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3D-printed scaffold engineered to grow complex tissues

A fluorescent dye reveals the "ink" held inside a groove engraved into the curved turn of a scaffold fiber. Diaz-Gomez et al., Bioprinting

Advances in 3D printing techniques have led to hope for improvements in regenerative medicine. This area of research aims to use stem cells and other technologies—such as engineered biomaterials—to repair or replace damaged cells, tissues, or organs.

Much work in regenerative medicine has focused on the idea of creating scaffolds. Scaffolds are structures of artificial or natural materials on which new tissue can be grown to replace damaged tissue. Such scaffolds could be prepared outside the body—for example, to begin growing a piece of bone in the laboratory that could then be surgically implanted. They might also be used to directly promote repair inside the body.

Research in this area has run into several technological hurdles. It’s proven hard to distribute cells predictably on many 3D printed scaffolds. The even and controlled distribution of cells is required to grow complex tissues like bone and cartilage, which are made up of many different cell types.

Creating the “bioinks” used to print cells onto scaffolds has also proved challenging. They have been developed to be thick and viscous to keep the bioink from running off of the scaffolds. But this viscosity can damage cells during the printing process.

Researchers led by Dr. Antonios Mikos from Rice University have been testing ways to improve 3D scaffolds and bioink for printing biomaterials. In their new study, they tested whether engraving grooves onto printed scaffold fibers could help keep cells in place and allow for less viscous bioink to be used. The work was funded in part by NIH’s National Institute of Biomedical Imaging and Bioengineering (NIBIB). Results will be published in the June 2020 issue of Bioprinting.

CT image of a 3D-printed scaffold with grooves. Rice Biomaterials Lab

The researchers created fibers using one print head and then, when the fibers cooled, used an engraving head that was able to create grooves and channels of different heights for different purposes. The general structure of the printed fibers was not damaged by the engraving, and when the fibers were layered together at 90° angles, the resulting scaffolds kept their strength under compression.

When the grooves were then filled with low viscosity bioinks, they held them in place without overfilling and spreading.

The team next tested the survival of structure-making cells called fibroblasts when printed onto the engraved scaffolds using low-viscosity ink. At 24 hours after printing, large numbers of cells remained alive in the grooves.

“This new technology allows us to print multi-layered scaffolds seeded with different cell types in each layer,” says Mikos. “The aim is to grow tissues that better mimic the original structure to create a more functional and durable repair.”

The technique may also allow for the printing of fragile molecules, such as growth factors, onto scaffolding. The researchers are now exploring ways to better control the creation of different sized grooves, with the aim of using the technology in scaffolds made of very thin materials or to make deeper grooves when needed.