23 Oct 2014

3D Bioprinting Body Parts

From Our Changing World, 9:05 pm on 23 October 2014

By Ruth Beran

The 3D bioprinter at the University of Otago, Christchurch is a metre high, a metre wide, and has a lamina flow system attached to the top of it, so it’s also sterile.

“If we want to try and manufacture scaffolds, but in particular print with patient’s cells, that process has to remain sterile - like any other cell culture we would do in the lab,” says senior research fellow Dr Tim Woodfield.

A photo of Ben Schon and Tim Woodfield in front of the 3D bioprinter

From left to right: Ben Schon and Tim Woodfield in front of the 3D bioprinter Photo: RNZ / Ruth Beran

In the future, the 3D bioprinter will be used to create materials or tissues that are implanted into the body to replace or regenerate damaged tissue, such as cartilage or bone. So instead of a metal hip implant, a person could have a biocompatible, 3D printed implant which uses their own cells.

Like any other colour printer, the 3D bioprinter has cartridges or print heads. Some cartridges have degradable, biocompatible polymer materials, which are heated up, melted and extruded out. “A bit like toothpaste,” says Tim.

Other cartridges use hydrogels, which are like jelly. They are gelatine based, have a high water content, and can contain cells which are kept at body temperature.

“So the gelatine is denatured collagen, so it is a naturally-derived material,” says postdoctoral fellow Khoon Lim. “It has been previously shown to support a lot of cell proliferation and promote tissue formation.”

“So we’re trying to put the cells in an environment where they are most happy,” says Tim.

However, gels are structurally quite weak, but with some clever chemistry, they can be combined with the printed synthetic polymers which form the structural component.

“A real sort of scaffolding, like around a building, where they provide a temporary support,” says Tim.

Shining UV light onto the hydrogels cross-links them. “Once it’s cross-linked, it’s kind of like set in concrete,” says Tim.

So gels are put into the print heads, printed between the fibres as the structure is created, and the UV light is shone on later to solidify it.

The cells themselves are grown in a tissue culture lab. For example, chondrocytes, or cartilage cells are taken out of patients and then grown up in a 3D environment to create 1mm tissue spheres or clusters of cells. “Those spheroids are a collection of about 250,000 cells,” says Tim.

Then, like little LEGO blocks, the spheres can be added together. “In almost a high throughput way we can use these as little modules, or little tissue building blocks, to assemble a much more complex tissue,” says Tim, “that’s why we also need the automated capability of our 3D printing.”

Printing is done layer by layer, and models of patient’s body parts, like their knee, can be taken from a CT or MRI image, and software can instruct the printer to print complex shapes made of multiple materials.

A photo of Khoon Lim in front of the 3D bioprinter, and some printed biocompatible scaffolds

Khoon Lim in front of the 3D bioprinter, and some printed biocompatible scaffolds Photo: University of Otago, Christchurch

“And the 3D printer also allows us to make the shapes that we want and to make it bigger as well,” says postdoctoral fellow Ben Schon. “That’s really important, especially if you want to put it in a person eventually.”

The scaffold used in the 3D printing also determines how strong the implant is. “So by tailoring how we’re controlling the lay down of each of these fibres…we can make something that is really, really stiff or we could make something that’s really, really soft,” says Tim.

In the future, it is envisaged that this technology will be located in, or close to, surgery. However, there are some limitations before body parts could be printed for operations. Firstly, although imaging could be done prior to surgery to design the implant, another preliminary surgery would need to happen beforehand to harvest the patient’s own tissue so the cells can be grown and expanded for the printing process. Also, the regulatory framework is quite complicated and would need to be to be considered before commercial applications.

“We’re aware of some of those challenges, and trying to come up with ways where we might be able to get around some of those levels of complexity. It requires quite a bit of development and further testing,” says Tim.