Developing Innovative Bioengineering Platforms to Recapitulate Cell Microenvironments In Vitro

Bioprinting has recently emerged as a promising fabrication technique for developing 3D biologically functional, tissue-like constructs. Amongst the various bioprinting approaches, stereolithography (SLA) offers the highest feature resolutions that can be utilised to mimic the complex hierarchical architectures found within human tissues and organs. While significant efforts have been directed towards harnessing digital light processing (DLP) SLA techniques, less attention has been given towards the use of laser-based SLA and the corresponding development of cytocompatible bioresins for such setups. In this work, a novel hydrogel material system to be used as a bioresin was developed based on the biosynthetic polypeptide poly(L-glutamic acid) functionalised with tyramine moieties (PLGA-Tyr), and crosslinked using a visible light photoinitiator system. The gelation ability, swelling characteristics, degradation profiles, mechanical properties, and encapsulated cell viability were elucidated by varying the concentrations of PLGA-Tyr and the co-photoinitiator. This work also introduces a custom-built, cost-effective, single-photon laser SLA bioprinting system named the ‘MicroNC’. Methods to improve the diversity of scaffold geometries to be printed, feature resolution, and shape fidelity were systematically investigated using commonly used bioresins, achieving feature resolutions ranging between 8 to 20 µm. Most notably, it was shown that this bioprinting system could fabricate well-resolved hydrogel filaments (less than 8 µm in width) using the newly developed visible light hydrogel material system, which were capable of manipulating 2D single-cell morphology whilst supporting high cell viability (>90%) and proliferation up to 14 days. Overall, these experiments have underscored the exciting potential of using the visible light photoinitiated PLGA-Tyr material system for developing physiologically relevant in vitro hydrogel scaffolds for use in a wide range of biomedical applications such as tissue engineering, drug screening, disease modelling, and fundamental mechanobiological studies