I’ve been talking a lot about 3D bioprinting, but I haven’t actually explained what it is all about. So, let’s have a go! (you may want to grab a snack and a drink!)
Printing, in its many forms, has begun a long, long time ago (see timeline here). Inkjet printing was introduced in 1951, which is an example of 2D printing. In 1984, 3D printing was developed. Soon after, in 1988, Robert Klebe started using cells and proteins in a computer-assisted inkjet printer, which he termed cytoscribing (writing with cells). Since then, in the last two decades, technological advances have allowed 3D bioprinting to become a reality in many labs across the world and the applications are endless and very exciting. Basically, like a 3D printer that can be used to print 3D plastic objects (or other materials), 3D bioptinting builds up an object layer by layer. The main difference between 3D printing and 3D bioprinting is the material: 3D bioprinting uses live cells. This is technically more challenging, as the cells need to be kept alive and happy, but scientists and engineers are getting better and better at making sure this happens.
Cells are very small and need to be in cell culture medium (a special expensive broth full of goodies so that they are well fed and don’t dry out and die). So, printing this stuff can be quite tricky. If it’s too liquid, cells (and the liquid) will not stay in place, if it’s not liquid, cells will dry out, as well as die from being squished out of a cartridge’s nozzle. For this reason, it is common to mix them with a jelly-like material called hydrogel. It keeps the cells moist, helps them survive through being squeezed out of a nozzle and, because it’s viscous/kind of solid, we can draw shapes and it will stay in place (sort of like decorating a cake with frosting (hydrogel) containing little chocolate sprinkles – cells). Some researchers also use scaffolds, which provide shape and structure, onto which they print the cells. Virtually any type of tissue can be printed. What are these printed bits of tissue being used for? These techniques have many applications and some are already being used for therapy (regenerative medicine) or are currently being tested in clinical trials. Another important use is research, for example drug testing or disease models.
In our lab, we don’t use hydrogels or scaffolds. We use spheroids as our building blocks, which are basically balls of cells, and a printer that is able to aspirate each one individually.
These are picked up from each well (image below, on the right) by the nozzle of the printer and skewered through a tiny needle array (middle and left images below).
Here is a close-up of the nozzle holding a spheroid by suction and depositing it through a needle, in a pre-determined position, as designed using the software:
You can watch a video of the printer in action here and below is a diagram that summarizes the main steps of printing and maturation.
After maturation, this is what a tubular tissue looks like:
All images and videos are from Cyfuse.