The Challenge of Making 3D Printed Body Organs

Liquid-in-Liquid Printing: Meeting the Challenge

While it is true that 3D printing is able to produce tissues and organs for purposes as lab models for study, as drug screens for pharmaceutical products, and as transplant models for thousands of sufferers to prolong and maintain life, there is a single obstacle to a full realization of this good.

Organs like the heart, liver or lung are vascularized, a network of blood supply permeates their inner core and sustains the organ. Hence, in spite of 3D printing advances in organ manufacturing, replicating complicated body parts such as gastric tracts, windpipes, and blood vessels is a major challenge. Vascularized tissues are hard to build up in traditional solid layer-by-layer 3D printing without constructing supporting scaffolding that can later prove impossible to remove.

Researchers and scientists are investigating the problem by looking at liquid support structures. Though that has been experimented before, liquid structures tend to collapse as their surfaces shrink and their matrixes crumple. This time, they intend to replace support structures with liquid, a specially designed fluid matrix into which liquid designs could be injected before the ink is set and the matrix is drained away.

So, the researchers turned to hydrophilic or liquid polymers that create a stable membrane where they meet. They use different polymer combinations: a polyethylene oxide matrix and an ink made of a long carbohydrate molecule called dextran. With an injection nozzle, they pumped their ink into the matrix that can move through the liquid and even suck up and rewrite lines that have already been drawn.

The result was that the liquid structures hold their shape for as long as 10 days before they begin to merge. With the new method, they printed an assortment of complex shapes, like whirls, single and double helices, branched treelike shapes, among others. As soon as the printing is done, the shapes are set by adding polyvinyl alcohol to the inky portion of the structure. The results of their work appeared in Advanced Materials. This means that complex 3D-printed tissues made by including living cells in the ink could soon become a working reality.

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