Platelets play an important role in the bloodstream – if there’s an injury, the platelets are drawn to the site, where they clot and stop the bleeding. They also release growth factors that help repair soft tissue such as skin, muscle, tendons and blood vessels, as well as “recruiting” other cells to help start the healing process. Platelet-rich plasma is often used to help with treatment for certain joint injuries and post-operative treatments.
Researchers from the University of Nebraska-Lincoln, MIT and Massachusetts General Hospital have created a bio-ink from platelet-rich plasma. This 3D printable material is a mixture of cells and alginate that could one day be used for things such as skin grafts and regenerative tissue implants.
“The ultimate goal is to print functional tissue constructs that can be implanted to replace or repair damaged tissues,” said the University of Nebraska’s Ali Tamayol, Assistant Professor of Mechanical and Materials Engineering. “One of the challenges is to create structures that, when implanted in selected tissues or organs after an injury, will release growth factors that initiate the processes essential for healing and regeneration.”
Jeremy Ruskin, Professor of Medicine at Harvard Medical School, worked with colleagues at Massachusetts General Hospital to show that the bio-ink can accommodate an optimal concentration of platelet-rich plasma and dispense its growth factors over several days. When testing the performance of the bio-ink against a platelet-less ink, the platelet-rich bio-ink greatly outperformed its competitor.
In less than a day, the platelet-rich ink stimulated enough cell migration to cover about 50 percent of an artificial scratch, while the platelet-less ink covered only about five percent. The platelet-rich bio-ink also encouraged twice as many mesenchymal stem cells to migrate toward the wound within 24 hours. The researchers also tested the bio-ink’s ability to stimulate the repair of blood vessels, and found that found that vessel-specific cells not only reproduced twice as fast but also organized into vessel-like tubes that were significantly longer and more complex than those formed by the platelet-less ink.
To make the bio-ink more suited to 3D printing, the researchers added calcium chloride to the alginate to form bonds among some of the material’s polymer chains, giving it strength without making it too viscous to be 3D printed. They tested the ink by 3D printing shapes such as a tree, a grid and a serpentine line, then immersed the structures in a calcium chloride solution to further strengthen them. According to Tamayol, the body raises calcium at injury sites, which could help to strengthen the alginate.
Ultimately, the alginate could be mixed with a patient’s own cells and platelets to minimize the risk of an immune response.
“There is a trend toward using personalized therapies in many areas of medicine,” said Negar Faramarzi, the lead author of a new study detailing the bio-ink. “We tried to incorporate the growth factors in a way that keeps us on track for those personalized therapies.”
The study is called “Patient-Specific Bioinks for 3D Printing of Tissue Engineering Scaffolds,” and can be accessed here. Authors include Negar Faramarzi, Iman K. Yazdi, Mahboubeh Nabavinia, Andrea Gemma, Adele Fanelli, Andrea Caizzone, Leon M. Ptaszek, Indranil Sinha, Ali Khademhosseini, Jeremy N. Ruskin, and Ali Tamayol.
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