3D bio-printed fabrics can now be stored in

image: 2D cryo-printed sample in a snowflake pattern
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Credit: Hossein Ravanbakhsh

A major obstacle to the widespread study and clinical use of 3D tissues is their short shelf life, which can range from a few hours to a few days. As in the case of an organ transplant, a bioprinted tissue must be transported quickly to where it is needed, otherwise it will not be viable. In the review Matter December 21st, researchers at Brigham and Women’s Hospital and Harvard Medical School describe their work combining 3D bioprinting with cryopreservation techniques to create tissues that can be stored in a -196 ° C freezer and thawed in minutes to immediate use.

“For conventional bioprinting, there is virtually no shelf life. It’s just a matter of printing and then using, in most cases, ”says lead author Y. Shrike Zhang (@shrikezhang), biomedical engineer at Brigham and Women’s Hospital. “With freeze-printing, you can print and store frozen for as long as you want. “

The use of 3D bioprinting to create artificial human tissue first appeared twenty years ago. As in conventional 3D printing, an ink is extruded layer by layer through a nozzle in a predefined shape. In the case of bioprinting, the ink usually consists of a gelatin-like scaffold encrusted with living cells. Cryobioimprinting works the same way, except that printing is performed directly on a cold plate maintained at temperatures down to -20 ° C. After the tissues are printed, they are immediately transferred to cryogenic conditions for long term storage.

Low temperature printing has the added benefit of being able to create more complex shapes than traditional bioprinting methods. “The bioink filament freezes within milliseconds of reaching the cold plate, so it doesn’t have time to lose its original shape,” says Zhang. “Then you can build layers on top of each other, eventually creating a free-standing 3D structure that can support its own weight. “

The use of cryogenic temperatures also alleviates limitations on the types of biological ink that can be used. In conventional bioprinting methods, the bioprinting must be viscous to retain its shape, but at lower temperature most fluids are naturally more viscous.

To survive cryogenic temperatures, cells must be accompanied by a cryopreservative agent, which prevents osmotic shock and limits the formation of ice crystals that can damage their cell membranes. Zhang’s team focused most of their efforts on finding the combination of cryopreservatives that gave the highest cell viability.

They demonstrated that the tissues could last for at least three months before being brought back to life. “Reviving tissue is quite easy,” says Zhang. “It’s like reviving any type of cryo-stored cells. You put them back in a warm medium and use a rapid defrost process.

To show that tissues can retain their original functionality, Zhang and his colleagues performed a series of cell viability tests that demonstrated that cells could undergo differentiation as before.

In the future, 3D bio-printed tissues could serve as realistic models for testing new drugs or helping patients in need of tissue replacement after injury or illness. The ability to freeze bioprinted tissues for an extended period will allow for further collaboration between researchers to develop these applications and allow for extended storage for use in preclinical and clinical settings.

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Matter, Ravanbakhsh et al. : “Cryogenic printing loaded with free cells for the manufacture and storage of ready-to-use tissues” https://www.cell.com/matter/fulltext/S2590-2385(21)00613-5

Matter (@ Material_CP), published by Cell Press, is a new journal dedicated to multidisciplinary and transformative research in materials science. The papers explore scientific advances across the spectrum of materials development – from fundamentals to application, from nano to macro. Visit: https://www.cell.com/matter. To receive Cell Press media alerts, please contact [email protected]


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