Preparation Of Multifunctional Hydrogel Actuator And Its Application In Biomimetic Blood Vessel

Hydrogel actuators have broad application prospects in biomimetic devices,soft robotics,environmental sensors and information storage.Poly(N-isopropylacrylamide)(PNIPAAm)is a typical temperature responsive polymer with good biocompatibility,has been widely used to construct thermo-responsive hydrogel actuators.In this thesis,a variety of bilayer hydrogel actuators based on PNIPAAm were constructed through light initiated radical polymerization.Combining with spiropyran or TA-Fe3+endowed the hydrogel with solvent/temperature or NIR triggered deformation behaviors.The potential applications of the bilayer hydrogels in biomimetic blood vessel scaffolds were investigated.The main contents of this paper are as follows:In chapter 1,the background and progress of hydrogel actuators were reviewed and their applications in different fields were also summarized.In chapter 2,the P(NIPAAm-SP)/PNIPAAm bilayer hydrogel actuator was prepared by blue light initiated radical polymerization.Spiropyran is a kind of fluorescent dyes,which can undergo reversible photoisomerization under UV/Vis irradiation.It can switch reversibly between the non-fluorescent spiropyran(SP)and the fluorescent merocyanine(MC).Thus,the bilayer hydrogel not only possessed solvent/temperature responsive deformation behaviors,but also showed the multi-responsive color changing abilities.The effects of solvent/temperature on the fluorescence intensity were studied in details.The applications of bilayer hydrogel as temperature-controlled grippers and biomimetic devices were explored.In chapter 3,a near-infrared responsive hydrogel actuator by incorporating of a complex of tannic acid(TA)and iron ion(Fe3+)as a photothermal agent into a PNIPAAm/PEG bilayer hydrogel was prepared.The local high temperature of the hydrogel induced by near-infrared irradiation caused PNIPAAm layer undergo volume phase transition and the de-swelling,and thus triggered the deformation of the hydrogel.Due to its near-infrared response characteristics,the hydrogel actuator achieved remote and accurate actuating,even can bend in the air.In chapter 4,inspired by the multilayer tubular structure of the native vascular,the potential applications of the P(NIPAAm-SP)/PEG bilayer hydrogel in biomimetic vascular scaffolds were explored owing to its characteristics of self-rolling into a tubular structure above its VPTT.When the temperature was higher than VPTT,the bilayer hydrogel would bend into a tubular structure;below the VPTT,the hydrogel was flat.Moreover,the PNIPAAm-SP layer was hydrophobic at 37?,which was conducive to cell adhesion;at room temperature,the PNIPAAm-SP layer became hydrophilic,which was favorable for the detachment of the cells.Human umbilical vein endothelial cells(HUVEC)were cultured on the P(NIPAAm-SP)layer.We found cell would adhere on the inner layer of the tube and endothelial cell sheet with specific reticular structure was formed.Immunostaining results showed that the F-actin and VE-cadherin were all expressed,indicating the sufficient cytoskeleton development and the firm cell-cell junctions.The above results revealed that it was beneficial of "self-rolling" hydrogel actuator to the vascular endothelium remolding.In this paper,functional bilayer hydrogel actuators were constructed,realizing solvent,temperature and near-infrared responsive actuating abilities.Above VPTT,the hydrogel membrane achieved the tube structure by self-rolling and HUVEC had excellent adhesion and proliferation ability in this stent,demonstrating its potential to be applied in tissue-engineered vascular scaffolds.