Engineers are exquisitely aware that the structural framework for things like buildings or cars provide the necessary strength and shape for the constructed material. Now, bioengineers from Penn State University (PSU) believe they have just found a way to create the structural framework for growing living tissue using an off-the-shelf 3D printer. Findings from the new study—published recently in the Journal of Advanced Healthcare Materials in an article entitled “3D Near-Field Electrospinning of Biomaterial Microfibers with Potential for Blended Microfiber-Cell-Loaded Gel Composite Structures”—could help create a novel, low-cost, and efficient method for fabricating high-resolution and repeatable 3D polymer fiber patterns on nonconductive materials for tissue engineering with available hobbyist-grade 3D printers.
“We are trying to make stem-cell-loaded hydrogels reinforced with fibers like the rebar in cement,” explained senior study investigator Justin Brown, Ph.D., associate professor of biomedical engineering at PSU. “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.”
The method that the research team used was a combination of 3D printing and electrospinning, a method that uses an electric charge to spin nanometer threads from either a polymer melt or solution.
Currently, nearly all complex transplant tissues, from hearts and kidneys to tendons, come from living or dead donors. The researchers are looking for a way to grow replacement tissues reliably using inexpensive methods. The combination of 3D printing and electrospinning to produce a scaffold for tissue engineering might also enable the production of combined muscles and tendons, or tendons and cartilage.
“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,” noted lead study investigator Pouria Fattahi, a doctoral student in Dr. Brown’s laboratory. “Others have created these combination tissues using a microextrusion bioprinter.”
Current tissue creation strategies generate the different tissues separately and then combine them using some adhesive or connector. However, in the body, tissues such as cartilage and bone, and tendons and muscles, grow seamlessly together. In the current study, the PSU team used the electrospinner to replace the extruder nozzle on the 3D printer. The printer can deposit a precise pattern of fibers in three dimensions to form a scaffold in a hydrogel on which cells can grow. Once the tissue has grown sufficiently, the scaffolding can be dissolved, leaving only a structured tissue appropriate for use.
If two different tissues—muscle and tendon—are needed, the 3D printer can alter the pattern of threads in such a way that the transition could be seamless with the appropriate cells, resulting in a naturally formed, two-part tissue replacement. Currently, the researchers are working on tissues that are a little less than 1-inch cubes, but even that might have some utility.
Using near-field electrospinning, the researchers first produced exceptionally thin threads in the micron and nanometer range—showing that they could grow cells on these fibers and finally, deposited patterned fibers into a collagen gel loaded with cells.
“The fabrication of various fiber patterns, which are subsequently translated to unique cellular patterns, was demonstrated,” the authors concluded. “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.”