3D Bioprinting Of Heterogeneous Tumor Models For Drug Screening Studies

Bioprinting of cell-laden hydrogel constructs providing three-dimensional(3D)spatial pattern capacity and suitable cellular microenvironment have become essential tools in the field of tissue engineering.However,for heterogeneous tissue construction,there is an urgent need for an efficient and flexible printing method that can deposit multiple cellular components in a controlled manner.Therefore,this thesis develops a novel dot extrusion printing(DEP)system for one-step generation of cell-laden gelatin methacryloyl(Gel Ma)hydrogel beads(GHBs).This technique allows flexible control of the size and deposition location of GHBs by programming G-code parameters,and also enables the construction of three-dimensional heterogeneous tissues by integrating multiple printheads to print GHBs laden with different cellular components.As an application example,the DEP system was used to construct breast cancer models and pancreatic cancer models in vitro as a way to study tumor-stroma interactions and tumor drug resistance in different microenvironments.The main research and innovation points of this paper are as follows:Firstly,the DEP system was established and optimized.By exploring the printing parameters including: printhead and receiving platform temperature control,driving pressure,and extrusion time,stable printing of GHBs was achieved,and it was demonstrated that the DEP system can generate GHBs of controllable size and uniformity on demand.By adjusting the spacing of GHBs,3D structure printing was realized and the printed structure remained stable for a long time,which proved that the DEP system had the ability to print GHBs into 3D structure.Secondly,the DEP system was used to construct a breast cancer tumor-stroma coculture model.The DEP system was demonstrated to have good biocompatibility and the ability to provide a stable culture environment by performing live-dead tests and long-term culture of the printed cell-laden GHBs.Two different tumor-stroma breast cancer co-culture models were constructed by spatially regional printing of breast cancer cells and human normal fibroblasts to form juxtapositional or overlapping microcapsule structures as a way to study tumor-stroma interactions in different microenvironments.Finally,the DEP system was used to construct the pancreatic cancer drug screening model.The pancreatic cancer tumor model with fibrous barrier characteristics was constructed by printing GHBs laden with pancreatic cancer cells and fibroblasts.The modifiable stromal microenvironment was achieved by regulating stromal cell density to study cellular interactions and drug responses in different stromal microenvironments.In summary,the DEP system provides a powerful manufacturing tool for tumor research with its ability to simply and flexibly control and generate GHBs laden with different cellular components.