A recent article published in Materials Horizons by McGill University’s Mechanical Engineering department demonstrates a novel bioprinting method for creating tunable, porous, cell-laden scaffolds that are activated by physiological temperatures.
As stated by the McGill team, “To realize this mechanism in bioprinting, the researchers prepared the bioink by suspending cells within a chitosan solution at a slightly acidic condition. The bioink can be printed into a pH-controlled supportive gelatin slurry with predefined shapes using BioAssemblyBot®.” This slurry or a phase-separation inducing matrix (PSIM) not only provides mechanical support to the printed material, but importantly contains compounds that chemically react with the porous viscoelastic hydrogel or PVH to form cell-sized pores in the scaffold. Next, the tissue model is heated up 37C which triggers micropore formation and strengthens the scaffold while melting away the support bath – resulting in a mechanically robust, biodegradable, and porous scaffold that is highly tunable to changes in pH without requiring the addition of crosslinking compounds or mechanisms, thereby enabling the fabrication of scaffolds that mimic more tissue-specific characteristics.
Empowered by the six-axis bioprinting versatility of BioAssemblyBot®, the McGill team biofabricated small replicas of complex, porous human tissues including large vessels, intervertebral discs, kidneys, and vocal folds. “The bioprinting process and the resulting porous viscoelastic hydrogels (PVHs) are highly cytocompatible.”
To further illustrate a key application of their TMF technology, the McGill team built multi-cellular scaffolds for vocal fold tissue engineering. Using TSIM® & BioAssemblyBot®, they designed and biofabricated a bilayer vocal fold construct out of human vocal fold fibroblasts (hVFFs) and human bronchial epithelial cells (hBEpCs) and found that the spreading of fibroblasts within the scaffold was substantially improved compared to non-porous hydrogels.
The McGill team believes the TMF process will enable a new suite of bioprinting applications, since they can now tune certain structural and viscoelastic gradients for applications such as tissue repair, regenerative medicine, organ-on-chip, drug screening, organ transplantation, and disease modeling.