Preparation And Properties Of Natural Polysaccharide-Based Polymeric Gene Carrier

Gene therapy as a new treatment for cancer holds a good application prospect.In recent years,great progress has been achieved in clinical trials,however many challenges still remain concerning the gene therapy technique,the biggest of which is the urgent need for development of safe and efficient carriers.Polymeric carriers have attracted considerable attention because by being a polymeric gene carrier is probably the most promising to carry many advantages such as low immunogenicity,controllable structure,variety and low cost.Coventional polymeric carriers mainly refer to materials like polylysine(PLL),polyethyleneimine(PEI),polyamide amine(PAMAM),poly(2-dimethylaminoethyl methacrylate)(PDMAEMA),however,most of them suffer from significant cytotoxicity,low transfection efficiency,serum-intolerance or non-targetability in gene delivery.Therefore,it has become a research problem to obtain gene vector with low toxicity,high efficiency and targetability.In this paper,in order to solve the above problems,a series of glycopolymers were designed and synthesized using polysaccharides as backbone,because natural saccharide have many advantages such as excellent biocompatibility,biodegradable and targeted activity.Firstly,we introducted natural polysaccharides into traditional polymers,and the cytotoxicity is significantly reduced.To further improve the serum-intolerance and non-targetability of traditional polymeric carriers,galactose-containing polymer/poly(ethyleneimine)(PEI)were designed for gene delivery in order to exert the synergistic effect of both polymer carriers.In addition,amphiphilic polymeric gene carrier with low toxicity and high transfection efficiency was prepared,and this carrier was proved to be able to encapsulate and release anticancer drugs,with the form of a new multifunctional polymeric micelle.The details are as follows:1)In order to design a polymer gene vector with low toxicity and high transfection efficiency,nontoxic and degradable polysaccharide dextran and GAMA were introduced into the traditional cationic polymer PDMAEMA.We synthesized a series of comb-shaped glycopolymers Dextran-g-P(DMAEMA-b-GAMA)and Dextran-g-P(DMAEMA-r-GAMA)by atomic transfer radical polymerization(ATRP)These glycopolymers have strong proton buffering capacity in a pH range from 5 to 7,and can effectively condense DNA into nano-sized particles(<200nm)with positive zeta potential.The results of cell tests showed that the introduction of saccharides significantly improved the biocompatibility of polymers,all the comb-shaped polymers have lower cytotoxicity than PEI,among them,Dextran-g-P(DMAEMA28-r-GAMA10)has lower cytotoxicity than Dextran-g-P(DMAEMA27-b-GAMA9),meanwhile,Dex-g-P(DMAEMA27-b-GAMA9)has similar transfection efficiency than PEI,and it is highly expected to be proceeded into a efficient and safe novel non-viral gene vector.2)In the internal environment,cationic polymer/DNA complexes will non-specifically interact with proteins of serum,which causes difficulties like colloidal aggregation for entering the target cells.For solving the shortcomings of traditional polymer gene carriers,such as serum-intolerance,low transfection efficiency and non-targetability,we introduced galactose with targeting functions towards hepatoma cells and PEI with high transfection efficiency into polymer carriers.We synthesized the galactose-polymers dextran-g-poly(2-dimethyl-aminoethyl methacrylate-r-2-lactobionamidoethyl methacrylate)(DDrLs)via ATRP.Then DDrLs/PEI were investigated for gene delivery.DDrLs/PEI can effectively complex DNA and form nanoscale particles(100?200 nm),and the DDrLs/PEI/DNA complexes can remain stable in the serum environment.Cell tests proved that DDrLs and PEI have synergistic effect,the DDrLs/PEI/DNA complexes at specific mass ratio exhibit lower cytotoxicity and efficient transfection efficiency compared to PEI/DNA complexes and DDrLs/DNA complexes,and excellent serum resistance,hepatoma cell targeting.Complexes can still maintain efficient transfection efficiency in 30%serum environment.As a conclusion,this polymeric gene vector canditate has a commendable application prospect in gene therapy for targeting hepatoma cells.3)In order to improve the transfection efficiency of glycopolymers,we introduced curdlan into polymers,the amphiphilic polymer Curdlan-g-PDMAEMA was synthesized by ATRP.The amphiphilic polymer can not only deliver gene but also encapsulate and release anticancer drug.The experimental results exhibited that Curdlan-g-PDMAEMA can form micelles with particle size of 80?110 nm in water,and have lower cytotoxicity and better transfection efficiency than PEI.Furthermore,Curdlan-g-PDMAEMA can successfully encapsulate curcumin and achieve long-term drug release.Curdlan-g-PDMAEMA40 can increase the water solubility of curcumin,and show higher toxicity to cancer cells than pure curcumin.The delivery system provides new ideas for the combination of gene therapy and chemotherapy.In this paper,a series of glycopolymers were prepared by introducing nontoxic and biodegradable polysaccharides into traditional polymer carriers,and these gene vectors significantly improve cell viability and gene transfection efficiency.This strategy provides prospective new method for gene vectors of glycopolymer in gene therapy.