In an effort to scale up the manufacture of biomaterials, researchers at UC Berkeley have combined bioprinting, a robotic arm, and flash freezing in a method that may one day allow living tissue, and even whole organs, to be printed on demand. By printing cells into 2D sheets and then freezing them as assembled, the new technique improves cell survival during both building and storage.

Biomaterials have a tremendous potential in medicine and improving quality of life in general. By printing out cells like drops of plastic to form complex 3D structures, it opens up the possibility of replacing transplant organs with ones specially printed on demand, using stem cells from the patient to allow for complete tissue compatibility.

The problem is that current bioprinting processes are slow and don't scale up very well, because the cells have difficulty surviving the process without a very rigid control of the temperature and chemical environment. This is complicated by the fact that the printed tissues and organs also have problems with storage and transportation.

To overcome these issues, the Berkeley team has fallen back on what is called parallelization. That is, instead of, for example, printing out an entire organ at one go, the tissues are simultaneously printed in 2D layers that are then stacked by a robotic arm to create the final 3D structure.

This already speeds up the process, but to reduce cell deaths the layers are immediately dipped into a cryogenic bath to freeze them. According to the team, this fuses the layers together and optimizes conditions for surviving storage and transportation, as well as the the process of freezing itself.

"Right now, bioprinting is primarily used to create a small volume of tissue," says Boris Rubinsky, professor of mechanical engineering. "The problem with 3D bioprinting is that it is a very slow process, so you can't print anything big because the biological materials will deteriorate by the time you finish. One of our innovations is that we freeze the material as it is being printed, so that the biological material is preserved, and we can control the freezing rate."

The team says that such a layered approach to manufacturing isn't new, but its application to biomaterials is an innovation. Unlike metals and plastics, tissues are made largely of water, so the tissue layers incorporate hydrophilic and hydrophobic rigid surfaces. This allows the layers to be printed in one location and then transported to another for assembly.

In addition to creating live organs, the technique has other applications, such as in the manufacture of frozen foods on an industrial scale.

The research was published in the Journal of Medical Devices.

The video below shows the tissue-stacking robotic arm in action.

Source: UC Berkeley