This research was funded in part by the National Institute of Health under award numbers R43GM137651, R61HL154249, R16GM146687, and NSF grant CBET 2150798. The authors thank the RIT Machine Shop for aluminum mold fabrication. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

This design can be used in various modes based on experimental requirements and the preferences of the end user. Prior to each experiment, consult the decision flow chart presented in Figure 2 to determine the necessary steps and modules for the protocol. For example, if the user intends to maintain the open-well format throughout an experiment to directly compare it with the Transwell-type system, the patterning stencil is not required for cell seeding. The core module is commercially available (see Table of Materials), and the ultrathin nanomembrane can be selected from a library of materials with different porosity and pore sizes to suit experimental needs.
1. Fabrication of the patterning stencil
NOTE: The patterning stencil serves to position cells exclusively on the porous region of the membrane chip, preventing cells from settling onto the surrounding silicon layer where they could potentially experience damage after the flow module is added16 (refer to Figure 3). Damage to the monolayer can adversely affect barrier integrity and compromise experimental outcomes. The stencil is unnecessary in an open, static culture, as there is no risk of damage.
<ol>
	<li>Purchase, machine, or 3D print a mold using the design provided in Supplementary Coding File 1 (Figure 4A). 
	NOTE: The stencil walls are tapered to increase media capacity and minimize bubble trapping compared to high aspect ratio straight-walled features.</li>
	<li>Attach a 130 &#181;m pressure-sensitive adhesive (PSA) film to a 3.2 mm acrylic sheet using a cold roller (see Table of Materials).</li>
	<li>Laser cut the acrylic sheet according to the design provided in Supplementary Coding File 2 to create an array of cavities (Figure 4B).</li>
	<li>Peel off the protective layer from the PSA film and attach the acrylic sheet to the mold. 
	NOTE: Ensure that the laser-cut sheet is aligned with the mold so that the mold features are centered within the cavity (Figure 4C). The accuracy of cell positioning on the membrane depends on this step.</li>
	<li>Thoroughly mix the PDMS prepolymer (using a 10:1 base to catalyst ratio) (see Table of Materials) and degas it in a vacuum chamber until no visible bubbles remain (5-15 min).</li>
	<li>Slowly pour the PDMS into the mold cavities, leveling it with a flat edge. 
	NOTE: To prevent bubble entrapment, pour the PDMS into each cavity slowly. If bubbles are present after pouring, place the mold in the vacuum chamber and degas it again.</li>
	<li>Cure the PDMS on a hotplate at 70 &#176;C for 1 h, and then allow it to cool to room temperature.</li>
	<li>Extract the stencils from the mold cavities using flat-tipped tweezers.</li>
</ol>
2. Fabrication of the flow module
NOTE: The flow module shares a similar footprint with the clover-shaped well of the core module and includes a molded microchannel (width = 1.5 mm, height = 0.2 mm, length = 5 mm). The clover shape aids in aligning the channel over the porous culture region (Figure 5).
<ol>
	<li>Use standard soft lithography techniques18 to create a silicon mold with features defined by the design provided in Supplementary Coding File 3 (Figure 4D).</li>
	<li>Attach a 130 &#181;m PSA film to a 3.2 mm thick acrylic sheet.</li>
	<li>Laser cut the acrylic sheet based on the design given in Supplementary Coding File 4 to create an array of clover-shaped cavities (Figure 4E). 
	NOTE: The height of the cavity determines the height of the flow module, which must be slightly taller (by 0-0.1 mm) than the height of the core module well to ensure proper sealing.</li>
	<li>Remove the protective layer from the PSA film and then attach the laser-cut sheet to the silicon mold by aligning the triangular alignment marks on the silicon mold with those on the laser-cut sheet. 
	NOTE: Similar to step 1.4, ensure that the laser-cut acrylic sheet is aligned with the silicon mold so that the mold features are centered within each cavity (Figure 4F). This step determines the position of the microchannel relative to the footprint.</li>
	<li>Slowly pour the degassed PDMS onto the mold cavities and level it with a flat edge. 
	NOTE: If bubbles are present after pouring, degas the mold until the bubbles are removed.</li>
	<li>Place the mold on a hotplate and bake the PDMS at 70 &#176;C for 1 h, then allow the mold to cool to room temperature.</li>
	<li>Carefully remove the flow modules from the mold cavities using flat-tipped tweezers.</li>
	<li>Orient the flow module with the microchannel features facing upward, and position the core inlet and outlet ports at the end of the channel using a biopsy punch (see Table of Materials).</li>
</ol>
3. Fabrication of lower and upper acrylic housings
NOTE: The core module fits into the lower housing. The attraction between embedded magnets in the housings compresses and seals the flow module to the core module (Figure 6).
<ol>
	<li>Laser-cut a 2 mm acrylic sheet using the design provided in Supplementary Coding File 5 to create the upper housing with holes for magnet insertion.</li>
	<li>Attach a 130 &#181;m PSA film to a 3.5 mm acrylic sheet.</li>
	<li>Laser-cut the acrylic sheet based on the design given in Supplementary Coding File 6 to create the lower housing with holes for magnet insertion. 
	NOTE: The thickness of the lower housing is a critical parameter and must match the overall thickness of the core module to prevent leakage during flow.</li>
	<li>Remove the PSA protective layer and attach the lower housing to a glass coverslip.</li>
	<li>Press-fit 4.75 mm nickel-plated neodymium magnets (see Table of Materials) into the laser-cut holes of the housings. 
	NOTE: Ensure that magnets in the lower and upper housings are placed with opposite polarity to ensure magnetic attraction (Figure 6).</li>
</ol>
4. Fabrication of the flow circuit
NOTE: The closed-loop flow circuit contains two sample collection vials as reservoirs (Figure 7). The inlet reservoir has a polyvinylidene difluoride (PVDF) filter to allow the cell media to equilibrate with the CO2 concentration in the incubator.
<ol>
	<li>Use a 1 mm biopsy punch to create two holes in the cap of a sample collection vial.</li>
	<li>Use biopsy punches to create two holes (1 mm and 4 mm) in the cap of a separate sample collection vial, and create a 1 mm hole in the lower part of this vial.</li>
	<li>Insert 20 G dispensing tips into each of the 1 mm holes and seal them with hot glue.</li>
	<li>Place a 0.22 &#181;m PVDF filter (see Table of Materials) in the 4 mm hole and seal it with hot glue.</li>
	<li>Laser-cut a 1.5 mm acrylic sheet using the design provided in Supplementary Coding File 7 to create a sample holding stage.</li>
	<li>Position the reservoirs on the acrylic stage.</li>
	<li>Connect the dispensing tips using micro flow tubes (see Table of Materials).</li>
	<li>Link the tubes to the inlet and outlet of the flow module using 21 G dispensing tips.</li>
	<li>Utilize a peristaltic pump (see Table of Materials) for flow circulation. 
	&#8203;NOTE: Syringe or pneumatic pumps can also be used to introduce flow if desired. The flow rate should be determined based on experimental needs. A comprehensive table, derived from an experimentally validated COMSOL model, is provided in Supplementary Table 1 to assist users in selecting the necessary flow rate to achieve the desired shear stress at the cell monolayer16.</li>
</ol>
5. Cell seeding
NOTE: Similar to conventional membrane inserts, different cell types can be cultured on the nanomembrane. A secondary cell type can also be co-cultured on the other side of the membrane in the bottom channel15.
<ol>
	<li>Coat the membrane with 5 &#181;g/cm2 of fibronectin (see Table of Materials) at room temperature for 1 h to improve cell attachment. 
	NOTE: The chosen cell type may influence the required coating and cell density. The procedure described here is for Human umbilical vein endothelial cells (HUVECs, see Table of Materials).</li>
	<li>Aspirate the coating solution using a P200 pipette and place a patterning stencil in the core module well.</li>
	<li>Add cell media to the well and bottom channel of the device.</li>
	<li>Seed HUVECs at a density of 40,000 cells/cm2 into the well. 
	NOTE: HUVECs at this density typically form a confluent monolayer after 24 h of incubation16,19.</li>
	<li>Place the device in a Petri dish. Add a 15 mL conical tube cap with DI water to the Petri dish to maintain local humidity.</li>
	<li>Transfer the Petri dish to the incubator. 
	&#8203;NOTE: Cell media in the top well and bottom channel of the device should be changed every 24 h. To change the media in the bottom channel, gently inject fresh media into one of the ports to displace the old media from the other port.</li>
</ol>
6. Reconfiguration to microfluidic mode
<ol>
	<li>Sterilize the upper housing, lower housing, flow module, reservoirs, tubes, and dispensing tips by placing them in a UV sterilization chamber for 30 min prior to assembly. Circulate 70% ethanol and then sterile PBS in the flow circuit.</li>
	<li>Fill the reservoirs and tubes with Endothelial Cell Growth media (see Table of Materials).</li>
	<li>Place the lower housing on the sample stage. Insert the open-well core module into the lower housing.</li>
	<li>Aspirate cell media from the well of the module. Place the flow module in the well.</li>
	<li>Place the upper housing to seal the flow module in the core module well. Connect the inlet and outlet dispensing tips to the flow module ports.</li>
	<li>Start the peristaltic pump to introduce fluid flow into the system.</li>
</ol>
7. Conducting downstream analysis in open-well format after flow introduction
NOTE: The culture time here depends on the experimental goals. Users can conduct downstream analysis (e.g., Immunocytochemistry, RNA extraction) either in the open-well or microfluidic formats based on their preference. For instance, if an open-well format is preferred, the system should be reconfigured to conduct assays based on standard protocols16,19.
<ol>
	<li>Stop the pump when the desired time for shear flow exposure is reached. Remove the inlet and outlet dispensing tips.</li>
	<li>Remove the upper housing. Gently remove the flow module from the well using tweezers.</li>
	<li>Add 100 &#181;L of cell media to the well. Conduct desired assays based on standard protocols.</li>
</ol>

A Reconfigurable Barrier Tissue Platform with Open-Well and Microfluidic Modes

<ol>
	<li>Claesson-Welsh, L., Dejana, E., McDonald, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Permeability+of+the+Endothelial+Barrier:+Identifying+and+Reconciling+Controversies.">Permeability of the Endothelial Barrier: Identifying and Reconciling Controversies.</a> Trends in Molecular Medicine. 27 (4), 314-331 (2021).</li><li>Vera, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineering+tissue+barrier+models+on+hydrogel+microfluidic+platforms.">Engineering tissue barrier models on hydrogel microfluidic platforms.</a> ACS Applied Materials &amp; Interfaces. 13 (12), 13920-13933 (2021).</li><li>Wang, Y. I., Abaci, H. E., Shuler, M. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfluidic+blood-brain+barrier+model+provides+in+vivo-like+barrier+properties+for+drug+permeability+screening.">Microfluidic blood-brain barrier model provides in vivo-like barrier properties for drug permeability screening.</a> Biotechnology and Bioengineering. 114 (1), 184-194 (2017).</li><li>Sakolish, C. M., Esch, M. B., Hickman, J. J., Shuler, M. L., Mahler, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modeling+barrier+tissues+in+vitro:+methods,+achievements,+and+challenges.">Modeling barrier tissues in vitro: methods, achievements, and challenges.</a> eBioMedicine. 5, 30-39 (2016).</li><li>Kaisar, M. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+experimental+models+of+the+blood-brain+barrier+for+CNS+drug+discovery.">New experimental models of the blood-brain barrier for CNS drug discovery.</a> Expert Opinion on Drug Discovery. 12 (1), 89-103 (2017).</li><li>Tan, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+high-throughput+microfluidic+microphysiological+system+(PREDICT-96)+to+recapitulate+hepatocyte+function+in+dynamic,+re-circulating+flow+conditions.">A high-throughput microfluidic microphysiological system (PREDICT-96) to recapitulate hepatocyte function in dynamic, re-circulating flow conditions.</a> Lab on a Chip. 19 (9), 1556-1566 (2019).</li><li>Ayuso, J. M., Virumbrales-Mu&#241;oz, M., Lang, J. M., Beebe, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+role+for+microfluidic+systems+in+precision+medicine.">A role for microfluidic systems in precision medicine.</a> Nature Communications. 13 (1), 3086 (2022).</li><li>Katt, M. E., Shusta, E. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vitro+models+of+the+blood-brain+barrier:+building+in+physiological+complexity.">In vitro models of the blood-brain barrier: building in physiological complexity.</a> Current Opinion in Chemical Engineering. 30, 42-52 (2020).</li><li>Ingber, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+organs-on-chips+for+disease+modelling,+drug+development+and+personalized+medicine.">Human organs-on-chips for disease modelling, drug development and personalized medicine.</a> Nature Reviews Genetics. 23 (8), 467-491 (2022).</li><li>Duncombe, T. A., Tentori, A. M., Herr, A. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfluidics:+reframing+biological+enquiry.">Microfluidics: reframing biological enquiry.</a> Nature reviews. Molecular cell biology. 16 (9), 554-567 (2015).</li><li>Williams, M. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+low-cost,+rapidly+integrated+debubbler+(rid)+module+for+microfluidic+cell+culture+applications.">A low-cost, rapidly integrated debubbler (rid) module for microfluidic cell culture applications.</a> Micromachines. 10 (6), 360 (2019).</li><li>Ahmed, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineering+fiber+anisotropy+within+natural+collagen+hydrogels.">Engineering fiber anisotropy within natural collagen hydrogels.</a> American Journal of Physiology-Cell Physiology. 320 (6), C1112-C1124 (2021).</li><li>Ahmed, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microengineered+3D+collagen+gels+with+independently+tunable+fiber+anisotropy+and+directionality.">Microengineered 3D collagen gels with independently tunable fiber anisotropy and directionality.</a> Advanced Materials Technologies. 6 (4), 2001186 (2021).</li><li>&#321;ach, A., Wnuk, A., W&#243;jtowicz, A. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+models+to+study+the+functions+of+the+blood-brain+barrier.">Experimental models to study the functions of the blood-brain barrier.</a> Bioengineering. 10 (5), 519 (2023).</li><li>McCloskey, M. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Modular+&#181;SiM:+A+mass+produced,+rapidly+assembled,+and+reconfigurable+platform+for+the+study+of+barrier+tissue+models+in+vitro.">The Modular &#181;SiM: A mass produced, rapidly assembled, and reconfigurable platform for the study of barrier tissue models in vitro.</a> Advanced Healthcare Materials. 11 (18), 2200804 (2022).</li><li>Mansouri, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+modular+&#181;sim+reconfigured:+integration+of+microfluidic+capabilities+to+study+in+vitro+barrier+tissue+models+under+flow.">The modular &#181;sim reconfigured: integration of microfluidic capabilities to study in vitro barrier tissue models under flow.</a> Advanced Healthcare Materials. 11 (21), 2200802 (2022).</li><li>Hudecz, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modelling+a+human+blood-brain+barrier+co-culture+using+an+ultrathin+silicon+nitride+membrane-based+microfluidic+device.">Modelling a human blood-brain barrier co-culture using an ultrathin silicon nitride membrane-based microfluidic device.</a> International Journal of Molecular Sciences. 24 (6), 5624 (2023).</li><li>Joshi, I. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microengineering+3D+Collagen+Matrices+with+Tumor-Mimetic+Gradients+in+Fiber+Alignment.">Microengineering 3D Collagen Matrices with Tumor-Mimetic Gradients in Fiber Alignment.</a> bioRxiv. , (2023).</li><li>Hsu, M. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+miniaturized+3D+printed+pressure+regulator+(&#181;PR)+for+microfluidic+cell+culture+applications.">A miniaturized 3D printed pressure regulator (&#181;PR) for microfluidic cell culture applications.</a> Scientific Reports. 12 (1), 10769 (2022).</li><li>Rogers, M. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+high-throughput+microfluidic+bilayer+co-culture+platform+to+study+endothelial-pericyte+interactions.">A high-throughput microfluidic bilayer co-culture platform to study endothelial-pericyte interactions.</a> Scientific reports. 11 (1), 12225 (2021).</li><li>Wettschureck, N., Strilic, B., Offermanns, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Passing+the+vascular+barrier:+endothelial+signaling+processes+controlling+extravasation.">Passing the vascular barrier: endothelial signaling processes controlling extravasation.</a> Physiological Reviews. 99 (3), 1467-1525 (2019).</li><li>Wang, Y. I., Shuler, M. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=UniChip+enables+long-term+recirculating+unidirectional+perfusion+with+gravity-driven+flow+for+microphysiological+systems.">UniChip enables long-term recirculating unidirectional perfusion with gravity-driven flow for microphysiological systems.</a> Lab on a Chip. 18 (17), 2563-2574 (2018).</li><li>Nayak, L., Lin, Z., Jain, M. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=34;Go+with+the+flow&amp;#34;:+how+Kr&#252;ppel-like+factor+2+regulates+the+vasoprotective+effects+of+shear+stress.">34;Go with the flow&amp;#34;: how Kr&#252;ppel-like factor 2 regulates the vasoprotective effects of shear stress.</a> Antioxidants &amp; Redox Signaling. 15 (5), 1449-1461 (2011).</li><li>Satoh, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+pneumatic+pressure-driven+multi-throughput+microfluidic+circulation+culture+system.">A pneumatic pressure-driven multi-throughput microfluidic circulation culture system.</a> Lab on a chip. 16 (12), 2339-2348 (2016).</li><li>Abhyankar, V. V., Wu, M., Koh, C. Y., Hatch, A. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Reversibly+sealed,+easy+access,+modular+(seam)+microfluidic+architecture+to+establish+in+vitro+tissue+interfaces.">A Reversibly sealed, easy access, modular (seam) microfluidic architecture to establish in vitro tissue interfaces.</a> PLOS ONE. 11 (5), e0156341 (2016).</li><li>Ahmed, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Local+extensional+flows+promote+long-range+fiber+alignment+in+3D+collagen+hydrogels.">Local extensional flows promote long-range fiber alignment in 3D collagen hydrogels.</a> Biofabrication. 14 (3), 035019 (2022).</li><li>Hasan, M. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=One-step+fabrication+of+flexible+nanotextured+PDMS+as+a+substrate+for+selective+cell+capture.">One-step fabrication of flexible nanotextured PDMS as a substrate for selective cell capture.</a> Biomedical Physics &amp; Engineering Express. 4 (2), 025015 (2018).</li><li>Ahmed, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microengineering+3D+collagen+hydrogels+with+long-range+fiber+alignment.">Microengineering 3D collagen hydrogels with long-range fiber alignment.</a> Journal of Visualized Experiments. 187, e64457 (2022).</li></ol>

J.L.M. is a co-founder of SiMPore, Inc. and holds an equity interest in the company. SiMPore is commercializing the ultrathin silicon-based technologies, including the membranes used in this study.

The aim of this protocol is to develop a practical method for incorporating flow capabilities into an open-well platform featuring an ultrathin nanomembrane. In this design, a magnetic latching approach is utilized, allowing switching between open-well and fluidic modes during experiments and combining the advantages of both approaches. Unlike conventional permanently bonded platforms, magnetic latching allows the platform to be disassembled at convenient points during the experimental workflow16<...

Vascular barriers serve as a critical interface that separates the blood compartment from the surrounding tissue. They play a critical role in preserving homeostasis by attracting immune cells, controlling molecular permeability, and shielding against the intrusion of pathogens into the tissue1,2. In vitro culture models have been developed to mimic the in vivo microenvironment, enabling systematic investigations into the factors and conditions that impact barrier properties in both healthy and diseased states3,4.
The most widely used approach for such culture models is the Transwell-like &#34;open-well&#34; configuration5, where a porous, track-etched culture membrane separates media-filled compartments (Figure 1A). In this format, cells can be seeded on either side of the membrane, and a wide range of experimental protocols has been developed. However, these systems are limited in their ability to provide the fluid flows essential for supporting barrier maturation and mimicking immune cell circulation seen in vivo5,6. Consequently, they cannot be used for studies requiring dynamic flows that introduce drug doses, mechanical stimulation, or fluid-induced shear stresses6,7,8.
To overcome the limitations of open-well systems, microfluidic platforms that combine porous culture membranes with individually addressable fluidic channels have been developed9. These platforms offer precise control over fluid routing, perfusion, and the introduction of chemical compounds, controlled shear stimulation, and dynamic cell addition capabilities7,10,11,12,13. Despite the advanced capabilities provided by microfluidic platforms, they have not seen widespread adoption in bioscience laboratories due to complex microfluidic protocols and their incompatibility with established experimental workflows4,10,14.
To bridge the gap between these technologies, we present a protocol that employs a magnetically reconfigurable, module-based system. This system can be easily switched between open-well and microfluidic modes based on the specific needs of the experiment. The platform features an open-well device, known as m-&#181;SiM (modular microphysiological system enabled by a silicon membrane), with a 100 nm thick culture membrane (nanomembrane). This nanomembrane possesses high porosity (15%) and glass-like transparency, as illustrated in Figure 1B. It physically separates the top compartment from a bottom channel, allowing for molecular transport across physiological length scales15. Unlike conventional track-etched membranes, which have known challenges in imaging live cells with bright-field imaging, the nanomembrane&#39;s favorable optical and physical properties enable clear visualization of cells on either side of the membrane surface15,16,17.
The present protocol outlines the fabrication of specialized seeding and flow modules and explains the magnetic reconfiguration of the platform. It demonstrates how the platform can be employed to establish endothelial barriers under both static and dynamic conditions. This demonstration reveals that endothelial cells align along the flow direction, with an upregulation of shear-sensitive gene targets under shear stimulation.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>0.5 x 0.86 Micro Flow tubes</td>
			<td>Langer Instruments</td>
			<td>WX10-14 &#38; DG Series</td>
			<td></td>
		</tr>
		<tr>
			<td>1 mm Disposable Biopsy Punches, Integra Miltex</td>
			<td>VWR</td>
			<td>95039-090</td>
			<td></td>
		</tr>
		<tr>
			<td>1x PBS 7.4 pH</td>
			<td>ThermoFisher Scientific</td>
			<td>10010023</td>
			<td></td>
		</tr>
		<tr>
			<td>20 GAUGE IT SERIES DISPENSING TIP</td>
			<td>Jensen Global</td>
			<td>JG20-1.5X</td>
			<td></td>
		</tr>
		<tr>
			<td>21 GAUGE NT PREMIUM SERIES ANGLED DISPENSING TIP</td>
			<td>Jensen Global</td>
			<td>JG21-1.0HPX-90</td>
			<td></td>
		</tr>
		<tr>
			<td>3M 467 MP Pressure senstitive adhesive (PSA)</td>
			<td>DigiKey</td>
			<td>3M9726-ND</td>
			<td></td>
		</tr>
		<tr>
			<td>3M 468 MP Pressure senstitive adhesive (PSA)</td>
			<td>DigiKey</td>
			<td>3M9720-ND</td>
			<td></td>
		</tr>
		<tr>
			<td>AlexaFluor 488 conjugated phalloidin</td>
			<td>ThermoFisher Scientific</td>
			<td>A12379&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>Applied Biosystems&#160;TaqMan Fast Advanced Master Mix</td>
			<td>Thermo Fisher Scientific</td>
			<td>4444556</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine Serum Albumin (BSA), Fraction V, 98%, Reagent grade, Alfa Aesar, Size = 10 g</td>
			<td>VWR</td>
			<td>AAJ64100-09</td>
			<td></td>
		</tr>
		<tr>
			<td>Clear Scratch- and UV-Resistant Cast Acrylic Sheet</td>
			<td>McMaster-Carr</td>
			<td>8560K171</td>
			<td>12&#34; x 12&#34; x 1/16&#34;</td>
		</tr>
		<tr>
			<td>Clear Scratch- and UV-Resistant Cast Acrylic Sheet</td>
			<td>McMaster-Carr</td>
			<td>8589K31</td>
			<td>12&#34; x 12&#34; x 3/32&#34;</td>
		</tr>
		<tr>
			<td>Clear Scratch- and UV-Resistant Cast Acrylic Sheet</td>
			<td>McMaster-Carr</td>
			<td>8560K191</td>
			<td>12&#34; x 12&#34; x 7.64&#34;</td>
		</tr>
		<tr>
			<td>Corning Fibronectin, Human, 1 mg</td>
			<td>Corning</td>
			<td>47743-728</td>
			<td></td>
		</tr>
		<tr>
			<td>Cover Glasses, Globe Scientific, L x W = 24 x 60 mm</td>
			<td>VWR</td>
			<td>10118-677</td>
			<td></td>
		</tr>
		<tr>
			<td>DOW SYLGARD 184 SILICONE ENCAPSULANT CLEAR 0.5 KG KIT</td>
			<td>Ellsworth Adhesives</td>
			<td>4019862</td>
			<td></td>
		</tr>
		<tr>
			<td>EGM-2 Endothelial Cell Growth Medium-2 BulletKit</td>
			<td>Lonza</td>
			<td>CC-3162</td>
			<td></td>
		</tr>
		<tr>
			<td>Fixture A1&#38;A2</td>
			<td>SiMPore Inc.</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>Fixture B1&#38;B2</td>
			<td>SiMPore Inc.</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>High Capacity cDNA Reverse Transcription Kit with RNase Inhibitor</td>
			<td>Thermo Fisher Scientific</td>
			<td>4374966</td>
			<td></td>
		</tr>
		<tr>
			<td>Human umbilical vein endothelial cells (HUVEC)</td>
			<td>ThermoFisher Scientific</td>
			<td>C0035C</td>
			<td></td>
		</tr>
		<tr>
			<td>LIVE/DEAD Cell Imaging Kit (488/570)</td>
			<td>Thermo Fisher Scientific</td>
			<td>R37601</td>
			<td></td>
		</tr>
		<tr>
			<td>Molecular Probes Hoechst 33342, Trihydrochloride, Trihydrate</td>
			<td>Thermo Fisher Scientific</td>
			<td>H3570</td>
			<td></td>
		</tr>
		<tr>
			<td>Nickel-plated magnets (4.75 mm diameter, 0.34 kg pull force)</td>
			<td>K&#38;J Magnetics</td>
			<td>D31</td>
			<td>3/16&#34; dia.&#160;x 1/16&#34; thick</td>
		</tr>
		<tr>
			<td>Paraformaldehyde, 4% w/v aq. soln., methanol free, Alfa Aesar</td>
			<td>Fisher Scientific</td>
			<td>aa47392-9M</td>
			<td></td>
		</tr>
		<tr>
			<td>Peristaltic Pump</td>
			<td>Langer Instruments</td>
			<td>BQ50-1J-A</td>
			<td></td>
		</tr>
		<tr>
			<td>Photoresist SU-8 developer solution</td>
			<td>Fisher Scientific</td>
			<td>NC9901158</td>
			<td></td>
		</tr>
		<tr>
			<td>PVDF syringe filters</td>
			<td>PerkinElmer</td>
			<td>2542913</td>
			<td></td>
		</tr>
		<tr>
			<td>Silicon wafer</td>
			<td>University wafer,USA</td>
			<td>1196</td>
			<td></td>
		</tr>
		<tr>
			<td>SU-8 3050</td>
			<td>Fisher Scientific</td>
			<td>NC0702369</td>
			<td></td>
		</tr>
		<tr>
			<td>Target gene: eNOS (Hs01574659_m1)</td>
			<td>ThermoFisher Scientific</td>
			<td>4331182</td>
			<td></td>
		</tr>
		<tr>
			<td>Target gene: GAPDH (Hs02786624_g1)</td>
			<td>ThermoFisher Scientific</td>
			<td>4331182</td>
			<td></td>
		</tr>
		<tr>
			<td>Target gene: KLF2 (Hs00360439_g1)</td>
			<td>ThermoFisher Scientific</td>
			<td>4331182</td>
			<td></td>
		</tr>
		<tr>
			<td>Thermo Scientific&#160;Pierce 20x PBS Tween 20</td>
			<td>Thermo Fisher Scientific</td>
			<td>28352</td>
			<td></td>
		</tr>
		<tr>
			<td>Transport Tube Sample White caps, 5 mL, Sterile</td>
			<td>VWR</td>
			<td>100500-422</td>
			<td></td>
		</tr>
		<tr>
			<td>TRI-reagent</td>
			<td>ThermoFisher Scientific</td>
			<td>AM9738</td>
			<td></td>
		</tr>
		<tr>
			<td>Ultrathin Nanoporous Membrane Chip</td>
			<td>SiMPore Inc.</td>
			<td>NPSN100-1L</td>
			<td>The design is&#160; compatible with all of SiMPore membranes</td>
		</tr>
		<tr>
			<td>uSiM component 1</td>
			<td>SiMPore Inc.</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>uSiM component 2</td>
			<td>SiMPore Inc.</td>
			<td>NA</td>
			<td></td>
		</tr>
	</tbody>
</table>

transforming static barrier tissue models into dynamic microphysiological systems

Microphysiological systems are miniaturized cell culture platforms used to mimic the structure and function of human tissues in a laboratory setting. However, these platforms have not gained widespread adoption in bioscience laboratories where open-well, membrane-based approaches serve as the gold standard for mimicking tissue barriers, despite lacking fluid flow capabilities. This issue can be primarily attributed to the incompatibility of existing microphysiological systems with standard protocols and tools developed for open-well systems.
Here, we present a protocol for creating a reconfigurable membrane-based platform with an open-well structure, flow enhancement capability, and compatibility with conventional protocols. This system utilizes a magnetic assembly approach that enables reversible switching between open-well and microfluidic modes. With this approach, users have the flexibility to begin an experiment in the open-well format using standard protocols and add or remove flow capabilities as needed. To demonstrate the practical usage of this system and its compatibility with standard techniques, an endothelial cell monolayer was established in an open-well format. The system was reconfigured to introduce fluid flow and then switched to the open-well format to conduct immunostaining and RNA extraction. Due to its compatibility with conventional open-well protocols and flow enhancement capability, this reconfigurable design is expected to be adopted by both engineering and bioscience laboratories.

The open-well core module is initially positioned within a specific cavity created by a lower housing and a coverslip, as illustrated in Figure 6A. Subsequently, the flow module, which includes a microchannel and access ports, is inserted into the well of the core module. The flow module is securely sealed against the silicon support layer of the membrane due to the magnetic attraction force between magnets embedded in the lower and upper housings, as depicted in Figure ...

Watch this Scientific Journal Video about Author Spotlight: Developing a Unique Modular Microphysiological System to Mimic Human Barrier Tissue at JoVE.com

Author Spotlight: Developing a Unique Modular Microphysiological System to Mimic Human Barrier Tissue

This protocol describes a reconfigurable membrane-based cell culture platform that integrates the open-well format with fluid flow capabilities. This platform is compatible with standard protocols and allows for reversible transitions between open-well and microfluidic culture modes, accommodating the needs of both engineering and bioscience laboratories.

Transforming Static Barrier Tissue Models into Dynamic Microphysiological Systems

Microphysiological systems are miniaturized cell culture platforms used to mimic the structure and function of human tissues in a laboratory setting. ...

transforming-static-barrier-tissue-models-into-dynamic

Research

JoVE Journal

Bioengineering

881 Views.  Rochester Institute of Technology. This protocol describes a reconfigurable membrane-based cell culture platform that integrates the open-well format with fluid flow capabilities. This platform is compatible with standard protocols and allows for reversible transitions between open-well and microfluidic culture modes, accommodating the needs of both engineering and bioscience laboratories.

Video: Author Spotlight: Developing a Unique Modular Microphysiological System to Mimic Human Barrier Tissue

Microfabricated Platforms for Mechanically Dynamic Cell Culture

The ability to systematically probe in vitro cellular response to combinations of mechanobiological stimuli for tissue engineering, drug discovery or fundamental cell biology studies is limited by current bioreactor technologies, which cannot simultaneously apply a variety of mechanical stimuli to cultured cells. In order to address this issue, we have developed a series of microfabricated platforms designed to screen for the effects of mechanical stimuli in a high-throughput format. In this protocol, we demonstrate the fabrication of a microactuator array of vertically displaced posts on which the technology is based, and further demonstrate how this base technology can be modified to conduct high-throughput mechanically dynamic cell culture in both two-dimensional and three-dimensional culture paradigms.

In this protocol, we demonstrate the fabrication of a microactuator array of vertically displaced posts on which the technology is based, and how this base technology can be modified to conduct high-throughput mechanically dynamic cell culture in both two-dimensional and three-dimensional culture paradigms.

The ability to systematically probe in vitro cellular response to combinations of mechanobiological stimuli for tissue engineering, drug discovery or ...

Finite Element Modelling of a Cellular Electric Microenvironment

Clinical studies show electrical stimulation (ES) to be a potential therapy for the healing and regeneration of various tissues. Understanding the mechanisms of cell response when exposed to electrical fields can therefore guide the optimization of clinical applications. In vitro experiments aim to help uncover those, offering the advantage of wider input and output ranges that can be ethically and effectively assessed. However, the advancements in in vitro experiments are difficult to reproduce directly in clinical settings. Mainly, that is because the ES devices used in vitro differ significantly from the ones suitable for patient use, and the path from the electrodes to the targeted cells is different. Translating the in vitro results into in vivo procedures is therefore not straightforward. We emphasize that the cellular microenvironment's structure and physical properties play a determining role in the actual experimental testing conditions and suggest that measures of charge distribution can be used to bridge the gap between in vitro and in vivo. Considering this, we show how in silico finite element modelling (FEM) can be used to describe the cellular microenvironment and the changes generated by electric field (EF) exposure. We highlight how the EF couples with geometric structure to determine charge distribution. We then show the impact of time dependent inputs on charge movement. Finally, we demonstrate the relevance of our new in silico model methodology using two case studies: (i) in vitro fibrous Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT-PSS) scaffolds and (ii) in vivo collagen in extracellular matrix (ECM).

This paper presents a strategy for building finite element models of fibrous conductive materials exposed to an electric field (EF). The models can be used to estimate the electrical input that cells seeded in such materials receive and assess the impact of changing the scaffold's constituent material properties, structure or orientation.

Clinical studies show electrical stimulation (ES) to be a potential therapy for the healing and regeneration of various tissues. Understanding the ...

Assessing Functional Metrics of Skeletal Muscle Health in Human Skeletal Muscle Microtissues

Three-dimensional (3D) in vitro models of skeletal muscle are a valuable advancement in biomedical research as they afford the opportunity to study skeletal muscle reformation and function in a scalable format that is amenable to experimental manipulations. 3D muscle culture systems are desirable as they enable scientists to study skeletal muscle ex vivo in the context of human cells. 3D in vitro&#160;models closely mimic aspects of the native tissue structure of adult skeletal muscle. However, their universal application is limited by the availability of platforms that are simple to fabricate, cost and user-friendly, and yield relatively high quantities of human skeletal muscle tissues. Additionally, since skeletal muscle plays an important functional role that is impaired over time in many disease states, an experimental platform for microtissue studies is most practical when minimally invasive calcium transient and contractile force measurements can be conducted directly within the platform itself. In this protocol, the fabrication of a 96-well platform known as &#39;MyoTACTIC&#39;, and en masse production of 3D human skeletal muscle microtissues (hMMTs) is described. In addition, the methods for a minimally invasive application of electrical stimulation that enables repeated measurements of skeletal muscle force and calcium handling of each microtissue over time are reported.

This manuscript describes a detailed protocol to produce arrays of 3D human skeletal muscle microtissues and minimally invasive downstream in situ assays of function, including contractile force and calcium handling analyses.

Three-dimensional (3D) in vitro models of skeletal muscle are a valuable advancement in biomedical research as they afford the opportunity to study ...

Developing 3D Organized Human Cardiac Tissue within a Microfluidic Platform

The leading cause of death worldwide persists as cardiovascular disease (CVD). However, modeling the physiological and biological complexity of the heart muscle, the myocardium, is notoriously difficult to accomplish in vitro. Mainly, obstacles lie in the need for human cardiomyocytes (CMs) that are either adult or exhibit adult-like phenotypes and can successfully replicate the myocardium&#39;s cellular complexity and intricate 3D architecture. Unfortunately, due to ethical concerns and lack of available primary patient-derived human cardiac tissue, combined with the minimal proliferation of CMs, the sourcing of viable human CMs has been a limiting step for cardiac tissue engineering. To this end, most research has transitioned toward cardiac differentiation of human induced pluripotent stem cells (hiPSCs) as the primary source of human CMs, resulting in the wide incorporation of hiPSC-CMs within in vitro assays for cardiac tissue modeling.
Here in this work, we demonstrate a protocol for developing a 3D mature stem cell-derived human cardiac tissue within a microfluidic device. We specifically explain and visually demonstrate the production of a 3D in vitro anisotropic cardiac tissue-on-a-chip model from hiPSC-derived CMs. We primarily describe a purification protocol to select for CMs, the co-culture of cells with a defined ratio via mixing CMs with human CFs (hCFs), and suspension of this co-culture within the collagen-based hydrogel. We further demonstrate the injection of the cell-laden hydrogel within our well-defined microfluidic device, embedded with staggered elliptical microposts that serve as surface topography to induce a high degree of alignment of the surrounding cells and the hydrogel matrix, mimicking the architecture of the native myocardium. We envision that the proposed 3D anisotropic cardiac tissue-on-chip model is suitable for fundamental biology studies, disease modeling, and, through its use as a screening tool, pharmaceutical testing.

The goal of this protocol is to explain and demonstrate the development of a three-dimensional (3D) microfluidic model of highly aligned human cardiac tissue, composed of stem cell-derived cardiomyocytes co-cultured with cardiac fibroblasts (CFs) within a biomimetic, collagen-based hydrogel, for applications in cardiac tissue engineering, drug screening, and disease modeling.

The leading cause of death worldwide persists as cardiovascular disease (CVD). However, modeling the physiological and biological complexity of the heart ...

Fibroblast Derived Human Engineered Connective Tissue for Screening Applications

Fibroblasts are phenotypically highly dynamic cells, which quickly transdifferentiate into myofibroblasts in response to biochemical and biomechanical stimuli. The current understanding of fibrotic processes, including cardiac fibrosis, remains poor, which hampers the development of new anti-fibrotic therapies. Controllable and reliable human model systems are crucial for a better understanding of fibrosis pathology. This is a highly reproducible and scalable protocol to generate engineered connective tissues (ECT) in a 48-well casting plate to facilitate studies of fibroblasts and the pathophysiology of fibrotic tissue in a 3-dimensional (3D) environment. ECT are generated around the poles with tunable stiffness, allowing for studies under a defined biomechanical load. Under the defined loading conditions, phenotypic adaptations controlled by cell-matrix interactions can be studied. Parallel testing is feasible in the 48-well format with the opportunity for the time-course analysis of multiple parameters, such as tissue compaction and contraction against the load. From these parameters, biomechanical properties such as tissue stiffness and elasticity can be studied.

Presented here is a protocol to generate engineered connective tissues for a parallel culture of 48 tissues in a multi-well plate with double poles, suitable for mechanistic studies, disease modeling, and screening applications. The protocol is compatible with fibroblasts from different organs and species and is exemplified here with human primary cardiac fibroblasts.

Fibroblasts are phenotypically highly dynamic cells, which quickly transdifferentiate into myofibroblasts in response to biochemical and biomechanical ...

A Microphysiological System to Study Leukocyte-Endothelial Cell Interaction during Inflammation

Leukocyte-endothelial cell interactions play an important role in inflammatory diseases such as sepsis. During inflammation, excessive migration of activated leukocytes across the vascular endothelium into key organs can lead to organ failure. A physiologically relevant biomimetic microfluidic assay (bMFA) has been developed and validated using several experimental and computational techniques, which can reproduce the entire leukocyte rolling/adhesion/migration cascade to study leukocyte-endothelial cell interactions. Microvascular networks obtained from in vivo images in rodents were digitized using a Geographic Information System (GIS) approach and microfabricated with polydimethylsiloxane (PDMS) on a microscope slide. To study the effect of shear rate and vascular topology on leukocyte-endothelial cell interactions, a Computational Fluid Dynamics (CFD) model was developed to generate a corresponding map of shear rates and velocities throughout the network. The bMFA enables the quantification of leukocyte-endothelial cells interactions, including rolling velocity, number of adhered leukocytes in response to different shear rates, number of migrated leukocytes, endothelial cell permeability, adhesion molecule expression and other important variables. Furthermore, by using human-related samples, such as human endothelial cells and leukocytes, bMFA provides a tool for rapid screening of potential therapeutics to increase their clinical translatability.

In this protocol, a biomimetic microfluid assay, which can reproduce a physiologically relevant microvascular environment and reproduce the entire leukocyte adhesion/migration cascade, is employed to study leukocyte-endothelial cell interactions in inflammatory disease.

Leukocyte-endothelial cell interactions play an important role in inflammatory diseases such as sepsis. During inflammation, excessive migration of ...

Reconstituting Cytoarchitecture and Function of Human Epithelial Tissues on an Open-Top Organ-Chip

Nearly all human organs are lined with epithelial tissues, comprising one or multiple layers of tightly connected cells organized into three-dimensional (3D) structures. One of the main functions of epithelia is the formation of barriers that protect the underlining tissues against physical and chemical insults and infectious agents. In addition, epithelia mediate the transport of nutrients, hormones, and other signaling molecules, often creating biochemical gradients that guide cell positioning and compartmentalization within the organ. Owing to their central role in determining organ-structure and function, epithelia are important therapeutic targets for many human diseases that are not always captured by animal models. Besides the obvious species-to-species differences, conducting research studies on barrier function and transport properties of epithelia in animals is further compounded by the difficulty of accessing these tissues in a living system. While two-dimensional (2D) human cell cultures are useful for answering basic scientific questions, they often yield poor in vivo predictions. To overcome these limitations, in the last decade, a plethora of micro-engineered biomimetic platforms, known as organs-on-a-chip, have emerged as a promising alternative to traditional in vitro and animal testing. Here, we describe an Open-Top Organ-Chip (or Open-Top Chip), a platform designed for modeling organ-specific epithelial tissues, including skin, lungs, and the intestines. This chip offers new opportunities for reconstituting the multicellular architecture and function of epithelial tissues, including the capability to recreate a 3D stromal component by incorporating tissue-specific fibroblasts and endothelial cells within a mechanically active system. This Open-Top Chip provides an unprecedented tool for studying epithelial/mesenchymal and vascular interactions at multiple scales of resolution, from single cells to multi-layer tissue constructs, thus allowing molecular dissection of the intercellular crosstalk of epithelialized organs in health and disease.

The present protocol describes the capabilities and the essential culture modalities of the Open-Top Organ-Chip for the successful establishment and maturation of full-thickness organ-on-chip cultures of primary tissues (skin, alveolus, airway, and intestine), providing the opportunity to investigate different functional aspects of the human epithelial/mesenchymal and vascular niche interface in vitro.

Nearly all human organs are lined with epithelial tissues, comprising one or multiple layers of tightly connected cells organized into three-dimensional ...

Designing a Bioreactor to Improve Data Acquisition and Model Throughput of Engineered Cardiac Tissues

Heart failure remains the leading cause of death worldwide, creating a pressing need for better preclinical models of the human heart. Tissue engineering is crucial for basic science cardiac research; in vitro human cell culture eliminates the interspecies differences of animal models, while a more tissue-like 3D environment (e.g., with extracellular matrix and heterocellular coupling) simulates in vivo conditions to a greater extent than traditional two-dimensional culture on plastic Petri dishes. However, each model system requires specialized equipment, for example, custom-designed bioreactors and functional assessment devices. Additionally, these protocols are often complicated, labor-intensive, and plagued by the failure of the small, delicate tissues.
This paper describes a process for generating a robust human engineered cardiac tissue (hECT) model system using induced pluripotent stem-cell-derived cardiomyocytes for the longitudinal measurement of tissue function. Six hECTs with linear strip geometry are cultured in parallel, with each hECT&#160;suspended from a pair of force-sensing polydimethylsiloxane (PDMS) posts attached to PDMS racks. Each post is capped with a black PDMS stable post tracker (SPoT), a new feature that improves the ease of use, throughput, tissue retention, and data quality. The shape allows for the reliable optical tracking of post deflections, yielding improved twitch force tracings with absolute active and passive tension. The cap geometry eliminates tissue failure due to hECTs slipping off the posts, and as they involve a second step after PDMS rack fabrication, the SPoTs can be added to existing PDMS post-based designs without major changes to the bioreactor fabrication process.
The system is used to demonstrate the importance of measuring hECT function at physiological temperatures and shows stable tissue function during data acquisition. In summary, we describe a state-of-the-art model system that reproduces key physiological conditions to advance the biofidelity, efficiency, and rigor of engineered cardiac tissues for in vitro applications.

Three-dimensional cardiac tissues bioengineered using stem-cell-derived cardiomyocytes have emerged as promising models for studying healthy and diseased human myocardium in vitro while recapitulating key aspects of the native cardiac niche. This manuscript describes a protocol for fabricating and analyzing high-content engineered cardiac tissues generated from human induced pluripotent stem-cell-derived cardiomyocytes.

Heart failure remains the leading cause of death worldwide, creating a pressing need for better preclinical models of the human heart. Tissue engineering ...

Analysis of Blood-Brain Barrier Models via Immunofluorescence Staining

Use of the MicroSiM (&#181;SiM) Barrier Tissue Platform for Modeling the Blood-Brain Barrier

The microSiM (&#181;SiM) is a membrane-based culture platform for modeling the blood-brain barrier (BBB). Unlike conventional membrane-based platforms, the&#160;&#181;SiM provides experimentalists with new capabilities, including live cell imaging, unhindered paracrine signaling between &#39;blood&#39; and &#39;brain&#39; chambers, and the ability to directly image immunofluorescence without the need for the extraction/remounting of membranes. Here we demonstrate the basic use of the platform to establish monoculture (endothelial cells) and co-culture (endothelial cells and pericytes) models of the BBB using ultrathin nanoporous silicon-nitride membranes. We demonstrate compatibility with both primary cell cultures and human induced pluripotent stem cell (hiPSC) cultures. We provide methods for qualitative analysis of BBB models via immunofluorescence staining and demonstrate the use of the &#181;SiM for the quantitative assessment of barrier function in a small molecule permeability assay. The methods provided should enable users to establish their barrier models on the platform, advancing the use of tissue chip technology for studying human tissues.

Author Spotlight: Advancing the Use of Tissue Chip Technology for Studying Human Tissues 

This report provides protocols for assembly, cell culture, and assays on the &#181;SiM platform for the construction of blood-brain barrier models.

The microSiM (&#181;SiM) is a membrane-based culture platform for modeling the blood-brain barrier (BBB). Unlike conventional membrane-based platforms, ...

Transendothelial Resistance Measurement to Assess Cell Barrier Integrity

Barrier Functional Integrity Recording on bEnd.3 Vascular Endothelial Cells via Transendothelial Electrical Resistance Detection

The blood-brain barrier (BBB) is a dynamic physiological structure composed of microvascular endothelial cells, astrocytes, and pericytes. By coordinating the interaction between restricted transit of harmful substances, nutrient absorption, and metabolite clearance in the brain, the BBB is essential in preserving central nervous system homeostasis. Building in vitro models of the BBB is a valuable tool for exploring the pathophysiology of neurological disorders and creating pharmacological treatments. This study describes a procedure for creating an in vitro monolayer BBB cell model by seeding bEnd.3 cells into the upper chamber of a 24-well plate. To assess the integrity of cell barrier function, the conventional epithelial cell voltmeter was used to record the transmembrane electrical resistance of normal cells and CoCl2-induced hypoxic cells in real-time. We anticipate that the above experiments will provide effective ideas for the creation of in vitro models of BBB and drugs to treat disorders of central nervous system diseases.

Author Spotlight: Applications of TEER Detection to Assess Cell Barrier Integrity 

This protocol describes a dependable and efficient in vitro model of the brain blood barrier. The method uses mouse cerebral vascular endothelial cells bEnd.3 and measures transmembrane electrical resistance.

The blood-brain barrier (BBB) is a dynamic physiological structure composed of microvascular endothelial cells, astrocytes, and pericytes. By coordinating ...