Frost & Sullivan predicts the medical industry will see large-scale adoption of 3-D printing by 2018, but also warns of side effect impacts concerning legal liability issues, disruption to medical device supply chains, government regulations (what agencies, what regulations, how quickly both can be resolved), copyright and patent claims and counterclaims, and even ethical and moral questions.

“It can be expected that in another decade, 3-D printing will be able to address most of the unresolved healthcare issues we have now. With the convergence of nanotechnology and genetic engineering, it can be expected that it will play a significant role in life extension,” Allada concluded.

“Though some of the future applications may sound bizarre and absurd, it will ultimately rest on the technology developers and adopters to decide which applications are to be pursued and which rejected. From the vast scope for application of the technology, it is expected the health care industry will be one of the top industries in driving the growth and adoption of the 3-D printing market in the next decade.”

Atala and Yoo identified three primary approaches to 3-D bioprinting, all of which, individually and in combination, probably will be required to print complex 3-D biological structures:

1. Biomimicry – manufacturing structures identical to the cellular and extra-cellular components of a tissue or organ; it requires duplication of the organ’s microenvironment as well as form and structure
2. Autonomous self-assembly – based on natural embryonic organ development, where the cell drives tissue formation through the production of extra-cellular matrix and autonomous organization and patterning, which require detailed knowledge of the developmental mechanisms of embryonic tissue and organs
3. Mini-tissues – a combination of biomimicry and self-assembly; organs and tissues are composed of smaller, functional building blocks that can be fabricated for assembly into larger structures

“As the field of bioprinting moves forward, new types of printers will likely be designed to meet the goal of printing functional replacement organs,” they wrote. “Currently, there are three main printer types used to deposit and pattern biological materials – inkjet, microextrusion and laser-assisted. In addition, our institute has designed a system that is integrated, allowing for the printing of both solid and flexible materials.”

Inkjet printers – originally commercial desktop models modified with a third axis and ink replaced with a biologic material – deliver controlled volumes of liquid to predefined locations. Inkjets have been used in preclinical studies to regenerate functional skin and cartilage and fabricate bone constructs.

Microextrusion printers use mechanical or pneumatic dispensers to extrude continuous material segments. Structures first are printed in 2-D with hydrogel, then solidified – either physically or chemically – for combining into 3-D shapes.

The principles of laser-induced foreign transfer comprise the third printer type – laser-assisted bioprinting – using a focused pulsed laser beam and a “ribbon” with donor transport support, a layer of biological material and a receiving substrate. To date, they have successfully been applied to biological materials such as peptides, DNA, and cells.

Future focus areas to achieve that include developing new biocompatible materials able to withstand external stress and maintain their shape after implantation; improving printer resolution to duplicate the detailed inner architecture of complex organs; creating new ways to vascularize and innervate 3-D-printed tissue and organs, especially complex volumetric organs; increasing printer speed while overcoming current issues of extrusion-based cell damage; and developing in vivo bioprinting for real-time tissue regeneration at the point of injury or during surgery.

“As scientists move away from hand-fashioning scaffolds to bioprinting them, additional biomaterials will need to be identified. The material must not only be printable, but also must be compatible with the body and support cellular attachment, proliferation and function,” the Wake Forest researchers noted.

“Also important is how quickly the material will degrade in the body. The degradation rates of the scaffold must match the cells’ activity in building a ‘home’ from their own extracellular matrix, the molecules they secrete to provide structural and biochemical support.”