在3D列印技術中，組織工程所面臨最大的挑戰在於如何將這些血管與器官形成一個有效的系統，能夠執行運輸、傳送等功能。而最近，加利福尼亞州聖地亞哥大學（University of California San Diego）的奈米工程師透過3D列印技術，將一個栩栩如生且具功能的血管網路完整列印出，未來將邁向於人工器官和再生療法。
The new research, led by nanoengineering
professor Shaochen Chen, addresses one of the biggest challenges in tissue
engineering: creating lifelike tissues and organs with functioning vasculature
-- networks of blood vessels that can transport blood, nutrients, waste and other
biological materials -- and do so safely when implanted inside the body.
Researchers from other labs have used
different 3D printing technologies to create artificial blood vessels. But
existing technologies are slow, costly and mainly produce simple structures,
such as a single blood vessel -- a tube, basically. These blood vessels also
are not capable of integrating with the body's own vascular system.
"Almost all tissues and organs need
blood vessels to survive and work properly. This is a big bottleneck in making
organ transplants, which are in high demand but in short supply," said
Chen, who leads the Nanobiomaterials, Bioprinting, and Tissue Engineering Lab
at UC San Diego. "3D bioprinting organs can help bridge this gap, and our
lab has taken a big step toward that goal."
Chen's lab has 3D printed a vasculature
network that can safely integrate with the body's own network to circulate
blood. These blood vessels branch out into many series of smaller vessels,
similar to the blood vessel structures found in the body. The work was
published in Biomaterials.
Chen's team developed an innovative
bioprinting technology, using their own homemade 3D printers, to rapidly
produce intricate 3D microstructures that mimic the sophisticated designs and
functions of biological tissues. Chen's lab has used this technology in the
past to create liver tissue and microscopic fish that can swim in the body to
detect and remove toxins.
Researchers first create a 3D model of the
biological structure on a computer. The computer then transfers 2D snapshots of
the model to millions of microscopic-sized mirrors, which are each digitally
controlled to project patterns of UV light in the form of these snapshots. The
UV patterns are shined onto a solution containing live cells and
light-sensitive polymers that solidify upon exposure to UV light. The structure
is rapidly printed one layer at a time, in a continuous fashion, creating a 3D
solid polymer scaffold encapsulating live cells that will grow and become
"We can directly print detailed
microvasculature structures in extremely high resolution. Other 3D printing
technologies produce the equivalent of 'pixelated' structures in comparison and
usually require sacrificial materials and additional steps to create the
vessels," said Wei Zhu, a postdoctoral scholar in Chen's lab and a lead
researcher on the project.
And this entire process takes just a few
seconds -- a vast improvement over competing bioprinting methods, which
normally take hours just to print simple structures. The process also uses
materials that are inexpensive and biocompatible.
Chen's team used medical imaging to create
a digital pattern of a blood vessel network found in the body. Using their
technology, they printed a structure containing endothelial cells, which are
cells that form the inner lining of blood vessels.
The entire structure fits onto a small area
measuring 4 millimeters × 5 millimeters, 600 micrometers thick (as thick as a
stack containing 12 strands of human hair).
Researchers cultured several structures in
vitro for one day, then grafted the resulting tissues into skin wounds of mice.
After two weeks, the researchers examined the implants and found that they had
successfully grown into and merged with the host blood vessel network, allowing
blood to circulate normally.
Chen noted that the implanted blood vessels
are not yet capable of other functions, such as transporting nutrients and
waste. "We still have a lot of work to do to improve these materials. This
is a promising step toward the future of tissue regeneration and repair,"
Moving forward, Chen and his team are
working on building patient-specific tissues using human induced pluripotent
stem cells, which would prevent transplants from being attacked by a patient's
immune system. And since these cells are derived from a patient's skin cells,
researchers won't need to extract any cells from inside the body to build new
tissue. The team's ultimate goal is to move their work to clinical trials.
"It will take at least several years before we reach that goal," Chen
原文連結：University of California - San Diego. " Nanoengineers 3-D print biomimetic blood vessel networks.
" ScienceDaily, 2 March, 2017.
參考文獻：Wei Zhu et al., Direct 3D bioprinting of
prevascularized tissue constructs with complex microarchitecture. Biomaterials,
2017. DOI: 10.1016/j.biomaterials.2017.01.042