3D Bioprinting cell-laden bioinks for engineering neural tissues and potential models for Parkinson's disease.

Parkinson's disease (PD) is the second most common age-related neurodegenerative disorder after Alzheimer's disease, affecting over ten million people worldwide. It is characterized by motor symptoms such as tremors, rigidity, and gait disturbances. Current treatments focus on alleviating symptoms and slowing down brain degeneration, but no cure exists, leading to a progressive decline in patients' quality of life. Three-dimensional (3D) bioprinting has emerged as a powerful technique for developing constructs that engineer neural tissues with complexities mimicking physiological conditions. These constructs can serve as vehicles for controlled drug delivery and potential substitutes for neurodegeneration. This article aims to compile new research data and review the current state of PD models engineered by 3D bioprinting, focusing on the desired biochemical features of bioinks for cell protection during printing, cell behavior, and differentiation into 3D constructs. Additionally, it discusses the physical, mechanical, and chemical characterization of bioprinted scaffolds and the importance of post-printing assessment to ensure printability, shape fidelity, appropriate construct degradation, and extracellular matrix production rates for developing complex 3D bioprinted constructs. Finally, it proposes opportunities for models that can be used to study novel therapeutics and immunomodulatory responses in tissues engineered for PD and other neurodegenerative diseases.