Design And Synthesis Of Stimuli-responsive Smart Hydrogels

Due to their ability to change volume,gel state or other properties under external stimuli,smart hydrogels have been widely applied in drug delivery,sensing,and tissue engineering.Herein,two kinds of smart hydrogels were constructed based on the constitutional dynamic chemistry,including dynamic reversible covalent bonds and non-covalent bonds.Furthermore,their applications in biomedical field were explored.The specific content includes the following two parts:?1?A near-infrared?NIR?light-induced self-healing nanocomposite hydrogel was constructed and explored its potential application as drug carriers.The self-healing PVA-MoS₂ composite hydrogel?PM hydrogel?,based on polyvinyl alcohol?PVA?and modified MoS₂ nanosheets,was prepared by a simple freezing/thawing method.The temperature of the PM hydrogel quickly increased to 46.6?after NIR light irradiated for 3 min due to excellent photothermal conversion effect of MoS₂nanosheets,which triggered the movement of the polyvinyl alcohol chain and re-formation of the hydrogen bonds at the fracture interface.As a result,the hydrogel self-healed rapidly and the healing efficiency was as high as 91.8%.In addition,the effects of PVA content,ce-MoS₂nanosheet content and light irradiation time on self-healing properties were systematically studied.The results showed that the PM hydrogel containing 25 wt%of PVA,0.05 wt%of MoS₂ and 3 min irradiation time had a best self-healing effect.When the fracture surface was separated for 24 h,the PM hydrogel healing efficiency was as high as 60.6%,showing good resistance to interfacial separation.Cytotoxicity analysis and drug release experiments indicated that PM composite hydrogel has good cytocompatibility and long-term drug release ability,which lays a foundation for further application of composite hydrogel in biomedical field.?2?Combined with metal-ligand coordination and complexation of phenylboronic acid with cis-diol,a multi-stimuli responsive smart hydrogel based on nucleotide?AMP?,AgNO₃ and 4-arm-PEG-NH₂was constructed.Due to the optical properties of silver nanoclusters and the dynamic reversibility of the coordination bonds,the smart hydrogel exhibited multi-stimuli responsiveness to light,pH,ions,forces,glucose and enzymes,showing gel-sol transition and variation of the fluorescence signals.Moreover,the nanofiber network structures and AMP ligands showed stabilizing effect on silver nanoclusters,which can prevent silver nanoclusters from aggregating in solution or being further reduced to large silver nanoparticles,avoiding the fluorescence quenching.