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Composite Nanofibers Developed for Orthopedic Biomaterials

Composite nanofibers (Brendan Baker, University of Pennsylvania)

Composite nanofibers (Brendan Baker, University of Pennsylvania)

Biomedical engineers at University of Pennsylvania in Philadelphia developed a technology for creating composite nanoscale fibers for replacement tissue to treat orthopedic injuries. The team led by Penn medical school professor Robert Mauck published its findings online this week in the journal Proceedings of the National Academy of Sciences (paid subscription required).

Recent advances in tissue engineering for orthopedic injuries involve the use of scaffolding made from nanoscale fibers on which tissue cells accumulate to create new tissue; 1 nanometer equals 1 billionth of a meter. For orthopedics, say the authors, this method sometimes runs into problems when fibers in the scaffolds are too tightly packed, which inhibits the growth of tissue-forming cells.

Mauck’s team at Penn devised a different scaffolding method, which generates nanoscale fibers in a structure loose enough for cells to colonize and create new tissue, while still able to instruct the cells on how to form the new tissue. The new technology makes use of an old method called electrospinning that dates back to the 1930s, and which produces polymer fibers using electrostatic force.

Mauck’s team created two types of composite fibers: a slow-degrading polymer and a water-soluble polymer that can be selectively removed to increase or decrease the spacing between fibers. Using electrospinning, the researchers electrically charge solutions of dissolved polymers, causing the solution to become a fine spray of fibers that fall on a rotating drum and collect as a stretchable fabric.

The researchers say this textile can be implanted into damaged tissue for neighboring cells to colonize, but can also be shaped or formed for other medical applications. In this study, the team discovered they could increase the proportion of the dissolving fibers to enhance the ability of host cells to colonize the nanofiber mesh. Increasing the proportion of the dissolving fibers also encourages migration of those fibers to achieve a uniform distribution and form three-dimensional tissue.

The results also show that despite the removal of more than 50 percent of the initial fibers, enough of the the remaining scaffold architecture remains to align cells and direct the formation of a highly organized extracellular matrix by collagen-producing cells. This resulting matrix led to development of a biologic material with tensile properties nearly matching human meniscus tissue, in lab tests of tissue mechanics.

“This approach transforms what was once an interesting biomaterials phenomenon — cells on the surface of nanofibrous mats,” says Mauck, “into a method by which functional, three-dimensional tissues can be formed.”

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