A 3D-printed scaffold of a nose made with the new material. Photo: WSU.
A 3D-printed scaffold of a nose made with the new material. Photo: WSU.

Arda Gozen, associate professor in Washington State University (WSU) School of Mechanical and Materials Engineering, looks to a future in which doctors can hit a button to print out a scaffold on their 3D printers and create custom-made replacement skin, cartilage or other tissues for their patients.

Gozen and a team of colleagues have developed a unique scaffolding material for engineered tissues that can be fine-tuned for the tricky business of growing natural tissue. The team, including researchers from WSU's School of Chemical Engineering and Bioengineering as well as from the University of Texas-San Antonio (UTSA), Morehouse College and the University of Rochester, reports its work in a paper in Bioprinting.

In recent decades, researchers have been working on using biological material in 3D printing to create tissues or organs for patients recovering from injury or disease. Also known as additive manufacturing, 3D printing makes it possible to print complex, porous and personalized structures, and could allow doctors someday to print out tissue for a patient's particular body and needs. To create biological structures, biological materials known as 'bioinks' are dispensed out of a nozzle and deposited layer-by-layer, creating complex 'scaffolds' for real biological material and providing a nice place for cells to grow.

So far, however, nature has proved more complicated than researchers can keep up with. Real biological cells like to grow on a scaffold that approaches their own properties. So, for instance, a skin cell wants to grow on a scaffold that feels like skin while a muscle cell will only develop on a scaffold that feels like muscle.

"The success of this method in manufacturing functional tissues relies heavily on how well the fabricated structures mimic the native tissues," Gozen said. "If you want to grow cells and turn them into functional tissue, you need to match the mechanical environment of the native tissue."

The way that researchers have traditionally varied their scaffolds has been to remove trusses to make them softer or stiffer – a method that is too simple to address the required complexity in tissue engineering. "We don't have a lot of knobs to turn," Gozen said. "You need more degrees of freedom – to create something softer or harder without changing the structure."

The team of researchers has developed a new bioink material that allows for customizing properties so they more closely approach what cells might need. The ingredients for their scaffold include gelatin, gum Arabic and sodium alginate, which are all common thickening agents used in many processed foods.

Similar to the way a thick rope is made of braided strands, the researchers used three separate chemical processes to tie their three ingredients together into one scaffold material for printing. Playing with the separate chemical processes provides a way to finely tune the mechanical properties of the material, allowing them to make a softer or stiffer final scaffold.

"That gives you the capability of tuning the properties without changing the scaffold design and gives you an additional degree of freedom that we are seeking," Gozen explained. Adjusting the chemical bonds between the rope strands didn't change the material significantly, and it proved amenable for growing cartilage cells.

This work is still in its early stages, and the researchers would like to figure out how to tune the process and the final material more precisely. They might look at varying the composition of their three materials or printing at different temperatures.

Trying to imitate the vast complexity of natural tissue remains a challenge. For instance, even a simple millimeter-sized piece of cartilage on the knee has three separate and distinct layers, each with different mechanical properties and functions.

"You're not assembling Legos here; it's always about replicating nature that works with the body," Gozen said. "You can make living structures, but they look nothing like the native tissue. Precision is key because there is no single mechanical property target for a single piece of tissue."

This story is adapted from material from Washington State University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.