A three-dimensional material could one day mimic the behavior of living cells in tissues, new research shows. The tissue-like materials, developed by Haygan Bayley, Ph.D., of Oxford University and colleagues Gabriel Villar and Andrew J. Heron, were described this week’s Science and Science Express.

The tissue-like constructs consist of thousands of connected water droplets, encapsulated within lipid films. These printed “droplet networks” could, the authors say, form the building blocks of a new kind of technology for drug delivery, potentially replacing or interfacing with damaged human tissues.

In an earlier publication, the authors described structures—“multisomes”—in which networks of aqueous droplets of defined compositions were encapsulated within small drops of oil in water. The encapsulated droplets adhere to one another and to the surface of the oil drop to form interface bilayers that allow them to communicate with each other and with the surrounding aqueous environment through membrane pores.

The droplet contents can be released by changing the pH or temperature of the surrounding solution, and, they said, the multicompartment framework of multisomes mimics a tissue. In the current application, the authors used a three-dimensional printer that ejects individual water droplets containing all of the necessary chemicals and biochemicals.

The printed networks are then assembled on a tray that moves to establish the position of each ejected droplet. The droplets stick together and are separated by a single thin membrane into which pores can be placed to allow communication between neighboring droplets. The researchers demonstrate that the printed material can make folding movements similar to muscle-like activity and has communication networks that operate like neurons.

Dr. Bayley said of the printing advance reported in Science this week, “Conventional 3D printers aren’t up to the job of creating these droplet networks, so we custom built one in our Oxford lab to do it. 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. 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.”

He added, “We aren’t trying to make materials that faithfully resemble tissues but rather structures that can carry out the functions of tissues. 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.”

Gabriel Villar of Oxford University’s department of chemistry and the inventor of the 3D printer used in the currently reported research said, “We have created a scalable way of producing a new type of soft material. 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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