WFIRM Scientists Work to Establish Measurement Standards for Bioinks

Bioinks, which are used to print complex tissues, are substances made of living cells. Naturally-derived hydrogel materials are commonly used as bioink materials due to their biological and physical properties. Wake Forest Institute of Regenerative Medicine (WFIRM) scientists are working to create a universal bioink to apply advanced manufacturing to regenerative medicine which is needed to speed up the availability of replacement tissues and organs to patients. 

“A lot of work is being done to improve the bioinks, but the current problem is there are no standards or quantitative comparison for their printability,” said WFIRM associate professor Sang Jin Lee, Ph.D., who is senior author of the study, published in the journal Biofabrication. “This study establishes a quantitative approach to measure bioink printability.”

For this study, the solid and fluid characteristics of two commonly used bioink materials -- gelatin and alginate – were studied. They were mixed at various concentrations to obtain hydrogel formulations with a wide range of properties. 

Lee leads the bioprinting team at WFIRM that worked to develop a framework for evaluating bioink printability with three measures: extrudability – how much pressure does it take to extrude the bioink at a given flow rate – so the less pressure required, the better extrudability; extrusion uniformity – extrusion lines can either be uniform or have a bumpy architecture which reduces the resolution; and structural integrity – a tube shape was printed and measured. 

“We found the printability window that delivered good uniformity and structural integrity,” said Gregory Gillespie, a Ph.D. student in biomedical engineering at Wake Forest University who is a co-author on the paper. 

In addition to the characterization of a common bioink, the methodology introduced in this paper could also be used to evaluate the printability of other bioinks in the future, he added. 

“If we are going to scale up to reach the patient population, we need better bioinks and we need ways to compare them to each other,” Lee said. 

The authors declare no competing interests. Study funding was provided through a five-year, $10 million grant to apply advanced manufacturing to regenerative medicine awarded to the RegenMed Development Organization, a non-profit dedicated to advancing regenerative manufacturing. The funding was awarded through a public-private partnership that involves the U.S. Army Medical Research and Materiel Command and the Medical Technology Enterprise Consortium (MTEC).

Co-authors include: co-author Teng Gao, Ph.D., a WFIRM Summer Scholar from 2015; Joshua S. Copus, a graduate student researcher; Anil Kumar Pallickaveedu Rajan Asari, Ph.D., visiting clinician; Young-Joon Seol, former postdoctoral researcher; James Yoo, M.D., Ph.D., and Anthony Atala, M.D., all of WFIRM.