Research Of Embedded 3D Bio-printing Based On Aqueous Two-phase System

3D bio-printing prints a mixture of living cells,growth factors and biocompatible substances into a complex structure that functions as real human tissues or organs.These structures can be used for high-throughput drug screening,transplantable materials,and medical devices for regenerative medicine.The main challenge of this technology before it is used in clinical treatment is to replace traditional materials such as resins and thermoplastics with finely constructed biomaterials to precisely replicate the multi-scale structure of the vascular network and its corresponding biological functions.In a series of printing strategies of multi-scale structure of vascular network,extrusion printing is most widely used owing to its compatible with various ink materials and nozzle design.Its principle is to quickly solidify the ink into a two-dimensional structure,then layer by layer into a three-dimensional structure.However,such layer-by-layer stacking principle cannot construct arbitrary free structures,especially free tubular network structures with precise spatial definition characteristics,such as gastric tube,tubular trachea,tumor vascular network,etc.This led to the concept of "embedded printing",in which liquid ink is squeezed out of the surrounding matrix to support free-form structures.These substrates include viscous oils,elastomers,self-healing hydrogels,and granular gel suspensions.Although the previous researches in this field have made some progress,it is still a challenge to combine the geometric structure,mechanical properties and biochemical functions of the printed products.To overcome the above challenges,this thesis put forward innovative aqueous two-phase system based embedded 3D biological printing method,which uses the embedded print strategy print aqueous two-phase system.The real free form vascular network structure has been printed through the regulation of the rheological properties of aqueous two-phase system and the introduction of hydrogen bond.Its geometric structure,mechanical properties and biochemical functions have been maintained well.The specific research content mainly includes the following three parts:1.Basic research on aqueous two-phase system.A series of aqueous two-phase systems were designed and prepared.The feasibility of printing was studied by phase splitting experiment.The influence from different systems,pH and PAA concentrations on the stability of two-dimensional structures,and the optimal system design was studied by spiral contrast experiments.The causes of the differences in the stability of two-dimensional structures and the design principles of the system are analyzed through rheological test and interfacial tension test.The formation of hydrogen bond membrane was studied by interface observation experiment,and the selective transmittance of hydrogen bond membrane was confirmed by diffusion experiment.2.Research on 3D printing based on aqueous two-phase system.The reference equation of printing accuracy was studied by establishing the theoretical model.The reasonable range of print parameters was studied by comparative experiments.On this basis,a complex 3d all-water structure was printed.The dynamic modification ability was verified by the modification experiment.Different curing methods were explored by temperature variation and ultraviolet irradiation.3.Research on living cell printing.The cell compatibility of the system was verified by single channel and double channel cell printing experiments,which demonstrated the potential of this method in the construction of real vascular networks.