While the prospect of 3D printers pumping out biological tissues andreplacement organs has many justifiably excited, researchers at Oxford University have gone in a slightly different direction with the creation of a custom 3D printer capable of producing synthetic materials that have some of the properties of living tissues. Rather than being intended for supplying spare parts for damaged replicants, the new materials could be used for drug delivery or replacing or interfacing with damaged tissues inside the human body.
The new 3D-printed materials take the form of “droplet networks,” which are made up of thousands of connected water droplets that are encapsulated within lipid films. Lipids are naturally occurring molecules whose main biological function is energy storage, signaling and as structural components of cell membranes. The researchers say that, because the droplet networks don’t contain a genome and don’t replicate, they don’t have some of the problems found in other artificial tissue creation methods, such as those that use stem cells.
“We aren't trying to make materials that faithfully resemble tissues but rather structures that can carry out the functions of tissues," said Professor Hagan Bayley of Oxford University's Department of Chemistry, who led the research. 'We’ve shown that it is possible to create networks of tens of thousands connected droplets. The droplets can be printed with protein pores to form pathways through the network that mimic nerves and are able to transmit electrical signals from one side of a network to the other.”
At about 50 microns in diameter, each droplet is around five times larger than living cells, but the researchers believe it should be no problem to make them smaller. The droplet networks also remain stable for weeks.
“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,” added Professor Bayley. “For our experiments we used two different types of droplet, but there's no reason why you couldn't use 50 or more different kinds.”
As you’d expect, conventional consumer 3D printers aren’t up to the task of creating the droplet networks, so Gabriel Villar, a DPhil student in Professor Bayley’s group and lead author of the paper reporting the team’s findings, built a custom device.
The unique droplet network printer is even able to produce droplet networks designed to fold themselves into different shapes after printing. This folding relies on the differences in osmotic concentration that generate water transfer between droplets and enables the creation of shapes, such as a hollow ball, that can’t be obtained by direct printing.
“'We have created a scalable way of producing a new type of soft material,” said Villar. “The printed structures could in principle employ much of the biological machinery that enables the sophisticated behavior of living cells and tissues.”
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