The biophysical and biochemical requirements of bioinks for cardiac tissue bioprinting

Bioprinting is a promising technique for the 3D assembly of biomaterials, cells and macromolecules. Given the major health burden posed by cardiovascular disease, there is great interest in developing bioprinting of clinically applicable cardiovascular tissues. However, the complex anatomy and physiology of the heart make it a particularly challenging tissue to replicate. In a review paper by Hu et al., the authors summarized the physical and chemical properties of a bioink that could produce functional cardiac prints.

Current bioinks are primarily adapted from extracellular matrix proteins, such as gelatin, and each have pros and cons for cardiac mimicking. “Cardiac cells have a really high demand for oxygen and nutrients and at the same time are very sensitive to environmental conditions,” said co-author Vahid Serpooshan. These conditions include sheer stresses, high cell density, a relatively soft elastic stiffness in the range of 1-18kPa, and the ability to withstand repetitive mechanical contractions inherent to the heart. To better mimic the biochemical environment, the authors highlighted efforts to introduce small molecules native to cardiac tissue into bioinks.

Crosslinking of components is another key area that remains to be optimized. UV-induced crosslinking is currently the most common, but because of the safety concerns surrounding UV-induced DNA damage, the authors suggested that future researchers should also explore chemical methods for the goal of clinical implementation.

Serpooshan pointed out that embedding vasculature into bioprinted scaffolds is an important consideration in providing adequate mass transfer of nutrients and oxygen to cells. However, crosslinking while maintaining these hollow structures will be a challenge. Serpooshan hopes that this review will aid the development of cardiac-specific bioinks and that a combination of specific inks may advance the functionality of cardiac bioprinted tissues.

Source: “Cardiovascular tissue bioprinting: Physical and chemical processes,” by James B. Hu, Martin L. Tomov, Jan W. Buikema, Caressa Chen, Morteza Mahmoudi, Sean M. Wu, and Vahid Serpooshan, Applied Physics Reviews (2018). The article can be accessed at https://doi.org/10.1063/1.5048807 .