Oct 13, 2015 | By Kira

A team of researchers in Texas have developed a new technique for 3D printing hydrogels that allows for unprecedented durability and precise processing control thanks to the addition of alginate. Given its combination of flexibility and strength, similar to our own natural tissues, the biomaterial could be used to 3D print load-bearing body parts such as knee cartilage and reduce the need for joint replacements for those who have suffered sports injuries or other traumas.

Damage to articular cartilage—the soft white cartilage that allows or bones and joints to move smoothly, absorbing the shocks and forces to articulated body parts, such as our knees—is not to be taken lightly. Usually occurring during sports injuries or other accidents, or due to misalignment or obesity, damaged cartilage cannot heal on its own, and continues to break down over time, resulting in stiffened joints, severe inflammation, loss of motion and excruciating pain. Eventually, the cartilage can wear away so much that the bones touch on each side of the joint, requiring artificial joint replacement surgery. Due to a severe shortage of donors and biocompatibility issues, successful transplants are rare.

To overcome these obstacles, scientists from the Texas Tech University and Texas A&M University have turned to the possibilities offered by bioprinting and biocompatible materials—a relatively new yet dramatically expanding area in 3D printed medical applications that could eventually see complex 3D printed tissue and cell scaffolds performing as well or better than the original tissue, and replacing the need for human donors.

Hydrogels are a network of hydrophilic polymerchains that, for simple tissues and cell scaffolds, have already proven to be excellent biocompatible materials. This is because their high water content gives them a flexibility that mimics natural tissues. However, the attractiveness of this flexibility is undermined by its correlating limitation: hydrogels are not particularly strong, and are notorious for losing their shape, meaning that they cannot yet support a load-bearing joint such as a knee.

“Because of their low viscosity and large gelling temperature range, precise 3D printing of agar hydrogels has not been achieved,” wrote the researchers in the paper 3D printing of an extremely tough hydrogel, published in the chemical sciences journal RSC Advances. “In this work, a super tough agar double network hydrogel was precisely printed by adding alginate. The addition of alginate not only increases the ink viscosity and printable period, but also improves its rheological characteristics towards precise processing control.”

To translate that into English, the gelatinous properties of alginate, a viscous gum-like polymer, were ‘woven’ into the loose hydrogel network, making it tougher, more resistant, and able to hold a precise given shape while being 3D printed.

Furthermore, calcium ions were introduced by submerging the hydrogel structure in a calcium chloride solution. These ions formed crosslinks with the alginate that made it even stronger. The resulting tensile strength of the calcium and alginate hydrogel was higher than any other hydrogel biomaterial, and on par with natural human cartilege.

The research was conducted by Junhua Wei, Jilong Wang, Siheng Su, Shiren Wang, Jingjing Qui, Zhenhuan Zhang, Gordon Christopher, Fuda Ning and Weilong Cong. “A major challenge for tissue engineering is producing constructs of the clinically relevant size, shape and structural integrity. 3D bioprinting has the potential to meet this goal,” said Anthony Atala a practicing surgeon and director of the Wake Forest Institute for Regeneragive Medicine in North Carolina, who was not involved in the study. “This is a first-rate piece of research that illustrates the many variables and challenges that must be considered in order for 3D bioprinting to be clinically translatable." Previously, we covered a study in Argentina that combined liquid alginate and calcium with a unique dual syringe 3D printer that could accurately print biopolymers. 


Posted in 3D Printing Applications



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