Labtimes 2017-06

page 58 Lab Times 6-2017 Methods I t’s December, 2067, your grand-daugh- ter, Sophie (now 65 years old), is at- tending her appointment for a liver re- placement. Now a routine doctor’s job, she watches a 3D bioprinter through the win- dow that opens into the lab next door. A high resolution scan has modelled her own liver, down to the very details of the vascu- lature and the network of ducts. An algo- rithm designed to recreate what the liver would look like, were it only 20 years old, turns the clock back half a century. Pluripo- tent stem cells derived from her own body have been reprogrammed and printed, lay- er by layer, as her brand new, custom-built liver builds up. In a couple of days, once the artificial organ has matured, she will have the liver implanted. Back to 2017, where this is still just a dream. But one, if the enthusiasm of many is to be believed, that is sure to become re- ality. 3D bioprinting is the application of 3D printing techniques to biological materi- als. The basic idea behind 3D printing is really quite simple. All you do is print a se- ries of thin sheets, each representing a 2D slice through the 3D object you are trying to make, and then simply glue them all to- gether. For example, to print a 3D cylinder you would glue a series of discs into a stack. Make the discs progressively smaller and you get a cone. You get the idea. What about overhangs? 3D printing yields ultra-fine polymer slices and then automatically fuses them to- gether. Ah, you say, what about overhangs? Yes, that indeed has been a serious chal- lenge. But there is a trick (and it will be use- ful to remember this when we talk about bioprinting): you print your section where there is an overhang (so this will, in fact, be two bits with a space between them), then fill in the gaps with some sacrificial materi- al. Glue it all together and when it is set, dis- solve away the sacrificial material. Or you can print using an ink that can be polymer- ised, using a laser or other external input. Applying 3D printing to bioprinting is conceptually very simple. Here, the “ink” is some sort of cell suspension and, usual- ly, another ink is used to provide support. But hold on before you rush out and try it with your HP inkjet. Your desktop printer can be very rough with its ink and will not respect the narrow tolerance of living cells. High temperatures and shear forces alone would be fatal. Bioprinters have to solve the challenge of reconciling the engineer- Method Special: Bioprinting Bioprinting in the Lab and the Doctor’s Surgery 3D printing is the Next Big Thing since the printing press. When applied to living tissues, it offers the exciting promise of printed tissues and organs to order. But is it versatile enough to deliver a consistent and flexible platform for making organs? Foto: American Chemical Society Photo: University of South Florida Photo: Wake Forest Institute for Regenerative Medicine

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