MatSciCon2023: Biohybrid material is robust but flexible, performing like cartilage.

Scientists have struggled to make biomaterials that work as well as cartilage and tendons, but a novel material developed at Cornell University suggests a promising new strategy for emulating real tissue.

The findings, which were made public on July 8 in the Proceedings of the National Academy of Sciences, offer a fresh method for putting together medical treatments for injured tissue. 

The tissue must be malleable enough to bend and flex while tough enough to tolerate sustained loading, such as the weight that a knee tendon must bear. Collagen hydrogels and synthetic materials may be used to replace worn-out or injured tissue, but neither by itself provides the ideal blend of biological and mechanical characteristics of real tissue.

Now, Cornell scientists have created a biohybrid composite material with many of the same properties as a real tissue. Collagen, which provides the substance its softness and biocompatibility, and a synthetic zwitterionic hydrogel, which has positively and negatively charged chemical groups, are the two main components of the substance.

The interaction between these charge groups and the negatively and positively charged groups in the collagen is what allows the materials to dissipate energy and achieve high levels of toughness, according to Lawrence Bonassar, co-lead author of the study and Daljit S. and Elaine Sarkaria Professor in Biomedical Engineering in the College of Engineering.

The biohybrid composite has 11 times the fracture energy (a measure of durability) and 40% more flexibility than the zwitterionic material alone, which brings it closer to the performance of articular cartilage and other biological tissues.

The study's co-lead author and assistant professor of mechanical and aerospace engineering Nikolaos Bouklas explained that the material's biocompatibility enables it to draw in and sustain cells. 

Finally, Bouklas added, "We aim to develop something for regenerative medicine, such as a scaffold that can sustain some initial pressures until the tissue fully regenerates. "Using this substance, you could 3D print a porous scaffold containing cells that could eventually produce the actual tissue around the scaffold," the researcher said. 

Additionally, once the two components are combined, the biohybrid material self-assembles, according to Bouklas, producing "the same interconnected network of collagen seen in real cartilage, which otherwise would be incredibly impossible to make."

Four research labs from three distinct departments were involved in the study. The zwitterionic hydrogel was created by study co-authors Emmanuel Giannelis, the Walter R. Read Professor of Engineering in the Department of Materials Science and Engineering, and Robert Shepherd, an associate professor in the Sibley School. Bonassar's lab had already been working on the collagen used in the biohybrid composite. 

The authors of the study are still investigating the substance and the molecular mechanisms underlying its creation. The material, according to Bonassar, is ideal for the type of bioprinting that his team invented, and the authors have started experimenting with using it in 3D printing.

Cameron Darkes-Burkey et al, Simple synthesis of soft, tough, and cytocompatible biohybrid composites, Proceedings of the National Academy of Sciences (2022).  DOI: 10.1073/pnas.2116675119

Journal information: Proceedings of the National Academy of Sciences