Ugaz's work, which was undertaken with colleague Arul Jayaraman and appears in the July online version of "Advanced Materials," is funded by the National Institutes of Health.
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.
"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 Ugaz. "We've also looked at characteristics of the network, and we've shown that there are similarities to natural-occurring vasculature."
Providing man-made replacement parts to people in need of organ transplants (and bypassing the need for suitable donors) has been a chief aim of tissue engineering, but so far the field's biggest successes have been the production of skin and cartilage. This is largely due to the fact that tissue engineers have yet to effectively produce a three-dimensional vasculature that can serve as a network of artificial arteries, veins and capillaries. This network of channels is needed to support larger structures such as kidneys, Jayaraman explains.
"Developing scaffolds for tissue engineering with built-in vasculature is a high priority area in tissue engineering as the ability to provide nutrients to all depths of growing tissue is extremely critical," says Jayaraman, assistant professor in the department. "Typically, as the tissue grows, the inner regions tend to be nutrient-limited, which affects the overall viability of the tissue-engineered product. The development of 3-D vascular networks in bio-compatible materials addresses this specific need in the tissue engineering community."
Without such a network in place, the tissue created by engineers is dependent upon diffusion for the transport of nutrients and waste products. Diffusion, however, is a slow process, taking about 17 minutes to traverse a span of 200 microns, or about twice the thickness of a human hair. Increase that distance to an inch, and it takes close to four months for diffusion to occur. That length of time won't support cell growth, Ugaz notes.
"That's just a fundamental limit of this diffusion mechanism – the timescale," Ugaz says. "If your aim is to manufacture artificial organs, you'll need a network that has the ability to supply all of the cells in a three-dimensional volume with nutrients while moving waste products out and keeping these processes going in a certain timescale.
"The way this is all accomplished [in nature] is with a type of branched network, similar to how a tree is naturally structured. There is a trunk, and distribution occurs throughout a large volume by branches of various lengths and thicknesses that emanate from that trunk. This allows transport to penetrate inside a large volume, until the distance between branches and stems is minimized. It's all really an issue of transport."
Framing the challenge in those terms, Ugaz began contemplating how such a complex architecture could be artificially mimicked. He was well aware of a phenomenon known as the Lichtenberg effect. Named after German physicist Georg Christoph Lichtenberg, the effect is responsible for the creation of a fractal pattern as a stored electrical charge is released. This branching pattern occurs on the surface or interior of insulating materials during an electric discharge.
The patterns are similar to the branching patterns seen in a lightning strike. They also can be seen on the skin of lightning-strike victims or on the ground at the point where a lightning strike occurred. A more common example of this effect can be seen in crystal blocks that are often sold as decorative pieces.
Observing these patterns, Ugaz saw the similarities to the artificial network he envisioned creating and wondered if liquid could be transported through these branching pathways, similar to the way nutrients are transported through a tree's vasculature.
He went to work, teaming with Texas A&M's National Center for Electron Beam Research to implant a high level of electric charge inside an acrylic block using electron beam irradiation. When a point of release for the charge was created, Ugaz was left with the expected fractal patterns.
In his laboratory, he and his research group continue to account for such variables as size, range of size, angles, average area ratios and diameters, as well as how all of this relates to the intensity and frequency of charge. Together with Jayaraman, Ugaz is working to translate these microchannels into a biomedical application.
Their work appears promising. So far, the team has found that these fractal pathways can indeed serve as an elaborate vasculature that is capable of sustaining transport in manner suited for tissue engineering purposes. What's more, by adjusting certain variables, Ugaz can reliably reproduce these architectures not only in acrylic blocks but in biodegradable porous materials that allow for cell cultures to be embedded in the area surrounding the vasculature. He's even begun widening the vascular channels to facilitate flow through them and interconnecting separate networks to form larger vasculatures.
And unlike other methods of creating artificial vasculatures, Ugaz's method enables large, complex, three-dimensional networks to be instantaneously constructed in a way that enables them to be mass-produced.
Ugaz emphasizes that his findings thus far are simply the first step in a lengthy process of applying his work to tissue engineering applications. There's still much work to be done, including developing a means of lining his microchannels with cells that would help preserve the network while directing the surrounding material to break down.
Contact: Victor Ugaz at (979) 458-1002 or via email: firstname.lastname@example.org or Arul Jayaraman at (979) 845-3306 or via email: email@example.com or Ryan A. Garcia at (979) 845-9237 or via email: firstname.lastname@example.org.
About research at Texas A&M University: As one of the world's leading research institutions, Texas A&M is in the vanguard in making significant contributions to the storehouse of knowledge, including that of science and technology. Research conducted at Texas A&M represents an annual investment of more than $582 million, which ranks third nationally for universities without a medical school, and underwrites approximately 3,500 sponsored projects. That research creates new knowledge that provides basic, fundamental and applied contributions resulting in many cases in economic benefits to the state, nation and world. For more news about Texas A&M University, go to http://tamunews.tamu.edu.
Follow us on Twitter at http://www.twitter.com/aggielandnews
Move over, Superman! NIST method sees through concrete to detect early-stage corrosion
27.04.2017 | National Institute of Standards and Technology (NIST)
Control of molecular motion by metal-plated 3-D printed plastic pieces
27.04.2017 | Ecole Polytechnique Fédérale de Lausanne
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
27.04.2017 | Life Sciences
27.04.2017 | Physics and Astronomy
27.04.2017 | Earth Sciences