First off, tissue engineering is not only for paper products; it can also mean engineering of living tissue. In fact, fabricating tissue is one of the cornerstones of bioengineering. Many artificial organs will be built from engineered tissue. Currently the most successful tissue biomaterials are used for replacement skin and cartilage, but the field is heading toward rapid expansion.
One of the most important steps will be to produce biomaterials that mimic (or reproduce) biological functionality, for example blood flow. The vascular structure (veins, arteries, capillaries) of living tissue is complex, and efforts to reproduce these three-dimensional structures in engineered biomaterials have not been successful. Now a team of researchers has developed an approach using the fractal structure found in natural occurrences, such as the pattern lightning makes in the sky. The pattern, called the Lichtenberg Effect (for Georg Christoph Lichtenberg, a German physicist), is found in the discharge of stored electrical energy. The multiple branches, which have the trunk-branch-stem pattern also found in trees, are efficient for transporting fluids throughout a three-dimensional area. The team wondered if, when recreated in biomaterials, the same vascular properties would be maintained.
The first experiments involved creating the fractal pattern in an acrylic block using electron beam irradiation.
When the electric charge was released, a three-dimensional fractal pattern of the expected pattern remained. By adjusting certain variables, the same patterns were reproduced in further testing in biodegradable porous materials, which are suitable for embedding cell cultures in the surrounding area – thus creating a biomaterial vasculature.
“I think we’ve learned how to make these 3-D channels, and we can make them in the kinds of materials that people would use for tissue-engineering applications, in biomaterials,” says Victor Ugaz, associate professor in the Artie McFerrin Department of Chemical Engineering at Texas A&M University.
The findings detail the construction of an elaborate network of fractal channels that mimic the naturally occurring vasculatures found in trees as well as in the human body.
The controlled manufacturing of these networks, which are capable of supporting transport of fluid, is the first step in translating this work to a tissue engineering application where it potentially stands to make a significant impact, Ugaz says.
[Source: Texas A&M University]
Potentially, an advantage for this fractal approach is that it can more easily be mass produced (however that is defined) for medical purposes than approaches requiring a more customized ‘cell-by-cell’ technique. It’s important to understand that as a piece of bioengineering this approach is just barely beyond the conceptual – proof of concept phase. There is a long way to go before it could become a viable technique for producing certain kinds of vascular tissue. Nevertheless, it is representative of the kind of ‘new materials’ innovation that is occurring in labs around the world.