Stable gene transfection mediated by polysulfobetaine/PDMAEMA diblock copolymer in salted medium

Abstract

Cationic polyplexes would aggregate immediately after intravenous injection due to the plasma proteins and high ionic strength. A cationic polyplexes with long-term and salt stability was very important for a systemic gene therapy. In this research, a polysulfobetaine-b-polycation diblock copolymer composed of cationic block of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and zwtterionic block of poly(propylsulfonate dimethylammonium ethylmethacrylate) (PSPE) was conveniently synthesized by atom transfer radical polymerization method to obtain a cationic polymers with long-term and salt stability. The results of agarose gel electrophoresis and transmission electron microscope indicated that copolymerization of PSPE did not compromise the DNA condensation ability of PDMAEMA, meanwhile exhibiting lower cytotoxicity. The effect of salt on the absorbance and particle size of PDMAEMA100/DNA and PDMAEMA100-PSPEy/DNA complexes was investigated, which showed that PSPE block could increase the resistance of polyplexes against salt-induced aggregation owing to the antielectrolyte effect. In comparison with PDMAEMA homopolymer, PDMAEMA100-PSPEy retained more stable gene transfection in a certain range of salt concentration. The expression of red fluorescence protein (RFP) was evaluated by small animal in vivo fluorescence imaging system and the results showed that the expression of RFP was much higher in the mice injected with PDMAEMA100-PSPE20/pDNA-RFP than with PDMAEMA/pDNA-RFP. Both in vitro and in vivo results suggested that PDMAEMA-PSPE diblock copolymer may be potentially used as a vector for systemic gene therapy.

Mixed Polyplex Micelles with Thermoresponsive and Lysine-Based Zwitterionic Shells Derived from Two Poly(vinyl amine)-Based Block Copolymers

“…The modification of polycations with nonionic polymers such as poly­(ethylene glycol) is a frequently employed strategy to improve polyplex stability and polymer-DNA interactions, whereas poly­(ethylene glycol)-modified cationic polymers suffer from the limited cellular uptake and insufficient transfection efficiency. ,− As an alternative, numerous researchers have attempted the incorporation of zwitterionic units, such as phosphorylcholine, − sulfobetaine, − and carboxybetaine, to polycations into a block sequence, as the modified block polymers show improved biocompatibility and can preserve the high internalization level in cells, in addition to possessing enhanced colloidal stability, diverse functional features, and unique properties. Even if sulfobetaine-based zwitterionic polymers are known to exhibit a UCST because of intra- and interchain electrostatic association of zwitterionic groups, which can be interrupted by the addition of counterions, less attention has been devoted to the effect of UCST behavior of block copolymers composed of cationic and sulfobetaine components on the polyplex formation through DNA binding. ,− Zwitterionic vinyl polymers bearing amino acid pendant groups are recognized as a new class of neutral chiral polymers because they have fascinating properties and biological functions such as reduced protein adsorption, excellent biocompatibility, stimuli responsiveness, and unique antifouling characteristics. − Several amino acid-derived zwitterionic polymers have drawn increasing attention as promising candidate DNA carriers. For instance, poly­(ε- N -methacryloyl- l -lysine) has been reported to be a biocompatible polymer with nontoxicity, which can be converted into a polycation by the addition of Zn 2+ ions; the resulting polycation can form an ion complex with DNA, leading to efficient introduction of genes into specific cells. ,, Our group recently reported the synthesis of lysine-based block copolymers comprising temperature-sensitive PNIPAM with zwitterionic poly­( N -acryloyl- l -lysine) (PALysOH) and cationic methylester derivative, PALysOMe, by the reversible addition–fragmentation chain transfer (RAFT) polymerization and chemical modifications .…”