Preparation And Characterization Of Spiropyran-based Photo-responsvie Fluorescent Hydrogel

Fluorescent hydrogel possesses advantages of both traditional hydrogel and fluorescent materials,and has been extensively applied in drug release,biosensors,tissue engineering.Spiropyran,as photo-responsive fluorescent dyes,can undergo fatigue resistant photo-isomerization between ring-opening merocyanine(MC)and ring-closing spiropyran(SP)with UV/Vis light irradiation.The MC and SP isomers of the spiropyran exhibited vastly different physicochemical properties like polarity and emission et al.Poly(N-isopropylacrylamide)(PNIPAAm)exhibits good biocompability and can also response to temperature.Based on the photochromic and the thermal-responsive properties of the spiropyran and PNIPAAm respectively,spiropyran monomer SPMA and water-soluble spiropyran derivative a-CD-SP-DA have been synthesized and a series of novel photo-responsive fluorescent hydrogel with PNIPAAm as the main matrix have been prepared via blue light irradiation and free radical polymerization.The photochromic property,photo-switchable fluorescent behavior and fluorescence fatigue resistance of the hydrogel were investigated.The main work in this thesis was as follows:In chapter 1,the background and development status of responsive hydrogel and fluorescent hydrogel were reviewed,with emphases on the preparation and application of photo-responsive,thermal-responsive hydrogel and fluorescent hydrogel in biomedical field.In chapter 2,the photo-responsive fluorescent dye spiropyran SPMA has been synthesized and the photochromic fluorescent hydrogel prepared via blue light irradiation in water and dioxane mixed solvents.The ability of metal ions detection of the SPMA and the swelling ratio,photochromic property,fluorescence behaviors of the hydrogel have been evaluated.The results revealed that the SPMA monomer can chelate with some kinds of divalent metal ions.The hydrogel can undergo reversible photo-isomerization and the fluorescence emission can be reversibly switched"on/off' by UV/Vis light irradiation.In chapter 3,a water-soluble spiropyran derivative,namely,spiropyran-functionalized acryloyl-?-cyclodextrin(a-CD-SP-DA)has been synthesized and the photochromic fluorescent hydrogels with varied crosslink-density were prepared with the APS/TEMED as the redox initiator.The swelling ratio,photochromic property,fluorescent behavior,thermal-enhanced fluorescent behavior and biocompatibility of the hydrogel were characterized.The photo-isomerization and the fluorescence emission of the hydrogel can be reversibly switched "on/off" by UV/Vis light irradiation,and the fluorescence slightly increased with the increase of the cross-linker concentration and increased significantly when the hydrogel took place phase inversion.UV/Vis light irradiation cycles revealed the reversibility of the photo-isomerization and photo-switchable fluorescent behavior.Fluorescence image conducted with photo-mask successfully demonstrated the real-time spatiotemporal precision fluorescent behavior of the hydrogel with UV/Vis light irradiation.The MTT result showed good cytocompatibility of the hydrogel as their cell viabilities are higher than 80%.The outstanding advantages of the hydrogel such as good biocompability,photochromic property,photo-switchable and thermal-enhanced fluorescent behavior would have great potential in data storage,thermal sensors and bioimaging.