests within the recess 5 of the assay plate, the upper surface 2 of the assay plate 1 and the recesses 5 define ten conduits in the assay plate system, one conduit for each row of wells to allow movement of fluid across the wells in the row from the fluid inlet conduit to the fluid outlet conduit.

[0072] Figures 3A to 3C illustrate an assembled assay plate system of the invention, indicated generally by the reference numeral 20, with the gasket plate 10 nested snugly within the recess 5 of the assay plate 1 . Referring initially to Figure 3C, each well 6 of the assay plate 1 has a upper part 6A and a lower part 6B. The upper part 6A of the well has a curved conical recess shape with a width across the top of about 3.5 mm and a width across the bottom of about 2.5mm. The lower part 6B has a concave hemispherical recess shape with a radius of curvature of about 1mm. The well has a height of about 2.5mm. A surface of the well 6 may be coated with surface coatings such as poly-L-lysine, poly-D-lysine, gelatin, collagen, fibronectin, PVA or Pluronic.

[0073] The projections 13 of the gasket plate 10 are dimensioned such that when the gasket plate 10 nests within the recess 5 of the assay plate, the projections extend into a centre of the wells 6 of the assay plate 1 leaving a gap 19 for fluid flow between the projection and the wall of the well. A gap of about 100 to 3000 microns may be employed to modify the shape and fluid flow dynamics of the wells sufficiently to allow efficient perfusion of the wells with a test fluid without disturbing or moving a microtissue disposed within the well. The gap chosen depends on a number of variables, for example the dimensions of the wells, the type of microtissue being assayed, the type of test fluid, and the type of assay being performed. In the embodiment shown, each projection 13 has a cylindrical stem part 14 and a head part 15 having a proximal flange section 16, an intermediate curved conical section 17 and a distal rounded tip section 18. The intermediate curved conical section 17 and a distal rounded tip section 18 are dimensioned to match the curvature of the well and ensure a gap of about 850 microns between the projection and the well.

[0074] In use, the assay plate system is assembled providing ten fluidic conduits, each fluidic conduit in fluid communication with four wells containing a heart microtissue (first well), a liver microtissue (second well), a kidney microtissue (third well), and a lung microtissue (fourth well). An assay fluid is then pumped through the fluidic conduits of the base plate and the fluid inlet conduits of the assay plate to perfuse the microtissues in the rows of wells. The projections in the wells modified the fluid flow dynamics inside the wells to reduce the risk of disturbing or dislodging the microtissues from the wells while ensuring that the microtissues are adequately perfused with test fluid. This fluid exits through the fluid outlet conduits of the assay plate and the fluidic conduits of the base plate and is not recirculated. The assay plate system is configured to provide a different fluid to each row of wells. For example, a first row of wells may be provided with a fluid containing a first concentration of a first test molecule, a second row of wells may be provided with a fluid containing a second concentration of the first test molecule, a third row of wells may be provided with a fluid containing a first concentration of a second test molecule, and a fourth row of wells may be provided with a fluid containing a second concentration of the second test molecule, This fluidic system is then closed, and a fluid recirculation system (described in WO 2024 / 013301) for the ten fluidic conduits is actuated to recirculate fluid across the rows of wells to assay the effect that metabolites produced by one microtissue type has on another microtissue type.

[0075] Equivalents

[0076] The foregoing description details presently preferred embodiments of the present invention. Numerous modifications and variations in practice thereof are expected to occur to those skilled in the art upon consideration of these descriptions. Those modifications and variations are intended to be encompassed within the claims appended hereto. Reference Numerals

[0077] Assay plate 1

[0078] Upper surface 2 (of assay plate)

[0079] Lower surface 3 (of assay plate)

[0080] Peripheral sidewall 4 (of assay plate)

[0081] Recess 5

[0082] Wells 6

[0083] Upper part 6A (of well)

[0084] Lower part 6B (of well)

[0085] Fluid inlet conduit 7

[0086] Fluid outlet conduit 8

[0087] Gasket plate (or spacer plate) 10

[0088] Underside 11 (of gasket plate)

[0089] Elongated recesses 12

[0090] Projections 13

[0091] Assay plate system 20

[0092] Cylindrical stem part 14 (of projection)

[0093] Head part 15 (of projection)

[0094] Proximal flange section 16 (of head part)

[0095] Intermediate curved conical section 17 (of head part)

[0096] Distal rounded tip section 18 (of head part)

[0097] Gap between projection and well sidewall / base 19

Claims

CLAIMS:1 . An assay plate system (20) for assaying a cell culture model, the assay plate system comprising: an assay plate (1) comprising an upper surface (2) and at least one row of wells (6), each well comprising a recess formed in the upper surface having an open top flush with the upper surface, a sidewall, and a closed transparent base; and a gasket plate (10) having a top surface, a bottom surface (11), and at least one elongated recesses (12) formed in the bottom surface that together with the upper surface (2) of the assay plate defines a fluidic conduit for the at least one row of wells (6) when the upper surface of the assay plate and bottom surface of the gasket plate abut, characterised in that the elongated recess (12) comprises at least one projection (13) configured to project into one of the wells (6) when the upper surface (2) of the assay plate (1) and bottom surface (11) of the gasket plate (10) abut to modify fluid flow conditions in the well by providing a fluid flow path in the well all around the projection2. An assay plate system (20) according to Claim 1 , in which the projection (13) is configured to reduce the effective volume of the well by at least 40%(v / v) when the upper surface (2) of the assay plate (1) and bottom surface (11 ) of the gasket plate (10) abut.

3. An assay plate system (20) according to Claim 1 , in which a fluid flow gap (19) defined between the projection and the sidewall and base of the well is 100 to 3000 microns.

4. An assay plate system (20) according to Claim 3, in which the fluid flow gap (19) is about 700 to 1000 microns.

5. An assay plate system (20) according to Claim 3 or 4, in which the projection (13) is centered in the well when the upper surface of the assay plate and bottom surface of the gasket plate abut.

6. An assay plate system (20) according to any preceding Claim, in which the well (6) has an upper part (6A) and a lower part (6B), in which the upper part has a curved conical recess shape and the lower part has a concave rounded recess shape.

7. An assay plate system (20) according to Claim 6, in which the upper part (6A) of the well (6) has a maximum width of about 1-7mm and the lower part of the well has a maximum width of about 0.5 to 4mm.

8. An assay plate system (20) according to any preceding Claim, in which the projection (13) has a proximal stem part (14) and a distal head part (15), in which the distal head part is dimensioned to nest within the well (6) spaced-apart from the sidewall and base of the well.

9. An assay plate system (20) according to Claim 8, in which the distal head part (15) has a curved conical section (17) and a distal rounded tip (18).

10. An assay plate system (20) according to Claim 8, in which the distal head part (15) comprises a proximal flange section (16) , wherein the system is configured such that when the when the assay plate and gasket abut, the proximal flange section is flush with and spaced-apart from the upper surface (1) of the assay plate (2).

11. An assay plate system (20) according to Claim 9 or 10, in which a shape and curvature of the curved conical section (17) and the distal rounded tip section (18) match a curvature of the sidewall and base of the well (6).

12. An assay plate system (20) according to any preceding Claim, in which the projection is configured to reduce the effective volume of the well by at least 40%.

13. An assay plate system (20) according to any preceding Claim, in which the assay plate comprise a grid array of the wells including at least three rows of wells, and the gasket plate a grid array of projections corresponding to the grid array of wells.

14. An assay plate system for assaying a cell culture model, the assay plate system comprising: an assay plate comprising an upper surface and at least one row of wells, each well comprising a recess formed in the upper surface having an open top, a sidewall, and a closed transparent base; and a gasket comprising a plate having a top surface, a bottom surface, and at least one elongated recesses formed in the bottom surface that together with the upper surface of the assay plate defines a fluidic conduit for at least one row of wells when the upper surface of the assay plate and bottom surface of the gasket plate abut, wherein the elongated recess comprises at least one projection configured to project into one of the wells when the upper surface of the assay plate and bottom surface of the gasket plate abut, characterised in that the projection is configured to reduce the effective volume of the well by at least 50%(v / v).

15. An assay plate system for assaying a cell culture model, the assay plate system comprising: an assay plate comprising an upper surface and at least one row of wells, each well comprising a recess formed in the upper surface having an open top, a sidewall, and a closed transparent base; and a gasket comprising a plate having a top surface, a bottom surface, and at least one elongated recesses formed in the bottom surface that together with the upper surface of the assay plate defines a fluidic conduit for at least one row of18wells when the upper surface of the assay plate and bottom surface of the gasket plate abut, wherein the elongated recess comprises at least one projection configured to project into one of the wells when the upper surface of the assay plate and bottom surface of the gasket plate abut, characterised in that the projection comprises a curved conical section and a distal rounded tip having a shape and curvature that matches a shape and curvature of the sidewall and base of the well.

16. An assay plate system for assaying a cell culture model, the assay plate system comprising: an assay plate comprising an upper surface and at least one row of wells, each well comprising a recess formed in the upper surface having an open top, a sidewall, and a closed transparent base; and a gasket comprising a plate having a top surface, a bottom surface, and at least one elongated recesses formed in the bottom surface that together with the upper surface of the assay plate defines a fluidic conduit for at least one row of wells when the upper surface of the assay plate and bottom surface of the gasket plate abut, wherein the elongated recess comprises at least one projection configured to project into one of the wells when the upper surface of the assay plate and bottom surface of the gasket plate abut, characterised in that the projection is dimensioned to provide a fluid flow gap (19) of 100 pm to 3000 pm between the projection and the sidewall and base of the well when the upper surface (2) of the assay plate (1 ) and bottom surface (11 ) of the gasket plate (10) abut.

17. A method of assaying a cell culture model comprising the steps of: providing an assay plate system according to any of Claims 1 to 16 comprising a cell culture model disposed in a well of the assay plate system; delivering a fluid comprising a test agent to the well of the assay plate system so that the test agent comes into contact with the cell culture model; and imaging the cell culture model through the transparent base of the well with an imaging device.

18. A method according to Claim 17, in which the test agent is a compound, molecule or cell.

19. A method according to Claim 18, in which the test agent is an immune cell and the cell culture model is a cancer microtissue.20

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