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3-D Printed Scaffold Helps Regrow Soft Tissue

Printed tissue scaffolds

3-D printed tissue scaffolds (University of Birmingham)

5 July 2021. Researchers developed a biodegradable polymer for printed implant scaffolds that in lab rodents maintains its shape to encourage cell and tissue growth. A team from University of Birmingham in the U.K. reports its findings in today’s issue of the journal Nature Communications.

A team from the Birmingham lab of chemistry professor Andrew Dove is seeking better techniques for growing new tissue to repair surgical incisions, wounds, and burns. Dove’s lab studies materials for tissue engineering and regenerative medicine, particularly polymers that help repair soft tissue, such as skin and cartilage, but safely degrade and are absorbed. Three-dimensional printing offers a promising technique for producing scaffolds, implanted frameworks on which new cells and tissue can grow. However, say the researchers, current materials for these scaffolds do not adequately degrade, are too toxic, or are not easily produced on 3-D printers.

The Birmingham team led by postdoctoral researcher Andrew Weems, now on the engineering faculty at Ohio University in Athens, sought flexible, non-toxic, and biodegradable polymers produced from resin inks on a 3-D printer for implanted tissue repairing scaffolds. The researchers focused on a class of polymers called poly-carbonate urethanes with potential for meeting these specifications. The team then modified the poly-carbonate urethane’s chemistry, with light waves and other techniques, to improve its support for cell and tissue growth. Among those properties is the ability to fill an irregular tissue void, such as a surgical incision, then maintain its shape over time while new tissue regrows.

Cell growth after two months

The researchers call this shape-filling property over time a fourth dimension, added to the three dimensions of 3-D printing, and thus they name the new polymers 4-D materials. Lab tests show the 4-D polymer meet the strength, porosity, and light sensitivity requirements for tissue scaffold implants, and can be produced on 3-D printers from resin inks. Simulations with alginate gel show scaffolds made from the polymer can fill tissue voids with irregular shapes, and degrade slowly to allow new cells and tissue to grow, yet still eventually disintegrate and be absorbed.

The team then tested scaffolds made from the 4-D polymer in lab rats with tissue voids. Two months after implanting, the scaffolds show signs of new precursor cells of skin, fat, and blood vessels suggesting normal tissue formation rather than inflammation indicating an adverse immune response. After four months, a thin capsule of the protein collagen found in soft tissue begins forming around the scaffolds, with small blood vessels also forming. Also after four months, the scaffold shows signs of degrading, losing about 20 percent of its material, while conventional biocompatible polymers implanted in other lab rodents do not degrade.

“We have demonstrated,” says Dove in a university statement, “that it’s possible to produce highly porous scaffolds with shape memory, and our processes and materials will enable production of self-fitting scaffolds that take on soft tissue void geometry in a minimally invasive surgery without deforming or applying pressure to the surrounding tissues.”

Dove is a co-founder and chief scientist of the start-up company 4D Biomaterials in Nottingham, U.K. a developer of resin inks for printed tissue-engineering scaffolds. The company licenses the Dove lab technology, marketing the inks under the brand name 4Degra.

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