WO2007055705A1

WO2007055705A1 - Micro organ bath system and methods

Info

Publication number: WO2007055705A1
Application number: PCT/US2005/042104
Authority: WO
Inventors: Michael E. Bradley; Ryan C. Smith
Original assignee: Creighton University
Priority date: 2005-11-11
Filing date: 2005-11-11
Publication date: 2007-05-18

Abstract

Organ baths having tissue chambers are provided. The organ bath system can include a block into which are formed a tissue chamber and associated passages or channels for providing and removing fluid from the tissue chamber. Methods of maintaining organs within an organ bath having tissue chambers, and associated passages or channels for providing fluid to and removing fluid from the tissue chamber, are also provided.

Description

MICRO ORGAN BATH SYSTEM AND METHODS

FIELD OF THE INVENTION

The subject invention relates to organ bath assemblies. The subject invention also relates to methods for maintaining and testing tissues using organ bath assemblies.

BACKGROUND OF THE INVENTION

Organ baths are routinely used in research laboratories to help study the effects that certain pharmacological agents may have on tissues. In general, an organ bath functions to provide a chamber in which a sample of living tissue is maintained and studied. In order to keep the tissue alive, the chamber is configured to hold an amount of osmotically-balanced nutrient solution. The solution is replenished at a relatively constant rate to ensure that the tissue sample does not deplete the nutrient solution in the chamber, which would result in a concomitant decrease in tissue responsiveness, followed ultimately by tissue death. To maintain the tissue sample at a particular temperature, warm water is circulated in a space that surrounds the tissue chamber, which in turn heats the nutrient solution and tissue sample.

Figure 1 shows a section of a conventional organ bath 2. The illustrated organ bath 2 includes a tissue chamber 14 into which a nutrient solution 16 is circulated, and a water jacket 6 that surrounds the tissue chamber 14. The volume of the tissue chamber 14 in systems of this sort typically ranges from 5 ml to 30 ml. Nutrient solution 16 is provided to the tissue chamber 14 from a supply 18 through a supply line 20. From the supply line 20, the nutrient solution 16 travels through a nutrient inflow line 21, which wraps several times around the exterior wall 8 of the tissue chamber 14. The nutrient solution 16 then enters the tissue chamber 14 from a bottom region 18 thereof- As nutrient solution 16 flows into the tissue chamber 14, excess solution 16 flows into a nutrient solution outflow line 22, and then into a waste receptacle 24 or drain (not shown). The organ bath 2 Is typically slidably attached to a metal scaffold (not shown) to permit the horizontal and/or vertical adjustment of the position of the organ bath 2, as well as to permit mechanical tensioning of the tissue in organ bath 2.

Further as to conventional organ bath 2 illustrated in Figure 1 , heated water is supplied to the water jacket 6 through a water inflow line 10. The water circulates within the water jacket 6 and around the tissue chamber 14 and nutrient inflow line 21, thereby heating the nutrient solution 16 that is incoming as well as that which is in the tissue chamber 14.

The nutrient solution 16 within the tissue chamber 14 may be optionally drained from the tissue chamber 14 through drain tube 25. The drain tube 25 includes a valve 26 for selectively removing nutrient solution 16 from the tissue chamber 14 for further testing and analysis according to the user's preferences.

Certain known organ baths do not include attachment structures within the chamber for attaching and securing the tissue sample being studied, and thus a separate organ holder is required to hold the tissue sample while being studied; this also physically isolates the tissue from the organ bath which can reduce vibrational artifacts, for example. Figures 2A and 2B show a known separate organ holder 40 mounted onto a scaffolding 46. The organ holder 40 includes a vertical member 42 attached to a transverse member 44, which is slidably attached to the scaffolding 46. The vertical member also has a post 56 mounted on the face of the vertical member 42 near the bottom. A tissue sample 50 is attached at a bottom end to the post 56 with a tether 53 formed of a length of silk cord. A second tether 52 is attached at one end to the top end of the tissue sample 50, and at the other end to a transducer 58 that is also slidably connected to the scaffolding 46. Once assembled in this manner, the organ holder assembly is lowered into the tissue chamber of the organ bath (not shown) until the nutrient solution 16 reaches the level of approximately dashed line 62.

Once the tissue sample 50 on the organ holder 40 is positioned in the tissue chamber, the tissue sample 50 can be studied. In performing such studies, pharrnacologically-active agents are added to the nutrient solution 16, and samples of the nutrient solution 16 are drawn off and analyzed. !n gdcϋtioπ, tissue tension testing may be performed by coupling the transducer 58 to an analog-to-digital (A/D) board (not shown) mounted in a computer 60. If the tissue sample 50 is muscle, for example, contractions of the muscle will pull the tether 52, which is connected at another end to a lever (not shown) operatively connected to the transducer 58. Movements of the lever cause a change in voltage proportional to the muscle contraction to occur within the transducer's circuitry. This analog signal is then passed through the A/D board's circuitry, which converts the signal from analog to digital. The digital signal can then be recorded by the computer 60 that is running software to capture, analyze, and display the data. Additional organ bath assemblies (i.e. organ bath 2 and organ holder 40) may be set up on additional scaffolding 46 at the user's option, and connected to the same supply 18 and waste container 24.

Existing organ baths for the study of tissue samples under a variety of conditions have a variety of limitations associated with them. Basic pharmacological principles dictate that drugs must be used at sufficient concentrations (i.e. mass/volume) in order to have any effect. As such, tissues maintained in smaller volumes require treatment with smaller masses (i.e. fewer total grams) of drugs. However, conventional organ baths are made up of individual, and often hand-made, organ baths, which are both expensive and difficult to miniaturize.

Likewise, the volume of the tissue chamber affects the nutrient solution concentrations of the substances released from the tissue sample. Because the volumes of typical conventional tissue chambers are large, relatively low concentrations (g/L) of substances released from the tissue sample develop in the nutrient solution. This condition makes the detection and analysis of such released substances difficult.

Known tissue chambers are typically individually-constructed and fragile, especially if they are constructed of glass. As previously described, existing tissue chambers are comprised of a network of circulatory passages and chambers constructed of thin-walled glass or plastic. These passages and chambers for many known systems are relatively unprotected and highly susceptible to breakage and failure, such as through ordinary handling in a laboratory setting.

A demand therefore exists for a durable organ bath system that provides small tissue chamber volumes at a low cost. An additional demand also exists for methods of organ bathing and testing that allow for bathing tissue samples in small volumes to minimize the mass of drugs required to perform the testing, and increase the concentrations of substances released from tissue samples into the surrounding nutrient solution. The present invention satisfies these demands.

SUMMARY OF THE INVENTION

The present invention relates generally to organ baths, and advantageously can be used in laboratory settings wherein the researcher desires to maintain and evaluate tissue samples in a tissue chamber. Preferred embodiments of the present invention include blocks for creating chambers in which to harbor tissue samples. For the purposes of this Application, the term "block" means any material suitable for use in connection with tissue testing in which passages and chambers may be formed, and which is either substantially biologically and chemically inert or that may be coated with a substantially biologically and chemically inert material. In preferred embodiments, the present invention includes a block for superfusing tissue with a fluid that includes a block body. The block includes a tissue chamber having a chamber volume with a defined capacity formed in the block body, an inflow passage in communication with the tissue chamber for providing the fluid to the tissue chamber, and an overflow passage in communication with the tissue chamber for receiving the fluid that exceeds the defined capacity of the chamber volume from the tissue chamber and directing the fluid away from the tissue chamber.

One object of the invention is to provide a low-cost, durable micro-organ bath to perform tissue testing in vitro. In certain embodiments, a cast acrylic block is provided into which are formed one or more tissue chambers. Cast acrylic has the advantages of being inexpensive as compared to laboratory- grade glass, and having little natural porosity- in addition, unlike known tissue chambers that are formed of numerous distinct components, cast acrylic blocks may have a tissue chamber and associated passages formed directly in them by, for example, drilling or milling. Such passages may include, for example, those for providing fluid to the tissue chamber, directing excess fluid away from the tissue chamber, and for removing fluid samples from the tissue chamber.

Another object of the invention is to provide a material into which tissue chambers having small volumes may be formed. In performing certain assays on tissue samples, it is often desirable to maintain the tissue sample in a small- volume tissue chamber so that metabolites and other substances released by the tissue sample into the nutrient solution in the chamber have a relatively high concentration (g/L). In addition, it is desirable to maintain a tissue sample in a small-volume tissue chamber so that less total grams of reagents or pharmacologically-active agents are required to achieve a desired concentration (g/L). Use of a block according to embodiments of the present invention allows formation of a small-volume tissue chamber because the tissue-chamber volume is generally only limited by the ability to form them in the block. As such, the present invention allows researchers to use smaller amounts of reagents and pharmacologically-active agents to carry out testing on the tissue samples. Likewise, the small tissue chamber volumes function to provide higher mass to volume ratios of any metabolites released into the nutrient solution by the tissue under evaluation, which facilitates easier identification and analysis.

Another object of the invention is to provide modular blocks having a single tissue chamber and associated passages formed therein. Embodiments of the present invention utilizing such blocks allow a user to selectively set up and test a tissue sample within a tissue chamber without disturbing any other tissue sample being studied in a tissue chamber in a separate block.

Advantages of embodiments using a single-block system include the ability to perform long-term and short-term tissue testing in the same water bath, and the ability to cycle blocks used for short-term tissue testing into and out of a water bath without disturbing blocks used for long-term testing. Other preferred embodiments of the present invention include a plurality of tissue chambers with each tissue chamber having a chamber volume with a defined capacity formed in the block body. Each of the plurality of tissue chambers further includes an inflow passage in communication with the tissue chamber for providing the fluid to said tissue chamber, and an overflow passage in communication with the tissue chamber for receiving the fluid that exceeds the defined capacity of the chamber volume from the tissue chamber and directing the fluid away from the tissue chamber. In addition, this embodiment may include at least two overflow passages that are connected.

It is another object of the present invention to provide methods for superfusing a tissue sample. The method includes the steps of providing a block body, forming a tissue chamber within the block body, and forming an inflow passage in communication with the tissue chamber for providing fluid to the tissue chamber. The method also includes forming an overflow passage in communication with the tissue chamber for receiving excess fluid from the tissue chamber and directing the fluid away from the tissue chamber, securing a tissue sample within the tissue chamber, and providing superfusing solution through the inflow passage to provide the nutrient solution to the tissue chamber.

The present invention will be further appreciated, and its attributes and advantages further understood, with reference to the detailed description below of some presently contemplated embodiments, taken in conjunction with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates a cross section of an organ bath according to the prior art;

Figure 2A illustrates a front view of an organ holder assembly according to the prior art;

Figure 2 B illustrates a side view of an organ holder assembly according to the prior art; Figure 3A illustrates a top view of a micro organ bath block according to the present invention;

Figure 3B illustrates a transverse cross-section of a micro organ bath block according to the present invention;

Figure 3C illustrates an exploded view of a portion of a transverse cross- section of a micro organ bath block according to the present invention;

Figure 4A illustrates an orthogonal view of a bracket for use within a tissue chamber of a micro organ bath block according to the present invention;

Figure 4B illustrates a front cross-sectional view of a tissue chamber of a micro organ bath block according to the present invention;

Figure 5 illustrates an orthogonal view of another embodiment of a micro organ bath block according to the present invention;

Figure 6 illustrates a schematic of a micro organ bath assembly according to the present invention; and

Figure 7 is an orthogonal view of an embodiment of a shelf for use in suspending a micro organ bath within a water bath according to the present invention. DETAILED DESCRIPTION OF A PRESENTLY PREFERRED EMBODIMENT

A system according to the present invention is identified in the following as 101. System 101 includes an organ bath block 102. Without limiting the application of the scope of the invention, the following will describe certain preferred embodiments of the present invention.

Figures 3A-C show one preferred embodiment of the system 101 that includes a block 102. As shown in Figures 3A and 3B, block 102 includes a block top 103, front 146, bottom 148, and back surfaces 107, and two opposed side surfaces (not shown). Block 102 may be of unitary construction, such as one formed from cast acrylic into which are formed one or more tissue chambers 142 and associated passages for providing nutrient solution to the tissue chambers 142 and removing nutrient solution from the tissue chambers 142. The surfaces of block 102, including the surfaces of the tissue chambers and passages, can be cast or machined to be substantially smooth. Cast acrylic is available from McMaster-Carr Supply Co., Part No. 8560K321. One skilled in the art will readily recognize that other materials may also be used to form the block without deviating from the scope of the invention.

As shown in Figure 3B and 3C, an embodiment of a tissue chamber 142 includes an opening 155 in the top surface 103 of the block 102, and extends down substantially vertically through the block 102. The tissue chamber 142 is configured and sized to hold a desired volume of nutrient solution to maintain a tissue sample (not shown) therein. In a preferred embodiment, for example, a tissue chamber 142 of a desired volume may be formed in the block 102 by drilling down through a top surface 103 of the block 102 to a depth of approximately 1.8 centimeters using a 4mm drill bit. Other tissue chamber 142 volumes may also be created by using different depths and different sizes of drill bits, or a combination thereof.

A fluid inflow passage 105 of a desired size can be formed in the block 102 to provide a passage through which a supply of nutrient solution may be provided to the tissue chamber 142. In one preferred embodiment of the invention, the fluid inflow passage 105 is substantially horizontal, and is formed through the front side 146 of the block 102 at a level generally corresponding to the lower part of the tissue chamber 142. The fluid inflow passage 105 is preferably formed through a block front side 146 at a region corresponding to the level of a lower part of the tissue chamber 142. The fluid inflow passage 105 is preferably further countersunk at the block front side. The countersunk region 106 may be tapped to allow a threaded adapter to be connected to the fluid inflow passage 105 for providing nutrient solution, as described below.

A fluid drain passage 150 of a desired size is formed in a block side to provide a drain through which nutrient solution within the tissue chamber 142 may be withdrawn for further testing and analysis. In a preferred embodiment, fluid drain passage 150 is formed in the bottom side 148. The fluid drain passage is preferably substantially vertical, and is formed through the bottom side 148 of the block 102 at a region generally corresponding to the vertical axis of the tissue chamber 142 and preferably connecting to the tissue chamber 14 M. at the lowest point thereof. In a preferred embodiment, the fluid drain passage 150 is further countersunk at the opening on the block bottom side 148. The countersunk region 151 may be tapped to allow a threaded adapter to be connected to the fluid drain passage 150 for removal of nutrient solution from the within tissue chamber 142. As explained in more detail below, the fluid drain passage 150 is closed during normal operation of the micro organ bath assembly to prevent nutrient solution from draining out of the tissue chamber 142. One skilled in the art will recognize that other passage sizes and configurations may optionally be used for creating one or both of the fluid inflow passage 105 and the fluid drain passage 150 without departing from the scope of the invention.

The embodiment shown in Figure 3C includes a fluid inflow passage 105 and fluid drain passage 150 adapted to receive threaded adapters 172 that are fitted on the end of tubing 104, 175. In a preferred embodiment, the threaded adapter 173 is a LUER-LOK^® adapter attached to the end of NALGENE^® tubing 104, 175. As explained in more detail below, a fluid supply line 142 may be further attached via an intervening manifold to a fluid supply 112 for supplying nutrient solution to the tissue chamber 142. Also, the fluid drain line 175 is further preferably attached to a syringe (not shown) at a second end thereof for collecting the nutrient solution from the tissue chamber 142 for further analysis.

Each tissue chamber may further selectively include a drainage system formed within the block 102. During operation of the micro organ bath system, nutrient solution is typically provided to the tissue chamber 142 at a relatively constant rate through the fluid inflow passage 105. Consequently, the ongoing supply of nutrient solution to the tissue chamber 142 will force excess nutrient solution out of the tissue chamber 142. As shown in Figures 4A and 4B, a fluid overflow channel 152 may be formed in a rear wall of the tissue chamber 142 at a predetermined depth and length. Because the fluid overflow channel 152 is lower than the top surface 103 of the block 102, excess nutrient solution accumulating within the tissue chamber 142 will exit the tissue chamber 142 by flowing through the fluid overflow channel 152 before overflowing onto the top surface 103 of ths block 102. After flowing through fluid overflow channel 152, the excess nutrient solution fluid flows down a series of steps 158, 160, 164, and into sink 168. In addition, as shown in Figure 3A, the drainage channels from each tissue chamber may each use a common sink 168, which is preferably located at the lowest point of the drainage channel system 152, 158, 160, 162.

As described in more detail below, fluid from the sink 168 may be removed from the sink 168 and into a waste container, or, at the user's option, the solution from sink 168 may be held for further testing. The drainage system of block 102, as shown in Figures 4A and 4B, is preferably formed by use of an end mill mounted in a vertical milling machine, which can easily create the channels within an acrylic block. However, one skilled in the art will readily recognize that other methods of creating the channels can also be used without departing from the scope of the invention.

Other embodiments of the present invention may use different drainage channel configurations than those described above. For example, the channels need not be stepped, but may instead be sloped downwardly from the tissue chamber towards a sink. In addition, the drainage channels need not communicate with each other at all, and may instead have separate, dedicated sinks for each tissue chamber 142, which would allow the long-term collection and testing of the nutrient solutions from each individual tissue chamber 142 without contamination from any other tissue chamber 142. Such a block 202 is shown in Figure 5, and includes a plurality of tissue chambers 242 each having a drainage channel 252 terminating at a respective sink 268. The tissue chambers 242 are otherwise configured similar to those described above with respect to Figures 4A-C, and each may include a fluid inflow passage 205 with countersunk tapped region 206, and fluid drain passage 250 with countersunk tapped region 251. Each may further include tapped hole 242 for accepting a fastener therein for securing a bracket (not shown) within the tissue chamber 242, as explained in more detail below.

Another embodiment of the present invention may include a simplified version of block 202 that includes a single tissue chamber 242 and associated fluid inflow passage 205, drainage passage 250_; and overflow channel 252, rather than a plurality of tissue chambers 242 and associated drainage systems 252. Such single blocks could be formed by, for example, cutting the block 202 at dashed lines 299, or by forming the individual blocks from pre-cut or preformed blocks of appropriate size. The resulting individual blocks have a block front, back, top, and bottom surfaces, and two opposed side surfaces.

As shown in Figures 4A and 4B, a tissue sample 179 may be secured within the tissue chamber 142 and bathed in a superfusing nutrient solution 182, which functions to keep the tissue sample 179 alive. Among other tissue, the tissue sample 179 may be murine uterine smooth muscle tissue. Such a tissue sample 179 is ordinarily procured by euthanizing a female mouse, removing its uterus, and submerging the uterus in nutrient solution. Then, using sharp dissection, a section approximately 10 mm long, 1 mm wide and 1 mm thick is prepared; other tissue sample sizes may also be used without departing from the scope of the invention.

The nutrient solution may be virtually any solution deemed appropriate by the user. In a preferred embodiment, the nutrient solution is "Hanks buffer" solution, which provides an osmotically-balanced solution for maintaining the cells of the tissue sample in a live state during testing within the tissue chamber 142. The ingredients of the Hanks solution are as follows:

Once the tissue sample 179 has been procured, and before it is positioned within the tissue chamber 142, It may be secured to a bracket 190 of the type shown in Figure 4A. The bracket 190 preferably includes a vertical member 195 having a first and second end with first and second transverse members 191 , 193 attached to respective ends. The first transverse member 191 may include hole 192 for securing the bracket to the top surface 103 of the block 102, as shown and described below with respect to Figure 4B. The second transverse member 193 may include hole 194 for securing one end of a tether thereto, which will anchor the tissue sample 179 within the tissue chamber 142 when positioned therein. The bracket 190 is preferably sized to be positioned within a tissue chamber for securing a tissue sample within the tissue chamber.

As shown in Figure 4B, the tether 180, which is preferably a silk suture cord, may be secured to the tissue sample 179 and through hole 194 of the bracket 190 with a double overhand knot at each end. Likewise, tether 181 is secured to a top end of the tissue sample 179 at a first end, and may be attached at its other end to a force transducer (not shown), as described in more detail below with respect to Figure 6. The bracket 190 and tissue sample 179 assembly may then be positioned within the tissue chamber 142, and the first transverse member 191 of bracket 190 can be secured to the top surface 103 of the block 102 by securing screw 126 in tapped hole 178. Superfusing nutrient solution 182 may then be provided to the tissue chamber 142 through the fluid inflow passage (not shown).

Figure 6 shows a schematic representation of a micro organ bath system

101 according to a preferred embodiment of the present invention. The block

102 may be connected to a supply 112 of superfusing nutrient solution by way of fluid supply lines 104 that are connected to fluid inflow passages 105, as previously discussed with respect to Figure 3C. To eliminate the need for multiple fluid supply lines connected directly to a fluid supply, the fluid supply lines 104 are connected to respective ports on a manifold 120. The manifold 120 is preferably a LUER-LOK^® manifold that includes valves 121 to allow the user to selectively turn on or off the supply of nutrient solution available through any one of the ports. The manifold 120 is preferably connected to the nutrient solution supply 112 by way of a single fluid supply lin© 116 having a flow regulator 118 with flow-adjustment means 119 associated therewith. In a preferred embodiment, the flow regulator is of the mechanical type typically used in association with intravenous fluid lines in a hospital setting, having a wheel that may be spun to impinge on the NALGENE® tubing, which thereby reduces the flow of fluids therethrough. One skilled in the art will appreciate that other flow regulators may also be used without departing from the scope of the invention.

The fluid supply 112 contains the superfusing nutrient solution, and may also hold a fritted stone oxygenator 114 for maintaining sufficient oxygenation levels within the nutrient solution. The fluid 112 is preferably a glass jar filled with, for example, Hanks buffer solution, and having a spigot on a lower end thereof, to which is connected the fluid supply line 116. In a preferred embodiment, the fluid supply 112 is placed at a higher elevation than the block 102. Connected in this way, the tissue chambers 142 of the block 102 may be gravity-fed without the need for mechanical pumps and the like to supply the nutrient solution. Indeed, a broad range of flow rates are available through use of such a system by combining the pressure generated by the elevated fluid supply 112, as well as the flow regulator 118 and the valves 121 on the manifold 120. Nevertheless, one skilled in the art will readily appreciate that mechanical pumps and the like may optionally be employed to pump nutrient solution to the tissue chambers.

As previously explained, the tissue sample and bracket assemblies may be affixed within the tissue chambers by way of screw 126 securing the assemblies within the chambers. And, as previously explained, tethers 181 may be secured at one end to the top of the tissue sample. As shown in Figure 6, the free end of the tethers 181 may be attached to respective transducers 132 at their free end by securing them to hooks 130. The hooks, in turn, are connected to transducer lever-arms (not shown), and serve to transmit force imparted by the tether 181 to the lever arm. The transducers 132 are preferably slidably attached to a horizontal member 133 of a scaffold in order to suspend the transducers 132 above the tissue chambers; the horizontal member 133 may be slideably attached at either end to a first and second vertical member 131 , which allows the horizontal member to be adjusted vertically.

The transducers 132 are each typically connected to voltage amplifiers 136, which, in a preferred embodiment, amplify voltages from the range of 0-0.5 V to the range of 0-5.0 volts. The amplifiers 136, in turn, are connected to an A/D board 138, which converts the analog voltage signal generated by the transducers 132 into a digital signal. The A/D board 138 is further coupled to a computer 140 which is capable of capturing, analyzing and displaying the digital signal provided by the A/D board 138. Software to capture and display digital signals from an A/D board, as well as A/D boards themselves, are ubiquitous in laboratory environments where tissue testing is carried out, and one skilled in the art will readily recognize that any suitable software or electronics could be selected without departing from the scope of the invention.

The block 102 may be further installed in a heated water bath 108 for heating the block 102 and the nutrient solution within the block. The block 102 (which is attached to the transducers and the fluid supply) may be lowered into the water bath 108 in the direction indicated by the arrow to rest upon shelf 139. As shown in Figure 7, shelf 139 is preferably constructed of a perforated sheet of sheet metal that allows close association of the block 102 with the water 110 in the water bath 108, through the perforations in the shelf 139. Preferably, the shelf 139 will be installed within the water bath 110 such that, when the block is placed on the shelf 139, the water level does not rise above the top surface 103 of the block 102 and swamp the tissue chambers.

In a preferred embodiment, the water 110 in the water bath 108 is maintained at a temperature of approximately 37⁰C. The heated water 110 in the water bath 108 serves to heat the block 102, the tissue chambers, and all the lines and channels submerged therein, thereby maintaining the nutrient solution and tissue samples therein at approximately 37°C as well. In a preferred embodiment, a predetermined length of each supply line is submerged in the water bath 108 in order to preheat the nutrient solution within the supply lines 104 before the nutrient solution enters a tissu© chamber. In a preferred embodiment, the water bath is a PRECISION INSTRUMENTS^® Model 180 water bath.

Waste fluid from within sink 168 can be drawn out of sink 168 by way of fluid waste line 106, which can be further operatively connected to peristaltic pump 122. Specifically, a first end of fluid waste line 106 is inserted into sink 168 (as, for example, shown in Figures 3A and 6). A segment of fluid waste line 106 is further operatively associated with peristaltic pump 122, which pumps the waste nutrient solution into the waste receptacle 124. One skilled in the art will readily recognize that a wide variety of peristaltic pumps or the like may be used in connection with the disclosed inventions; however in a preferred embodiment, the peristaltic pump is a MASTERFLEX^® Model No. 7021-24. And, as previously mentioned, the waste fluid from sink 168 need not be deposited in waste receptacle 124. Rather, if desired, the user can collect the excess nutrient solution for further testing and analysis. In addition, to the extent a block is used that includes separate drainage channels, such as the one disclosed in Figure 5, separate waste lines 106 and peristaltic pumps 122 may be used for each drainage channel 252.

To operate the system once it is assembled and the block is positioned within the preheated water bath 110, the user may selectively open the flow regulator 118 and one or more valves 121 on the manifold 120. This causes nutrient solution to begin to flow to the tissue chambers to nourish the tissue samples. In a preferred embodiment, the flow rate is between about 50 μl/minute to 10 ml/minute. Likewise, the excess or waste superfusing fluid is generally drawn off at approximately the same or higher rate in order to prevent excess waste nutrient solution from building up within the drainage channels and contaminating the tissue chambers. In addition, to the extent that tissue tension testing is being performed, the computer 140 is typically continuously recording and displaying data captured from the signals provided by the transducers 132.

While operating the micro organ bath system, it is often desirable to introduce reagents or pharmacologically-active compounds into the tissue chamber 142 In order to evaluate the effects such compounds have on me tissue sample 179 within the chamber 142. To do so, the supply of nutrient solution from fluid supply 112 may be stopped either by shutting off valves 121, adjusting the flow regulator 118, or both. The reagents or compounds may then be directly introduced into the tissue chambers 142 by means of a micropipette. After waiting a predetermined amount of time, the superfusate from within the tissue chamber 142 may optionally be withdrawn through fluid drain passage 150 (as shown in Figure 3B), through a length of tubing, and into an attached syringe. Following drainage of the tissue chamber, the valves 121 and/or the flow regulator 118 may be reopened to allow nutrient solution within the fluid supply 112 to reenter the tissue chambers 142, thereby resuming normal operation of the micro organ bath system. The withdrawn sample may then be further analyzed as the user sees fit. It is also possible to simply add the desired pharmacological agent to the superfusing solution contained in fluid supply 112 such that the desired concentration is achieved and so that the tissues will be bathed with the desired concentration until the superfusing solution is removed from the supply 112.

Although the micro organ bath system shown and described with respect to Figure 6 depicts use of a single block 102 having a plurality of tissue chambers, other configurations are also possible. For example, a plurality of blocks 102 may be positioned within the same water bath 108, space permitting. Also, a plurality of blocks each having a single tissue chamber (as, for example, those described with respect to Figure 5) may similarly be positioned within the water bath 108.

Thus, while the invention has been disclosed and described with respect to certain embodiments, those of skill in the art have recognized modifications, changes, other applications and the like which will nonetheless fall within the spirit and ambit of the invention, and the following Claims are intended to capture such variations.

Claims

WHAT IS CLAIMED IS:

1. A block for superfusing tissue with a fluid, comprising: a block body; a tissue chamber having a chamber volume with a defined capacity formed in said block body; an inflow passage in communication with said tissue chamber for providing the fluid to said tissue chamber; and an overflow passage in communication with said tissue chamber for receiving the fluid that exceeds said defined capacity of said chamber volume from said tissue chamber and directing the fluid away from said tissue chamber.

2. The block of claim 1 , further including a sink for collecting the fluid that exceeds the defined capacity of said chamber volume from said tissue chamber, said sink being formed in said block body at a location spaced apart from said tissue chamber, and wherein said overflow passage is in communication with said sink.

3. The block of claim 2, further including a fluid outflow line in communication with said sink, wherein said fluid outflow line is capable of receiving fluid collecting in said sink and directing the fluid away from said sink.

4. The block of claim 3, further including a pump operatively associated with said fluid outflow line.

5. The block of claim 1, further including a drain passage formed in said block body for draining fluid from said tissue chamber, wherein said drain passage is in communication with said tissue chamber.

6. The block of claim 5, further including:

a container for receiving and holding fluid; and

a drain line having first and second ends, wherein the first end is connected to said drain passage, and the second end is in communication with said container.

7. The block of claim 6 wherein said container is comprised of a syringe.

8. The block of claim 1, further including a fluid supply for supplying fluid to said tissue chamber, wherein said fluid supply is in fluid communication with said tissue chamber.

9. The block of claim 8, further including:

a fluid supply line for supplying fluid to said tissue chamber, said fluid supply line including a first end and a second end, and wherein the first end is attached to said fluid supply, and the second end is connected to said inflow passage.

10. The block of claim 9 further including a flow regulator operatively associated with said fluid supply line.

11. The block of claim 8 further including:

a manifold, said manifold including a manifold inflow port and at least one manifold outflow port;

a first fluid supply line having first and second ends, and wherein the first end is attached to said fluid supply and the second end is attached to said manifold inflow port; and

a second fluid supply line having first and second ends, and wherein the first end is attached to said inflow passage in said block and the second end is attached to said at least one manifold fluid outflow port.

12. A block for superfusing tissue with a fluid, comprising: a block body having a chamber volume with a defined capacity; a plurality of tissue chambers formed in said block body, each of said plurality of tissue chambers further including: an inflow passage in communication with said tissue chamber for providing fluid to said tissue chamber; and

an overflow passage in communication with said tissue chamber for receiving the fluid that exceeds said defined capacity of said chamber volume from said tissue chamber and directing the fh i'-A =>»Ό\» from <SCMH ficci O ph?mKor

13. The block of claim 12 wherein at least two of said overflow passages are connected.

14. The block of claim 13, further including a sink, said sink being formed in said block body at a location spaced apart from said plurality of tissue chambers, and wherein said at least two overflow passages are in communication with said sink.

15. The block of claim 14, further including a fluid outflow line in communication with said sink, wherein said fluid outflow line is capable of receiving fluid collecting in said sink and directing the fluid away from said sink.

16. The block of claim 15, further including a pump operatively associated with said fluid outflow line.

17. The block of claim 12, further including a drain passage formed in said block body for draining fluid from at least one of said plurality of tissue chambers, wherein said drain passage is in communication with said at least one of said plurality of tissue chambers.

18. The block of claim 17, further including:

a container for receiving and holding fluid; and

19. The block of claim 18, wherein said container is comprised of a syringe.

20. The block of claim 12, further including a fluid supply for supplying fluid to at least one of said plurality of tissue chambers, wherein said fluid supply is in fluid communication with said at least one of said plurality of tissue chambers.

21. The block of claim 20, further including at least one fluid supply line, said at least one fluid supply line including a first end and a second end, and wherein the end is connected to said fluid supply, and the second end is connected to said inflow passage that is in communication with said at least one of said plurality of tissue chambers.

22. A method for superfusing a tissue sample, comprising: providing a block body; forming a tissue chamber within said block body; forming an inflow passage in communication with said tissue chamber for providing fluid to said tissue chamber;

forming an overflow passage in communication with said tissue chamber for receiving the fluid from said tissue chamber and directing the fluid away from said tissue chamber;

securing a tissue sample within said tissue chamber; and

providing superfusing solution through said inflow passage to provide the nutrient solution to said tissue chamber.

23. The method of claim 22 wherein the step of securing the tissue sample within the tissue chamber includes:

disposing a bracket within said tissue chamber, said bracket being adapted to attach to a surface of said block body; attaching said bracket to said surface of said block body; and

attaching the tissue sample to said bracket.

24. The method of claim 23, further including forming a sink in said block body at a location spaced apart from said tissue chamber, wherein said sink is in fluid communication with said overflow passage.

25. The method of claim 22, further including:

providing a heat source, said heat source being capable of transmitting heat to said block body; and

placing said block body proximate said heat source.

26. The method of claim 25 wherein:

providing a heat source includes providing a heated water bath; and

placing said block body proximate said heat source includes partially submerging said block body in said heated water bath.