Contribution Of Surface And Core Structure To Gene Delivery Efficiency For PDMAEMA Based Amphiphilic Copolymer Nanoparticles

Gene therapy is the potential method in treatment, cancer, viral infections andcardiovascular diseases. The key of problem in gene therapy is to find efficientdelivery system. Although viral vectors have excellent cell targeting and efficientgene delivery, their application is limited by potential immunogenicity problems.Currently, cationic polymers as non-viral vectors become research focus, howeverurgent problems to be solved are high toxicity and poor delivery efficiency. Ourresearch group preliminary studied the cationic nanocarriers basing graft or blockcopolymer nanoparticles composed by poly (2-(N, N-dimethylamino) ethylmethacrylate)(PDMAEMA), polycaprolactone (PCL) and polyethylene glycol (PEG).Herein the contribution of the surface modified layer and a hydrophobic core of thestructure on the nanoparticle gene delivery function are further studied.Our previous studies have showed that element complexes form throughelectrostatic interactions between polyglutamate grafted PEG (PGA-g-PEG, GP) andcationic nanoparticles of PCL-g-PDMAEMA NPs/DNA (NP-D) can improve thebiocompatibility of the carrier, while reduce the transfection efficiency. In this article,we synthesized a series of GP with different molecular weights of main and sidechains with, examined physicochemical properties of the ternary complexes includinghydrodynamic diameters, zeta potential and DNA binding ability, and explored theeffect of PGA and PEG molecular weight on cytotoxicity, intracellular uptake andgene transfection effect in vitro. When PGA molecular weight is46KDa, the threeelement complexes have highest transfection efficiency and optimum endocytosis,and within the experimental range molecular weight of PEG has minimal impact. Forthe same GP, optimal charge ratio of the ternary complex NP-D-GP is10/1/5, whichshows better cell compatibility and transfection efficiency. So, the optimal structurefor the better NP-D-GP complex is NP-D-G46P5charge ratio of10/1/5.It is well known PEG modification on the surface of the carrier can improvebiocompatible and provide long-circulating performance in vivo, but it also brings‘PEG dilemma’, reducing endocytosis and lysosomal escape ability. To this end, wechose hyaluronic acid (HA) instead of PGA, synthesized PEGylate hyaluronic acid(HA-g-PEG, HP) with different grafting ratio of PEG, examined diameter, zeta potential, gel electrophoresis, endocytosis and transfection both in vitro and in vivo,and evaluated function of polyanions with different PEG grafting rate on genedelivery. As the outer layer of the ternary complex components, HP, compared to GP,presented better positive charge shield ability on surface of binary complex NP-D,effectively improve cell compatibility. Through HA performance of tumorcell-specific receptor-mediated endocytosis and hyaluronidase (Hyal-1) degradationof the response characteristics to deshelling both intracellular and extracellular, tumorcells endocytosis and endosomes escape ability were efficiently improved, as a resultincreasing cell transfection efficiency in vitro and tumor targeted delivery in vivo.To further explore the structure contribution of the hydrophobic segments toDNA binding, endocytosis and gene transfection efficiency, we synthesized differentblock cationic copolymer PEG-PCL-PDMAEMA (PEC) with different molecularweights of PCL and cyclic ether side groups modified PCL block copolymers toexplore effects of hydrophobic segment structure. The results presented that theincrease of PCL molecular weight can enhance the resistance of PEC NPs/DNA toenzymatic degradation of DNA, promote cell binding and improve endocytosis andtransfection efficiency. The introduction of cyclic ether side groups in PCL segmentcan improve transfection efficiency, yet its functional mechanism need to be furtherexplored.