Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
  • B01L3/00—Containers or dishes for laboratory use, e.g. laboratory glassware; Droppers
  • B01L3/50—Containers for the purpose of retaining a material to be analysed, e.g. test tubes
  • B01L3/502—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures
  • B01L3/5027—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip
  • B01L3/502769—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip characterised by multiphase flow arrangements
  • B01L3/502776—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip characterised by multiphase flow arrangements specially adapted for focusing or laminating flows
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12Q—MEASURING OR TESTING PROCESSES INVOLVING ENZYMES, NUCLEIC ACIDS OR MICROORGANISMS; COMPOSITIONS OR TEST PAPERS THEREFOR; PROCESSES OF PREPARING SUCH COMPOSITIONS; CONDITION-RESPONSIVE CONTROL IN MICROBIOLOGICAL OR ENZYMOLOGICAL PROCESSES
  • C12Q1/00—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
  • B01L3/00—Containers or dishes for laboratory use, e.g. laboratory glassware; Droppers
  • B01L3/50—Containers for the purpose of retaining a material to be analysed, e.g. test tubes
  • B01L3/502—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures
  • B01L3/5027—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip
  • B01L3/502746—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip characterised by the means for controlling flow resistance, e.g. flow controllers, baffles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
  • B01L3/00—Containers or dishes for laboratory use, e.g. laboratory glassware; Droppers
  • B01L3/50—Containers for the purpose of retaining a material to be analysed, e.g. test tubes
  • B01L3/502—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures
  • B01L3/5027—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip
  • B01L3/502761—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip specially adapted for handling suspended solids or molecules independently from the bulk fluid flow, e.g. for trapping or sorting beads, for physically stretching molecules
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
  • C12M21/00—Bioreactors or fermenters specially adapted for specific uses
  • C12M21/06—Bioreactors or fermenters specially adapted for specific uses for in vitro fertilization
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
  • C12M23/00—Constructional details, e.g. recesses, hinges
  • C12M23/02—Form or structure of the vessel
  • C12M23/16—Microfluidic devices; Capillary tubes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
  • B01L2200/00—Solutions for specific problems relating to chemical or physical laboratory apparatus
  • B01L2200/06—Fluid handling related problems
  • B01L2200/0636—Focussing flows, e.g. to laminate flows
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
  • B01L2200/00—Solutions for specific problems relating to chemical or physical laboratory apparatus
  • B01L2200/06—Fluid handling related problems
  • B01L2200/0647—Handling flowable solids, e.g. microscopic beads, cells, particles
  • B01L2200/0668—Trapping microscopic beads
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
  • B01L2300/00—Additional constructional details
  • B01L2300/08—Geometry, shape and general structure
  • B01L2300/0809—Geometry, shape and general structure rectangular shaped
  • B01L2300/0816—Cards, e.g. flat sample carriers usually with flow in two horizontal directions
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
  • B01L2400/00—Moving or stopping fluids
  • B01L2400/04—Moving fluids with specific forces or mechanical means
  • B01L2400/0403—Moving fluids with specific forces or mechanical means specific forces
  • B01L2400/0415—Moving fluids with specific forces or mechanical means specific forces electrical forces, e.g. electrokinetic
  • B01L2400/0418—Moving fluids with specific forces or mechanical means specific forces electrical forces, e.g. electrokinetic electro-osmotic flow [EOF]
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
  • B01L2400/00—Moving or stopping fluids
  • B01L2400/04—Moving fluids with specific forces or mechanical means
  • B01L2400/0475—Moving fluids with specific forces or mechanical means specific mechanical means and fluid pressure
  • B01L2400/0487—Moving fluids with specific forces or mechanical means specific mechanical means and fluid pressure fluid pressure, pneumatics
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
  • B01L2400/00—Moving or stopping fluids
  • B01L2400/08—Regulating or influencing the flow resistance
  • B01L2400/084—Passive control of flow resistance
  • B01L2400/086—Passive control of flow resistance using baffles or other fixed flow obstructions

Definitions

• the present invention generally concerns handling of embryos.
• the invention also concerns handling of oocytes (prefertilized embryos), and eggs.
• Embryo as used herein, therefore encompasses oocytes, and eggs as well as fertilized embryos.
• the invention more specifically concerns microfluidic handling of embryos for culturing, manipulation, and analysis.
• BACKGROUND ART Technology assisted reproduction techniques in which embryos are handled independently from their mammalian biological source are growing in importance and frequency of use. Such techniques have great direct benefit to persons unable to have babies through unassisted sexual reproduction.
• the agricultural industries also increasingly rely upon such assisted reproduction techniques.
• Embryo manipulation is used in livestock reproduction to control such things as the faster genetic evolution of cattle and permitting the genetic characteristics of a single exceptional cow or bull to be passed on to far greater numbers of offspring than would be possible through unassisted sexual reproduction. Livestock embryo manipulation is becoming more routine due to the development of gene manipulation, cloning, and in vitro fertilization (IVF) techniques.
• the overall goal of embryo manipulation in livestock is to increase production efficiency, especially with regard to reproduction, milk production or production of specific milk components, lean tissue growth with reduced fat content and decreased susceptibility to specific diseases.
• Embryo transfer is also used to introduce or rescue valuable germplasm and propagate rare breeding animals such as endangered exotic species.
• An improved embryo handling device and method which addresses problems in known embryo handling techniques.
• An improved embryo handling device and method should provide for an improved simulation of natural conditions. It should also provide a building block upon which larger and/or more powerful and accurate instruments may be based, such as embryo culturing systems, embryo analysis systems, embryo storage systems, and similar systems. There is a further need for improved evaluation of embryo viability.
• the invention simulates biological rotating of embryos.
• An embryo fluidic channel moves an embryo inserted therein with fluid, and is sized on the same scale as the particular type of embryo or embryos to be handled.
• the sizing and fluid communication produces a simulated biological rotating of embryos.
• the fluid flow with and around the embryo or embryos prevents stagnation, reducing the likelihood of the embryo or embryos developing "bed sores".
• the invention also permits the biological medium fluid to be altered gradually, having significant advantages compared to repeatedly manually transferring an embryo from one medium to another medium in a pipet or petri dish. Gradual changes avoid the shock from sudden changes in local environment.
• the microfluidic system of the invention further permits the co-culturing of an embryo with other embryos, co-culturing of an embryo or embryos with cells upstream of the embryo(s), and maintenance of a separate control culture that shares a common biological medium with a subject embryo(s) thereby ensuring that test embryos see the same environmental conditions as the subject embryo(s).
• Other aspects of the invention concern specific uses of the broader principles of microfluidic embryo handling to manipulate, evaluate and position embryos.
• One aspect concerns the use of a gradual series of constrictions to remove surrounding material from an embryo. This has been demonstrated to remove surrounding cumulus from oocyte. A first few constrictions cut the cumulus, which can then be sucked off of the oocyte in a final small constriction which is sized to prevent passage of the oocyte.
• Embryo evaluation is also realized in accordance with the basic invention principles.
• surface properties and compliance (deformation) properties of embryos are evaluated.
• the microfluidic channels provide the opportunity for fine controls of pressure to conduct various evaluations at forces slightly below which damage to embryos is known to occur. Measurement of the distance and/or speed which embryos roll in a same pressure gradient microfluidic channel provides information, with healthy embryos traveling slower or a shorter distance as they demonstrate more stiction to channel walls. Positioned at a constriction, healthy embryos also appear to deform less than unhealthy embryos that are more readily pulled into a constriction. In addition, healthy embryos appear to resume their shape better.
• Fluid from microfluidic channels is easily collected downstream without altering the embryo environment, providing a better opportunity for chemical analysis of fluid chemical analysis than convention manual handling and sampling techniques.
• all of the fluid collected from a microfluidic channel has passed over the embryo. This provides better evaluation information than fluids stagnant around an embryo in a Petri dish.
• medium can continuously or periodically pass over embryos and be collected downstream, eliminating additional handling required in a petri dish technique.
• the invention provides more consistent fluid samples since fluid can be repeatedly collected in the same manner, whereas samples taken from petri dishes may vary based upon placement of the pipette that suctions medium, i.e., how far or how close to an embryo.
• clear channel sections allows for many types of optical analysis. Stains or dyes may be added for visual inspection at clear sections. Clear sections also provide the opportunity to use image analysis devices, since the microfluidic channels may be configured to precisely position an embryo at a location for analysis by imaging equipment.
• Precise position of embryos using channels and constrictions of the invention, and/or flow manipulation further enables an improved method for zona pellucida removal of mammalian embryos. Embryos are moved through flow to a precise location where lysing agent can be washed over the embryo to achieve zona removal.
• FIG. 1 shows a cross section of a preferred microfluidic embryo handling device constructed in accordance with the present invention
• FIG. 2(a) is a top view showing a preferred narrow microfluidic channel constriction for embryo positioning
• FIG. 2(b) is a cross-sectional view of an alternate preferred shallow microfluidic channel constriction for embryo positioning
• FIGs. 2(c) and 2(d) are schematic views of an alternate preferred fluid dynamic constriction
• FIG. 2(e) is a schematic view of an alternate preferred fluid dynamic constriction
• FIG. 2(f) illustrates an alternate preferred mechanical constriction geometry
• FIG. 2(g) shows a particular flow pattern in the FIG. 2(e) fluid dynamic constriction useful, for example, for zona treatment
• FIG. 3(a) is a perspective view of a preferred gravity flow driven microfluidic culturing and testing device constructed in accordance with the present invention
• FIG. 3(b) is a schematic cross-section of microfluidic channel for a zona pellucida removal procedure of the invention
• FIG.4 is a block diagram of an embryo analysis device constructed in accordance with the present invention.
• FIGs. 5(a) - 5(c) illustrate preferred embryo microfluidic channel insertion and removal structures in accordance with the present invention
• FIGs. 6(a) - 6(b) illustrate a preferred culturing device constructed in accordance with the present invention
• FIGs. 7(a) and 7(b) schematically illustrate a constricted channel geometry useful for cumulus removal from oocytes
• FIGs. 8(a) and 8(b) illustrate a complete prototype device for cumulus removal
• FIGs. 8(c) - (f) illustrate steps used in experiments with the FIG. 8(a) and 8(b) prototype to remove cumulus from an oocyte
• FIGs. 9(a) - 9(d) illustrate a deformation evaluation of an embryo used as an indicator of embryo viability
• the present invention provides a microfluidic embryo handling device which reduces stress to embryos handled outside their natural biological host.
• the device and method reproduce simulated biological rotating of an embryo through fluid assisted movement in a channel that encourages embryo slipping and rotating.
• Rotating as used herein, may include complete rotation or partial rotation. Partial rotation might also be referred to as a rocking motion.
• FIG. 1 shown is a cross-section of a microfluidic embryo handling device 10 including a embryo transport network 12 formed at least in part by a generally embryo scale channel 14.
• An embryo 16 in the channel 14 will move with fluid flow in the channel 14, while the close dimensions of the channel cause the embryo 14 to move with a simulated biological rotating motion.
• Channels up to ten times the embryo size have been used to create rolling and slipping.
• developing embryos in their initial stages of development move toward the uterus to which they will attach with a rotating and slipping motion.
• the microfluidic channel 14 produces a simulation of such motion.
• Sizing of a channel is important to establish the biological rotating.
• Height is the critical dimension, and it has been found that heights up to about three times the diameter of an embryo induce the rotating. This ratio may be determined to vary somewhat because fluid flow also plays a role, but the three to one maximum ratio has been found to produce the rotating.
• the channel width is less important. The width may be selected arbitrarily. Thus, if embryos are to be kept in single order, then the width would be less than twice the embryo diameter. If more embryos are desired, larger width channels may be used.
• Networks of the channels 14 provide a means to culture embryos, as well as to move and place embryos to desired locations. During its initial stages of development, the size of most mammalian embryos remain generally constant during the first few days after fertilization. Thus, the size of the channels 14 provide no impediment to culturing an embryo therein.
• the embryo 16 may be kept moving and/or may have a continuous or pulsed fluid flow passed around it to avoid potential detrimental biological effects on the embryo 16.
• a preferred exemplary construction of a device 10 including a channel is also illustrated in FIG. 1.
• the microfluidic channel 14 may be formed by any suitable micromachining technique into a suitable material, such as a silicon wafer 18. The material chosen must be capable of being sterilized and should not pose a biological threat to embryos.
• the channel(s) 14 of the device are sealed through a cover 20.
• Forming the cover of glass or other transparent material allows convenient visual monitoring of embryos in channel(s) 14.
• a bonding agent 22 bonds the cover 20 to the wafer 18. Additionally, the material of the cover could be formulated to shield harmful radiation from the embryo(s) in channel(s) 14.
• Typical mammalian preimplantation embryos of interest are 90 to 180 ⁇ m diameter spheres.
• a membrane surrounds each cell (blastomere) and the zona pellucida, a glycoprotein membrane or shell, surrounds the entire cell mass.
• the cells divide several times during the first few days after fertilization, the volume of the embryo remains constant and an egg may be fertilized and cultured to a blastocyst in the same device constructed based upon the principles of the invention.
• the blastocyst is the final stage before an embryo implants in the uterus.
• Also important to production of such a device and similar devices is the ability to handle individual embryos, or small numbers of embryos. Positioning embryos to given locations, moving to alternate locations, and maintaining constant or changing biological conditions around the embryo(s) are abilities provided by basic principles of the present invention, and permit the construction of fertilization, culturing, testing, and other devices which rely on some or all of those abilities. For continuous movement of an embryo through a culture period of time, long channels may be created, or a loop may be formed. Alternately, a parking of an embryo may occur at a culturing station like those shown in FIGs. 6(a) and 6(b). A compartment or channel of limited size may also be used to roll an embryo back and forth therein by changing fluid flow, as will be further discussed with respect to FIGs. 6(a) and 6(b).
• FIG. 2(a) is a top view of a cross section of a narrow constriction 24 formed in a microfluidic channel 14.
• Fig. 2(a) is a top view of a cross section of a narrow constriction 24 formed in a microfluidic channel 14.
• Analysis instruments built into the device may require an embryo to be precisely positioned at electrodes, a photodetector, the focal point of a microscope, or other similar sensing device. Transporting an embryo to the constriction 24 permits such required positioning without resort to feedback systems. An embryo 16 is freed from the constriction 24 simply by reversing the flow of biological fluid medium 30.
• FIG. 2(b) shows a side cross-section of an alternate shallow constriction 26 where the fluid biological medium 30 is similarly able to pass when an embryo 16 is positioned at the constriction.
• Other shapes of constriction are also possible. Generally, any shape which prevents passage of an embryo 16 while simultaneously allowing fluid flow through the constriction, e.g., asymmetric shapes and comb-like fibers, is acceptable to position embryos in a device 10 according to the invention.
• constriction be sized such that positioning of an embryo prevents the embryo from passing without an increased pressure from the fluid pressure used in a device 10 to move embryos. Constriction length should also be kept small enough to avoid fluid control problems since the constriction portion of a microfluidic channel will have much higher fluidic resistance per unit length than unrestricted portions of the microfluidic channels 14.
• Fluid dynamics within microfluidic channels 14 may also be used to position embryos. Whereas the constrictions of FIGs. 2(a) and 2(b) are physical constrictions, an effective fluid dynamic constriction is realized in FIGs. 2(c)and 2(d) without a physical ba ⁇ ier to passage of an embryo.
• an increased depth microfluidic channel well portion 14a defines a position where an embryo 16 may be intentionally held by control of fluid dynamics, i.e., the flow over and through the well portion 14a.
• high laminar or nonlaminar flows will cause an embryo 16 to stay in the well portion because flow separation occurs at the leading edge of the well portion 14a.
• FIG. 2(e) shows an alternate strategy for positioning an embryo 16.
• a T-junction 14b is formed at the intersection of microfluidic channels 14.
• FIG. 2(f) shows an indent or other small physical shape.
• FIGs. 2(a) - 2(f) With the geometries and flows of FIGs. 2(a) - 2(f) it is possible to position an embryo at a precise location within a network of microfluidic channels. This affords an opportunity for visual inspection, embryo removal, embryo testing, analysis of the embryo by imaging or other devices and treatment of an embryo. Many mechanical manipulations of the embryo can accordingly be effected, and any treatment, analysis, or manipulation that would benefit from such accurate positioning an moving of the embryos, and the ability to manipulate and control the flow environment therefore benefits from application of the invention.
• a specific exemplary treatment technique using constrictions and microfluidic channel flows to position an embryo in a device like the FIG. 2(a) - 2(e) devices is zona pellucida removal from an embryo.
• the zona pellucida is a glycoprotein matrix surrounding embryonic cells.
• a chimera a single animal with two DNA sets, is made by removing the zona pellucida and bringing the separate embryonic cells together. Zona thinning or removal is also important to transgenic procedures, IVF, and cell biopsy.
• a parking location is defined for zona removal, see, e.g., FIG. 2(f).
• the low aspect ratio, on the order of .01, for the top section of constriction in FIG. 2(f) may require support to avoid collapse.
• microfluidic channels are configured such that a controlled wash of acidic solution can be caused to flow a parked embryo or embryos.
• an acidic inlet can t-junction into a main flow leading to the parking area of FIG. 2(f).
• a lysing plug for example, provides acidic solution into the main channel near and upstream of the constriction for a short period to achieve zona removal.
• precise control of the flow is achieved for a required period of time.
• syringe connections to a main microfluidic channel including the constriction and a "T" intersection channel were used to control embryo positioning and flows over positioned embryos. Syringes offer precise control of fluid, and computer controlled microsyringes will add precision to flow control and timing.
• An alternate mechanical method of removing a zona involves mechanical damage to the zona. This is achieved, for example, by passing the zona through a microfluidic channel of the invention including a mechanical structure to nick or cut the zona.
• the precise fluid control of the invention also creates the possibility of a laminar flow method to "nick" a zona.
• two separate flows of two different solutions meet at the "T” and flow into a single channel, as shown in FIG. 2(g), where a dotted line indicates separation of flow. These flows may be kept separate in the single channel by laminar flow.
• One flow (on the left) contains, for example, acid for zona thinning.
• Driving pressures control the lateral position of the interface between the two solutions such that the zona of an embryo 16 is "nicked" by the acid.
• FIG. 3(a) A culture and test device 31 including a constriction like that shown in FIG. 2(a) for positioning an embryo is illustrated in FIG. 3(a).
• the device 31 has fluid flow in a network 32 of microfluidic channels 14 driven by gravity based upon levels of fluid 30 in a plurality of fluid reservoirs 34.
• Any suitable means for driving fluid 30 is contemplated as being compatible with the general principles of the invention, e.g. pumping, but the gravity method illustrated in FIG. 3(a) is prefe ⁇ ed for its simplicity and efficiency. Directions of flows are controlled simply by levels of fluid in reservoirs 34.
• an embryo 16 held at a constriction 24 for culturing or examination by a suitable instrument is positioned by first setting fluid levels to cause its travel from inlet port 36 to constriction 24, and is released when fluid flow is reversed through the constriction 24. Removal of the embryo 16 is accomplished by causing fluid flow to move it to exit port 38.
• the embryo(s) roll and slip to simulate natural movement of embryos toward a uterus in a mammalian host, as discussed above.
• This desirable manner of moving may be aided by a suitable surfactant such as BSA (bovine serum albumin).
• BSA bovine serum albumin
• the surfactant will help to promote some slippage of the embryo as it rolls.
• FIG. 3(a) also illustrates an additional advantage of the invention, in the provision of a parallel additional microfluidic handling and culturing device 31a.
• the additional device 31a has a structure similar to that of device 31, but may have fewer or even a single microfluidic channel. Ideally, the structure is the same.
• the important feature of the device 31a is that it shares a common fluid source with inlet port 36 and outlet port 38 of primary device. Embryo(s) handled in the device 31a are isolated biologically from embryo(s) in primary device 31, but experience the same biological conditions through sharing the same fluid source, pressure and/or the same biological medium condition.
• FIG.4 is a block diagram of an embryo analysis device.
• FIG. 4 device a network 32 of microfluidic channels 14 moves embryos to one or more analysis stations 40a, 40b or 40c. Embryos are positioned at a given analysis station through constrictions like those described above.
• the analysis stations may include any instrument capable of obtaining information concerning an embryo, with the constriction being formed to position embryos at the proper sensing point for the particular instrument used in an analysis station. Embryos are moved out of the device through one or more exit ports 38a, 38b, which might alternately lead to a culturing station in the form of a parking area for an embryo, an additional length of microfluidic channel 14, or a microfluidic channel loop for continuous movement of an embryo during culturing.
• Inlet and outlet ports used in devices of the invention may comprise any conventional manner or structure for embryo insertion or removal. However, additional prefe ⁇ ed structures for insertion and removal are shown in FIGs. 5(a) - 5(c).
• a well 42 which is in fluid communication with a microfluidic channel 14 is used. Fluid in the well 42 preferably also comprises a gravity feed which helps drive microfluidic flow in the channel 14.
• An embryo 16 is placed in the well 42 and moves into the channel 14 with biological medium, or simply sinks unaided into the channel 14 if no flow condition is created.
• a second similar well 42 may be used to remove an embryo using a pipet 44 or similar device, which might also be used for insertion.
• a hanging drop 46 at the end of a channel 14 is used for insertion and removal.
• the hanging drop 46 is held by surface tension.
• fluid may be added at that point, or the embryo may be sucked in by fluid flow in the device. Alternately, the device may be inclined to promote embryo movement away from the hanging drop 46.
• a funnel shaped hole 48 in direct communication with channel 14 is used for insertion and removal. The funnel shape aids positioning of a pipet 44 or similar device. Surface tension at a small diameter hole 48 will prevent fluid from leaking out, but the pressure in channel 14 must not exceed the point that would defeat surface tension and cause fluid to leak out.
• FIG. 5 any of the FIG. 5 techniques may be combined with each other or conventional techniques for insertion and removal in a given handling device.
• the wells 42 or holes 48 may be covered by a removable cover or flap as protection against contamination and/or evaporation.
• Fluid medium flow in the culture device 50 is in either direction between a medium inlet 52 and a medium outlet 54.
• the device includes a number of traps or compartments 56.
• the traps 56 comprise deep regions separated by shallow regions 58.
• Fluid flow between inlet 52 and outlet 54 is over shallow regions and through deep regions to move embryos back and forth within the deep region compartments 56.
• Embryos are inserted and removed through access holes 60, which may be formed by any of the prefe ⁇ ed methods in FIGs. 5(a) through 5(c).
• FIGs. 6(a) and 6(b) show a top loading embodiment for placing embryos within the compartment
• the device will also work in a bottom loading a ⁇ angement, essentially inverted from that shown in FIGs. 6(a) and 6(b).
• An alternate embodiment might comprise a gap in place of shallow constrictions where embryos cannot pass through the gaps but fluid flow may occur therebetween and the depth of the gaps may be the same as those of the embryo holding compartments.
• Prototype devices like that shown in FIG. 3(a) have been produced and tested. Typical prototypes are described here for the sake of completeness. Artisans will appreciate that the manner of fabricating the prototypes may be accomplished by any other convention micro fabrication techniques. Artisans will also appreciate that production device manufacturing may differ significantly, and that specific numerical dimensions and conditions of the prototype devices do not limit the invention in the breadth described above.
• a pressure gradient of 1 Pa/mm causes the medium to flow on the order of 10 ⁇ 10 m 3 /s (100 nl/s), with an average speed of 1 to 2 mm/s.
• the embryos roll along the bottoms of the channels; traveling at speeds ranging from Vz to ⁇ h that of the fluid that would otherwise be in the same region of the channel.
• the embryos can be transported to (and retained at) specific locations including culture compartments and retrieval wells. Embryos fill a considerable portion of the channel, thereby greatly altering the flow of medium.
• the flow of medium through the channels is laminar.
• Networks of prototype microfluidic channels have been fabricated in a device like that shown in FIG. 3(a) by etching trenches in 3-inch ⁇ 100> silicon wafers, and then bonding glass covers to form channels.
• Devices including microfluidic channels have also been made by micromolding techniques in elastomers. Other plastics and techniques are also likely to be suitable, including, for example, injection molding of thermoplastic materials.
• Typical channel networks contain several branch microfluidic channels that intersect near the center of the device. The branches, which range from 1.5 to 2.5 cm in length, are 160 to 200 ⁇ m deep and 250 to 350 ⁇ wide at the top.
• a first step in producing prototype devices involves patterning silicon nitride (SiN) coatings on using conventional photolithography techniques.
• the microfluidic channels are anisotropically etched with a potassium hydroxide (KOH) solution. Access holes in the glass covers are drilled, either conventionally using carbide tipped bits or ultrasonically. Glass covers are bonded to the wafers using UV curable epoxy (NOA 61, Norland Products, Inc, New Brunswick, NJ) or Pyrex 7740 covers are anodically bonded to the wafers using 500V in a 450 °C environment. The nitride coatings are removed using buffered oxide etchant (BOE) before anodic bonding.
• BOE buffered oxide etchant
• Glass wells are bonded to the glass cover at the end of each branch of the channel network with either an epoxy (Quick Stick 5 Minute Epoxy or 5 Hour Set Epoxy Glue; both from GC Electronics, Rockford, IL) or a silicone adhesive (RTV 108 and RTV 118 from General Electric Co., Waterford, NY, or Sylgard ® Brand 184, Dow Corning Corp., Midland, MI).
• an epoxy Quick Stick 5 Minute Epoxy or 5 Hour Set Epoxy Glue; both from GC Electronics, Rockford, IL
• silicone adhesive RTV 108 and RTV 118 from General Electric Co., Waterford, NY, or Sylgard ® Brand 184, Dow Corning Corp., Midland, MI.
• B6SJL/F2 two-cell mouse embryos
• medium Ml 6 Sigma, St. Louis, MO
• BSA bovine serum albumin
• All embryos were cultured at 37°C in a 5% CO 2 in air atmosphere for 96 h. Developmental rates of embryos were examined every 24 h. The percentage of embryos that reached the blastocyst stage for each material was compared with the percentage from the control group. Mouse embryos that reach the blastocyst stage, the latest possible stage before embryo transfer, are probably not developmentally hindered.
• Tests were run to examine several aspects of the prototype devices. Different tests required devices with different channel configurations. In all the tests, a halogen bulb via optical fibers illuminated the channel, which was viewed under a stereomicroscope. A graduated cylinder and a stopwatch were used to determine flow rates. Since the fluid is incompressible, the average fluid velocity in any section of channel is just the flow rate divided by the cross-sectional area.
• mice embryos were placed in the inlet well, at the channel entrance.
• the channel has 2 or 3 different widths.
• Widths measured at the surface of the wafer, range from 275 to 480 ⁇ m. In the na ⁇ owest segments, the embryos were geometrically constrained to travel on a V-groove while in the other regions along a flat-bottomed channel. The speed of travel and rotating characteristics were observed and compared for different segments.
• a pressure gradient of 0.16 Pa/mm drives the flow through the channel at an average velocity of approximately 380 ⁇ m/s.
• the embryos rolled at 187 - 250 ⁇ m/s, 49 to 66% of 380 ⁇ m/s.
• the embryos roll faster, slipping as they roll.
• the actual speed of travel and the tendency to stick varies from one embryo to the next
• One embryo has been observed to travel 25% quicker than another at the same time in the same channel, in almost the same path line.
• the velocity is linear with pressure gradient.
• the average fluid velocity and embryo speed is greater in a channel with smaller cross-sectional area.
• the average fluid velocity and embryo speed is greater in a channel with larger cross-sectional area.
• embryos travel slower on V- grooves than on flat-bottomed channels. Embryos are also more likely to become wedged and stuck in a V-groove than on a flat-bottomed channel.
• Fluid under electroosmotic flow also caused embryos to roll through channels.
• Switching on the voltage caused the mouse embryo to roll along the channel bottom 20 ⁇ m/s faster, at approximately 30 ⁇ m/s, toward the well with the negative electrode. With the voltage polarity reversed, the embryo rolled at approximately 10 ⁇ m/s in the reverse direction.
• No surfactant, such as BSA was used so there was little or no slipping.
• Electrical assistance, if used to move embryos, must be applied under carefully controlled conditions to avoid undesirable heating of the medium.
• the medium had an average velocity of 380 ⁇ m/s under a pressure gradient of 0.16 Pa/mm.
• Finite element analyses determined the centerline velocity to be 815 ⁇ m/s under these conditions.
• the embryo When traveling in the channel, the embryo was tangent to the bottom and one wall.
• the average velocity of the fluid traveling through this circle when the embryo is not present is 480 ⁇ m/s.
• the embryos rolled at only 187 - 250 ⁇ m/s, 39 - 52% as quickly, in both PBS and PBS BSA media.
• the velocity profile encourages the embryo to roll forward and along the wall, which confirms visual observations. In sum, embryos roll at Vs to Vz the speed at which fluid would flow in the same region of the cross section.
• the constrictions greatly increase fluid resistance in the channels.
• Standard analytical formulas can help approximate the resistance, but the cross-sectional shapes of the constrictions vary with position.
• Three- dimensional models of the constrictions were analyzed before masks were designed and wafers were etched. The information gained from the finite element analyses led to optimally-sized constrictions.
• the shallow constrictions sized individually for the geometry of the device, balance the need for minimal flow resistance and robust fabrication. Typical constrictions have a minimal depth of 20 ⁇ m.
• Electroosmotic flow is useful for assisting embryo movement, and can assist formation of plugs used for embryo treatment and fertilization. Electrical control of fluid flow must be carefully managed since high voltages can harm the embryos in several ways.
• Microfluidic transport free of electrical assistance offered through gravity fed devices like that in FIG. 3(a), or through pumped fluid pressure devices, offers an important advantage.
• the medium can be easily altered with time to meet the changing requirements of the developing embryos. Gradually changing the composition of the medium avoids inducing stresses upon the embryo from the abrupt environmental changes that often accompany transfer from one petri dish to a second dish with a different medium.
• the microfluidic handling of embryos by the invention is not physically harsher than transfer with pipets and definitely less damaging than many techniques in conventional practice including some which pierce the outer membrane.
• FIGs. 7(a) and 7(b) A particular geometry of microfluidic channels is schematically represented in FIGs. 7(a) and 7(b), and has been demonstrated to enable cumulus removal from oocytes.
• the geometry is a series of gradually more constricted sections of microfluidic channels, which are located in the curved sections. Though FIGs. 7(a) and 7(b) have curved constricted sections, the constricted sections need not be curved. Inner surfaces of the constricted sections preferably have protrusions in the form of teeth or se ⁇ ations to aid cutting of the cumulus as it passes.
• the last section in a series has protrusions separated at a distance apart to avoid damage to the oocyte, with the preceeding sections having protrusions spaced at gradually smaller distances apart to cut portions of su ⁇ ounding cumulus as fluid pressure forces the oocyte through a constricted section.
• multiple constricted sections curved sections each individually have protrusions with equal spacing, with a downstream section from a previous section using a lesser spacing.
• the FIG. 7(a) and 7(b) geometry has been used to remove cumulus from cattle oocytes.
• FIGs. 8(a) and (b) A complete prototype device for cumulus removal is depicted in FIGs. 8(a) and (b), while FIGs. 8(c) - (f) illustrate steps used in experiments withe the FIG. 8(a) and 8(b) prototype to remove cumulus from an oocyte.
• a polypropylene well is bonded to a loading port to provide a larger fluid reservoir at the inlet shown in FIG. 8(a).
• An acrylic syringe connection module exit ports so that standard syringes or other fittings can be connected to the device.
• Syringes enable manual pressure control, or a syringe pump can serve as a precise flow controller the plexi-glass and PDMS prototypes allowed for embryo positioning throughout a channel network and parking of the oocyte at desired locations during testing.
• the prototype devices provide complete optical access (important for embryo analysis), rapid prototyping, and easy integration with future analysis sensors.
• Loading oocytes in the device is simplified through the use of a funnel-shaped inlet well (inset in FIG. 8(b)).
• the funnel shape is molded at the entrance to the channel with the tip of the funnel connected to the head of the channel. This wide funnel configuration allows an oocyte complex to be easily inserted. Oocytes will typically sink to the funnel bottom.
• the complex is passed through two constricted regions (FIG. 8(c)). These na ⁇ owed regions force the cumulus into two main clumps at the front and back of the oocyte, as shown in FIG. 8(d).
• the two constricted cumulus conditioning regions (FIG. 8(a) were 200 and 150 ⁇ m wide, respectively. The cumulus gets damaged and bunched in the conditioning regions and then flows to removal ports (see FIGs.
• Microfluidic channels of the invention have also been used to realize novel methods of embryo health evaluation, by analysis of mechanical properties of the embryos.
• Specific mechanical properties demonstrated to distinguish health embryos include surface properties and deformation properties of embryos. The tendency of an embryo to return its shape after being deformed to a point short of permanent damage is believed to be an indicator of health because embryos actively maintain their shape.
• Embryos selectively transport ions through their membranes and the proteins of the zona pellucida are constantly reorienting themselves to resist external forces. Transport of ions and other substrates/metabolites into and out of the embryonic cells is a function of the health of the embryo.
• Unhealthy embryos have degraded ability to transport ions, and a co ⁇ esponding degraded ability to return their shape after being deformed to a point that avoids permanent damage.
• the control of pressure and the ability to position embryos at constrictions offers the opportunity to deform embryos with a control that prevents permanent deformation of health embryos. Deformation testing has been conducted keeping pressure gradients below 0.1 Pa/m (1 mm water/cm) and fluid velocities at or below a few millimeters per second.
• FIGs. 9(a) - 9(d) illustrate a deformation evaluation of an embryo used as an indicator of embryo viability.
• a constriction is sized to cause deformation of an embryo as it passes through due to fluid pressure.
• a healthy embryo better returns its shape in FIG. 9(d) after having passed through the constriction.
• an embryo might be deformed at constriction sized to prevent passage. After for a period of deformation at a constriction, flow is reversed, reversed and stopped, or stopped, allowing the embryo to return its shape.
• microfluidic channels The precise control of pressure offered by microfluidic channels also permits evaluation of embryo stiction to channel walls, as healthy embryos will stick more. Thus, a healthy embryo can quantitatively be measured to travel more slowly down a channel as compared to an unhealthy embryo. Alternatively, distance of travel can be similarly compared, with a healthy embryo traveling a shorter distance under identical flow and pressure conditions.
• Fluid analysis of embryos is better enabled by devices incorporating microfluidic channels of the invention. Fluid is collected from a downstream channel of a microfluidic channel culturing device of the invention. In accordance with devices formed according to the invention, the collected fluid will have flowed past an embryo since devices of the invention avoid stagnant conditions and sizing of the microfluidic channels causes fluid in the channels to pass close to an embryo.
• downstream fluid When downstream fluid is collected, it may be desirable to add a similar amount of upstream fluid to maintain pressures and flows within a microfluidic device from which fluid samples are being collected.
• Programmable syringe pumps can be used for removal of fluid samples and insertion of additional upstream fluid.
• all of fluid downstream an embryo could be collected. This fluid is then analyzed, such as by chemical or optical analysis.
• Systems of the invention can be used for complete oocyte maturation, fertilization and embryo culturing without harsh manipulation techniques.
• the ability to control fluid and position embryos offers the chance to mature an oocyte, bring sperm into contact, and then simulate biological embryo culturing, all within a single device of the invention.
• Maturation (IVM), fertilization (IVF) and culturing (EC) require different media, sperm capacitation and rinsing procedures.
• Systems of the invention using microfluidic channels allow rapid change and precise control of such conditions, allowing changing of the composition of the fluidic medium over the course of hours or days to simulate secretion and growth factor accumulation in the female reproductive tract and embryo movement to different parts of the tract.
• Medium can be controlled to flow slowly past each embryo (or oocyte) to provide a fresh supply of nutrients. Periodic flows, e.g. once an hour, as opposed to continuous flows, would allow a limited build-up of beneficial autocrine and paracrine factors without allowing waste products to accumulate. All of the cu ⁇ ent IMF, IVF and EC techniques can be performed in a single device of the invention such that a given oocyte - embryo does not have to be handled or moved during a sequential IMF, IVF and EC procedure or during any one of the individual procedures.
• Systems of the invention may reduce rates of polyspermy, use smaller numbers of spermatozoa, and incorporate a swim-up technique to select the most motile sperm.
• the egg is su ⁇ ounded by 50,000 to 100,000 sperm in a 0.5 to 1.0 ml drop of medium. This number could be reduced since the microfluidic channels provide a flow control to bring sperm and oocyte together.
• microfluidic channels cause sperm to pass very close to oocytes, e.g., about 30 ⁇ m.
• the time interval in which the sperm are near the oocyte can be controlled by controlling the rate of media flow.
• a parked oocyte positioned according to the invention can be held very close to the point of insertion of a comparatively small fluid packet of sperm, providing a high concentration of sperm near the oocyte while reducing the chance of polyspermy.
• Discrete plugs or boluses may deliver one to a few sperm to create a situation analogous to the situation in vivo in the oviduct where there are few numbers of sperm at any one time.
• This ability with a T- junction or other physical or effective constriction to position an embryo, allows for delivery of one to a few sperm to the proximity of the ovum to reduce the chance of polyspermy.
• channel geometry being embryo scaled allows for increased contact between the ovum and the sperm. Sperm and "bounce" off the side walls and increase the effective contact between the sperm and the egg.
• Cryopreservation is another technique that would benefit from the ability to position embryos according to the invention, and the ability to precisely control the fluid environment around the embryo.
• Cryopreservatives may be delivered to a positioned or moving embryo in a device of the invention, which can then later be used to reverse the cryopreservation process. Change of the fluid can then be used to conduct maturation, fertilization, and culturing, as described above.

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