Bioprinting of a human neuron model for quantifying pollutant toxicity

This study developed a 3D bioprinted human neural progenitor cell model for studying the neurotoxicity of environmental pollutants in a mechanically tunable human-relevant tissue environment. Human iPSC-derived neural progenitor cells were encapsulated at high density in gelatin methacrylate bioink and patterned into brain-shaped scaffolds using an in-house digital light processing bioprinter. By changing DLP light exposure, the authors created mechanically distinct soft and stiff GelMA constructs with Young’s moduli of approximately 2 and 4 kPa, respectively. The mechanically tuned models were then exposed to the organophosphate pesticide chlorpyrifos and its metabolite chlorpyrifos-oxon. Increasing chlorpyrifos concentration reduced cell viability, and prolonged 5-day exposure caused greater toxicity than 3-day exposure. Matrix stiffness also influenced the response to toxic injury: the stiffer constructs generally showed greater viability after chlorpyrifos exposure, while the soft and stiff models exhibited different transcriptional responses. Stiff constructs showed greater PAX6 and Nestin expression, whereas softer constructs showed greater SOX2 expression and stronger trends in Alzheimer’s disease-associated markers. Chlorpyrifos-oxon produced a distinct response characterized by approximately 20-fold Nestin upregulation, increased beta-amyloid-associated expression, and significant AChE downregulation despite causing less overall viability loss than the parent chlorpyrifos compound. To demonstrate broader toxicology-screening utility, the authors also exposed the model to benzo[a]pyrene. Stiffer constructs again showed better short-term viability, while benzo[a]pyrene exposure increased SOX2 and reduced AChE expression. Overall, the study shows that DLP bioprinting can generate neural tissue models with controlled mechanical stiffness and that matrix mechanics can influence cellular susceptibility and transcriptional responses to environmental neurotoxins, providing a scalable platform for human-relevant toxicology studies.