Synthesis And Self-Assembly Properties Of DNA-Hydrophobic Polymer Grafted Copolymer

With the exhaustive study in traditional amphiphilic block copolymers,more attention was paid to DNA amphiphilic block copolymers(DABCs),where DNA strands function as hydrophilic segments.DABCs are a kind of materials where DNA strands are covalently attached to synthetic polymers.The moiety of synthetic polymers can introduce several functional groups;DNA sequences can be designed arbitrarily according to our needs,which are very programmable.In addition,DNA has a sophisticated complementary base-pairing effect,pH response,temperature response and the formation of complex secondary structure,which gives the DABCs larger design space and more extensive functionality.DABCs usually self-assemble into micelles,the hydrophobic polymers particularly tend to form the hydrophobic core and surrounded by a corona of the hydrophilic DNA segments.These micelles have many potential applications in many fields,including drug delivery,templates for chemical reactions,DNA detection and nano-hydrogels.In this paper,DNA strands were attached as side chains to PPMA backbones through click chemistry.Then,its self-assembly behaviors in solutions and applications in drug delivery were studied.The main contents includes the following three parts.First,propargyl methacrylate(PMA),1,4-dioxane and azobisisobutyronitrile were respectively selected as monomers,solvent and initiator to synthesis PPMA backbone through the solution polymerization.The reaction was carried out under 65℃ for 6 hours.The structure of the PPMA was verified by FT-IR spectrum and 1H-NMR,gel permeation chromatography(GPC)and mass spectrometry(MS)were used to measure the molecular weight of PPMA.Second,the copper-catalyzed azide-alkyne(CuAAC)reaction and thiol-yne click reaction were used to covalently graft azide-modified DNA mercapto-modified DNA onto PPMA backbones.2%agarose gel electrophoresis was applied to characterize the product DNA-g-PPMA.Third,the self-assembly activities of DNA36-g-PPMA and DNA72-g-PPMA in DMF/H2O mixed solvent were studied,both of them self-assembled into spherical micelles and nanofibers at pH 5 and 8 separately,but some difference in fine structure and size could be discovered.The morphologies,diameter and stability of the micelles were verified by Transmission electron microscopy(TEM)and Dynamic light scattering(DLS).Moreover,spherical micelles could transfer to nanofibers reversibly through tuning the pH of assembling solvent.The micelles were allowed to co-assembly with DNA modified gold nanoparticles,Au nanoclusters and Au nano-lines were achieved.Finally,Au nanoclusters were selected as drug carriers to test its releasing effect,DOX and Nile Red acted as hydrophilic and hydrophobic drug model here.The results showed that the carriers were sensitive to enzyme,pH and heat.Consequently,more than 80%drug could be released in the study time.