Abstract
A bioreactor (1) for the culture of cells (C) comprising a stack of carriers (7) for cell (C) adherence and liquid medium (M) distribution. The carriers (7) are stacked so as to define levels (6) between adjacent carriers (7) for the flow of the liquid medium (M). Adjacent levels (6) are fluidly interconnected via open spaces (2) so that the liquid medium (M) can flow from one level (6) to an adjacent level (6). The open spaces (2) between a first and an adjacent second level (6′) do not overlap with the one or more open spaces (2) between the second level (6′) and an adjacent third level (6″). One or more of the carriers may also include an area adapted to prevent cell adhesion or growth, thereby allowing for the viewing of cell growth on adjacent carriers from a vantage point external to the bioreactor. Related methods are also disclosed.
Claims
1.-122. (canceled)
123. A bioreactor for use in culturing cells, comprising: a plurality of carriers, each of the plurality of carriers having a first area adapted for cell adherence, and at least one of the plurality of carriers having a second area adapted for preventing cell adherence; and a piece of optically transparent material associated with each of the at least one of the plurality of carriers having the second area, the piece of optically transparent material positioned in a space between adjacent carriers such that the space is completely filled to provide a substantially continuous optical path from an external vantage point through the plurality of carriers to a desired area of cell growth in one of the plurality of carriers.
124. The bioreactor according to claim 123, further comprising a second piece of optically transparent material associated with each of the at least one of the plurality of carriers having the second area, the piece of optically transparent material positioned in a space between adjacent carriers such that the space is completely filled to provide a second substantially continuous optical path is created to a second desired area of cell growth in one of the plurality of carriers.
125. The bioreactor according to claim 123, wherein the second area adapted for preventing cell adherence is hydrophobic.
126. The bioreactor according to claim 123, further including a single housing for receiving the plurality of carriers.
127. The bioreactor according to claim 123, wherein the plurality of carriers include stackable trays or cubes.
128. The bioreactor according to claim 123, wherein the second area for preventing cell adherence constitutes a window.
129. The bioreactor according to claim 123, wherein each of the plurality of carriers includes a separate inlet.
130. The bioreactor according to claim 123, wherein each of the plurality of carriers includes open spaces configured to ensure the most desirable flow of fluid, oxygen, and nutrients to layers of cells formed on the plurality of carriers.
131. A bioreactor comprising a stack of carriers and an optically transparent solid material positioned in a space between adjacent carriers and completely filling said space such that an optically transparent path is created from a vantage point external to the bioreactor through at least one carrier to one or more inner carriers.
132. The bioreactor according to claim 131, wherein a cell growth area is on a surface of the one or more inner carriers.
133. The bioreactor according to claim 132, wherein the optically transparent solid material is associated with each of the at least one carrier stacked on top of the one or more inner carriers, but not the one or more inner carriers.
134. The bioreactor according to claim 133, wherein the optically transparent solid material prevents cell growth on an area of each of the at least one carrier for which said material is associated.
135. The bioreactor according to claim 131, wherein the stack is vertical.
136. A method for viewing growth of cells in a cell culture device from an external vantage point, comprising: providing a stack of carriers C.sub.a . . . C.sub.n forming the cell culture device; generating a surface area on each carrier C.sub.a . . . C.sub.n−1 wherein cells do not grow; creating an optically transparent line of sight from the external vantage point to carrier C.sub.n through carriers C.sub.a . . . C.sub.n−1; and viewing an area of cell growth on carrier C.sub.n.
137. The method according to claim 136, wherein the cell culture device is a bioreactor.
138. The method according to claim 136, wherein the viewing step includes utilizing a microscope.
139. The method according to claim 136, wherein the generating step includes utilizing a chemical treatment to prevent cell adherence or growth on the surface area of each carrier C.sub.a . . . C.sub.n−1.
140. The method according to claim 136, wherein the generating step includes utilizing an optically transparent material associated with each carrier C.sub.a . . . C.sub.n−1 but not carrier C.sub.n.
141. The method according to claim 140, wherein the utilizing step includes completely filling a space between adjacent carriers with the optically transparent material.
142. The method according to claim 136, further including the steps of: generating a second surface area on each carrier C.sub.a . . . C.sub.n−3 wherein cells do not grow; creating a second optically transparent line of sight from another external vantage point to carrier C.sub.n−2 through carriers C.sub.a . . . C.sub.n−3; and viewing a second area of cell growth on carrier C.sub.n−2.
Description
BRIEF DESCRIPTION OF THE FIGURES
[0115] The bioreactor according to the invention will be further elucidated with reference to the figures, in which:
[0116] FIG. 1 shows a diagrammatical view of a bioreactor provided with an external circulation system, according to an embodiment of the disclosure;
[0117] FIG. 2 shows a diagrammatical cross-sectional view of a bioreactor comprising a circulation system integrated in the bioreactor according to an embodiment of the disclosure;
[0118] FIG. 3 shows a diagrammatical top view of a carrier according to a design for use in a bioreactor according to an embodiment of the disclosure;
[0119] FIG. 4 shows a diagrammatical top view of a carrier according to a design for use in a bioreactor according to an embodiment of the disclosure;
[0120] FIG. 5 shows a diagrammatical top view of a carrier according to a design for use in a bioreactor according to an embodiment of the disclosure (left); it also shows a graph showing that the overall surface area (A) covered by the open space in the carrier increases faster with increasing radial distance (D) to the geometrical center of the carrier;
[0121] FIG. 6 shows a diagrammatical top view of a carrier according to a design for use in a bioreactor according to an embodiment of the disclosure;
[0122] FIG. 7 shows a diagrammatical top view of a carrier according to a design for use in a bioreactor according to an embodiment of the disclosure;
[0123] FIG. 8a-8c shows figures for explanation of the flow in a bioreactor according to embodiments of the disclosure;
[0124] FIGS. 9 and 10 show diagrammatical cross-sectional views of further embodiments of the disclosure wherein the bioreactor comprises carriers including a non-perpendicular angle relative to the principal direction in the bioreactor;
[0125] FIGS. 11 and 12 show diagrammatical cross-sectional views of further embodiments of the disclosure wherein the bioreactor comprises carriers including a non-perpendicular angle relative to the principal direction in the bioreactor;
[0126] FIGS. 13a-13a show a method according to an embodiment of the second aspect of the disclosure;
[0127] FIG. 14 shows a diagrammatical cross-sectional view of a bioreactor according to an embodiment of the disclosure;
[0128] FIG. 15 shows a diagrammatical top view of a carrier according to a design for use in a bioreactor according to an embodiment of the disclosure;
[0129] FIG. 16 shows a perspective view of a carrier according to a design for use in a bioreactor according to an embodiment of the disclosure;
[0130] FIG. 17 shows a diagrammatical top view of a carrier according to a design for use in a bioreactor according to an embodiment of the disclosure (left); it also shows a graph showing that the overall surface area (A) covered by the open space in the carrier increases faster with increasing radial distance (D) to the geometrical center of the carrier;
[0131] FIG. 18 shows a cross-sectional view of the edge of a stack of carriers for use in an embodiment of a reactor according to the disclosure.
[0132] FIG. 19 shows a perspective view of a stack of carrier according to an embodiment of the disclosure.
[0133] FIGS. 20-26 relate to a bioreactor according to an embodiment of the disclosure.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0134] The disclosure will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention. It should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.
[0135] Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.
[0136] Furthermore, some of the embodiments are described herein as a method or combination of elements of a method that can be implemented by a processor of a computer system or by other means of carrying out the function. Thus, a processor with the necessary instructions for carrying out such a method or element of a method forms a means for carrying out the method or element of a method. Furthermore, an element described herein of an apparatus embodiment is an example of a means for carrying out the function performed by the element for the purpose of carrying out the invention.
[0137] In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.
[0138] FIG. 1 shows a diagrammatical view of a first embodiment of the bioreactor according to the invention. The bioreactor 1 is provided with a first side 11 and an opposite second side 12. A stack of carriers 7, which are preferably, is present in the bioreactor 1. The carriers are stacked along a principal direction P extending from the first side 11 to the second side 12. The carriers 7 are provided with open spaces (not shown). The bioreactor 1 of this embodiment is provided with an external circulation system 30. The external circulation system 30 comprises a medium storage tank 32 that is coupled to the bioreactor 1 through tubes 36. An external pump 33 is present for enabling flow of medium through the bioreactor 1. Medium flowing through the tubes enters the bioreactor 1 at inlet port 21 on the first side 11 of the bioreactor 1. It passes each carrier 7 within the bioreactor 1 through the open spaces therein, and then leaves the bioreactor at outlet port 22 on the second side 12 of the bioreactor 1. The medium storage tank 32 is in this example provided with a filter 34 for gas exchange and with means or transporter 35 for addition of components. The means 35 may be embodied as a tube, but could alternatively be embodied as means for addition of components in solid form. While the medium storage tank 32 is shown here in a typical laboratory implementation, e.g., a beaker glass, it will be clear that implementations of larger scale are not excluded. While the medium storage tank 32 is shown here to be coupled to a single bioreactor 1, it is not excluded that it is coupled to a plurality of bioreactors 1, suitably arranged in parallel. Though not shown, it is preferred that the composition and physical conditions of the bioreactor 1 are monitored. Hereto, sensors may be present inside the bioreactor. Alternatively, composition and physical conditions of the external circulation system may be monitored, for instance between the outlet port 22 of the bioreactor 1 and the medium storage tank 32. A separate sensing vessel may be foreseen for this. Typical conditions to be measured include the pH, the temperature, the oxygen and CO.sub.2 content of the medium, the amount of biological material, and/or the effective flow rate.
[0139] FIG. 2 is a cross-sectional diagrammatical view of a second embodiment of the bioreactor 1. The embodiment shown here is a bioreactor in which a circulation system is integrated. In this example the reactor is provided with a lower cavity 3, an upper cavity 4 and a fluid channel 5 extending between the lower and upper cavity 3, 4 along the principal direction P of the bioreactor 1. The fluid channel 5 is in the example shown here a columnar channel located in the center of the bioreactor 1, which is preferably of cylindrical shape. The carriers 7 are stacked along the same direction. The stacking occurs in one embodiment by means of mechanical connections defining the side wall of the columnar channel 5. These mechanical connections may fix the orientation of each carrier in the stack, but alternatively may leave freedom for independent rotation of each of the carriers. Clearly, it is by no means excluded that the stack of carriers including the columnar channel could be manufactured as one piece, for instance by means of a moulding process, and/or that adhesive or mechanical fixtures (screw or the like) are used for fixing portion of the stack. However, separate manufacture of the carriers has the advantage that the stack becomes modular, so as to be made larger or shorter dependent upon the intended use and needed conditions.
[0140] Preferably, as shown in this FIG. 2, the columnar channel 5 does not have connections to individual levels 6 extending between adjacent carriers 7 in the bioreactor 1. This has the advantage that the columnar channel 5 may be used as a mixing and dissolution vessel. In this example, the bioreactor 1 is provided with several ports 13, 14, 15, e.g., a filter 13 for gas exchange, a port 14 for the addition of liquid components, in particularly a solvent, solution, suspension, dispersion, and a port 15 for the addition of gaseous components, for instance air, oxygen or CO.sub.2. Particularly any bubbles 16 resulting from the addition of gaseous components are better prevented from entering the levels 6 between the carriers 7. The bioreactor 1 is provided with an impeller 9 for stirring the medium. The impeller is typically, and particularly in laboratory versions of the present bioreactor 1, a magnetic impeller. However, a mechanically driven impeller is not excluded.
[0141] This impeller 9 is further responsible for providing the flow of medium through the bioreactor. However, if desired, a separate pump may be used to control and drive such flow. The impeller 9 may be provided in the lower cavity 3, at the end of the columnar channel 5. It is observed that the lower cavity 3 may be separated from the columnar channel by means of a wall having one or more apertures, i.e., access ports for the medium. Such separation allows that the flow in the columnar channel 5 is more vigorous than in the levels 6 of the reactor 1. In such a manner both an appropriate mixing and an appropriate flow rate for the cells may be achieved.
[0142] The bioreactor 1 of this embodiment is provided with at least one inlet port 21 at its first side. This inlet port 21 is primarily intended for filling and emptying of the reactor. However, it is by no means excluded that this inlet port 21 forms the port to an external circulation system that is used in addition to the internal circulation system. In such case, typically, at least one outlet port is present on the second side 12 of the reactor. If desired, the inlet port 21 and such outlet port 12 may be reversed.
[0143] As shown in FIG. 2, the inlet ports 13-15 are suitably present in the upper cavity 4. This cavity 4 further leaves space for sensors 23. It will be understood by the skilled person that the bioreactor 1 is at its second side 12 preferably closed so as to maintain physical conditions in the best probable manner.
[0144] FIGS. 3 to 7 show a plurality of diagrammatical top views of the different embodiments of the carrier 7 in accordance with the inventions. All these embodiments show circular carriers 7 with open spaces 2 that are provided along several lines from the center 17 of the carrier 7 to its edge 18 so as to include rotational symmetry. It is however by no means excluded that the carriers 7 may have another shape. It is moreover not excluded that the open spaces 2 are oriented along circles at around the center 17 rather than on radial lines. The carrier comprises open spaces 2 and solid carriers 27.
[0145] FIGS. 3 and 5 show embodiments based on hole-shaped open spaces 2. FIGS. 4, 6 and 7 show embodiments based on groove-shaped open spaces 2, wherein grooves extend substantially from the center 17 to the side edge 18. Though not shown, the groove-shaped open spaces and the hole-shaped open spaces may be combined into a single carrier 7 design. Though not shown, the groove-shaped open spaces may be subdivided into a series of trench-shaped open spaces and the hole-shaped open spaces may be widened to get such trench-shaped open spaces.
[0146] FIGS. 3 and 4 show embodiments in which the surface area of the open space 2 is independent of the distance to the center 17. FIGS. 5 and 6 show embodiments in which the overall surface area covered by the open spaces 2 in at least one of the carrier 7 increases faster with increasing radial distance to the geometrical center of the carrier 7. FIG. 6 shows a preferred embodiment in which the surface area of the open spaces 2 increases with the distance to the center 17.
[0147] FIG. 5 shows thereof an implementation in which the density of open spaces 2, each of uniform size, increases with increasing radial distance to the center, e.g., by reduction of the spacing between individual open spaces 2.
[0148] FIG. 6 shows an implementation in which the width of the open spaces 2 increases with the distance to the center 17.
[0149] FIG. 7 shows a specific embodiment, in which the fluid interconnects 2 are defined so as to follow rotational movement of the medium in the bioreactor 1, which rotational movement is generated by a pumping system
[0150] FIGS. 8a-8c demonstrate the flow in the bioreactor in accordance with one embodiment of the invention. For ease of representation, an implementation is shown here, in which the open spaces 2 in a first carrier 7 are laterally, e.g., rotationally displaced with respect to the open spaces 2 in an adjacent second carrier 7. FIG. 8a herein discloses the flow on a microscale, while FIG. 8c discloses the flow on a macroscale. FIG. 8b illustrates the microscale in further detail. It will be clear that even though the flow on macroscale is along the principal direction P of the bioreactor 1, it includes on microscale a major component 10 extending laterally. FIG. 8b shows hereof a detailed view clarifying that effectively the flow is primarily lateral instead of primarily vertical. This is achieved through design, e.g., design of the width of the level 6, the size and density of the open spaces 2.
[0151] FIGS. 9 and 10 is a cross-sectional diagrammatical view of other embodiments of the bioreactor 1. The bioreactors 1 of these third and fourth embodiments are quite similar so that they will be discussed together. In these embodiments, the stack of carriers 7 is of conical shape, i.e., each of the carriers comprises at least a portion that includes a non-perpendicular (i.e., oblique) angle to the principal direction of the bioreactor. One advantage of such conical shape is that it simplifies bubble elimination between individual carriers. Furthermore, emptying and harvesting of the reactor is improved as the risk of forming puddles when emptying the reactor is avoided. While typically only one side of a carrier 7 is used for cell adhesion, it is not impossible that both sides of the carrier 7 are used for cell adhesion. One implementation thereof is the use of an impeller both in the upper cavity and the lower cavity (see FIG. 14). The orientation of the bioreactor may then be reversed. This allows that in a first operation cells are inserted and are allowed time to settle on a first carrier. Thereafter, the reactor orientation is reversed, and further cells are inserted (if needed) are allowed time to settle on the second carrier.
[0152] FIG. 13a-g shows a procedure for using both sides of each carrier in a bioreactor according to embodiments of the disclosure. In a first step (FIG. 13a), cells C in a medium M are introduced in the bioreactor 1 and the cells C are distributed homogeneously via operation of the impeller 9. In a second step (FIG. 13 b), the cells C are allowed to settle on a first side of the carriers 7. The arrows stemming from the cells C show the direction of settlement. This is triggered by gravity. In a third step (FIG. 13 c), the medium M is removed from the bioreactor 1. In a fourth step (FIG. 13 d), further cells C in a medium M are introduced in the bioreactor 1 and the cells C are distributed homogeneously via operation of the impeller 9. In a fifth step (FIG. 13 e), the bioreactor 1 is turned upside down after having switched off the impeller 9. In a sixth step (FIG. 13 f), the cells C are allowed to settle on a second side of the carriers 7. In a seventh step (FIG. 13 g), the bioreactor 1 is turned back in its initial orientation and the cells C can now grow on both sides of each carriers 7.
[0153] FIG. 14 shows a bioreactor as in FIG. 2, wherein a second circulation means such as a pump is present in the upper cavity of the bioreactor. This reactor can operate upside down.
[0154] FIG. 15 shows a carrier for use in a bioreactor according to embodiments of the disclosure in which the width of the open spaces 2 in the carrier 7 increases with the distance to the center 17. The carrier 7 is here composed of alternating solid carriers 27 and open spaces 2 separating laterally the solid carriers 27.
[0155] FIG. 16 shows a portion of a carrier for use in a bioreactor according to embodiments of the disclosure in which open spaces 2 are bridged by ridges 19 thereby defining groove-shaped trenches 20.
[0156] FIG. 17 shows a diagrammatical top view of a carrier according to a design for use in a bioreactor according to an embodiment of the disclosure (left); it also shows a graph showing that the overall surface area A covered by the open space in the carrier increases faster with increasing radial distance D to the geometrical center of the carrier (right).
[0157] FIG. 18 shows a cross-sectional view of the edge of a stack of carriers 7 for use in an embodiment of a reactor according to the disclosure. Visible are ridges 10 determining the inter-distance between two adjacent carriers 7 and the outward projecting ridges 19 that are meant to be embedded in a polymer material.
[0158] FIG. 19 shows a perspective view of a bioreactor 1 for the culture of cells, comprising a stack of carrier 7 defining levels 6. The carriers 7 are of two alternative kinds. A first kind is hold in place by its edge and has a central open space. A second kind is hold in place by being attached to a central axis 24 and assures an open space for fluidly interconnecting two adjacent levels by not extending to the wall closing the stack.
[0159] FIGS. 20-25 relate to an embodiment in which a cell culture device, such as bioreactor 1, includes carriers 7.sub.a . . . 7.sub.n, and is further adapted for viewing the growth of the cells C on one or more of the inner carriers from an exterior vantage point. In one possible approach, this may be achieved by providing an optically transparent line of sight from the external vantage point V to carrier 7.sub.n through carriers 7.sub.a . . . 7.sub.n−1. In one particular embodiment, as shown in FIG. 20, this may be achieved by providing a surface area A on each carrier 7.sub.a . . . 7.sub.n−1 on which cells do not grow. This area may be achieved using a chemical treatment, such as by using a process to make the area hydrophobic to prevent cell adherence or growth, or instead by using a material that naturally retards or prevents cell adherence and adapting it for growth in areas besides area A (such as by using hydrophilization). These areas A among the carriers 7.sub.a . . . 7.sub.n−1 generally align, such that a substantially unobstructed line of sight is provided to a cell growth area A.sub.cg on carrier 7.sub.n. Thus, by using a microscope 0 or like device, the cells on this growth area A.sub.cg may easily be observed without interference from cell growth on carriers 7.sub.a . . . 7.sub.n−1. The area A may thus be considered as a window.
[0160] FIG. 21 shows an alternative embodiment, in which the desired line of sight is provided by providing an area A where cell growth is prevented by using an optically transparent material T associated with each carrier 7.sub.a . . . 7.sub.n−1, but not the carrier 7.sub.n for which the cell growth observation is desired. Preferably, this material completely fills the space between adjacent carriers, and thus provides a substantially continuous optical path from the desired vantage point V. As with the previous embodiment, multiple lines of sight may be provided to provide observations at different levels of the bioreactor. In both embodiments, it is preferred that the area A is as small as possible to avoid minimizing the cell growth area while still permitting the desired observation to be made.
[0161] With reference to FIG. 22, it should be appreciated that different lines of sight may be provided for different carriers in the same device, such as bioreactor 1. Thus, for example, to view the cell growth on carrier 7.sub.n, the arrangement is as shown in FIG. 20, with areas A.sub.1 on which cell growth is substantially prevented. For layer 7.sub.n−2, a different optical path is provided by similar areas A.sub.2 on the corresponding carriers 7.sub.a . . . 7.sub.n−3. Furthermore, the path may be extended in a different area A.sub.3 to reach the growth area of carrier 7.sub.n+3. As should be appreciated, this pattern may be repeated as necessary or desired to permit observation on one or more of the carriers.
[0162] While it is possible to use these approaches to viewing the cell growth area in the cell culturing apparatus, such as bioreactor 1 with stacked carriers 7 within the same housing, as described herein, it also may find use in other applications. Thus, for example, FIGS. 23-25 illustrate the use of the embodiments described above in a cell culture device (which may comprise a bioreactor 1) comprising a plurality of stackable carriers 7.sub.a, 7.sub.b, and 7.sub.c, each having a separate inlet. In FIGS. 22-24, carriers 7.sub.a and 7.sub.b include areas A for preventing cell growth, which allows for the external observation through these areas to the growth area A.sub.cg on carrier 7.sub.c. Similarly, in FIG. 25, the optically transparent material T positioned in “cube” style carriers 7.sub.a and 7.sub.b form areas A for preventing cell growth, which allows for the external observation through these areas to the growth area A.sub.cg on carrier 7.sub.c (which of course requires that any intervening portions of the carriers 7.sub.a and 7.sub.b are optically transparent to a sufficient degree to permit viewing in the desired manner). In either case, the ability to view lower layers avoids the costly and time-consuming need for having to unstack any upper carrier(s) in order to view the cell growth for the lower carrier(s).
[0163] FIG. 26 shows an embodiment where the carriers 7.sub.a . . . 7.sub.n include aligned openings to allow for the viewing of the cells on selected carriers. Specifically, the bioreactor 1 may include an inlet 21 and an outlet 22 positioned within a housing that contains a plurality of carriers arranged in a stacked configuration. A first carrier 7.sub.a may be arranged so as to provide at least one open space 2 for allowing a direct view through the first side 12 of the housing (which is at least partially transparent for this purpose) to a growth area A.sub.cg on the next-adjacent carrier 7.sub.b. In like manner, the first and second carriers 7.sub.a and 7.sub.b may provide aligned open spaces 2 for providing a substantially continuous optical path to the next-adjacent carrier 7.sub.c. This pattern may be repeated as necessary or desired to allow for the viewing of the growth areas on selected carriers from an external vantage point, with the first carrier preferably having a number of openings corresponding to the innermost carrier to be viewed, and each successive carrier providing one fewer opening than the preceding one. Additionally, it is possible to combine or adapt this approach to allow for the viewing of carriers from the second side 11, as indicated by open space 2 in carrier 7.sub.n (provided, of course, the housing is adapted for this purpose).
[0164] As should be appreciated, the open spaces 2 may also be arranged for ensuring the most desirable flow of fluid, oxygen, and nutrients to the layers, as outlined above. For instance, there may be two different sets of openings in the carriers (7), such as a first set devoted to “zig-zag” flow for cell nutrition, and a second set of aligned openings for observation (and, most preferably, arranged such that the “straight” flow through the aligned openings create is low relative to the main flow through the offset openings).
[0165] As used herein and unless provided otherwise, the term “comprising” is not synonym of the term “consisting” which has a narrower meaning. The term “comprising” should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression “a device comprising means A and B” should not be limited to devices consisting only of components A and B. It means that with respect to the disclosure, the only relevant components of the device are A and B. Moreover, the term “comprising” always includes the term “consisting” and when the term “comprising” appears in an embodiment of the disclosure, this same embodiment wherein the term “consisting” replaces the term “comprising” is always also an embodiment of the disclosure.
[0166] Furthermore, the terms “first”, “second”, “third” and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.
[0167] Moreover, the terms “top”, “bottom”, “over”, “under” and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other orientations than described or illustrated herein.
[0168] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.
[0169] As used herein and unless provided otherwise, the term “length” relates to the longest dimension of an object (e.g., an open space).
[0170] As used herein and unless provided otherwise, the term “width” relates to the largest dimension of an object taken at right angle to its length. The “width” is therefore never longer than the “length”.
[0171] The foregoing descriptions of various embodiments of the invention are provided for purposes of illustration, and are not intended to be exhaustive or limiting. Modifications or variations are also possible in light of the above teachings. The embodiments described above were chosen to provide the best application to thereby enable one of ordinary skill in the art to utilize the disclosed inventions in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention.
