Photo-controlled Release Of Metal Ion Using Triazoline-containing Amphiphilic Copolymer

Photo-controlled release is a new type of controlled release method that can release drugs or metal ions at regular,fixed-poin t and quantitative basis.Due to quick response and high spatial/temporal accuracy,it could be applied in biomedicines.A few metal complexes are known for detoxification,sterilization,diagnosis and treatment of diseases,however,the encapsulation and controlling release of those metal ions using polymer micelles are still a challenging issue.In this study,three amphiphilic polymer systems comprising triazoline structures were synthesized,According to the properties of complex metal ions and photoinduced nitrogen elimination,the photo-release properties of cobalt ions in polymer systems were studied.The main work and results are as follows:(1)Amphiphilic random copolymers with glycidyl methacrylate(GMA)and Oligo(ethylene oxide)methyl ether methacrylate(OE)and then converted to azide,followed by a 1,3-dipolar cycloaddition reaction to f'orm triazoline with norbornene.And the dynamics of the reaction process was tracked.The syntheses including the conversion kinetics were studied in details using FTIR.Thecycloaddition of PGO-N3 and norbornene is slow and approximately first order,with a rate constant k in the range of 0.02-0.035 d-1 The light-induced dinitrogenation kinetics of triazoline in PTA analyzed by 1H NMR spectroscopy was found to be first order with a rate constant of 3.85×10-3 min-1 under irradiation at 254 nm.According to UV-vis,the binding constant is 99.3 1 M-1 and the loading is 15.3%.The resulting random copolymers formed micelles with a critical micellar concentration(CMC)of 7.68×10-3 mg/mL.The triazoline moieties can coordinate to transition metal ions,e.g.CO2+,thus to encapsulate the metal ions to the core of micelles.Photo-induced denitrogenation of triazoline was able to disrupt the coordination of Co2+and triazoline,therefore leading to the release of Co2+ upon light irradiation.Viscosity,UV-vis spectroscopy,DLS and TEM were used to show that the coordination and release of Co2+ ions were successful upon exposure to light.According to the DLS and TEM studies,the particle size of the micelles increased from 11.0±2.2 nm to 21.6±3.8 nm,and the particle size recovered to 12.7±3.3 nm after UV irradiation.The coordination processing and photo-controlled releasing of the prepared polymer in aqueous solution is illustrated.(2)5-norbornene-2-carboxylic acid(NBCA)with 2-hydroxyethyl methacrylate(HEMA)using DCC/DMAP catalysis system to obtain a methacrylate monomer containing norbornene.At the same time,the aniline was diazotized to synthesize phenyl azide.And then,the synthesized monomer is randomly copolymerized with Oligo(ethylene oxide)methyl ether methacrylate(OE)to obtain a copolymer containing norbornene in the side chain.Finally,a 1,3-dipolar cycloaddition reaction to form triazoline with phenyl azide.Coordination of Co2+with triazoline was successful and confirmed by red shift of UV-vis.The binding constant of Co2+was calculated by UV-vis tracking to be 333.33 M-1 with 17.6%loading.The CMC of the copolymer was determined by fluorescent probe method to be 2.51×10-3 mg/mL.According to the DLS and TEM studies,the particle size of the micelles increased from 159.3±19.3 nm to 321.7±59.2 nm,and the particle size recovered to 180.2±22.7 nm after UV irradiation.The process of coordination and photo-controlled release of the polymer in aqueous solution is illustrated.(3)Synthesis of a block copolymer containing triazoline by RAFT polymerization using the same monomer in(2),the obtained block copolymer and Co2+ were coordinated to study their photo-controlled release properties.The success of coordination and releasing was confirmed by changes in the ultraviolet spectrum.The calculated coordination binding constant was 485.44 M-1 with 23.9%loading,and the photo-controlled release performance was highly controllable.The polymer was prepared into micelles and the CMC was 2.73 × 10-3 mg/mL.According to the DLS and TEM studies,the particle size of the micelles increased from 266.8±81.9 nm to 545.0±311.3 nm,and the particle size recovered to 275.9±87.1 nm after UV irradiation.The process of coordination and photo-controlled releasing of the polymer in aqueous solution is illustrated.