Coaxial Nozzle-Assisted Embedded 3D Printing of Single-Layered Channels Within a Yield-Stress Matrix Bath

Abstract

Creating multi-layered channels for mimicking human blood vessels in thick tissues is the main challenge to overcome in organ biofabrication. Current three-dimensional (3D) printing strategies cannot effectively manufacture hollow channels with multiple layers. This study aims to propose a coaxial nozzle-assisted embedded 3D printing method in which core-shell filaments can be formed in a yield-stress matrix bath by extruding different ink materials through the corresponding channels. The materials selected for the core ink, shell ink, and matrix bath are Pluronic F127 (F127) and calcium chloride (CaCl2), sodium alginate (NaAlg), and poly(ethylene glycol) diacrylate (PEGDA) and nanoclay, respectively. After crosslinking the matrix bath and shell, the core layer made from the sacrificial ink (F127) is removed to generate a hollow channel. In this work, the effects of ink material properties and operating conditions on core-shell filament formation have been systematically studied. The rheological and mechanical properties of the yield-stress matrix bath have been characterized as well. A thick tissue-like structure with embedded single-layered, hollow channels has been successfully printed for demonstration. Since it is feasible to design coaxial nozzles with a core-shell-shell architecture, the proposed method is technically extendable to create double-layered channels within a cellular tissue construct, accurately mimicking human blood vascular networks in thick tissues.

Coaxial 3D Bioprinting Process Research and Performance Tests on Vascular Scaffolds

“…Most methods for creating vascular channels are based on sacrificial printing, which typically involves four steps: printing the sacrificial biostructure, embedding the printed sacrificial biostructure into a hydrogel matrix through a molding process, unraveling the sacrificial biostructure to form a hollow vascular channel, and implanting endothelial cells on the surface of the hollow vascular channel by perfusing an endothelial cell suspension. Raymond et al [19] developed a coaxial nozzle-assisted embedded 3D printing method to directly print vascular structures within a matrix material. However, endothelial cells later perfused are difficult to successfully seed in the complex vascular structure.…”