Enhanced gene transfection and serum stability of polyplexes by PDMAEMA-polysulfobetaine diblock copolymers

Polyethylene glycol or phosphorylcholine is often introduced into polycationic non-viral vectors to inhibit the non-specific protein adsorption However the ability of vectors to condense DNA and the cellular internalization of complexes are unavoidably compromised In this work a polysulfobetaine-cationic methacrylate copolymer 2-(dimethylamino) ethyl methacrylate-block-(N-(3-(methacryloylamino) propyl)-N N-dimethyl-N-(3-sulfopropyl) ammonium hydroxide) (PDMAEMA-b-PMPDSAH) diblock copolymer was synthesized via atomic transfer radical polymerization method and investigated as a new non-viral vector for gene delivery Incorporation of polysulfobetaine into cationic methacrylate retained a better DNA condensation capability MTT assays revealed that the cytotoxicity of PDMAEMA(200)-PMPDSAH(n) copolymer was lower than that of PDMAEMA(200) PDMAEMA(200)-PMPDSAH(80) which was much superior to its homopolymer in mediating gene transfection demonstrated comparable efficiency to PEI25 kDa at a weight ratio of 8 in the presence of 10% serum At higher serum contents the transfection of PDMAEMA200 and PEI25 kDa was deteriorated whereas PDMAEMA(200)-PMPDSAH(80) still retained better transfection efficiency 4-5 fold more effective than PEI25 kDa For the sake of comparative study we synthesized structurally similar copolymer from DMAEMA and 2-methacryloyloxyethyl phosphorylcholine PDMAEMA(200)-PMPC80 PDMAEMA(200)-PMPDSAH(80) exhibited much higher gene transfer levels than PDMAEMA(200)-PMPC80 under the same conditions The results of flow cytometry indicated that highly hydrophilic MPC block profoundly impeded the cellular internalization of nanocomplexes in contrast incorporation of polysulfobetaine remained the increased cellular uptake Differential scanning calorimetry assay of thermodynamic phase transition of dipalmitoyl-sn-glycero-3-phosphocholine(DPPC) induced by polymer vectors demonstrated that MPC only marginally contributed to the perturbation of DPPC polysulfobetaine facilitated more evident perturbation of DPPC bilayer Instead an indication that polysulfobetaine units could aid in the endocytosis of nanocomplexes 2010 Elsevier Ltd All rights reserved