News in Science

3D printing creates synthetic 'tissue'

Ad Fab Synthetic material capable of performing some of the functions of living cells has been built using a specially modified 3D prototype printer.

Developed by researchers at Oxford University, the new materials, called 'droplet networks' could eventually be used to replace damaged human tissue or deliver drugs to specific locations.

"We aren't trying to make materials that faithfully resemble tissues, but rather structures that can carry out the functions of tissues," says Professor Hagan Bayley, who led the research reported in the journal Science.

The printed structures consist of networks of tens of thousands of connected water droplets, encapsulated in aqueous compartments about 50 microns in diameter and printed out of a lipid film which remains stable for weeks.

The film uses protein pores to form pathways which can mimic nerves, allowing them to transmit electrical signals from one side of the material to the other.

The droplet networks can be designed to fold themselves into different shapes after printing (see video), mimicking muscle movement by transferring water from one cell to another through osmosis.

"At the moment we've created networks of up to 35,000 droplets but the size of network we can make is really only limited by time and money," says Bayley.

The researchers used two different types of droplet, but say there's no reason why you couldn't use 50 or more different kinds.

Synthetic vs living tissue

3D printing lets you build an object as complex as an organ, layer by layer or droplet by droplet, explains Cameron Ferris a research associate from the ARC Centre of Excellence for Electromaterials Science at the University of Wollongong.

Ferris says there are advantages and disadvantages of creating synthetic cells.

"Because droplet networks are entirely synthetic, you don't have to harvest living tissue and the ethical issues associated with stem cells.

"It's cheaper and easier to access, store and transport [than living tissue] but it's far more complex to design and produce."

Ferris is part of a team at Wollongong, developing 3D printers to eventually create replacement organs using living cells.

"We're developing both materials and machinery using bio-inks to print muscle and nerve cells into living tissue.

"We use the same technology as ink jet printers however instead of inks we are using cell types.

Printing living tissue would allow the use of a patient's own cells to reproduce the tissue rather than a donor organ, which comes with rejection issues and the need for lifelong drugs, says Ferris.

But it too has disadvantages.

"It's incredibly expensive to harvest stem cells [for 3D printing], and the food you have to feed them, to grow and expand them so that you have enough stem cells to print takes some time.

"The end goal is to print a replacement tissue or organ in situ, but that's still a long way off."

Video: Time lapse movie of a flower-shaped printed droplet network spontaneously folding to form a hollow sphere. Courtesy Gabriel Villar, Alexander D. Graham and Hagan Bayley (University of Oxford)