Chuck Bednar for redOrbit.com – Your Universe Online
Researchers at the Shanghai University Rapid Manufacturing Engineering Center have for the first time developed an artificial blood vessel composed of three layers, according to a new study currently appearing in the American Institute of Physics journal AIP Advances.
The developers used a combination of micro-imprinting and electro-spinning techniques to make the tri-layered vascular graft, and their efforts could allow scientists to use separate materials that respectively possess mechanical strength and promote new cell growth, something that has been a significant issue for existing artificial blood vessels comprised of a single of double layer.
Vascular grafts are usually attached to an obstructed or unhealthy blood vessel by surgeons, and they allow blood flow to be permanently redirected around those damaged tissues. They work by repurposing existing vessels from a patient’s own body or from a matched donor.
However, such sources are often insufficient due to the limited supply in the individual’s body, and the artificial blood vessels could be affected by the original conditions that required the graft in the first place. As a result, there has been tremendous research towards the development of synthetic blood vessels capable of mimicking naturals ones.
“The composite vascular grafts could be better candidates for blood vessel repair,” Yuanyuan Liu, an associate professor at the Rapid Manufacturing Engineering Center, said in a statement on Monday. Liu’s team had previously worked with bone scaffolds, which are used to repair bone defects, prior to turning their focus to treating cardiovascular disease.
Typically, things like bone scaffolds or artificial blood vessels need to closely mimic the natural vasculature of their targeted tissue. For vascular grafts, this can be fabricated by electrospinning, a process that uses an electrical charge to draw liquid inputs (in this case, a mixture of chitosan and polyvinyl alcohol) into extremely fine fibers.
The electrospinning process also makes it possible for a high surface-to-volume ratio of nanofibers, which provides plenty of space for host cells to grow and connect, the study authors explained. These components naturally decompose over a period of six months to one year, and once they are gone, they are replaced by a new, intact, naturally grown blood vessel.
Three layers are better than 2
However, the structure is not very rigid, and in order to solve this problem, Liu and her colleagues developed the three-layer model. In this model, the mixture was electrospun onto both sides of a microimprinted middle layer of poly-p-dioxanone, a biodegradable polymer commonly used in biomedical applications. The ends of the sheet were then folded and attached, producing a tube-like vessel that more accurately simulates a real blood vessel.
The tri-layered scaffold was then seeded using rat fibroblast cells, which are said to be ideal for such purposes due to their ease of cultivation and quick growth rate, in order to test the efficacy of the scaffold in promoting the expansion and integration of cells.
They found that the cells on these scaffolds proliferated quickly, likely due to the functional amino and hydroxyl groups introduced by the chitosan. While human trials are still far off, the scientists said that they are optimistic about their work, adding that they next plan to test the implants in an animal model to observe its efficacy with live vascular cells.
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