What You Need to Know About Membrane-Based Culture Systems

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Tamlyn Oliver: Hi everyone, welcome to Biocompare’s Tech Insights Podcast where we speak to scientific experts about new technology that can help advance your research. I’m Tamlyn Oliver, Managing Editor of Biocompare. Today’s guest is Jun Park, Senior Scientist, CWT Applications Lead at MilliporeSigma. He’s going talk to us about membrane-based culture systems and the applications they support. Thanks for joining us, Jun.

Jun Park: Hi, it’s great to be here, thank you.

Tamlyn Oliver: Well you’re welcome. I have quite a few questions for you, so let’s just get started. At MilliporeSigma, what do you consider your most significant contributions to making cell culture models more relevant?

Jun Park: That would be our Cell ASIC microfluidics cell culture imaging platform, it is a microfluids plate with standard microplate form factor and environmental controls. It enables tissue culturing at microliter scale and conditions such as temperature, gas, flow of media and reagent can be precisely controlled while doing live cell imaging. We actually have well over 700 publications and its customer base is still growing.

Tamlyn Oliver: I think many people working with cell culture believe there isn’t that much to know about plates and inserts, that you’re either culturing on membranes or you’re not. What do you say to those people?

Jun Park: I think just because something has bene working that does not mean that critical mechanistic questions have been answered. For example, there are many unknowns when it comes to protein absorption to different surfaces, which will impact subsequent cell adhesion. But we already know that certain cell types require ECM precoating, yet alternatively, we do not know why nor the exact molecular mechanisms behind this. Now, for membranes, I think there are more open-minded questions that we often hear from scientists, such as pore size and density and time permitting, perhaps we can talk about this more?

Tamlyn Oliver: My next question is when would you recommend cell culturists choose membrane-based surfaces over traditional 2-D plastic surfaces?

Jun Park: Membrane-based surfaces are essential for creating more physiologically relevant in-vitro tissue models for many types of assays. A few examples come to my mind, one is Air Liquid Interphase where certain types of the epithelial cells are allowed to grow on membrane, as to create polarized cellular physiology with distinctive basolateral and apical features. These cells then can be further differentiated by exposing the apical side to open air. Currently, this assay is gaining a lot of attention due to COVID-19 for example. I think another great example is the classic Boyden chamber assay, introduced by Dr. Stephen Boyden in 1962, where he used a Millipore membrane to create chemotactic gradient and thus, enabled directional migration of cells towards a chemoattractant. A truly remarkable study and design, which to this day, bears his name.

Tamlyn Oliver: Membranes for cell culture are made of different materials. Why the diversity, and what does the pore density and pore size have to do with the results?

Jun Park: Currently, there are four major types of membranes, these are PTFE, mixed cellulose ester, polycarbonate, and PET, or polyester membranes as it is commonly known as. PTFE and cellulose ester membranes do not have defined pore structures and their pore sizes are based on indirect measure such bubble point measures. Polycarbonate and PET membranes are produced with technique known as track etching, which enables precise fabrication of membranes with define pore size and density. So, for these track etched membranes, smaller pore size of 0.4 or 1 micron are used to create in-vitro model such as aforementioned ALI where cellular type junction polarity are required. On the opposite side, larger pore size of 5 to 8 microns are mainly used to create migration and invasion assays where a larger pore size allows directional migration of cells, through the membrane towards the source of chemoattractant. Also, for the track etched membrane, pore density is inversely related to optical clarity. So the higher the pore density, less optically clear a given membrane will be, which will directly impact imaging applications.

Tamlyn Oliver: Okay, Jun, I have one final question. Organoid culture is one of the most exciting innovations in cell culture today. Have your culture offerings been involved in the expansion of this technique?

Jun Park: Sure, absolutely. So, we currently offer ready to order colon organoids and also associated optimized media for culturing them. We expect to increase our offering to include other types of organoids with optimized media and protocols. So please stay tuned.

Tamlyn Oliver: Okay, thanks Jun for the product updates, for clarifying some misconceptions and providing us with some useful tips and tricks. For a more in-depth description of the membrane-based culture systems that Jun has spoken about here, please read the related article “More Like Life: Microporous Membrane-Based Culture Systems.” And thanks so much for listening today. For more information on products, technologies and the latest scientific advancements, please visit Biocompare.com, and have a great day.