Study Of 3D Printing Dual-response Hydrogel By UV Cross-linked And Its Shape Memory Function

3D printing is a technology that uses computer software to control the material to manufacture a target model layer by layer.When it is applied to biomedical engineering,also known as "biological printing",that is,through computer-aided technology to form tissue and organs layer by layer with biological materials,living cells,growth factors,etc.The use of 3D bioprint technology can quickly,efficiently and accurately create different sizes of models,complex internal structure,and functionalize the model mixed with other materials and drugs,active factors,cells.However,there are still problems for bioprinting such as lack of biomaterials that can be printed,the harsh conditions of printing(high temperature,laser,etc.),the poor molding effect,and the complicated material preparation.Therefore,the chemical modification of Pluronic F127(PEO100-PPO65-PEO100)which has temperature response and UV response was used in 3D printer to realize the complex internal structure and drug release function in this paper.Additionally,Pluronic F127 was used as the base material,and then mixed with sodium alginate in a certain ratio to achieve shape memory function by 3D printing.1.Modification of F127 with Double Response Characteristics and Its Application in 3D PrintingIn this system,Pluronic F127(PEO100-PPO65-PEO100)was chemically modified with acryloyl chloride and triethylamine.Carbon-carbon double bond was introduced to the long segment to make the modified F127 maintain temperature-sensitive and light response characteristics.The diameter of the print head(0.25 mm),the printing platform temperature(40~45°C),the printing speed(30 mm/s),extrusion pressure(0.6 bar)and other printing parameters were determined by rotational rheometer and 3D printer(3D-Bioplotter).The modified F127 can be gelated with 365 nm UV light source under 5 seconds,which increase the efficiency of 3D printing.The results show that 3D printing is a layering process of physical state,and the mechanical properties of the model are improved with the increase of the printing ink concentration.Enhanced,the drug release behavior of 3D printing model was similar to the traditional preparation method but the release effect is better.High concentration of modified F127(0.20 g/mL)has good biocompatibility to meet the requirement that be applied after 3D printing without any postprocessing.2.3D Printing Shape Memory Hydrogels with Modification of F127 and Sodium AlginateSodium alginate is one of the most widely used materials in 3D printing.It has the biodegradability,non-toxicity and gelation ability under calcium ion.As the modified F127 can form a network structure with certain mechanical properties,so by mixing with sodium alginate in the appropriate ratio can realize 3D bioprinting and shape memory function under the exchange of calcium ions and carbonate ion.By evaluating the printing process,print accuracy,molding effect,shape memory effect(fixation rate,recovery rate),and the results can be draw that the bioink used in 3D bioprinting should be 0.16 g/mL modified F127 solution mixed with 0.04 g/mL sodium alginate solution.The mixed printing bioink can achieve ideal printing at a rate of 30 mm/s under a pressure of 0.8 bar in 35~40°C.The model can achieve shape memory function that transforming from temporary shape to fixed shape under 0.01 g/mL CaCl2 solution and 0.02 g/mL Na2CO3 solution.