Abstract
The present invention is related to the field of fluidic devices, and in particular, microfluidic cell culture systems. The present invention provides pumping, recirculation and sampling for a microfluidic device or devices. The present invention provides solutions to the control of microfluidics for both terrestrial and space applications, including the control over the movement of fluids in zero gravity or microgravity.
Claims
1-50. (canceled)
51. An assembly, comprising a) one or more flexible cell culture media reservoirs and b) one or more flexible reagent reservoirs contained within c) a container, said container i) in fluidic communication with d) a pump and e) a working fluid reservoir and ii) comprising a working fluid, said flexible cell culture reservoirs i) in fluidic communication with d) one or more microfluidic devices and ii) comprising cell culture media, said one or more flexible reagent reservoirs i) in fluidic communication with one or more microfluidic devices and ii) comprising reagent, wherein there is no mixing of said working fluid with said cell culture media.
52. The assembly of claim 51, wherein said container is rigid or flexible.
53. (canceled)
54. The assembly of claim 51, wherein said container is collapsible.
55. The assembly of claim 51, wherein said container is insulated.
56. (canceled)
57. The assembly of claim 51, wherein said container is sealed such that said working fluid can only enter or exit the container through conduits.
58. The assembly of claim 51, wherein said one or more microfluidic devices are outside said container.
59. The assembly of claim 58, wherein said one or more microfluidic devices are housed in a manifold.
60. The assembly of claim 51, wherein said one or more microfluidic devices comprise living cells on a surface.
61. The assembly of claim 60, wherein said surface is a microfluidic channel or portion thereof.
62. The assembly of claim 60, wherein said surface is a membrane.
63. The assembly of claim 51, further comprising valves to control the flow of said culture media out of said flexible reservoirs.
64. The assembly of claim 51, wherein said pump and working fluid reservoir are outside of said container.
65. The assembly of claim 51, wherein said pump is a displacement pump.
66. The assembly of claim 51, wherein said pump is selected from the group consisting of a volumetric pump, a pressure pump, a peristaltic pump and a syringe pump.
67. The assembly of claim 51, wherein each microfluidic device is in fluidic communication with a sampling conduit and a waste reservoir.
68. The assembly of claim 51, wherein there is no contact between the working fluid and the culture fluid.
69. The assembly of claim 51, wherein said working fluid comprises an oil or a gas.
70. (canceled)
71. The assembly of claim 51, wherein said container comprises first and second working fluids.
72. The assembly of claim 71, wherein said first working fluid is a gas and said second working fluid is a liquid.
73. The assembly of claim 51, further comprising a cooling conduit comprising a cooling fluid, wherein said cooling fluid does not mix with said working fluid or with said media.
74. The assembly of claim 73, wherein said cooling conduit comprises stainless steel tubing.
75. The assembly of claim 51, wherein said reagent is selected from the group consisting of a lysate reagent, a fixative reagent and a staining reagent.
76. The assembly of claim 51, further comprising a flow rate sensor configured to detect the flow rate of culture fluid.
77-89. (canceled)
90. A method of moving liquid, comprising: 1) providing an assembly, comprising a) one or more reservoirs contained within b) a container, said container i) in fluidic communication with c) a working fluid reservoir and ii) comprising a working fluid, said reservoirs i) in fluidic communication with d) one or more fluidic devices, and ii) comprising liquid, wherein there is no mixing of said working fluid with said liquid; and 2) applying a force to said container under conditions that said liquid in said one or more reservoirs is displaced and flows into said one or more fluidic devices, thereby moving said liquid.
91. The method of claim 90, wherein at least a portion of said container is deformable.
92. The method of claim 90, wherein said container is flexible.
93. The method of claim 90, wherein said container is collapsible.
94. The assembly of claim 90, wherein said container is insulated.
95. (canceled)
96. The method of claim 90, wherein said container is sealed such that said working fluid can only enter or exit the container through conduits.
97. The method of claim 90, wherein said one or more reservoirs are flexible.
98. The method of claim 90, wherein said one or more reservoirs comprise at least one deformable portion.
99. The method of claim 90, wherein applying a force comprises compressing at least a portion of said container.
100. The method of claim 90, further comprising cooling said working fluid.
101. The method of claim 100, wherein said working fluid is cooled with a cooling conduit comprising a cooling fluid, wherein said cooling fluid does not mix with said working fluid or with said liquid.
102. The method of claim 101, wherein said cooling conduit comprises stainless steel tubing.
103. The method of claim 90, wherein said liquid is heated after it is displaced but prior to it flowing into said one or more fluidic devices.
104. A method of moving liquid, comprising: 1) providing an assembly, comprising a) one or more liquid reservoirs contained within b) a container, said container i) in fluidic communication with c) a first working fluid reservoir and d) a second working fluid reservoir, said first working fluid reservoir comprising a first working fluid, said second working fluid reservoir comprising a second working fluid, said container further comprising a portion of said second working fluid, said one or more liquid reservoirs i) in fluidic communication with e) one or more fluidic devices, and ii) comprising liquid, wherein there is no mixing of said working fluid with said liquid; and 2) introducing said first working fluid from said first working fluid reservoir into said container under conditions that said pressure is imparted on said second working fluid such that liquid in said one or more reservoirs is displaced and flows into said one or more fluidic devices, thereby moving said liquid.
105. The method of claim 104, wherein said container is rigid or flexible.
106. (canceled)
107. The method of claim 104, wherein said container is collapsible.
108. The assembly of claim 104, wherein said container is insulated.
109. (canceled)
110. The method of claim 104, wherein said container is sealed such that said working fluid can only enter or exit the container through conduits.
111. The method of claim 104, wherein said one or more reservoirs are flexible.
112. The method of claim 104, wherein said one or more reservoirs comprise at least one deformable portion.
113. The method of claim 104, wherein said first working fluid comprises gas.
114. The method of claim 104, further comprising cooling said first or second working fluid, or both.
115. The method of claim 114, wherein said working fluid is cooled with a cooling conduit comprising a cooling fluid, wherein said cooling fluid does not mix with said working fluid or with said liquid.
116. The method of claim 115, wherein said cooling conduit comprises stainless steel tubing.
117. The method of claim 104, wherein said liquid is heated after it is displaced but prior to it flowing into said one or more fluidic devices.
118-130. (canceled)
131. A method of introducing reagent into microfluidic devices comprising: 1) providing an assembly, comprising a) one or more flexible cell culture media reservoirs and b) one or more flexible reagent reservoirs contained within c) a container, said container i) in fluidic communication with d) a pump and e) a working fluid reservoir and ii) comprising a working fluid, said flexible cell culture reservoirs i) in fluidic communication with d) one or more microfluidic devices comprising cells on a surface and ii) comprising cell culture media, said one or more flexible reagent reservoirs i) in fluidic communication with one or more microfluidic devices and ii) comprising reagent, wherein there is no contact or mixing of said working fluid with said cell culture media; 2) pumping said working fluid into said container with said pump under conditions that the culture media in the flexible reservoirs is displaced and flows into said one or more microfluidic devices, thereby perfusing said cells, wherein reagent in said flexible reagent reservoirs is not displaced; and 3) pumping said working fluid into said container with said pump under conditions that the reagent in at least one flexible reagent reservoir is displaced and flows into said one or more microfluidic devices, thereby introducing reagent into said one or more microfluidic devices.
132. The method of claim 131, wherein said assembly further comprises valves to control the flow of said culture media out of said flexible cell culture media reservoirs and valves to control the flow of reagent out of said flexible reagent reservoirs.
133. The method of claim 132, wherein a valve prevents reagent in said flexible reagent reservoir from being displaced in step 2).
134. The method of claim 132, wherein a valve permits reagent in at least one of said flexible reagent reservoir to be displaced in step 3).
135. The method of claim 131, wherein said one or more microfluidic devices are outside said container.
136. The method of claim 131, wherein said one or more microfluidic devices are housed in a manifold.
137. The method of claim 131, wherein said surface is a microfluidic channel or portion thereof.
138. The method of claim 131, wherein said surface is a membrane.
139. The method of claim 131, wherein said container is rigid or flexible.
140. (canceled)
141. The method of claim 131, wherein said container is collapsible.
142. The assembly of claim 131, wherein said container is insulated.
143. (canceled)
144. The method of claim 131, wherein said container is sealed such that said working fluid can only enter or exit the container through conduits.
145. The method of claim 131, further comprising cooling said working fluid.
146. The method of claim 145, wherein said working fluid is cooled with a cooling conduit comprising a cooling fluid, wherein said cooling fluid does not mix with said working fluid or with said liquid.
147. The method of claim 146, wherein said cooling conduit comprises stainless steel tubing.
148. The method of claim 131, wherein said liquid is heated after it is displaced but prior to it flowing into said one or more fluidic devices.
149. A method of collecting samples from microfluidic devices, comprising: 1) providing an assembly, comprising a) one or more reservoirs contained within b) a container, said container i) in fluidic communication with c) a pump and d) a working fluid reservoir and ii) comprising a working fluid, said reservoirs i) in fluidic communication with e) one or more microfluidic devices and ii) comprising cell culture media, said one or more microfluidic devices i) in fluidic communication with a sampling conduit and ii) comprising cells on a surface, wherein there is no mixing of said working fluid with said cell culture media; 2) pumping said working fluid into said container with said pump under conditions that the culture media in the reservoirs is displaced and flows into said one or more microfluidic devices, thereby causing fluid to exit said one or more microfluidic devices and enter said sampling conduit; and 3) collecting samples from said sampling conduit.
150. The method of claim 149, further comprising introducing gas into said sampling conduit to separate said fluid into discrete volumes.
151. The method of claim 149, wherein said container is rigid or flexible.
152. (canceled)
153. The method of claim 149, wherein said container is collapsible.
154. The assembly of claim 149, wherein said container is insulated.
155. (canceled)
156. The method of claim 149, wherein said container is sealed such that said working fluid can only enter or exit the container through conduits.
157. The method of claim 149, further comprising cooling said working fluid.
158. The method of claim 157, wherein said working fluid is cooled with a cooling conduit comprising a cooling fluid, wherein said cooling fluid does not mix with said working fluid or with said liquid.
159. The method of claim 158, wherein said cooling conduit comprises stainless steel tubing.
160. The method of claim 149, wherein said liquid is heated after it is displaced but prior to it flowing into said one or more fluidic devices.
161. A method of recirculating culture media through microfluidic devices without reversing the direction of fluid flow, comprising: 1) providing an assembly, comprising a) one or more reservoirs contained within b) a container, said container i) in fluidic communication with c) a pump and d) a working fluid reservoir and ii) comprising a working fluid, said reservoirs i) in fluidic communication with e) one or more microfluidic devices and ii) comprising cell culture media, said one or more microfluidic devices comprising i) cells on a surface and ii) inlet and outlet ports, said inlet and outlet ports in fluidic communication with a recirculation pathway, wherein there is no mixing of said working fluid with said cell culture media; and 2) pumping said working fluid into said container with said pump under conditions that the culture media in the reservoirs is displaced and flows into said one or more microfluidic devices in a direction, thereby causing fluid to exit said outlet port of said one or more microfluidic devices and enter said recirculation pathway, moving in the direction of said inlet port of said one or more microfluidic devices.
162. The method of claim 161, wherein said pumping causes said fluid moving in the direction of said inlet port to reach said inlet port, thereby recirculating said culture media without reversing the direction of fluid flow.
163. The method of claim 161, wherein said one or more microfluidic devices are housed on a manifold.
164. The method of claim 163, wherein said recirculation pathway is positioned on said manifold.
165. The method of claim 161, wherein said container is rigid or flexible.
166. (canceled)
167. The method of claim 161, wherein said container is collapsible.
168. The assembly of claim 161, wherein said container is insulated.
169. (canceled)
170. The method of claim 161, wherein said container is sealed such that said working fluid can only enter or exit the container through conduits.
171. The method of claim 161, further comprising cooling said working fluid.
172. The method of claim 171, wherein said working fluid is cooled with a cooling conduit comprising a cooling fluid, wherein said cooling fluid does not mix with said working fluid or with said liquid.
173. The method of claim 172, wherein said cooling conduit comprises stainless steel tubing.
174. The method of claim 161, wherein said liquid is heated after it is displaced but prior to it flowing into said one or more fluidic devices.
Description
BRIEF DESCRIPTION OF THE FIGURES
[0075] FIG. 1 is a schematic showing one embodiment of an assembly comprising a working fluid reservoir in fluidic communication with a pump in fluidic communication with a rigid container comprising working fluid that surrounds one or more flexible reservoirs, the flexible reservoirs in fluidic communication (via tubing or other conduit) with one or more microfluidic devices comprising inlet and outlet ports in fluidic communication with one or more microfluidic channels (in this case, a two channel microfluidic device).
[0076] FIG. 2 depicts one embodiment of the pass-through between the rigid container and the outside world. It needs to make a fluid seal around all tubing entering and leaving the container. A grommet (or multi-hole strain relief fitting) connects the flexible reservoir(s) and working fluid to external components of the assembly (e.g. the pump, the working fluid reservoir(s), etc.). Such grommets are available commercially from SealCon, LLC, Centennial, Colo. U.S.A., which has five holes that are 1.6 mm in diameter. As well, fluidic connections, such as luer locks, may be used as seen in FIG. 2.
[0077] FIGS. 3A and 3B are schematics showing the output flow rates with two reservoirs in the same rigid container of an assembly. FIG. 3A shows the results without resistance (uneven flow), while FIG. 3B shows the results with resistance (more even flow), as seen from output collection tubes.
[0078] FIG. 4 shows an alternative pump configuration involving a syringe/piston arrangement as part of the total assembly. Thus, the rigid container has a deformable portion (i.e. the piston or plunger).
[0079] FIG. 5 is a schematic showing one embodiment of a cooling system using a cooling fluid that is independent from the other fluids (e.g. independent from the working fluid or liquid in the flexible reservoirs). There is no mixing between fluids in this assembly. Cooling fluid from a cooling fluid reservoir flows through a conduit (e.g. stainless-steel tubingwhich is a good heat exchanger). The conduit can be outside or inside the rigid container (or both).
[0080] FIG. 6 is a schematic showing one embodiment of the system architecture for one embodiment of an assembly. In this case, the assembly with the cooling system shown in FIG. 5 is depicted in fluidic communication with a manifold and manifold enclosure (or incubator box), the manifold comprising one or more microfluidic devices or chips associated with fluid connectors and valves. The manifold enclosure functions as an incubator when governed by an environmental control loop, which controls temperature (T), humidity (H), and carbon dioxide levels (CO.sub.2).
[0081] FIG. 7 is a schematic showing one embodiment of a rigid container housing a flexible reservoir or bag, with the tubing passed through a grommet (or multi-hole strain relief fitting), some tubing connected to a flow rate sensor and/or pressure gauge.
[0082] FIGS. 8A and 8B are schematics showing one embodiment of a manifold with microfluidic devices associated with fluidic connectors and valves, the microfluidic devices comprising inlet and outlet ports in fluidic communication with one or more microfluidic channels (in this case, a two-channel microfluidic device). FIG. 8A is a top view schematic showing six microfluidic devices (or chips) mounted on a manifold, each chip associated with multiple valves and fluidic connectors. FIG. 8B is a side view schematic showing six microfluidic devices (or chips) on a manifold with associated valves and fluid connectors, the manifold contained within an enclosure or incubator box for temperature control.
[0083] FIGS. 9A and 9B are schematics showing how the six microfluidic devices on a manifold (depicted in FIG. 8A) might be valved, the microfluidic devices (or chips) comprising inlet and outlet ports in fluidic communication with one or more microfluidic channels (in this case, a two-channel microfluidic device, i.e. a device with a top channel and a bottom channel). FIG. 9A is a schematic separating out the fluidics for the top microfluidic channel (or TC) in an embodiment of an assembly comprising both reagent reservoirs (a lysate reservoir and a fixative reservoir are shown as examples of reagent reservoirs) and media reservoirs housed within the rigid container, with valves (depicted as unshaded opposing arrows ><) shown for controlling what fluid enters the chips, as well as the valves shown for controlling what fluid enters the sampling conduit and what fluid enters the waste reservoir. FIG. 9B is a schematic separating out the fluidics for the bottom microfluidic channel (or BC) in an embodiment comprising both reagent reservoirs (a lysate reservoir and a fixative reservoir are shown as examples of reagent reservoirs) and media reservoirs housed within the rigid container, with valves (depicted as unshaded opposing arrows ><) shown for controlling what fluid enters the chips, as well as the valves shown for controlling what fluid enters the sampling conduit and what fluid enters the waste reservoir.
[0084] FIGS. 10A and 10B are schematics showing how the six microfluidic devices on a manifold (depicted in FIG. 8A) might be valved, the microfluidic devices (or chips) comprising inlet and outlet ports in fluidic communication with one or more microfluidic channels (in this case, a two-channel microfluidic device, i.e. a device with a top channel and a bottom channel). FIG. 10A is a schematic separating out the fluidics for the top microfluidic channel (or T) in an embodiment of an assembly comprising both reagent reservoirs (a lysate reservoir and a fixative reservoir are shown as examples of reagent reservoirs) and media reservoirs housed within the rigid container, with valves (depicted as unshaded opposing arrows ><) shown for controlling what fluid enters the chips, as well as the valves shown for controlling what fluid enters the sampling conduit and what fluid enters the waste reservoir. FIG. 10B is a schematic separating out the fluidics for the bottom microfluidic channel (or B) in an embodiment comprising both reagent reservoirs (a lysate reservoir and a fixative reservoir are shown as examples of reagent reservoirs) and media reservoirs housed within the rigid container, with valves (depicted as unshaded opposing arrows ><) shown for controlling what fluid enters the chips, as well as the valves shown for controlling what fluid enters the sampling conduit and what fluid enters the waste reservoir.
[0085] FIG. 11 is a top side view schematic of one embodiment of an assembly comprising flexible reservoirs within two rigid containers, the flexible reservoirs in fluidic communication with six microfluidic devices or chips on a manifold, the manifold enclosed by an incubator box.
[0086] FIG. 12 is a side view schematic of a plurality of flexible reservoirs within one of the rigid containers shown in FIG. 11. Each flexible reservoir is in fluidic communication with capillary tubing which passes through the grommet. The rigid container is associated with cooling tubing.
[0087] FIG. 13 is a top side view schematic of one embodiment of an assembly comprising two rigid containers (housing flexible reservoirs, not shown) in fluidic communication with a pump for pumping the working fluid and the manifold housing the microfluidic devices, the manifold contained within an enclosure or incubated box. FIG. 13 shows a microprocessor or computer for controlling the operation of the assembly (e.g. the opening and closing of the valves, the environmental conditions of temperature, humidity etc.) and (an optional) air pump.
[0088] FIG. 14 is a schematic of IV bags suitable (in one embodiment) as flexible reservoirs, including one with trimmed edges.
[0089] FIGS. 15A and 15B show different concepts for handling tubing in the various assembly embodiments discussed herein, including but not limited to the tubing shown in FIG. 12. FIG. 15A is a drawing showing an outer basket concept. FIG. 15B shows an inner drum embodiment, where the tubing is wrapped around the drum.
[0090] FIGS. 16A, 16B and 16C show one embodiment of a bag header. FIG. 16A is a drawing of a 3D printed header. FIG. 16B is a top view drawing showing how the header engages that ends of the flexible bags or reservoirs. FIG. 16C is a side view drawing showing how the header engages and organizes the flexible bags or reservoirs.
[0091] FIG. 17 depicts one embodiment of a bag header engaging a plurality of flexible bags or reservoirs.
[0092] FIG. 18 shows one embodiment of a manifold engaging a microfluidic device for purposes of testing the ability to recirculate media through a recirculation pathway on the manifold.
[0093] FIG. 19 is a schematic showing one embodiment for arranging one embodiment of an assembly, the assembly comprising two rigid containers and a manifold comprising microfluidic devices and associated fluid connectors, where the containers are below and to the right of the manifold.
[0094] FIGS. 20A and 20B are schematics showing one embodiment for arranging one embodiment of an assembly, the assembly comprising two rigid containers and a manifold comprising microfluidic devices and associated fluid connectors, where the manifold is directly above the two rigid containers. FIG. 20A is a side view and FIG. 20B is a top side view, showing the positioning of the working fluid reservoir.
[0095] FIGS. 21A and 21B are schematics showing one embodiment for arranging one embodiment of an assembly, the assembly comprising two rigid containers (one slightly above the other and to the side) and a manifold comprising microfluidic devices and associated fluid connectors, where the manifold is on the same level as the lower container, but to the side. FIG. 21A is a side view and FIG. 21B is a top side view, showing the positioning of the working fluid reservoir and the plurality of microfluidic devices or chips positioned on the manifold.
[0096] FIGS. 22A and 22B are schematics showing one embodiment for arranging one embodiment of an assembly, the assembly comprising two rigid containers (one slightly above the other and to the side) and a manifold comprising microfluidic devices and associated fluid connectors, where the manifold is on the same level as the upper container, but to the side. FIG. 22A is a side view and FIG. 22B is a top side view, showing the positioning of the working fluid reservoir and the plurality of microfluidic devices or chips positioned on the manifold.
[0097] FIG. 23 is a schematic showing one embodiment of a sampling conduit where separation media (gas or liquid) is used to create discrete samples or plugs. The other components of the assembly are not shown.
[0098] FIG. 24 is a schematic showing one embodiment of a sampling conduit (first round) test setup where dye is used to distinguish samples from the separation media (gas or liquid).
[0099] FIG. 25 is a schematic showing first round results using a sampling conduit where dye was used to distinguish samples. The results showed successful discretization of fluorescent and non-fluorescent samples in 0.040 ID PEEK capillary tubing.
[0100] FIG. 26 is a schematic showing one embodiment of a sampling conduit (second round) test setup where dye is used to distinguish samples from the separation media (gas or liquid).
[0101] FIG. 27 is a schematic showing second round results using a sampling conduit where dye was used to distinguish samples. The results showed successful discretization of fluorescent and non-fluorescent samples in 0.031 ID FEP capillary tubing.
[0102] FIG. 28 shows an exemplary microfluidic device or chip comprising cells. By way of an example, the chip is comprised of two microchannels (Labeled 1&2) separated by a porous flexible-membrane. The material is functionalized with specific extracellular matrix proteins and cells are seeded into the different channels, e.g. endothelial cells are seeded in the bottom compartment and epithelial cells in the top compartment to emulate the basic functioning unit of an organ. Optionally, vacuum pressure can be applied to the side channels to mechanical stretch the membrane. Fluids can be continuously pumped through the channels to mimic shear forces, bring in nutrients, and wash away waste.
[0103] FIGS. 29A and 29B show one embodiment of a double-walled vacuum insulated rigid container for housing the flexible media reservoirs or secondary rigid containers. The container had a custom lid integrating strain-relief parts.
[0104] FIG. 30 shows a commercial off-the-shelf part for leak-proof routing of capillary tubes in and out of the rigid container as shown in FIGS. 29A an 29B.
[0105] FIG. 31 depicts the rigid container pressure as different media reservoir outlet channels are closed in order to demonstrate an ability to sense occlusions in the channels. The path from A to E shows pressure building in the rigid reservoir with all media reservoirs outlets closed. At E, the media valves are opened and media flows, relieving pressure until it almost reaches equilibrium at point F. At point F one of the media channels is closed to simulate a blockage (i.e. from a bubble), and a rise in pressure between F and G is seen. At point G another channel is closed and another pressure rise can be seen between points G and H. Finally, the final media channel is closed at point H, and it can be seen that there is a pressure rise between points H and I. The change in pressure increase, or delta, is an indication of how many channels are occluded.
[0106] FIG. 32 depicts a calculation summary of a mathematical heat transfer model of the internal hardware of the invention. In one embodiment of the invention, a cooling system may generate high levels of waste heat due to theorized inefficiencies. The internal hardware of the invention in that embodiment may have a limitation of how much waste heat it can reject due to the amount of power it can draw. The table illustrates mathematical calculations used to quantify the thermal situation within certain embodiments of the invention.
[0107] FIG. 33 depicts the coefficient of variation of the flow rate coming out of six flexible reservoirs or IV bags in a rigid reservoir. FIG. 33 shows that even flow across all of the independent, flexible reservoirs or IV bags may be achieved.
DESCRIPTION OF THE INVENTION
[0108] The present invention is related to the field of fluidic devices, and in particular, microfluidic cell culture systems. The present invention provides pumping, recirculation and sampling for a microfluidic device or devices. The present invention provides solutions to the control of microfluidics for both terrestrial and space applications, including the control over the movement of fluids in zero gravity or microgravity conditions.
[0109] With respect to space, an automated microfluidic research platform is contemplated for use to conduct experiments on the International Space Station (ISS), the platform comprising one or more of the assemblies described herein. Freed from the effects of gravity found on Earth, the International Space Station provides an environment where researchers can study human health in zero gravity or microgravity, allowing them to decouple the force of gravity from other effects that can impact cell function. Thus, embodiments described herein provide a unique research environment for enhancing knowledge to improve human health. The microfluidic devices in fluidic communication with other components of the assembly provide a living, micro-engineered environment that recreates the natural physiology and mechanical forces that cells experience within the human body.
[0110] A. Pumping and Moving Fluids
[0111] Moving fluids, particular moving fluids in a controlled manner under microgravity conditions, is difficult. In one embodiment, the present invention contemplates an assembly (such as the embodiment shown in FIG. 1), comprising one or more (or a plurality of) flexible reservoirs (4) (such as the flexible IV bags shown in FIG. 14) contained within a container (5) (preferably a rigid reservoir), said container (5) in fluidic communication with a pump (2) and a working fluid reservoir (1) and comprising a working fluid (liquid or gas) (8), said flexible reservoirs (4) in fluidic communication with one or more fluidic devices (including but not limited to microfluidic devices (6) or chips) and ii) comprising cell culture media, wherein there is no mixing of said working fluid with said cell culture media (preferably degassed media). It is not intended that the present invention be limited to nature or type of container (3) or nature or type of internal reservoirs (4). In one embodiment, said container is rigid. In one embodiment, said container is flexible. In one embodiment, said container is collapsible. In one embodiment, said container is insulated or is housed within a second insulated container. For cell cultures, such as in Organ Chips (6), it is beneficial maintain a temperature of about 37 C. for optimal cell maintenance. For cell media (9) it is beneficial to maintain a temperature of about 4 C. in order to avoid the degradation of key ingredients. Due to size constraints, these two components, optimally maintained at different temperatures, may have to reside next to each other. An insulated container (3) is one embodiment of maintaining these two separate temperatures. In one embodiment, the container comprises multiple (e.g. 2, 3, 4, etc.) vacuum insulated walls as seen in FIGS. 29A and 29B. In one embodiment the container is insulated with a material such as foam, reflective material, etc. In one embodiment the container is insulated with a fluid layer, either a gas or liquid. In one embodiment, said container (3) is sealed such that said working fluid can only enter or exit the container through conduits, such as a commercial off-the-shelf leak-proof capillary tube router (7) seen individually FIG. 30 and as part of the assembly in FIGS. 29A and 28B. In one embodiment, the working fluid (8) surrounds at least one internal reservoir (4). In one embodiment, the working fluid (8) surrounds a plurality of internal reservoirs (4). In one embodiment, there is more than one container (see FIGS. 11, 13, and 19-22), each container containing working fluid surrounding at least one internal reservoir. In one embodiment, said container (3) is rigid and said flexible reservoirs (4) can be compressed (e.g. with pressure via a working fluid) so that the fluid (9) in the bag exits the bag through tubing (5) (such as the embodiment shown in FIG. 2) or other conduit, and moves toward and into the fluidic devices, such as the microfluidic devices (6) shown in FIG. 1, entering and exiting the microfluidic devices via ports (26).
[0112] FIG. 2 depicts one embodiment of the pass-through between the rigid container and the outside world. The rigid container may make a fluid seal around all tubing entering and leaving the container. In one embodiment, a grommet (or multi-hole strain relief fitting) may connect the flexible reservoir(s) and working fluid to external components of the assembly (e.g. the pump, the working fluid reservoir(s), etc.). Such grommets are available commercially from SealCon, LLC, Centennial, Colo. U.S.A., which has five holes that are 1.6 mm in diameter. In one embodiment, fluidic connections (34), such as luer locks, may be used to connect the flexible reservoirs (4) to tubing (22).
[0113] Whether fluid (9) exits the internal reservoir (4) can be controlled further with one or more valves (17) (see FIGS. 9 and 10). Where there is more than one internal reservoir (4), each internal reservoir (4) can comprise a valve (17) to control fluid flow (e.g. in one position the valve blocks the fluid, while in another position the valve permits fluid flow). One or more pressure sensors (14) can be added to the assembly (see FIG. 7) so that clogging of a conduit can be detected and remedied.
[0114] In an exemplary embodiment, the invention presented herein has consistent flow rates in order to minimize experiment variability. FIG. 33 depicts the coefficient of variation of the flow rate coming out of six flexible reservoirs or IV bags in a rigid reservoir. FIG. 33 shows that even flow across all of the independent, flexible reservoirs or IV bags may be achieved when desired. However, it is not intended that the present invention be limited by equal flow across all of the flexible reservoirs. Per experiment requirements, flow may be the same or different amongst the one or more flexible reservoirs.
[0115] In one embodiment several internal reservoirs are held together using a bag header (25) as seen in FIG. 16A, FIG. 16B and FIG. 16C. The internal reservoirs (4) are oriented in the bag header (25) for the best tube packing density in order to fit into a system of limited size. In one embodiment the bag header (25) is made from stiff material, such as but not limited to plastic. The bag header (25) may be fabricated using 3D printing technology, injection molding, or other methods known by one having ordinary skill in the art. FIG. 17 depicts an alternative view of the internal reservoirs (4) held together using a bag header (25) with one internal reservoir (4) connected to tubing (22).
[0116] It is not intended that the present invention be limited to the positioning of the microfluidic devices. In a preferred embodiment, said one or more microfluidic devices are outside said container. In one embodiment, said one or more microfluidic devices are housed in a manifold (12) (see FIG. 6, FIGS. 8A and B, FIGS. 10A and B, FIGS. 11, 13, 21B, and 22B) along with one or more valves (17), such as diaphragm valves, and fluidic connectors (16), connecting to external fluid conduits, so that the microfluidic devices (6) on the manifold (12) are in fluidic communication with the reservoirs internal to the container, as well as in fluidic communication with any sampling conduits or recirculation pathways. In one embodiment, the manifold (12) comprises pins to align or even to attach the microfluidic devices (6) to the manifold (12). The manifold can comprise a plurality of microfluidic devices (6), each with their own associated valves (17) and fluidic connectors (16) (FIGS. 8A and 8B). In one embodiment, the manifold (12) is configured to heat liquid (9) prior to the liquid entering one or more microfluidic devices (6) (one example of just in time heating). In one embodiment, said liquid (9) is heated after it is displaced and while it begins flowing into said one or more fluidic devices (another example of just in time heating). In one embodiment, the manifold (12) is temperature controlled. In one embodiment, the manifold is temperature controlled by enclosing the manifold (12) in an enclosure (FIG. 8B) such as an incubator box (15) (allowing for the microfluidic devices to be exposed to temperatures consistent with cell growth and viability, such as 37oC+/2 degrees, as well as proper humidity and CO.sub.2 levels). In one embodiment, the incubator box (15) or the manifold (12) itself comprises a temperature sensor.
[0117] In one embodiment, an assembly (as seen in FIG. 13) comprises two rigid containers in fluidic communication with a pump for pumping the working fluid and the manifold housing the microfluidic devices, the manifold contained within an enclosure or incubated box. FIG. 13 also shows an embodiment where a microprocessor or computer (23) is used for controlling the operation of the assembly (e.g. the opening and closing of the valves, the environmental conditions of temperature, humidity etc.) and (an optional) air pump (24).
[0118] FIG. 4 shows an alternative pump configuration involving a syringe/piston arrangement as part of the total assembly. Thus, the rigid container (4) has a deformable portion (i.e. the piston or plunger). In this embodiment, the working fluid reservoir (1) is on the opposite side of the deformable portion as the media (9).
[0119] In one embodiment, resistance to flow is introduced through tubing connecting the flexible reservoirs to the manifold (FIG. 12), including but not limited to capillary tubing (22). In one embodiment, resistance can be manipulated by changing the cross-sectional diameter of the capillary tubing (22). By applying resistance to flow, greater control over flow is achieved. More specifically, by providing resistance one can achieve equal flow rates across multiple chips. By increasing resistance, one can reduce flow rate variability across multiple microfluidic devices (compare FIG. 3A with FIG. 3B).
[0120] It is not intended that the present invention be limited by the precise design of the fluidic or microfluidic devices (6). In one embodiment, the microfluidic devices have one or more microfluidic channels (19) which are channels with one or more dimensions that are 1 mm or smaller, and more typically 0.1 mm or smaller. The microfluidic device can also have (optionally) membranes. It is preferred that the microfluidic device comprises inlet and outlet ports (26) so that liquid (9) can enter and exit the microfluidic channels (19). In one embodiment, said one or more microfluidic devices (6) comprise living cells (32) on a surface (e.g. see FIG. 28). In one embodiment, said surface is a microfluidic channel (19) or portion thereof. In one embodiment, said surface is a membrane.
[0121] In one embodiment, the container is used to cool the working fluid. In one embodiment, the working fluid is used to cool (e.g. the internal reservoirs). In yet another embodiment (FIG. 5), the working fluid (8) is cooled using a cooling conduit (11) which can be aligned with the container (3) in a variety of ways (e.g. surrounding the container, outside the container, internal to the container, or a combination of both). The conduit (11) comprising a cooling fluid which can be in a cooling fluid reservoir (10), wherein said cooling fluid does not mix with said working fluid or with said liquid of the internal reservoirs (e.g. with the media).
[0122] FIG. 6 is a schematic showing one embodiment of the system architecture for one embodiment of an assembly. In this case, the assembly with the cooling system shown in FIG. 5 is depicted in fluidic communication with a manifold and manifold enclosure (or incubator box), the manifold comprising one or more microfluidic devices or chips associated with fluid connectors and valves. The manifold enclosure functions as an incubator when governed by an environmental control loop (13), which controls temperature (T) (33), humidity (H) (34), and carbon dioxide levels (CO.sub.2) (35).
[0123] The thermoelectric cooling system generates a significant amount of heat due to inefficiencies, and as such increases the need for an insulated container in which the media is to be stored. Without insulation the heating and cooling systems would require a significant amount of energy in order to maintain desired temperature gradients across the entire system. A mathematical representation of the thermal environment was built in order to quantify the temperature gradients across the system. FIG. 32 summarizes the mathematical calculations used in the temperature gradient representation.
[0124] In yet another embodiment, the present invention contemplates an assembly where there are two or more internal reservoirs (4) in a single container (3), but where different liquid (9) is in at least one reservoir (i.e. different from at least one other reservoir). For example, in one embodiment (FIG. 9), the present invention contemplates an assembly, comprising one or more flexible cell culture media reservoirs (4) and one or more flexible reagent reservoirs (18) contained within a container (3), said container i) in fluidic communication with a pump (2) and a working fluid reservoir (1) and ii) comprising a working fluid (8), said flexible cell culture reservoirs i) in fluidic communication with one or more fluidic devices (including but not limited to) microfluidic devices (6) and ii) comprising cell culture media (preferably degassed media), said one or more flexible reagent reservoirs (18) in fluidic communication with said one or more fluidic devices (including but not limited to microfluidic devices) and comprising reagent, wherein there is no mixing of said working fluid with said cell culture media. In one embodiment, said container (3) is sealed such that said working fluid can only enter or exit the container through conduits. In one embodiment, the working fluid (8) surrounds at least one internal reservoir (4). In one embodiment, said one or more fluidic devices are outside said container (3). In one embodiment, said one or more fluidic devices are microfluidic devices (6) housed in a manifold (12). In one embodiment, the manifold is configured to heat liquid prior to the liquid entering one or more microfluidic devices (one example of just in time heating). In one embodiment, said liquid is heated after it is displaced and while it begins flowing into said one or more fluidic devices (another example of just in time heating). In one embodiment, the manifold (12) is temperature controlled. In one embodiment (FIG. 8B), the manifold is temperature controlled by enclosing the manifold (12) in an enclosure or incubator box (15), allowing for the microfluidic devices to be exposed to temperatures consistent with cell growth and viability, such as 37 C.+/2 degrees, as well as proper humidity and CO.sub.2 levels). In one embodiment, the incubator box (15) or the manifold (12) comprises a temperature sensor. In one embodiment, said one or more microfluidic devices comprise living cells on a surface (FIG. 28). In one embodiment, said surface is a microfluidic channel (e.g. channel wherein one or more dimensions are 1 mm or smaller, and more typically 0.1 mm or smaller) or portion thereof. In one embodiment, said surface is a membrane. In one embodiment, the microfluidic device comprises inlet and outlet ports, said inlet and outlet ports in fluidic communication with said one or more microfluidic channels. In one embodiment, said microfluidic channels comprise cells. In one embodiment, said cells are on a membrane. In one embodiment (FIGS. 9 and 10), each microfluidic device (6) is in fluidic communication with a sampling conduit (21) and a waste reservoir (20). In one embodiment, said reagent in said reagent reservoir (18) is selected from the group consisting of a lysate reagent, a fixative reagent and a staining reagent. In one embodiment (FIG. 7), the assembly further comprises a flow rate sensor configured to detect the flow rate of culture fluid. In one embodiment, the assembly further comprises a pressure sensor configured to detect clogging and or blocking of flow of the culture fluid.
[0125] FIGS. 10A and 10B are schematics showing how, in one embodiment, the six microfluidic devices on a manifold (depicted in FIG. 8A) might be valved, the microfluidic devices (or chips) comprising inlet and outlet ports in fluidic communication with one or more microfluidic channels (in this case, a two-channel microfluidic device, i.e. a device with a top channel and a bottom channel). FIG. 10A is a schematic separating out the fluidics for the top microfluidic channel (or T) in an embodiment of an assembly comprising both reagent reservoirs (a lysate reservoir and a fixative reservoir are shown as examples of reagent reservoirs) and media reservoirs housed within the rigid container, with valves (depicted as unshaded opposing arrows ><) shown for controlling what fluid enters the chips, as well as the valves shown for controlling what fluid enters the sampling conduit and what fluid enters the waste reservoir. FIG. 10B is a schematic separating out the fluidics for the bottom microfluidic channel (or B) in an embodiment comprising both reagent reservoirs (a lysate reservoir and a fixative reservoir are shown as examples of reagent reservoirs) and media reservoirs housed within the rigid container, with valves (depicted as unshaded opposing arrows ><) shown for controlling what fluid enters the chips, as well as the valves shown for controlling what fluid enters the sampling conduit and what fluid enters the waste reservoir.
[0126] In operation, a working fluid (liquid or air) can then be pumped into the rigid container, causing displacement of the media in the flexible reservoirs into the downstream fluidics. Without limiting the invention in any manner to any particular mechanism, it is believed that the working fluid pumped into the hard reservoir puts pressure on flow fluid in soft reservoir. In one embodiment, the working fluid can be pumped into the rigid container using a displacement pump, an arrangement that allows for the flow rate of the working fluid to match the flow rate of the media, even if an occlusion changes the fluidic resistance downstream of the reservoirs. Positive displacement pumps have an expanding cavity on the suction side and a decreasing cavity on the discharge side. Liquid flows into the pumps as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses.
[0127] Multiple reservoirs can be used. Moreover, they need not be flexible; they can also be rigid reservoirs such as a syringe with a movable piston or surface. In any event, multiple reservoirs can be incorporated into a single container (preferably rigid container), and their flow rates can be set by a single pump moving the working fluid. This allows you to pump as many individual fluid reservoirs using a single pump. Resistance in the downstream fluidics allows one to get the individual reservoirs bags to flow at the same flow rate.
[0128] The working fluid does not mix (indeed, it is preferred there is no contact) with the cell culture media, making selection of pumps and flow sensors (27) easier. Fluid can be pressurized for applications such as reducing bubble size without increasing the gas concentration of the media.
Multiple media and reagent bags with valves can be incorporated into the same rigid container. The working fluid pump can always be operating, while the media/reagent being actively pumped can be controlled by the valves. This means one can control the flow of multiple fluid inputs to a device using a single pump. Additionally, one can have multiple rigid containers being fed by a single working fluid pump and a series of valves controlling the relative flow rates of incoming working fluids.
[0129] Where recirculation is desired, a given volume of culture media (e.g. all of it, a portion of it, etc.) is recirculated, whereas in non-recirculating perfusion, the culture media is perfused through the system and sent to directly to waste. Secreted factors and waste products in recirculating cultures are diluted into the total culture media volume (although this can be avoided by the use of a second reservoir, and the second reservoir can be avoided by using tubing). FIG. 18 shows one embodiment of a manifold engaging a microfluidic device for purposes of testing the ability to recirculate media through a recirculation pathway on the manifold.
[0130] It is important to have feedback on fluid flow to know if an occlusion (bubble, particle, etc.) has stopped or slowed the flow. These occlusions may be sensed and corrected for by flushing the occlusion out with a higher flow rate. In one embodiment, a flow sensor (27) is integrated into the flow lines. However, the choice of flow sensor (27) depends on the desired properties. For example, one can have a sensor that is biocompatible, inexpensive, disposable, as well as has a low dead-volume, easy electrical connections, etc. As an alternative to an integrated flow sensor (27), one embodiment, as depicted in FIG. 7, is an integrated pressure sensor (14) into the rigid container (3). The pressure sensor could monitor the pumping pressure of the working fluid and be able to sense if an occlusion has occurred. At steady state, the working fluid pump (2) infuses working fluid at a constant flow rate. The pumping of working fluid generates a pressure in the rigid reservoir (3) that is also constant at steady state. However, if there is a blockage in any of the fluid channels then the pressure within the container will increase as seen in FIG. 31. If additional channels are occluded, the pressure in the container will continue to increase in a step-wise fashion. An increase in pressure, as read by a pressure sensor (14), may be solved by closing all media channels but one and flushing media through at a high flow rate. The process may be repeated for each individual channel until the higher pressure abates.
[0131] FIG. 31 shows the rigid container (3) pressure as different media reservoir outlet channels are closed in order to demonstrate an ability to sense occlusions in the channels. The path from A to E shows pressure building in the rigid reservoir with all media reservoirs outlets closed. At E, the media valves are opened and media flows, relieving pressure until it almost reaches equilibrium at point F. At point F one of the media channels is closed to simulate a blockage (i.e. from a bubble), and a rise in pressure between F and G is seen. At point G another channel is closed and another pressure rise can be seen between points G and H. Finally, the final media channel is closed at point H, and it can be seen that there is a pressure rise between points H and I. The change in pressure increase, or delta, is an indication of how many channels are occluded.
[0132] The media flush to clear blockages may be done automatically, or the pressure signal rise may trigger an alarm to the user, who may then decide whether or not to initiate a flushing sequence. In a preferred embodiment capillary tubing (22) may be routed from inside the rigid container to the outside of the container where it is then attached to a gauge pressure sensor (14). In one embodiment the capillary tubing (22) is routed through a commercial off-the-shelf, leak-proof, strain-relief part.
[0133] B. Sampling Effluent
[0134] The invention further relates to sampling. In one embodiment, samples are obtained from effluent, i.e. sampling the fluid exiting a microfluidic device as described herein. Thus, the microfluidic devices are in fluidic communication with a sampling conduit for collecting (or removing) samples of effluent fluids, where effluent fluids may or may not include detached cells, secreted proteins and the like. In one embodiment, the microfluidic device comprises a top channel and bottom channel separated by a membrane. In some embodiments, effluent may be collected from media leaving the top channel. In some embodiments, effluent may be collected from media leaving the bottom channel. In some embodiments, effluent sampling is by hand. In some embodiments, the invention comprises an effluent sampling system. In one embodiment, the material exiting each microchannel outlet can be sent to one of three places: 1) the waste reservoir, 2) the recirculation pathway, or 3) the sampling conduit (which is, in a preferred embodiment, microbore capillary tubing ubiquitous in mass spectrometers due to their low compound absorption/adsorption and their low dead-volume). When the sample valve is switched on effluent from the chip (9) flows into the sample conduit until the desired volume is collected. The sample volume is driven by the pump flow rate, and the required volume for a given time point (driven by assays) sets the time needed for sample collection. After the appropriate volume of sample (9) has been collected, the sample valve is switched off and gas (or immiscible fluid) (30) is injected into the sampling conduit to ensure each sample is discrete in time and does not diffuse into samples from other time points. The sampling methodology will allow for high-temporal sampling resolution, without the size and added complexity of hundreds of sample reservoirs or bulky switching valves. It also allows for the sample reservoir/tubing to be routed to a separate thermal compartment in an adjacent CubeLab that will allow for storage of the effluent at 4 C. See, FIGS. 9A and B, FIGS. 10A and B, and FIG. 23 for illustrations of various embodiment showing sampling conduits in fluidic communication with microfluidic devices for sample collections (and testing). In one embodiment the sample handling tubing (22) in various assembly embodiments discussed herein, including but not limited to the tubing shown in FIG. 12, is wound using various techniques including those in FIG. 15A and FIG. 15B. FIG. 15A demonstrates one embodiment of tubing (22) wound in an outer basket. FIG. 15B shows an inner drum embodiment, where the tubing (22) is wrapped around the drum.
[0135] Samples, including effluent cell culture media from experiments (9), may be collected over time, for example, different time-points separated by seconds, up to minutes, up to hours, up to days apart depending upon the desired readout for an experiment. Samples may be labeled in part as sample 1, sample 2, etc., see FIGS. 24-26. One embodiment for separating sequential sample collection is to induce an air plug (30) in between the desired sample amounts (31). Sample amounts (31) may be in nanoliters, ul up to ml in amounts. One embodiment, the sampling is based on the ice core approach. For example, in one embodiment, sampling is continuous sampling (i.e. no gaps (30) to reduce or eliminate mixing between samples (31)). For microfluidics mixing is limited by laminar flow, and only diffusive mixing occurs. In one embodiment, sampling is discontinuous (use gaps (30) to avoid mixing). In one embodiment, a T-junction is used to introduce a gas (but could also be used to introduce other immiscible fluids).
[0136] In one embodiment, samples enter said sampling conduit in zero gravity or microgravity conditions.
[0137] In one embodiment, said samples are stored in said sampling conduit (e.g. in a manner similar to how ice cores are stored, i.e. with the different chronological samples stored together in one continuous conduit). In one embodiment, the sampling conduit is cooled by the working fluid. In one embodiment, the sampling conduit is stored cold in the rigid container. In one embodiment, the stored samples are later tested, e.g. the samples are either removed from (e.g. pushed out of) the sampling conduit or tested within the sampling conduit. In one embodiment a filter (28) is at the end of the capillary tubing (22) in which the samples are stored in order to maintain sterility.
[0138] C. Readouts on Effluent Sampling.
[0139] It is not intended that the present invention be limited by the nature of the testing done on samples. Exemplary readouts on effluent sampling can include but are not limited to: DNA analysis, RNA analysis; immunohistochemistry; detection of cytokine signals, etc. In one embodiment, the analysis will compare results between hypergravity, microgravity, and terrestrial conditions in addition to response to compounds, such as drugs, for reversing undesirable responses to a change in cell conditions.
[0140] D. System Assembly The system may be assembled in any configuration, such that the overall processes are carried out effectively, and also such that the overall assembly fits in a designated amount of space.
[0141] FIG. 19 is a schematic showing one embodiment for arranging one embodiment of an assembly, the assembly comprising two rigid containers and a manifold comprising microfluidic devices and associated fluid connectors, where the containers are below and to the right of the manifold.
[0142] FIGS. 20A and 20B are schematics showing one embodiment for arranging one embodiment of an assembly, the assembly comprising two rigid containers and a manifold comprising microfluidic devices and associated fluid connectors, where the manifold is directly above the two rigid containers. FIG. 20A is a side view and FIG. 20B is a top side view, showing the positioning of the working fluid reservoir.
[0143] FIGS. 21A and 21B are schematics showing one embodiment for arranging one embodiment of an assembly, the assembly comprising two rigid containers (one slightly above the other and to the side) and a manifold comprising microfluidic devices and associated fluid connectors, where the manifold is on the same level as the lower container, but to the side. FIG. 21A is a side view and FIG. 21B is a top side view, showing the positioning of the working fluid reservoir and the plurality of microfluidic devices or chips positioned on the manifold.
FIGS. 22A and 22B are schematics showing one embodiment for arranging one embodiment of an assembly, the assembly comprising two rigid containers (one slightly above the other and to the side) and a manifold comprising microfluidic devices and associated fluid connectors, where the manifold is on the same level as the upper container, but to the side. FIG. 22A is a side view and FIG. 22B is a top side view, showing the positioning of the working fluid reservoir and the plurality of microfluidic devices or chips positioned on the manifold. Experimental
[0144] A. Plug Sampling Concept Experiment
[0145] In an experiment, the ice core sampling concept was tested, which is illustrated in FIG. 23, where a separation media (gas or liquid) is used to create discrete samples or plugs. The plugs, stored in chronological order, stay separate due to capillary pressure. The tubing containing the plugs may be stored at a lower temperature during the experiment in order to maintain sample fidelity and then frozen after the experiment for later analysis. The other components of the assembly are not shown.
[0146] FIG. 24 is a schematic showing one embodiment of a sampling conduit (first round) test setup where dye is used to distinguish samples from the separation media (gas or liquid). It was desired to know if neighboring plugs would bleed into one another. The samples were manually pulled into the 1 mm internal diameter capillary tubing using a 1 mL syringe with 10 graduations. Plugs of cell effluent, cell media that had been in contact with the cells, (9) were alternately administered with Lucifer Yellow fluorescent dye and no dye, frozen for 24-48 hours before being thawed. By alternating plug media and measuring fluorescence of samples the degree of discretization could be analyzed. The cell media used in this experiment, PBS, does not fluoresce. Sample plugs were manually pushed out into individual wells on a 96 well plate using identical 1 mL syringes. A plate reader was then used to measure fluorescence. If there was bleed over, the fluorescent signal in the plugs that did not have dye was measured. A high raw intensity value as measured on a plate reader means higher fluorescent signal. Plug volumes were decreased from 100 L (a) to 20 L (e).
[0147] FIG. 25 is a schematic showing first round results from the test setup in FIG. 24 using a sampling conduit where dye was used to distinguish samples. The results showed successful discretization of fluorescent and non-fluorescent samples in 0.040 ID PEEK capillary tubing. Samples containing fluorescence had fluorescence signals between 253-399, while samples not containing fluorescence had fluorescence signals between 0-35. Control wells containing 100% Lucifer Yellow and 40% Lucifer Yellow had fluorescence measurements of 371 and 143 respectively. The results indicate that there was not a high amount of cross over between plugs.
[0148] FIG. 26 is a schematic showing one embodiment of a sampling conduit (second round) test setup where dye is used to distinguish samples from the separation media (gas or liquid). Instead of manually pulling the plugs into the tubing using a syringe the plugs were automatically pulled into the capillary tubing using a 5 mL syringe on a syringe pump. The capillary tubes with discretized sample plugs and air plugs were placed in a 80 C. freezer for about 4 days before fluorescence analysis. The tubing used in the experiment was 1/32 internal diameter, 1/16 outer diameter FEP capillary tubing. Two different tubes were used during the experiment. Sample plugs were automatically pushed into individual wells on a 96 well plate using identical 5 mL syringes on a syringe pump. A plate reader was used to measure fluorescence. The plate reader data was normalized to measured volume of sample in the plate.
[0149] FIG. 27 is a schematic showing second round results using a sampling conduit where dye was used to distinguish samples. The results showed successful discretization of fluorescent and non-fluorescent samples in 0.031 ID FEP capillary tubing. In the first sample run samples containing fluorescence had fluorescence signals between 319-382, while samples not containing fluorescence had fluorescence signals between 10-18. In the second sample run samples containing fluorescence had fluorescence signals between 310-531, while samples not containing fluorescence had fluorescence signals between 7-10. In the second sample run one plug (31) leading to a low error percentage of the system. Five control wells contained only Lucifer Yellow and five control wells contained only the cell culture media DPBS. The Lucifer Yellow control wells had fluorescence values between 378-443. The DPBS had fluorescence values between 4-5.
[0150] B. Thermal Environment Modeling
[0151] In a second experiment a mathematical representation of the thermal environment across the entire system was built to determine if two highly different temperatures, namely the 4 C. media temperature and the 37 C. Organs-on-Chip temperature, could coexist in such a small system. The mathematical calculations are summarized in FIG. 32. The model showed that the biggest increase in efficiency could be achieved by better insulating the container housing the flexible reservoirs and the working fluid. Adding foam insulation to the container improved efficiency modestly, but the mathematical model showed that a double-walled vacuum insulation would improve efficiency significantly enough in order to be able to achieve both temperature environments in the same small system. Heat gains for the rigid reservoir with quarter inch thick foam insulation was calculated to be 2.2 Watts. The heat gains decreased to 0.4 Watts when the foam insulation was replaced by double-walled vacuum insulation. There was a 50-fold improvement in efficiency.
[0152] Various double-walled vacuum containers that fit the size constraints were considered, however the most successful option was a double-walled vacuum flask. A custom cap was designed that would allow for the tubing routing in and out of the thermos. Fluid tubing was routed through a commercial off-the-shelf waterproof strain-relief fitting.
