3D bioprinting is a technique very similar to normal 3D printing, but instead of being used to make prototypes out of simple inorganic materials, it is used to make living three-dimensional tissues. It has been studies for a while now and several developments have been made in this field. So how close are we to the creation of the first 3D bioprinted organ ready to be transplanted into a patient?
In a regular 3D printer, plastic is melted and excreted through a head. This head moves in three dimensions and thus paints a three dimensional structure. This structure is printed all at once, with gaps inside or outside as desired. This is much better in certain ways than traditional molds, and it is also much cheaper for companies who develop a lot of prototypes before the final product. 3D printing is mainly used for that, prototyping. For anything else a traditional mold is usually much more efficient.
Now, 3D bioprinting is similar in that it is using a head and excretes material on a surface, with the head moving in three dimensions. But the material involved and the way it has to be treated is a lot more complex. Unlike plastic, living cells cannot be heated and cooled as easily to be melted and then fixed in a structure. They have to be set in certain temperatures and they need to be floating into structures like gels. And gels, as i will explain later ae very important for this.
The most common technique used for 3D bioprinting is the one mentioned above called extrusion printing. But both inkjet and laser assisted printed have been used. From my experience and what i have seem on studies the most popular technique is extrusion printing as it has far less challenges with temperature and layering.
Extrusion printing has been used in interesting ways for bioprinting, for example with using two heads, or heads with multiple feeds to deposit different proportions of cells in specific spots. Then there are different gels, that have different properties like UV stabilization and the ability to withstand temperatures in an incubator.
Some of the most popular organs attempted to be made by this technology are: Cartilage, Skin, Tumours etc. For now most of the efforts seem to be on making small 3D models of human organs to test drugs on. This would be a very efficient and much better alternative way of testing drugs compared to mice and in vitro tests.
Two good hydrogels used for 3D bioprinting are hyaluronic acid (HA) and methylcellulose (MC) and combinations of those (HAMC). And new studies try to find ways to develop channels in between those gels and cells to make a vascular system develop. And this is a big limitation, because in a 3D structure nutrient supply in the inner layers is limited but at the same time creating blood vessels is also a challenge.
We have attempted to make some full organs but the most successful attempt i could find was with bones. But progress shows promise and development appears fast. Even people appear to be interested although i am only talking based on people i know and see through my university, but i do see a lot of interested researchers and students.
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Sources: Progress in organ 3D bioprinting , 3D bioprinting: an emerging technology full of opportunities and challenges , Characterisation of hyaluronic acid methylcellulose hydrogels for 3D bioprinting
Image: By Dannycabrera [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)%5D, from Wikimedia Commons https://commons.wikimedia.org/wiki/File:Biobot_1_edited.jpg