New Elastic Biodegradable Hydrogel Could Help 3D Print Human Soft Tissue in the Future

Last year, Dr. Yi Hong, a Professor of Bioengineering at the University of Texas at Arlington (UTA), received an R21 grant from the National Institutes of Health (NIH) to develop materials for making 3D printed blood vessels for children suffering from vascular defects. Dr. Hong has been the primary investigator on research grants totaling over $850,000 since he began his career. Now, he’s continuing his work with 3D printing in the medical field by leading a team that’s created a highly elastic biodegradable hydrogel for 3D bioprinting materials that can mimic human soft tissue. The stretchy new substance could one day help generate several different types of tissue, including blood vessels, heart muscles, skeletal muscles, and skin.

Dr. Yi Hong, UTA professor of bioengineering and leader of the project, shows his new hyrdogel.

Dr. Hong explained, “Soft tissue bio-printing suffers from significant challenges as the hydrogels were often brittle and un-stretchable and could not mimic the mechanical behavior of human soft tissues.

“To overcome these challenges, we developed a simple system using a single cross-linking mechanism activated by visible light to achieve a highly elastic and robust, biodegradable and biocompatible hydrogel for cell printing.”

3D bioprinting, which involves the use of live cells within artificial tissue scaffolds, is set to eventually shake up the healthcare field as we know it. But hydrogels, while used often in 3D bioprinting applications, are not foolproof materials, and tend to break easily.

Dr. Hong said, “It’s not strong, it’s not soft, it’s not elastic.”

The researchers recently published a paper on their work, titled “Highly Elastic Biodegradable Single-Network Hydrogel for Cell Printing,” in the American Chemical Society’s ACS Applied Materials and Interfaces journal; co-authors include Cancan Xu, Wenhan Lee, Guohao Dai from Northeastern University in Boston, and Dr. Hong.

The abstract reads, “Cell printing is becoming a common technique to fabricate cellularized printed scaffold for biomedical application. There are still significant challenges in soft tissue bioprinting using hydrogels, which requires live cells inside the hydrogels. Moreover, the resilient mechanical properties from hydrogels are also required to mechanically mimic the native soft tissues. Herein, we developed a visible-light cross-linked, single-network, biodegradable hydrogel with high elasticity and flexibility for cell printing, which is different from previous highly elastic hydrogel with double-network and two components. The single-network hydrogel using only one stimulus (visible light) to trigger gelation can greatly simplify the cell printing process. The obtained hydrogels possessed high elasticity, and their mechanical properties can be tuned to match various native soft tissues. The hydrogels had good cell compatibility to support fibroblast growth in vitro. Various human cells were bioprinted with the hydrogels to form cell–gel constructs, in which the cells exhibited high viability after 7 days of culture. Complex patterns were printed by the hydrogels, suggesting the hydrogel feasibility for cell printing. We believe that this highly elastic, single-network hydrogel can be simply printed with different cell types, and it may provide a new material platform and a new way of thinking for hydrogel-based bioprinting research.”

In the paper, which was also chosen as an American Chemical Society Editors’ Choice, the researchers explain how their 3D printable hydrogel is formed by a tri-block biodegradable polymer of polycaprolactone – poly (ethylene glycol) – polycaprolactone (PCL-PEG-PCL) – together with two end groups of acrylates and a visible-light water-soluble initiator.

Dr. Hong shows the hydrogel’s stretch [Image via NBCDFW]

Dr. Hong said, “Polycaprolactone and poly (ethylene glycol) are already widely used in Food and Drug Administration-approved devices and implants, which should facilitate quick translation of the material into pre-clinical and clinical trials in the future. The tunability of the mechanical properties of this hydrogel to match different soft tissues is a real advantage.”

A provisional patent application has already been filed for the new elastic material, which can be used to create tissue patches that will help a patient’s natural tissue both heal and regrow.

“These colleagues may have created a new way of thinking about hydrogel bio-printing research. This work is also critical in advancing UTA’s strategic theme of health and the human condition through cross-disciplinary work,” said Michael Cho, UTA’s Chair of Bioengineering, as he congratulated Dr. Hong’s team on their work.

Preparation and characterization of highly elastic, visible-light cross-linked, single-network, biodegradable hydrogel for cell printing.

The goal of the research is to make new blood vessels for children with heart defects using the new hydrogel. However, Dr. Hong says that there are still years of testing ahead before this happens.

See more about this new material in the video below from NBCDFW.

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