Design Synthesis And Performance Of Polycationic Non-viral Gene Vector Modified By Thermoresponsive Polymer

Traditional polymers as gene vectors only have a few functions which can not meet gene therapy requirements, in light of this demerit it is necessary to decorate traditional polymer gene vectors and get an ideal gene delivery system with multifunction. Despite improvements in synthesize strategies of smart or intelligent polymer vectors, there are still faced many problems, toxieity, biodegradable, Endosome escape barriers, etc. In additon, traditional free radical polymerization can not designed well-defined structure and narrow polydispersity polymers. Hence, there is an urgent need to develop novel polycationics gene vectors which easily synthesized and smart.The goal of this work was to design and synthesize a mutifunctional polycation that could provide valuable ideas and methods for non-viral gene vectors. First, thermosensitive copoly(oligoethylene oxide) acrylates (POD) with tunable Lower Critical Solution Temperature (LCST) were prepared by the copolymerization of oligo(ethylene oxide) acrylate (OEGA) and di(ethylene oxide) ethyl ether acrylate (DEGEEA) using reversible addition-fragmentation chain transfer (RAFT) polymerization. After that, pH-sensitive poly(2-(dimethylamino)ethyl acrylate (PDMAEA) were synthesized via RAFT polymerization using BSPA and AIBN as chain transfer agent and initiator. Than, the block copolymer POD-b-PDMAEA were synthesized using POD as macromolecule chain transfer agent and DMAEA as monomer. Last, we designed miktoarm and blockarm star polymer by ’arm-first’ method using N,N’-double acryloyl cystamine (BAC) as crosslinking agent, AIBN as initiator, POD and PDMAEA or POD-b-PDMAEA served as arms.The chemical structure and composition were characterized and analyzed by 1H NMR spectroscopy (’H NMR) and Fourier Transform Infra Red Spectrophotometer (FT-IR). The morphology was studied using Transmission Electron Microscopy (TEM). The molecular weight and molecular weight distribution of the products were characterized and analyzed by Gel Permeation Chromatograph (GPC). The phase and aggregation behavior of polymers were evaluated in solution using UV-vis spectroscopy and Dynamic Light Scattering (DLS). Degradation and pH-responsive behavior were investigated by DLS and automatic potentiometric titrator. The cytotoxicity and hydrophilic were tested by MTT and contact angle device.Results show that linear and star polymers with well-defined structure and narrow polydispersity were synthesized successfully. The thermo responsive behavior of POD influenced by various parameters, including the content of OEGA, temperature, the species of added salts and pH. Increasing OEGA content, radius of anion or pH values leads to the increase in lowest critical solution temperature (LCST) values. LCST values could be closed to hunman temperture when the mole fractions of OEGA and DEGEEA is adjusted to 15/85. Block star polymer shows none pH responsive, while MAS shows both termo and pH-sensitive. The LCST of the solution increased with the increasing of PDMAEA. MAS polymer could self-catalyzed hydrolysis in water without the need for an internal or external degradation trigger. When polycationics was modified by thermosensive polymers they can not only have thermosreponsive but also have low toxicity. These results demonstrated that cationic biodegradable polymers are highly promsing for the combinatorial delivery of DNA or siRNA.