As of right now, almost every complex transplant tissue, whether it’s a tendon or a kidney or a heart, comes from donors who are living or dead. A research team of engineers from Penn State University are working to develop a reliable, inexpensive method for growing replacement tissues, and they think they’ve found a way to successfully create a structural framework for growing living tissue – similar to how a frame supports the structure of a house – by using an off-the-shelf 3D printer and 3D printed microfibers.
The researchers, with support from the National Institutes of Health (NIH), have developed a method that combines 3D printing and electrospinning, which uses an electric charge to spin nanometer threads from a polymer solution or melt and has been used in 3D printing medical research before. According to Penn State, this new method is called 3D near-field electrospinning, or 3DNFES, and can be used to place single micrometer-scale fibers, on several different substrates, in a “predefined spatial organization.”
Many researchers are currently working to fabricate tissue scaffolds with 3D printing, but by combining the technology with electrospinning to produce a tissue scaffold could be a precursor for creating combined tendons and cartilage, or tendons and muscles, using the same method.
Justin Brown, Associate Professor of Biomedical Engineering at Penn State, explained, “We are trying to make stem-cell-loaded hydrogels reinforced with fibers like the rebar in cement. If we can lend some structure to the gel, we can grow living cells in defined patterns and eventually the fibers will dissolve and go away.”
Pouria Fattahi, a doctoral student in bioengineering, undergraduate biomedical engineering student Jordan T. Dover, and Brown published the results of their research in a paper, titled “3D Near-Field Electrospinning of Biomaterial Microfibers with Potential for Blended Microfiber-Cell-Loaded Gel Composite Structures,” in the Advanced Healthcare Materials journal.
The abstract reads, “This paper describes the development of a novel low-cost and efficient method, 3D near-field electrospinning, to fabricate high-resolution, and repeatable 3D polymeric fiber patterns on nonconductive materials with potential use in tissue engineering. This technology is based on readily available hobbyist grade 3D printers. The result is exquisite control of the deposition of single fibers in an automated manner. Additionally, the fabrication of various fiber patterns, which are subsequently translated to unique cellular patterns, is demonstrated. Finally, poly(methyl methacrylate) fibers are printed within 3D collagen gels loaded with cells to introduce anisotropic properties of polymeric fibers within the cell-loaded gels.”
In the human body, tissues like tendons, muscles, cartilage, and bone grow together seamlessly. By using a microextrusion bioprinter, these different tissues are created separately, and later have to be combined using a connector or adhesive. Penn State’s 3DNFES method and 3D printing apparatus calls for an electrospinner to replace a 3D printer extruder nozzle, which deposits a precise, 3D pattern of fibers. These fibers then form a scaffold, in a hydrogel, for cells to grow on. The scaffolding can be dissolved once the tissue has grown enough, which will, according to Penn State, leave behind “only a structured tissue appropriate for use.”
The research team’s 3D printer is also able to seamlessly alter the thread pattern if two different tissues are needed, like tendon and muscle. Right now, they are only working on tissues that are less than one inch cubed. The team used its 3DNFES method to fabricate very thin threads in both the micron and nanometer range, and was actually able to successfully grow cells on the fibers, as well as deposit patterned fibers in a cell-filled collagen hydrogel.
“The overarching idea is that if we could multiplex electrospinning with a collagen gel and bioprinting, we could build large and complex tissue interfaces, such as bone to cartilage. Others have created these combination tissues using a microextrusion bioprinter,” said Fattahi, the lead author of the paper.
Even at such a small size, the researchers know that their method is still very useful for smaller body parts.
Fattahi said, “The anterior cruciate ligament, or ACL, is only about 2 to 3 centimeters (.8 to 1 inch) long and 1 centimeter (.8 inches) wide.”
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