3D printing soft tissue scaffolds

Tissue engineering often involves using a 3D printer to construct a scaffold on which living cells might be seeded to grow an approximation of a tissue. Now, scientists from Imperial College and King's College London have developed a 3D cryogenic printing technique that allows them to make a soft scaffold from a liquid hydrogel. Solid carbon dioxide is used to rapidly cool the hydrogel as it is extruded from the 3D printer. Once thawed, the gel closely resembles soft body tissue and does not collapse under its own weight, a problem with earlier techniques.

Being able to match the structure and softness of body tissues is a critical aspect of successful tissue engineering. Scaffolds must be biocompatible but must also closely resemble the texture and structure of tissues they aim to template for regeneration of damaged tissue. The aim of tissue engineering ultimately is to repair the body without the problems of transplant. Perhaps one day whole organs will be available through such techniques. Imperial College's Zhengchu Tan explains that, "At the moment we have created structures a few centimeters in size, but ideally we'd like to create a replica of a whole organ using this technique." [Forte et al. Sci Rep; DOI: 10.1038/s41598-017-16668-9]

Tissue engineering using scaffolds is becoming more widespread and the variety of applications is increasing. However, there are always drawbacks to any specific approaching. This new technique circumvents many of the problems that precluded advanced development of some of the earlier approaches. The "super-soft" scaffolds it generates resemble much more closely actual soft body tissues and so could help promote regeneration through cell seeding and allow much more facile incorporation and regrowth. Specifically, there may one day be the possibility of seeding neuronal cells for the repair of spinal cord injury and perhaps even of the brain.

The team has demonstrated proof of principle by 3D printing structures and seeding them with dermal fibroblast cells. Such cells generate connective tissue within the skin under natural conditions. They were able to demonstrate successful attachment and survival of the new cells on the scaffold. Such a success might be useful specifically in skin grafts or the removal of scar tissue.

Ultimately, such scaffolds might find universal applications when stem cells are used instead of specific types of cell. Stem cells grown on a scaffold might be nudged to differentiate into specific tissues types such as kidney, liver or other cells.

There is an additional prospect for such tissue scaffolds in that they might be used to construct synthetic organs not for transplant but for biomedical research and drug testing, for example. This could avoid the need for using animals in many experiments and allows tests to be carried out on living tissues where it would be impractical or unethical to use a live subject. Likewise, a synthetic, but living, organ might be useful in the context of education providing trainee doctors, surgeons, and other healthcare workers a safe environment on which to practice their skills.

"We want to improve the design of the printer by adding a conditioned chamber to attenuate the temperature gradient from the bottom to the top layer of the printed structures. This will enable us to obtain taller structures and a more stable printing process," IC's Antonio Elia Forte told Materials Today.

David Bradley blogs at Sciencebase Science Blog and tweets @sciencebase, he is author of the popular science book "Deceived Wisdom".