Synthesis And Properties Of Stimuli Responsive Aggregation Induced Emission Polymers

Stimuli responsive polymers are polymers that can change their chemical structure or physical properties when the external environment changes.Because many physiological conditions of tumor or other pathological tissues are different from those of normal tissues,stimulus responsive polymer assemblies are often used as drug carriers to enhance drug targeting and reduce harm to the body.Stimulus responsive aggregation induced luminescent polymers are widely used in drug delivery and other fields due to their AIE luminescent properties,stimulus responsive and good biocompatibility.In this study,a series of amphiphilic block copolymers POEGMA-bP(TPE-St-co-VBT-co-St)with different hydrophilic/hydrophobic ratios and different content of vinyl benzylthioacetate(VBT)were prepared by RAFT polymerization.The assembly behavior of the copolymers under certain conditions was studied.After hydrazinolysis,the polymer has different density of sulfhydryl groups in the hydrophobic section,which can be used to form cross-linking structure,which can not only increase the stability of micelle structure,but also achieve redox response.TPE group in polymer structure endows polymer with AIE behavior,which can be used to monitor drug delivery and rel ease process.The experimental results show that the morphology of self-assembly is related to the length of hydrophilic and hydrophobic segments.When the length of hydrophilic segment is fixed,the hydrophobic segment is assembled in a short time to form solid micelles with smaller particle size.With the increase of hydrophobic segment length,the structure changes from solid micelles to rod-shaped and then to vesicles with larger particle size.The stability and solvent resistance of the particles before and after crosslinking were investigated.It was proved that the cross-linked assemblies were stable in THF,and did not dissolve,and had a certain solvent resistance,while the non cross-linked assemblies dissolved rapidly in THF.The redox response of the polymer assembly was studied by the change of fluorescence intensity and particle size during GSH treatment.Under the condition of simulating the physiological microenvironment of tumor cells(GSH concentration is 10 mmol/L),the cross-linked assembly based on disulfide bond has obvious redox response.With the increase of treatment time,the disulfide bond in the cross-linked structure breaks continuously.When the particle size increases,the fluorescence intensity of TPE decreases due to the decrease of aggregation degree.When the treatment time reached 24 h or 48 h,aggregates with larger particle size began to appear,and the fluorescence intensity increased.The drug entrapment experiments show that DOX can be encapsulated in the hydrophobic region of the assembly through hydrophobic interaction.The drug loading is 3.5%and the entrapment rate is 7.1%by UV spectrophotometer.