Abstract Neurodegenerative disorders, such as Alzheimer's and Parkinson's diseases, are fundamentally characterized by neuronal damage and cell death. Development of adult and pluripotent stem cells for cellular therapies or therapeutic screening platforms may enable and accelerate novel treatment options for neuronal diseases. However, ensuring the precise differentiation of stem cells into functional neurons within 3D culture environments presents a significant challenge. To overcome this hurdle, this project aims to create novel bioprinting methodologies for the production of human stem cell-based organoids by developing novel functionally- optimized bioinks and optimized hydrogel formulations for pharmacological screens. Aim 1 focuses on developing a customized bioink, which includes water, biopolymers, ions, and cells, to optimize biochemical activity and mechanobiological responses. This endeavor aims to create a brain-like matrix under 100 μL using a multi-material approach involving proteins, polysaccharides, and functionalized nanoparticles. The goal is to reproducibly produce 3D constructs that reduce the variabilities introduced from under-defined commercial sources. For this research, the bioink formulation incorporates gelatin, collagen, crosslinking enzymes, photoinitiators, silica nanoparticles, neuron-inducing chemicals, and human stem cells. This formulation aims to foster the emergence of functional neurons 2-4 weeks after the 3D bioprinting process. Aim 2 focuses on the high-throughput (HT) assessment of neurotoxic chemicals' effects on the differentiation process of 3D hydrogel- encapsulated neural stem cells. Utilizing commercial hydrogels for initial tests, this research will explore chemical differentiation processes and evaluate the influence of neurotoxic chemicals on neuronal differentiation. Characterization efforts will involve high-throughput imaging analysis methods plus flow cytometry that will allow drawing correlations among bioink components and differentiation potentials. By comparing the outcomes with those obtained using custom bioink formulations (from Aim 1) vs. commercial products such as Matrigel and Geltrex, this project aims to identify a new bioink formulation that has the potential to revolutionize how we consider and conduct tissue engineering research, including high-throughput molecular screening work. This would accelerate progress toward the development of screening platforms and new therapies for neurodegenerative disorders.

Narrative Alzheimer's and Parkinson's diseases are fundamentally characterized by damage and death of brain cells. The development of reproducible and well-defined experimental procedures for cell (replacement) therapies is critical. The bioinks we will engineer may have the potential to be utilized in the creation of a wide range of cell therapy products and in the identification of new therapeutics.