The technique involves creating a network of microscopic tubes that branch out in a pattern, similar to that seen in the circulatory system, to provide oxygen and nutrients to liver or kidney cells that have been cultured in a lab. Using new fractal computational models, the network is designed and etched onto silicon surfaces which are then used as molds to transfer the pattern to biocompatible polymer films. Two films are then sealed together with a microporous membrane sandwiched between them.
"These technologies create a precise architectural framework for the liver or kidney cells that are responsible for the functional replacement of the vital organs," says Mohammad Kaazempur-Mofrad of MIT's department of mechanical engineering and division of biological engineering, lead researcher on the study, whose lab is in charge of designing the networks. Jeffrey Borenstein at Draper Laboratory oversees the microfabrication and polymer processing and the principle director of the entire project is Joseph Vacanti of Massachusetts General Hospital.
Conventional tissue engineering methods have been successful in the creation of new tissues including skin and cartilage, but have failed to create large, functional vital organs such as the kidneys and liver. The reason for this, says Kaazempur-Mofrad, is that while they provide a structural support for the cells of the tissue being created, they fail to provide vascular support (in the form of blood vessels to bring oxygen and nutrients) at the level necessary to maintain the cells of these vital organs. This new process addresses that need.
"Our microfabricated devices can efficiently supply oxygen and nutrients to sustain the viability of human liver and kidney cells for at least one week in the lab," says Kaazempur-Mofrad. Experiments showed that 96% of kidney cells survived for one week and 95% of liver cells survived for two weeks.
They also implanted an experimental liver device into rats which lasted a week. The device was only a single layer (researchers expect it could take from 30 to 50 layers to represent a fully functioning liver) so it did not replace the existing liver. Kaazempur-Mofrad and his colleagues plan investigate if this approach works in higher level animals next.
"So far we have succeeded in making individual, functioning units but the ultimate goal is to make whole, functional organs," says Kaazempur-Mofrad.
The ASM Conference on Bio-, Micro-, Nanosystems, held in collaboration with the IEEE Engineering in Medicine and Biology Society on July 7-10, 2003 at the Plaza Hotel in New York City, is intended to provide an interdisciplinary forum for microbiologists and engineers to explore ways in which microbiology can contribute to the growing field of nanotechnology. For further information on the meeting contact Jim Sliwa.