Aspects of a Suspended Bioprinting System Affect Cell Viability and Support Bath Properties

Abstract

Suspended hydrogel printing is a growing method for fabricating bioprinted hydrogel constructs, largely due to how it enables nonviscous hydrogel inks to be used in extrusion printing. In this work, a previously developed poly(N-isopropylacrylamide)-based thermogelling suspended bioprinting system was examined in the context of chondrocyte-laden printing. Material factors such as ink concentration and cell concentration were found to have a significant effect on printed chondrocyte viability. In addition, the heated poloxamer support bath was able to maintain chondrocyte viability for up to 6 h of residence within the bath. The relationship between the ink and support bath was also assessed by measuring the rheological properties of the bath before and after printing. Bath storage modulus and yield stress decreased during printing as nozzle size was reduced, indicating the likelihood that dilution occurs over time through osmotic exchange with the ink. Altogether this work demonstrates the promise for printing high-resolution cell-encapsulating tissue engineering constructs, while also elucidating complex relationships between the ink and bath, which must be taken into consideration when designing suspended printing systems.

Impact statement

This work demonstrates the ability to print viable chondrocyte-laden fibers at a resolution on the 50 μm scale, while maintaining viability during printing for up to 6 h using a thermogelling suspended bioprinting system. Factors that ultimately contributed to chondrocyte viability and support bath rheological properties were identified. Additionally, osmotic relationships between the ink and bath materials during the course of printing were observed and characterized, contributing to our understanding of the underlying principles of successful suspended bioprinting systems.