Stimulus-responsive Block Copolymer Self-assembled Micelles Performance Regulation And Drug Release Research

Multifunctional materials are a class of advanced(composite)materials that provide the perfect combination of the different properties of a single parent material and broaden their application range.This kind of multifunctional composite materials have designability,anisotropy and unique combined effects,including modularity,additivity,productness,and permeability.Based on this,combining Au nanoparticles with currently extensively-studied stimuli-responsive block copolymers can create entirely new multifunctional materials and broaden their application.This kind of multifunctional materials will have the ability to intelligently select and perform specific functions in response to changes in the local microenvironment.Therefore,they have found wide applications in fields of biomedical,biosensors,actuators,semiconductor materials,photovoltaic materials and catalysts.This article will discuss the property modulation of stimuli-responsive amphiphilic block polymers as drug controlled release carriers and the construction of gold nanoparticle-modified block copolymer multifunctional materials.The specific research content is as follows:(1)pH-sensitive H-type multiblock copolymers,poly(methacrylic acid)2-block-epoxidized hydroxyl-terminated polybutadiene-block-poly(methacrylic acid)2(PMAA2-b-epoHTPB-b-PMAA2),were synthesized through atom transfer radical polymerization and the follow-up in situ epoxidization of peracetic acid,and confirmed by 1H NMR,FT-IR and GPC techniques.The impact of epoxidation on the physicochemical and biomedical properties of the copolymer self-assembly micelle nanoparticles were investigated by fluorescent spectrometry,DLS,TEM and MTT assay.The experimental results indicated that the epoxidation resulted in formation of more Table copolymer micelle nanoparticles with lower critical micelle concentration,smaller micellar size and higher loading capacity and encapsulation efficiency of drug than those without epoxidization.especially,the epoxidized copolymer micelle nanoparticles exhibited reasonable pH-sensitivity at pH of 5.3-5.6.The hydrophobic anticancer drugs,paclitaxel(PTX),had faster release rates from the epoxidized nanomicelles than from the unepoxidized ones in PBS soLution of pH 4.8-6.6,whereas in PBS of pH 7.4 smaller PTX release amount from the epoxidized nanomicelles produces than from the unepoxidized ones.The epoxidized copolymer nanomicelles were reasonably biodegradable after the drug got released,and the degradation rate was faster than that of the unepoxidized counterpart.MTT assay was performed to uncover the biocompatibility of the epoxidized copolymer micelle nanoparticles and anticancer activities of the PTX-loaded nanomicelles,which was important for applications in the therapy of cancers as a controlled release drug carrier.(2)Synthesis of poly(ferrocene-formyloxyethyl methacrylate)-block-poly(N-isopropylacrylamide)(PMAEFc-b-PNIPAM)by a two-step continuous RAFT method.After self-assembly Into micelles,gold nanoparticles were attached to the surface of the micelles by in situ reduction to obtain poly(methylferroylformyloxyethylmethacrylate)-block-poly(N-isopropylacrylamide)modified by gold nanoparticles.(PMAEFc-b-PNIPAM@Au).The structure and morphology of the hybrid block copolymers were characterized by 1H NMR,FTIR,LLSGC,UV-vis,XRD and TEM techniques.Fluorescent spectrometry,UV-vis,DLS and cyclic voltammetry(CV)were used to investigate the physicochemical and electrochemical properties of the hybrid block copolymers in aqueous solutions.The experimental results showed that the hybrids could self-assemble into interesting and changeable micelle structures from globular,wormlike to rodlike shapes by altering the quality and compositions of solvents and ionic strength,and exhibited multifunctionality including quasi-reversible electrochemical behavior,redox-stress responsiveness and temperature sensitivity.The physicochemical and electrochemical properties were modulated by tailor-making the system compositions and redox reaction.The copolymer hybrids were expected to broaden their applications in nanobiomedicine including targeted drug carriers and magnetic resonance imaging,optical,electrochemical catalyst,optoelectronics and sensors etc.