Prellis Biologics has brought the science fiction dream of printing human organs for transplant a step forward by developing a fast, high-resolution 3D printing technique that can produce living tissue that includes viable blood-carrying capillaries. The new technique allows the cells to receive enough oxygen and nutrients to survive while building up complex structures.

According to the US government, 20 out of the over 114,000 people waiting for an organ transplant die each day in the United States alone. This is due mainly to the chronic shortage of donors, but issues of disease and tissue compatibility also contribute to the fact that there just aren't enough organs to go around.

If organs could be printed like plastic key fobs out of compatible, disease-free cells, it would go a long way to meeting the demand, but it isn't that simple. Printing living tissue involves laying down a scaffolding of a biocompatible material, like hydrogel, that stands in for the connective material that usually hold organ cells in place. Staring with a digital file, the printer first lays down the scaffold, then seeds it with stem cells that colonize the scaffolding and organize themselves into proper tissue.

The problem is that body cells need a constant supply of oxygen and nutrients, If they're deprived, they die in about 30 minutes. To prevent this, living tissue is vascularized. That is, it has an intricate network of tiny capillaries that carry blood throughout the tissue to feed and oxygenate the cells.

That's fine for natural tissue, but current 3D bioprinting technology tends to be on the slow end of the spectrum, which can take weeks to print a cubic centimeter of human tissue. Even if the printer was including capillaries in the structure, the tissue would be a mass of dead cells long before it was completed, so the usual technique is to print the tissue in very thin sheets that can be kept constantly bathed in a flowing stream of nutrients.

The Prellis approach is to work toward fully functional organs by using a holographic printing technique with a resolution of 0.5 microns, or 10 times smaller than conventional bioprinters, and 1,000 times faster. In other words, when its optical support system that quickly cures the hydrogel scaffold using an infrared laser is perfected, it will be able to print a block of tissue and its entire vascular system in less than 12 hours.

"The speed we can achieve is limited only by the configuration of the optical system," says Melanie Matheu, PhD, CEO and co-founder of Prellis Biologics. "We are now exploring custom optical system development, which will dramatically increase our capabilities. Our ultimate goal is to print the entire vascular system of a kidney in 12 hours or less."

Prellis says that if it can provide printed organs, it will not only have a significant impact on transplants, but it will also help lower medical costs by reducing the demand for oxygen systems, dialysis, insulin injections, and similar treatments. It will also aid in the fields of drug development and toxicology screening.

A white paper that describes the Prellis technique can be found here (PDF).

View gallery - 2 images