Construction and Gene Delivery Application of Smart Nonviral Vectors Based on Supramolecular Block Copolymers

Author:Wu Mai Er Ya Sen

Supervisor:zhu xin yuan


Degree Year:2018





Supramolecular chemistry,as a robust approach to construct functional materials and to create new materials,has already received growing interest from researchers in recent years.In particular,supramolecular chemistry has shown promising applications in many disciplines such as life sciences,materials sciences and nanosciences.As a bridge between polymer science and supramolecular chemistry,supramolecular polymers have been used as potential transport vehicles for the diagnosis and treatment of cancer.However,most of the reported supramolecular gene vectors are facile to be degraded under physiological conditions,leading to a significant reduction of gene transfection efficiency.Therefore,the key issue in this field is how to improve biostability of these supramolecular cationic polymers for overcoming cellular and tissue barriers,further achieving highly efficient gene expression.How to efficiently combine dynamic reversibility of supramolecular polymers with biological stability of conventional polymers is a cutting-edge scientific issue facing the field of supramolecular chemistry.In order to obtain a safe and efficient supramolecular gene vector,by a combination of biological stability of conventional polymers and dynamic reversibility of supramolecular polymers,this thesis designed and prepared a range of supramolecular diblock copolymers.Upon controlling charge density and environmental responsiveness of these gene vectors,their transfection efficiency in tumor tissues was further improved.This thesis is divided into three parts,the detailed research contents and conclusions are summarized as follows:1.Redox-responsive cationic supramolecular block copolymers for gene deliveryAs we all know,main-chain supramolecular polymers composed of small molecules are an important component of supramolecular chemistry,however,these supramolecular polymers readily subject to rapid degradation or depolymerization in the variable physiological environment,eventually leading to a significant decrease of its gene transfection efficiency.Therefore,how to improve the biological stability of these supramolecular gene vectors to overcome the cell and tissue barriers and further enhance their gene expression is an important scientific issue in the field of supramolecular chemistry.To this end,in this chapter,withβ-cyclodextrin monofunctionalized polyethylene glycol(PEG-CD)andβ-cyclodextrin/ferrocene end-capped pentaethylene hexamine(Fc-PEHA-CD),a kind of cationic supramolecular block copolymer with redox reaction was successfully prepared by the host-guest identification ofβ-cyclodextrin and ferrocene.Upon alternating addition of hydrogen peroxide(H2O2)and glutathione(GSH),such supramolecular block copolymers achieve reversible polymerization/depolymerization.Such cationic supramolecular copolymers show greatly enhanced biostability and biocompatibility compared to supramolecular homopolymers.Meanwhile,this type of supramolecular copolymer can not only efficiently condense plasmid DNA,but also controllably release of DNA triggered by H2O2.Using luciferase as a reporter gene,we further evaluated the transfection properties of these supramolecular block copolymers in different cell lines,demonstrating superior transfection performance over supramolecular homopolymers.Therefore,such supramolecular block copolymers can be used as a promising non-viral vector for in vivo gene therapy.2.Charge-regulated cationic supramolecular block copolymers as gene vectorsThe gene transfection efficiency of cationic vectors is not only highly dependent on the chemical structure of the polymers,but also greatly affected by their charge properties such as charge distribution,charge density and amino species.Optimization of the structural parameters of these gene vectors is often extremely complicated,and the cost of production is very high.Therefore,in order to achieve optimal gene delivery,the structure of the supramolecular block copolymer-based gene vectors needs to be further chemically modified to improve its transfection performance.To this end,based on the cyclodextrin/adamantane host-guest system,a series of charge-controllable supramolecular block copolymer gene vectors were successfully constructed and chemically modified with N,N-dimethyl ethylenediamine.The resulting optimized polymer vectors has relatively higher surface charge density and significantly enhanced plasmid DNA-condensing ability compared to the ones before modification.With the introduction of N,N-dimethyl ethylenediamine,this kind of supramolecular copolymers show more excellent physiological stability.In particular,it is noting that the increase in surface charge density of these modified vectors does not lead to a decrease in their biocompatibility.Using luciferase as a reporter gene,we further evaluated transfection performance of these supramolecular block copolymers in COS-7,HeLa and MCF-7 cell lines.Compared with the pre-modified supramolecular vectors,the resulting supramolecular copolymers exhibit remarkably enhanced gene transfection efficacy,particularly in tumor cells,which further provided a theoretical basis for the development of specific supramolecular non-viral vectors for cancer therapy.3.Dual-responsive supramolecular block copolymers for gene deliveryThe key scientific issue confronting supramolecular chemistry is to improve the biological stability of supramolecular non-viral vectors,in order to further achieve efficient gene expression in vitro or in vivo.Among them,intelligent supramolecular vectors usually have the ability to adapt to various variable enivironment.For instance,the light-responsive supramolecular polymers have attracted the attention of many scholars.However,it is necessary to further introduce specific stimuli-responsiveness into these supramolecular vectors to achieve highly efficient gene expression triggered by light.In this chapter,a class of cationic supramolecular block copolymers(SBC)that has excellent biostability and biocompatibility,and light/pH dual-responsive characteristics,have been successfully developed.Dimethylamino azobenzene groups endow the supramolecular block copolymer with visible light and pH responsiveness.This stimuli-responsive amphiphilic cationic supramolecular block copolymer demonstrates efficient plasmid DNA compression capacity and the ability to controlled release of plasmid DNA into cells under visible light irradiation.Notably,with 450 nm visible light irradiation,this kind of supramolecular block copolymers showed significantly enhanced gene transfection performance in both COS-7 and HeLa cells.We anticipate that this kind of ligh-responsive supramolecular gene vectors can eventually achieve specific gene therapy in vivo,especially tumor tissues.