Innovative Hybrid Printer Creates Cartilage Constructs

A new hybrid printer simplifies the process of creating implantable constructs to help patients regrow cartilage in specific areas, such as the joints.

Developed by researchers at Wake Forest University (Winston-Salem, NC, USA), the new printer is a combination of two low-cost fabrication techniques; a traditional inkjet printer and an electrospinning machine, which uses an electrical current to generate very fine fibers from a polymer solution. For the study, electrospinning of polycaprolactone (PCL) fibers was alternated with inkjet printing of rabbit elastic chondrocytes suspended in a fibrin-collagen hydrogel in order to fabricate a five-layer tissue construct. While the synthetic materials ensured the strength of the construct, the natural gel materials provided an environment that promotes cell growth.

The hybrid printer created flexible 10 cm2 mats with a thickness of 0.4 mm of constructs that showed increased mechanical stability when compared to those created by an inkjet printer using gel material alone. The researchers also inserted the constructs into mice for two, four, and eight weeks to see how they performed in a real life system. After eight weeks of implantation, the constructs appeared to have developed the structures and properties that are typical of elastic cartilage, demonstrating their potential for insertion into a patient. The study describing the hybrid printer was published ahead of print on November 21, 2012, in Biofabrication.

“The electrospinning machine allowed the composition of polymers to be easily controlled, producing porous structures that encouraged cells to integrate into surrounding tissue,” said study coauthor Prof. James Yoo, MD, PhD, of the Wake Forest Institute for Regenerative Medicine. “Other methods of fabrication, such as robotic systems, are currently being developed to further improve the production of implantable tissue constructs.”

Despite the ability to mimic the native properties of tissue, printed three-dimensional (3D) constructs that are composed of naturally derived biomaterials still lack structural integrity and adequate mechanical properties for use in vivo, thus limiting their development for use in load-bearing tissue engineering applications, such as cartilage. Using a multihead deposition system could provide the ability to combine synthetic polymers, which have higher mechanical strength than natural materials, with the favorable environment for cell growth provided by traditional naturally derived hydrogels.

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