Patent Application
20240131510
The general inventive concepts relate to the field of modified microfluidic device for cell-to-cell communication analysis.
Extracellular vesicles (EVs) are nano-sized, membrane-bound vesicles secreted from cells that can transport cargo such as lipids, nucleic acids, DNA, RNA, proteins, etc., between cells as a form of cell-cell communication (6). Progression of variety of disease states largely depend on the secretion and subsequent uptake of bioactive EVs (1). Different EV subtypes have been characterized on the basis of, for example, their biogenesis, release pathways, size, functions, etc. (6) These vesicles are heterogeneous in nature, and can range from 30 nm up to 10 μm in size (2). Some of these subtypes are illustrated in
Among these EVs, exosomes are a key player in the EV-based crosstalk that regulates disease progression (3,4). Their membranes and lumens are enriched with bioactive cargo molecules such as proteins, lipids, and nucleic acids that can be delivered to neighboring or distant recipient cells (5,7,8). Recently, exosomes have been shown to play a major modulatory role that can either promote or inhibit the progression of many human diseases, such as cancer, neurological disorders, cardiovascular diseases, and infectious diseases (3, 9-15). The potential of exosomes for use as diagnostic biomarkers or for the design of effective therapeutics and vaccines is being intensely investigated, given their potent regulatory function, availability in most bodily fluids, and incorporation of various disease-specific cargoes (16).
However, progress in mechanistic understanding of EV functions and relevance across many specific diseases is still extremely limited and much remains to be explored. This is in part due to the difficulty of working with EVs such as exosomes, both in vitro and in vivo. For example, the gold standard for performing in vitro EV studies can require lengthy and tedious series of centrifugation steps that include density gradient separations to purify them from the culture supernatant. Furthermore, large amounts of producer cells and culture media are needed per isolation to recover sufficient material (17). Alternative isolation methods such as size-exclusion chromatography are relatively costly and typically not able to sufficiently enrich the vesicles to obtain suitable yields for some applications, or to provide sufficient separation of exosomes from larger EVs (18).
Similarly, in vivo EV studies are inefficient. Due to their size and the complex tissue environment, direct observation of EVs in vivo is not easily achievable (19). Further, it is not yet readily possible to effectively target functionalized EVs to distinct cell types in vivo in order to monitor specific interactions and functions without potential complications arising from EV alteration (20). In addition to overcoming these limitations, it is highly desirable to have physiologically relevant functional assays that bridge purely in vitro and in vivo experimental designs and more closely replicate the in vivo setting, where EVs are constitutively exchanged between donor and recipient cells (21). Microfluidic technology has been utilized to alleviate some of the challenges associated with EV studies. This includes enhanced sorting, detection and isolation of EVs (18), efficient surface modification (22), and use in extrusion for the generation of new vesicles (23). However, current microfluidic technology (25) is limited with regard to simulating native exchange between co-cultured cells in order to enable functional studies. Further, they suffer from structural limitations that lead to, e.g., without limitation, cell aggregation within inlets and/or outlets of the microfluidic channels thereof, difficulty to retrieve the cells, negatively impacting the analysis and/or investigation of cell-cell communication of target subjects (e.g., EVs, particles, protein, etc.) (25).
There remains a need for improved microfluidic devices for investigating and analyzing intercellular communications, as well as methods of using the microfluidic devices for such investigation and analysis.
Provided is a microfluidic intercellular communication analysis device including a coverslip and a polydimethylsiloxane (PDMS) layer attached to upper surface of the coverslip. The PDMS layer includes a plurality of microfluidic channels each having an inlet and an outlet. The plurality of microfluidic channels includes a donor cell channel structured to receive a donor cell population, a recipient cell channel structured to receive at least a recipient cell population and a matrix channel including a diffusion barrier having pores, the diffusion barrier being structured to mimic extracellular matrix and conduit a target subject from the donor cell channel to the recipient cell channel through the pores, the donor cell channel and the recipient cell channel each comprising inlets and outlets having an arc angle ranging from 180° to 300°, the arc angle structured to prevent cell aggregation in the inlets, the outlets and/or channel surfaces of the donor cell channel and the recipient cell channel, wherein upon injection of the donor cell population and the recipient cell population into respective cell channels, the target subject is imaged by an imaging device couplable to the microfluidic intercellular communication analysis device and analyzed for intercellular communication thereof.
In some embodiments, the PDMS layer has a thickness of 3-4 mm such that the magnification of the imaging device required for the target subject is achieved without bending or damaging the coverslip.
In some embodiments, the matrix channel is selectively activated by a plasma pulse directed only at the matrix channel using an electrode placed in an outlet of the matrix channel and a tip of a plasma generator placed in an inlet of the matrix channel with inlets and outlets of the donor cell channel and the recipient cell channel being blocked.
In some embodiments, the diffusion barrier comprises a hydrogel. In further embodiments, the hydrogel is a porous hydrogel having a pore size appropriate for passing the target subject from the donor cell channel into the recipient cell channel via the matrix channel. In yet further embodiments, the porous hydrogel is Matrigel or PEGDA gel.
In some embodiments, inlet and outlet of the matrix channel each comprise a 16 gauge circumference so as to allow a larger pool of the diffusion barrier comprising a hydrogel to be injected into the matrix channel as compared to hydrogel pools allowed to be injected into matrix channels having inlets and outlets with an 18 gauge circumference.
In some embodiments, the matrix channel comprises first and second arrays of transversely spaced-apart matrix ribs, the first array of the transversely spaced-apart matrix ribs is offset from the second array of the transversely spaced-apart matrix ribs by a transverse distance so as to improve diffusion barrier injection into the matrix channel as compared to diffusion barrier injection made into matrix channels having transversely aligned first and second arrays of spaced-apart matrix ribs.
In some embodiments, the donor cell channel and the recipient cell channel each comprise inlets having a larger gauge circumference than cell channel inlets structured to accommodate only isolated cells such that the donor cell channel and the recipient cell channel are structured to accommodate target subjects larger than isolated cells, the target subjects comprising tissues or organoids.
In some embodiments, the donor cell channel and the recipient cell channel each comprise inlets having a larger gauge circumference than cell channel inlets structured to accommodate only isolated cells such that the donor cell channel inlet and the recipient cell channel inlet are structured to accommodate target subjects larger than isolated cells, the target subjects comprising tissues or organoids.
In some embodiments, inlets and outlets of the donor cell channel and the recipient cell channel are structured to have a specific gauge diameter such that a seal is created between surfaces of the inlets and surface of an injection device during cell population injection.
In some embodiments, the donor cell channel and the recipient cell channel are structured to have a height that prevents cell aggregation in the inlets, the outlets and/or the channel surfaces.
In some embodiments, the height ranges from 200 μm to 400 μm.
In some embodiments, the PDMS layer is hydrophobized at a temperature ranging from 180° C. to 250° C. for a period ranging from 60 minutes to 70 minutes.
In some embodiments, the donor or recipient cell population is injected into its respective cell channel via a tip of a pipette disposed within respective inlet for a predefined time and volume such that the cell population is transferred from the tip of the pipette to respective cell channel based on gravity, the pipette comprising the cell population.
In some embodiments, the donor or recipient cell population is extracted from its respective cell channel via an empty pipette tip disposed within respective outlet for a predefined volume, the cell population being pushed into the empty pipette tip by injecting cell media into respective inlet via a syringe pump.
In some embodiments, the target subject comprises extracellular vesicles (EVs), particles, proteins, small biological molecules, or nucleic acids. In some embodiments, intercellular communication of the target subject is analyzed for disease progression, utilizing the target subject for delivering medicine, applying therapeutic effects, diagnostic purposes, regenerative medicine, providing immunization against at least infectious diseases or cancer, and any other appropriate investigative research.
Provided is a microfluidic intercellular communication analysis system including a microfluidic intercellular communication analysis device including a coverslip and a polydimethylsiloxane (PDMS) layer attached to upper surface of the coverslip, the PDMS layer comprising a plurality of microfluidic channels each having an inlet and an outlet, the plurality of microfluidic channels comprising a donor cell channel structured to receive a donor cell population, a recipient cell channel structured to receive at least a recipient cell population and a matrix channel comprising a diffusion barrier having pores, the diffusion barrier being structured to mimic extracellular matrix and conduit a target subject from the donor cell channel to the recipient cell channel through the pores, the donor cell channel and the recipient cell channel each comprising inlets and outlets having an arc angle ranging from 180° to 300°, the arc angle structured to prevent cell aggregation in the inlets, the outlets and/or channel surfaces of the donor cell channel and the recipient cell channel, and an imaging device couplable to the microfluidic intercellular communication analysis device and structured to automatically and continuously acquire images of the target subject within the plurality of microfluidic channels for a period upon injection of the donor cell population and the recipient cell population into respective cell channels. In some embodiments, the acquired images are analyzed for intercellular communication of the target subject.
In some embodiments, the imaging device comprises a microscope, a camera or other appropriate image capture devices.
Provided is a method of performing intercellular communication of a target subject. The method includes providing a microfluidic intercellular communication analysis device that includes a coverslip and a Polydimethylsiloxane (PDMS) layer attached to upper surface of the coverslip, the PDMS layer comprising a plurality of microfluidic channels each having an inlet and an outlet, the plurality of microfluidic channels comprising a donor cell channel structured to receive a donor cell population, a recipient cell channel structured to receive at least a recipient cell population and a matrix channel comprising a diffusion barrier having pores, the diffusion barrier being structured to mimic extracellular matrix and conduit the target subject from the donor cell channel to the recipient cell channel through the pores, the donor cell channel and the recipient cell channel each comprising inlets and outlets having an arc angle ranging from 180° to 300°, the arc angle structured to prevent cell aggregation in the inlets, the outlets and/or channel surfaces of the donor cell channel and the recipient cell channel; injecting the donor cell population including the target subject into the donor cell channel via an inlet of the donor cell channel with an injection device; injecting the recipient cell population into the recipient cell channel via an inlet of the recipient cell channel with the injection device; acquiring images of the target subject within the plurality of microfluidic channels via the imaging device over a period; and analyzing the target subject based at least in part on the acquired images.
In some embodiments, the injecting the donor cell population and the injecting the recipient cell population each includes injecting into respective cell channel via an empty pipette tip of a pipette disposed within respective inlet for a predefined time and volume such that the cell population is transferred from the tip of the pipette to respective cell channel based on gravity, the pipette comprising the cell population.
In some embodiments, the method further includes extracting at least one of the donor cell population and the recipient cell population.
In some embodiments, the extracting at least one of the donor cell population and the recipient cell population includes placing an empty pipette tip within respective outlet; upon placing the tip of the empty pipette within respective outlet, injecting cell media into respective inlet via a syringe pump; and receiving the at least one of the donor cell population and the recipient cell population into the empty pipette via the tip for a predefined volume.
While the general inventive concepts are susceptible of embodiment in many forms, there are shown in the drawings, and will be described herein in detail, specific embodiments thereof with the understanding that the present disclosure is to be considered an exemplification of the principles of the general inventive concepts. Accordingly, the general inventive concepts are not intended to be limited to the specific embodiments illustrated herein.
It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.
The articles “a” and “an” are used herein to refer to one or more than one (i.e., to at least one) of the grammatical object of the article. By way of example, “a cell” means one cell or more than one cell.
“About” as used herein when referring to a measurable value such as an amount, a temporal duration, and the like, is meant to encompass variations of ±5%, preferably ±1%, and still more preferably ±0.1% from the specified value, as such variations are appropriate to perform the disclosed methods.
As used herein, the term “nanoscale” means particles having a size range between approximately 1 and 100 nanometers (nm).
As used herein, the term “nanometer” means 1/1,000,000,000 meter (m).
As used herein, the term “sub-micronscale” means particles having a size less than a micron (μm) and larger than 100 nm.
As used herein, the term “micron” means 1/1,000,000 meter (m).
As used herein, the term “microscale” means having a size of approximately 1 to 5 microns (μm).
In some embodiments of any of the compositions or methods described herein, a range is intended to comprise every integer or fraction or value within the range.
Embodiments described herein as “comprising” one or more features may also be considered as disclosure of the corresponding embodiments “consisting of” and/or “consisting essentially of” such features.
Conventional in vitro and in vivo approaches for studying EV function depend on time-consuming and expensive vesicle purification methods to obtain sufficient vesicle populations. Further, the existence of various EV subtypes with distinct functional characteristics and submicron size makes their analysis challenging. While microfluidic technology has been extensively used to alleviate some of the challenges associated with the EV studies, current microfluidic technology is limited with regard to simulating native vesicle exchange between co-cultured cells in order to enable functional studies. Thus, there exists a critical need to develop an improved device, system or method for real-time monitoring of cell-cell communication or exchange of EVs, particles or proteins between physically separated cell populations. Example embodiments of the microfluidic intercellular communication analysis device, system and method allow such cell-cell communications through selectively permeable barriers for functional analysis or collection, including barrier types that mimic the extracellular matrix. The example embodiments of the microfluidic intercellular communication analysis device simulates the ECM-cell interplay of an in vivo environment that allows for functional studies under physiologically relevant EV production and distribution conditions, while dispensing with the tedious and lengthy EV purification procedures. The small scale of the microfluidic intercellular communication analysis device and the micro-sized channels thereof help to avoid the resource-intensive setups typically needed, requiring very few cells and only a few microliters of media volume, and permit the PDMS layers to be bonded to standard-size coverslips for simple microscope-based observation of the vesicles and cell populations. The example microfluidic intercellular communication analysis device fully integrates cell culturing with microfluidic EV manipulation to create an in vitro EV assay. Further, the microfluidic intercellular communication analysis device provides a versatile tool for researchers across multiple disciplines to perform functional EV studies under physiologically relevant conditions.
In operation, a user (e.g., researcher, analyst, investigator, etc.) may place the microfluidic intercellular communication analysis device 1 on a stage 51 of the microscope 50 for review and analysis of the cell-cell communication. In some examples, the imaging device 50 may be communicatively coupled to a workstation 60 including an imaging software 70 (e.g., without limitation, Nikon's NIS-Elements) for remote viewing and monitoring of the cell-cell communication of the target subject within the microfluidic intercellular communication analysis device 1, uploading of images of the cell-cell communication and/or storing the images. The imaging software 70 may automatically and continuously acquire images of the cell-cell communication of the target subject within the microfluidic intercellular communication analysis device 1 and analyze the cell-cell communication over a period (e.g., without limitation, hours, days, weeks, etc.). The period may be determined for specific needs of an investigator, researcher, analyst, etc. The imaging software 70 may be uploaded from a cloud (not shown), a flash drive, or a shared network drive and stored in the controller or memory (not shown) of the work station 60. The controller may be, for example and without limitation, a microprocessor, a microcontroller, or some other suitable processing device or circuitry. The memory, which can be any of one or more of a variety of types of internal and/or external storage media such as, without limitation, RAM, ROM, EPROM(s), EEPROM(s), FLASH, and the like that provide a storage register, i.e., a machine readable medium, for data storage such as in the fashion of an internal storage area of a computer, and can be volatile memory or nonvolatile memory. In some examples, the user may create or reconfigure a set of instructions for the imaging software 70 via a user interface of the workstation 60 in order to adjust and/or control viewing parameters within the microfluidic intercellular communication analysis device 1.
The coverslip 12 has a thickness 14 of, e.g., without limitation, approximately 0.1 mm˜0.2 mm. This is advantageous in that it allows for a better visualization of the cell-cell communication of the target subject as compared to conventional microfluidic devices including a thicker glass layer (typically, 1 or 2 mm in thickness) attached to the PDMS layer. Due to extremely thin distance required between the microfluidic intercellular communication analysis device 1 and the imaging device for effective viewing (e.g., without limitation, 100× oil objective) of the target subject, the glass layer having 1-2 mm thickness is not practicable for such 100× objective viewing. As such, the coverslip 12 having a much smaller thickness than that of conventional glass layers is utilized to allow the required 100× oil objective viewing via the imaging device 50, thereby providing accurate visualization of intercellular communications of the EVs and/or particles.
The microfluidic intercellular communication analysis device 1 includes a plurality of microfluidic channels 2, 5, 8 each having an inlet 3, 6, 9 and an outlet 4, 7, 10 (24, 25) as shown in
The donor cell channel 5 is structured to receive a donor cell population (e.g., without limitation, a U937-XP cell population) via the inlet 6. The recipient cell channel 8 is structured to receive a recipient cell population (e.g., without limitation, a U937 cell population) via the inlet 9. The donor cell channel 5 and the recipient cell channel 8 have lengths of, e.g., without limitation, 19 mm and 16 mm, respectively. The donor cell channel 5 and the recipient cell channel 8 may have either the same lateral width or different lateral widths. For example, both cell channels 5, 8 may have the same width of, e.g., 200 μm, 500 μm, etc., depending on the type and/or size of the target subject. For example, the larger cell channel width allows for investigation of the cell migration between the cell channels.
The matrix channel 2 is partly coupled to a part of the donor cell channel 5 and a part of the recipient cell channel 8 (25). The matrix channel 2 includes two arrays of a plurality of transversely spaced-apart matrix ribs 16 and a main diffusion barrier reservoir 17 transversely running between the two arrays as shown in
Specific improvements to the microfluidic intercellular communication analysis device 1 are discussed in detail now. First, the PDMS layer 11 has been optimized to have a thickness 13 of, e.g., without limitation, 3-4 mm in order to address breakage of the thin coverslip 12. It has been shown that the 3-4 mm thickness of the PDMS layer 11 effectively prevents bending of the microfluidic intercellular communication analysis device 1 upon attaching the PDMS layer 11 to the coverslip 12. Further, for proper bonding, the PDMS layer 11 may be cleaned in order to remove all PDMS debris that may interfere with the bonding to the coverslip 12 with, e.g., without limitation, ethanol, instead of conventionally used isopropyl alcohol to lessen the PDMS becoming brittle after drying with air flow. Further, in order to strengthen the bonding, the surfaces of the PDMS layer 11 and the coverslip 12 may be plasma-activated (i.e., covalent-bonded) and then thermally bonded. A handheld corona treater can be used to plasma-activate the surfaces with settings at its maximum output voltage (e.g., without limitation, approximately 45 kV) for a short period (e.g., without limitation, less than 5 s). The activated PDMS layer 11 may then be placed on the activated coverslip 12 and air bubbles therebetween may be removed.
In addition, the donor cell channel 5 and the recipient cell channel 8 have been optimized to reduce or prevent cell aggregations in the inlets 6, 9, the outlets 7, 10 and channel pathways therebetween as shown in
Further, cell channel height 15 may be increased so as to reduce or prevent cell aggregation in the inlet 9, the outlet 10, and the channel surface 8A as shown in
Additionally, the inlets 6, 9 and the outlets 7, 10 of the cell channels 5, 8 may be further optimized to have 21 gauge, which is smaller than the inlet/outlet gauge (e.g., typically, 18 gauge) of the cell channels in the conventional microfluidic devices. The smaller gauge allows a more controlled injection of cell populations into the cell channels 5, 8. For example, in an example of pipette or syringe pump injection, the smaller gauge allows for a tighter seal over the tip of the pipette or syringe tubing (see
Furthermore, the matrix channel 2 of the microfluidic intercellular communication analysis device 1 has also been optimized. For example, the inlet 3 and the outlet 4 of the matrix channel 2 may have a 16 gauge circumference. As such, the inlet 3 and outlet 4 of the matrix channel 2 are larger than the matrix channel inlets and outlets (e.g., typically, 18 gauge) of the conventional microfluidic devices (25) so as to allow for a larger pool of hydrogel injected within the matrix channel 2 than is allowed in the matrix channels of the conventional microfluidic device.
Moreover, activating the matrix channel 2 has also been optimized by selectively activating via directed plasma pulsation to further improve hydrogel-PDMS interaction and enhance the matrix channel's hydrophilicity and bonding to the coverslip 12. First, the microfluidic channels 2, 5, 8 may be rendered hydrophobic by heating the devices at a temperature ranging from 180° C. to 250° C. for a period ranging from 60 minutes to 70 minutes. Advantageously, the 1-hour hydrophobization significantly reduces the time (e.g., without limitation, 24-hours or overnight at 70° C.) required to hydrophobize the PDMS by the conventional microfluidic devices (24, 25). The matrix channel 2 is then selectively made hydrophilic by directed plasma-activation from a handheld corona treater for efficient hydrogel infusion therein as shown in
In some examples, the matrix channel 2′ is modified for improved optimization of hydrogel loading. As shown in
In some examples, the donor cell channel inlet and the recipient cell channel inlet are modified for performing tissue or organoid studies. As shown in
Additionally, the microfluidic intercellular communication analysis device 1 advantageously allows selection of target EVs and/or soluble factors based on pore sizes of hydrogels 22 to be infused in the matrix channel 2.
The optimization and fabrication of the microfluidic intercellular communication analysis device 1 as well as other pertinent description (e.g., cell media preparation, etc.) are described further in the Materials and Methods section. Hereinafter, the microfluidic intercellular communication analysis device 1 or its component thereof (e.g., the PDMS layer 11) may also be referred to as “chip”.
In order to determine the effective diffusible particle size profile of Matrigel at working concentration of 8 mg/mL, diffusion of different-sized fluorescent particles 21′ across the matrix channel 2′″ was imaged real-time. The effective pore size for Matrigel has been previously shown to be approximately 140 nm, ranging to upwards of 350 nm (28). Liposomes were used to mimic diffusion of EVs across the Matrigel, which can be prepared to have specific diameter ranges. Liposomes fluorescently labeled with Cy5 were prepared by extrusion to produce monodisperse population sizes of 70 nm 21′ and 250 nm 21″ as shown in Table 1 below. Table 1 enumerates measured sizes of liposome preparations. The average diameters of 70 nm and 250 nm Cy5-liposome preparations measured using DLS are utilized. Table 1 lists the diameter and polydispersity (PDI) measurements for 2 independent readings and the mean values for each preparation.
The liposome solutions were then manually injected into the donor cell channel 5. Diffusion of the liposomes 21′, 21″ was imaged and compared between post-injection time points of 20 min and 24 hour after the injection of the liposomes 21′, 21″. Both liposome populations 21′, 21″ were able to diffuse through within the 24 hour period. As expected due to their smaller size, the 70 nm vesicles 21′ diffused through more rapidly than the 250 nm ones 21″ when compared at the 24 hour time points as shown by the diffused liposomes 21′, 21″ in the recipient channel 8′. To find an upper limit of the diffusion profile, 500 nm yellow-green fluorescing polystyrene beads 27 were also injected into the donor channel 5 of the Matrigel-loaded microfluidic intercellular communication analysis device 1′″, and the diffusion was imaged again at 20 min and 24 hour time points. There was no observed diffusion of the beads 27 even at the 24 hour time point as shown in the recipient channel 8′ of
As shown in
In
Donor U937-XPs 30 were injected into the donor cell channel 5 of the Matrigel-infused microfluidic intercellular communication analysis device 1′″ as shown in
Accordingly,
Furthermore, the study using suspended U937 cells and the previous implementation of the chip that used adherent HUVEC cells (25) demonstrate the versatility of the microfluidic intercellular communication analysis device 1,1′″, 1iv with respect to enabling the investigation of diverse cell types. The results with PEGDA hydrogel also provide a strategy for preventing EV diffusion without affecting the passage of soluble factors, thus serving as a negative control for confirming that any observed effects are due to EV exchange. Further highlighting the versatility of the microfluidic intercellular communication analysis device 1,1′″,1iv, the ability to adjust PEGDA pore size should also provide a means of selective size exclusion of the EVs that can migrate across the Matrigel barrier, thus allowing for functional studies of EV subtypes that can be distinguished based on size differences. Matrigel barriers and Transwell filter systems have been utilized previously, both to collect secreted EVs that have selectively diffused through the pores and accumulated in the supernatant (21), and to use pre-isolated EVs for cell migration studies (37). Transwell systems have also been extensively used with or without supplementary Matrigel layers to investigate the role of certain exosome populations in cell migration (38-42). The microfluidic intercellular communication analysis device 1,1′″,1iv circumvents the EV isolation process required for the aforementioned Transwell exosome functional strategies. In addition, it enables natural EV exchange between co-cultured donor and recipient cells, thus better recapitulating the physiological conditions. The Matrigel barrier in the microfluidic intercellular communication analysis device 1′″ also allows the observation of cell migration induced by exchange of bioactive molecules between cell populations in separate channels, as migratory cells can push through the Matrigel barrier. For instance, an accessory channel in a five-channel system can be used for conducting more elaborate experiments that also analyze the migratory behavior of cells towards the middle channel in response to the generation of stimulatory signals. Therefore, such studies can be performed without the need for prior isolation of biomolecules, similar to the utilization of the original chip design (25). Other microfluidic technologies that have been developed in recent years to study cell communication between co-cultured populations rely on more complicated fabrication methods and the use of non-physiological barriers, such as filters or channels with reduced width, and also do not enable cell migration studies (43-45). In future studies, the microfluidic intercellular communication analysis device 1, 1′″, 1iv may be further optimized for large-scale production in order to allow its use by various researchers.
The limited consistency of Matrigel loading, which requires precise manual pressure to be applied during chip preparation, prevents large-scale production of the microfluidic chips from yet being feasible. However, due to the flexibility and ease of chip design modifications, such improvements are achievable as shown with reference to at least
Additionally, the microfluidic intercellular communication analysis device 1, 1″, 1iv may be manipulated into a device for facile EV collection and purification. The functional assay capabilities of the microfluidic intercellular communication analysis device 1, 1′″, 1iv may be further demonstrated by integrating it into ongoing EV research. For instance, it has been shown that purified exosomes from cells infected with the Rift Valley fever virus (RVFV) can induce significant production of RIG-I-dependent interferon-beta (IFN-β) from naïve recipient cells, making them strongly refractory to infection with RVFV (4). This can be analyzed directly on the microfluidic intercellular communication analysis device 1, 1′″, 1iv by injecting RVFV-infected cells into the donor cell channel and naïve cells into the recipient cell channel. Furthermore, it can be tested whether exosomes that are, in turn, released by the recipient cells can also modulate the immune responses of naïve cells injected into the accessory channel. Such studies will further confirm the utility of the microfluidic intercellular communication analysis device 1, 1′″, 1iv and expand even further on the types and complexity of functional assays that can be performed.
Referring back to Figures,
At 910, a microfluidic intercellular communication analysis system is provided. The microfluidic intercellular communication analysis system includes a microfluidic intercellular communication analysis device includes a coverslip and a Polydimethylsiloxane (PDMS) layer attached to upper surface of the coverslip, the PDMS layer comprising a plurality of microfluidic channels each having an inlet and an outlet, the plurality of microfluidic channels comprising a donor cell channel structured to receive a donor cell population, a recipient cell channel structured to receive at least a recipient cell population and a matrix channel comprising a diffusion barrier having pores, including a type of diffusion barrier that can mimic extracellular matrix, that conduits the target subject from the donor cell channel to the recipient cell channel through the pores, the donor cell channel and the recipient cell channel each comprising inlets and outlets having an arc angle ranging from 180° to 300°, the arc angle being structured to prevent cell aggregation in the inlets, the outlets and/or channel surfaces of the donor cell channel and the recipient cell channel.
At 920, a donor cell population is injected into the donor cell channel via respective inlet.
At 930, a recipient cell population is injected into the recipient cell channel via respective inlet. The injections of the donor cell population and the recipient cell population may occur sequentially or simultaneously. Cell injections may be made using a syringe pump coupled to syringe tubes disposed within inlets and outlets of cell channels as shown in
At 940, it is determined if at least one of the donor cell population and the recipient cell population is to be extracted from respective cell channel. If yes, the method 900 proceeds to 945. If no, the method 900 proceeds to 950. At 945, the at least one of the donor cell population and the recipient population is extracted from respective outlet, at 947 the imaging device acquires images of the target subject from extracted cell population and at 949, the target subject in the extracted cell population are analyzed based on the images acquired and/or for performance of assays including functional characterizations of the extracted cell population. That is, the extraction of the cell population is not only for imaging purposes, but it could also be for performance of various assays, including functional characterizations, on the extracted cells. For extracting the at least one of the donor cell population and the recipient population, as shown in
At 950, the imaging device automatically and continuously acquires images of the target subject within the plurality of microfluidic channels over a period.
At 960, the target subject in non-extracted cell population is analyzed based on the images acquired and/or at least for attachment properties of suspension cells or cell cycle properties. The analysis includes intercellular communication or lack thereof of the target subject. For example, the migratory behavior of the target subject or lack thereof may be studied. A confirmed migratory behavior of a target subject can be utilized in delivering pharmaceutical products within the target subject for, e.g., without, limitation, disease treatment, therapeutic purposes, etc. For example, the EVs infected with the Rift Valley fever virus (RVFV) extracted from the recipient cell channel can be collected and purified. Such purified EVs have been shown to induce a significant production of RIG-I-dependent interferon-beta (IFN-β) from naïve recipient cells, making the latter strongly refractory to infection with the RVFV. Such refractory effect can be directly analyzed using the microfluidic intercellular communication analysis device by injecting the RVFV-infected cells into the donor cell channel and naïve cells into the recipient cell channel. Further, it can be further tested to determine if exosomes released by the recipient cells can also modulate the immune responses of naïve cells injected into a recipient cell channel. Such further tests and analysis can be used to explore the use of the purified EVs as a vaccine against the RVFV. Therefore, the utility and efficacy of the microfluidic intercellular communication device are expansive, allowing investigation and research of the areas and subjects that were not previously possible using the conventional isolation or cell-cell communication analysis devices.
Materials and Methods:
Some of materials and methods below are illustrated with reference to corresponding Figures (
Microfluidic Intercellular Communication Analysis Device Design: A CAD drawing with multiple chip replicates was made using AutoCAD. The CAD drawing was submitted to MuWells (San Diego, CA, USA) to produce a chrome mask from the CAD drawing and fabricate a positive mold on a silicon wafer. The Microfluidic Intercellular Communication Analysis Device and/or a part thereof may be also referred to as a “chip” herein.
Microfluidic Intercellular Communication Analysis Device Production/Optimization: Polydimethylsiloxane (PDMS; Sylgard 184) was mixed at a base-to-curing-agent ratio of 10:1. The silicon wafer was rinsed with isopropyl alcohol and dried with compressed air. The PDMS mixture was then poured onto the positive mold on the silicon wafer and degassed under vacuum for 30 min. Once all bubbles are removed, the PDMS was baked at 70° C. for 1 hour. A large slab of PDMS was cut from the wafer region containing the templates. The PDMS slab was carefully removed and subsequently cut into individual chips. Holes were punctured into the inlets/outlets using 21- and 16-gauge blunt-end needles for the central/side (e.g., cell channels 5, 8) and matrix channels 2, respectively. The PDMS chips and coverslips were then rinsed with ethanol and blown dry with compressed air to remove the PDMS debris. A handheld laboratory corona treater (BD-20AC, Electro-Technic Products, Chicago, IL, USA) was then used to plasma-activate the glass and PDMS surfaces for bonding, with settings at the maximum output voltage (˜45 kV) for less than 5 s. The activated PDMS chips were placed on the activated coverslips, and air bubbles were removed. The chips were then baked at 70° C. for 1 hour and transferred to a hot plate for incubation at 200° C. for 1 hour in order to hydrophobize the PDMS. Subsequently, the corona treater was used to apply a plasma jet through the matrix channel 2 in order to selectively activate it. To facilitate the selectivity of this activation, an electrode (e.g., without limitation, a copper ground wire 26) was inserted at the other end 9 of the matrix channel 2 and the other inlets 6, 9 and outlets 7, 10 were blocked with a slab of PDMS in order to use the pressure created by the plasma shock to funnel it through the matrix channel 2 and prevent leakage into the middle and side channels 5, 8. After activation, the chips 1 were sterilized by exposure to UV light (365 nm) for 10 min. A volume of 3 μL of growth-factor-reduced Matrigel (Dow Corning, Midland, MI, USA) was then injected into the matrix channel 2′″ and allowed to polymerize for 20 min at room temperature. After polymerization, the channels 5, 8 were coated with 0.05 mg/mL poly-D-lysine (Gibco, Waltham, MA, USA, REFA38904-01) for 1 hour and subsequently rinsed and filled with PBS until ready for cell injection. For use of poly(ethylene glycol) diacrylate (PEGDA) hydrogels, all preparation steps remained the same, except that the PEGDA solution was injected in place of Matrigel. PEG-400-DA was diluted in DI water to form a 20% w/v PEGDA solution. The photoinitiator, Irgacure (Sigma-Aldrich, St. Louis, MO, USA), was added to this solution at 0.5% w/v and vortexed for 30 s. This PEGDA/Irgacure solution was directly injected into the matrix channel 2iv. The injected matrix channel 2iv was polymerized under UV light for 15 min, and the chip 1iv was subsequently coated or filled with PBS.
Liposome Preparation: DMPC powder (850345P) and DOPE-PEG(2000)-N-Cy5 chloroform solution (880153C) were purchased from Avanti Polar Lipids (Alabaster, AL, USA); 70 nm and 250 nm liposome stock solutions (1 mg/mL) were produced by first dissolving DMPC in chloroform (Fisher Chemical, Waltham, MA, USA, C298-500) and then adding DOPE-PEG(2000)-N-Cy5 (99.9:0.1-DMPC:DOPE-PEG(2000)-N-Cy5) for future fluorescent visualization. The lipids were desiccated overnight in a vacuum chamber to form a lipid film. The next day, the lipids were dissolved in PBS (Gibco, 70011-044) and strongly vortexed. The lipid solution was then extruded through an Avanti Mini-Extruder (610000-1EA); 70 nm liposomes were passed through a 0.2 μm Nuclepore track-etched polycarbonate membrane filter (Whatman, Maidstone, UK, 800281), followed by a 0.05 nm filter (800308); 250 nm liposomes were passed through a 0.4 m filter (800282) and then a 0.2 μm filter; 10 mm filter supports were used (Avanti Polar Lipids, 610014-1Ea). The size of the liposomes (Table 1) was confirmed by dynamic light scattering (DLS) using a Zetasizer NanoSampler (Malvern, UK), and they were stored at 4° C. until further use.
Cell Line and Maintenance: U937 cells were purchased from the ATCC and maintained in RPMI 1640 medium supplemented with L-glutamine, 25 mM HEPES (Corning, 10-041-CV), and 10% exosome free heat-inactivated fetal bovine serum (FBS) (Corning, Corning, NY, USA, 35-010-CV) that was prepared by ultracentrifugation at 100,000×g to remove FBS exosomes. This culture medium is designated as RPMI++ in the manuscript. Cells were incubated at 37° C. with 5% CO2 and split every 3-4 days. Cell count and viability measurements were conducted using a Luna Automated Cell Counter (Logos Biosystems, Annandale, VA, USA, L10001) in fluorescence measurement mode and using AO/PI dyes (VitaScientific, College Park, MD, USA, F23001). Cells within chips 1 were also maintained in RPMI++, and the chips 1 were kept inside a humidity container to alleviate long-term dehydration.
Puromycin Kill Curve:
U937-XP Cell Line Generation:
Extracellular Vesicle (EV) Purification:
EV Fluorescence Measurement and Analysis of the EV Pellets: Fluorescence readings were taken for the 2K pellets, 10K pellets, and purified exosomes from both U937 and U937-XP cell lines using a Tecan Safire 2 multi-detection microplate reader and analyzed using Magellan software (Tecan, Minnedorf, Switzerland). A volume of 30 μL of each vesicle population was used for analysis; the protein concentrations of the 2K pellets, the 10K pellets, and the purified exosomes were on average 400 μg/mL, 30 μg/mL, and around 250 μg/mL, respectively. The experiment was performed in 3 biological replicates. Unpaired Student's t-tests were performed for statistical analysis and comparison between U937 and U937-XP vesicles.
Vesicle and Cell Injections into Chips: A 5 μl volume of either purified exosomes, liposomes (1 mg/mL), or 500 nm Fluoresbrite YG carboxylate microspheres (Polysciences, Warrington, PA, USA, 17152-10) (25 μg/mL) was injected into the chips by pipetting into the inlet ports of the donor channels. A 5 μL volume from a suspension of 2×107 cells/mL was injected into the recipient cell channels at a flow rate of 0.5 L/min using a Fusion 200 (Chemyx, Stafford, TX, USA) syringe pump, a 250 μL syringe (Hamilton, Reno, NV, USA 81175), and 24-gauge PTFE tubing (Component Supply, Sparta, TN, USA, TWTT-24-C) tightly inserted into the injection port. For cell injection into donor channels, a 10 μL volume of cell suspension at 2×107 cells/mL was injected at a flow rate of 1 μL/min. Excess solution was wiped away from the outlet port.
Fluorescent Imaging: The cells imaged on slides were first fixed by incubation in 2% PFA (Macron Fine Chemicals, Avantor, Center Valley, PA, USA, H121-08) in PBS for 20 min at room temperature, followed by two PBS washes. The cells were then mounted onto glass slides using DAPI-Fluoromount G (SouthernBiotech, Birmingham, AL, USA, 0100-20). Fluorescent imaging of the fixed cells and chips was performed using a Ti2 series inverted microscope (Nikon, Tokyo, Japan) outfitted with a 100× oil immersion objective, using standard bright-field and Cy5 (λEX: 625, λEM: 670 nm), DAPI (λEX: 360 nm, λEM: 460 nm), or GFP (λEX: 480 nm, λEM: 535 nm) filters. Z-stack imaging, merged channels, 3D deconvolution, and stitching were performed using Nikon's NIS-Elements AR software.
To sum, the microfluidic intercellular communication analysis device 1, 1′, 1″, 1′″, 1iv provides a novel and versatile microfluidic platform to enable future mechanistic investigations of real-time intercellular communication-including EV exchange studies-across various disciplines. In addition to Matrigel, the microfluidic intercellular communication analysis system 100 can also accommodate other diffusion barrier substances to allow for tailor-made studies, including hydrogels of variable pore size and composition. The microfluidic intercellular communication analysis system 100 can also be scaled to accommodate various study needs, as it has been demonstrated by adapting the microfluidic intercellular communication analysis device 1 from a three-cell lane design (25) to an optimized two-cell lane design. The ability to selectively inject the diffusion barrier (e.g., Matrigel or PEGDA hydrogel) within a single channel is a key feature to enable the facile preparation of the microfluidic intercellular communication devices 1, 1′, 1″, 1′″, 1iv which should facilitate their adoption and use. Further development and study-specific optimization of the diffusion barrier and matrix rib length will also enable control over the timescale of vesicle diffusion and vesicle communication study. In addition, the use of PEGDA or other hydrogel barriers with various pore sizes should provide a means of selecting EV subtypes that migrate across, or allow their retention, enabling functional studies of EV subtypes that can be distinguished based on size differences.
All publications and patents referred to herein are incorporated by reference. Various modifications and variations of the described subject matter will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been described in connection with specific embodiments, it should be understood that the invention as claimed should not be unduly limited to these embodiments. Indeed, various modifications for carrying out the invention are obvious to those skilled in the art and are intended to be within the scope of the following claims.
The instant application is entitled to priority under 35 U.S.C. § 119(e) to U.S. Provisional Application No. 63/380,164 filed Oct. 19, 2022, which is hereby incorporated by reference in its entirety.
This invention was made with government support under grant number AI137981 awarded by the National Institutes of Health. The government has certain rights in the invention.
| Number | Date | Country | |
|---|---|---|---|
| 63380164 | Oct 2022 | US |
