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Meng Zheng,Zhiyuan Zhong,Chunmei Yang,Fenghua Meng,Rui Peng 한국고분자학회 2012 Macromolecular Research Vol.20 No.3
1.8 kDa branched polyethylenimine (PEI) was modified with pH-sensitive degradable acetal containing hydrophobe, 2,4,6-trimethoxybenzylidene-tris(hydroxymethyl)ethane (TMB-THME), to enhance its DNA condensation under extracellular conditions as well as to achieve active DNA release inside cells. PEI-(TMBTHME)n conjugates in the amount of 1.8 kDa were prepared with varying degrees of substitution (DS) from 3.0, 5.7 to 10.1. Notably, dynamic light scattering (DLS) measurements showed that all three 1.8 kDa PEI-(TMB-THME)n conjugates could effectively condense DNA into nano-sized particles (189-197 nm) at N/P ratios ranging from 20/1 to 80/1. The surface charges of PEI-(TMB-THME)n polyplexes depending on DS and N/P ratios varied from +22 to +28 mV,which were comparable to or slightly higher than the unmodified 1.8 kDa PEI counterparts (~+22 to +23 mV). Under a mildly acidic condition mimicking that of endosomes, interestingly, 1.8 kDa PEI-(TMB-THME)n polyplexes were quickly unpacked to release DNA because of the pH-induced acetal degradation that transforms hydrophobic modification into hydrophilic modification. MTT assays demonstrated that all PEI-(TMB-THME)n polyplexes displayed low cytotoxicity (>80%) to 293T, and HeLa cells at N/P ratios ranging from 20/1 to 60/1. The in vitro gene transfection studies showed that the transfection activity of 1.8 kDa PEI was significantly enhanced by modifications with TMBTHME,in which transfection efficiencies increased with increasing DS. For example, 1.8 kDa PEI-(TMBTHME)10.1 polyplexes displayed 250-fold and 80-fold higher transfection efficiencies than those of the unmodified 1.8 kDa PEI counterparts in 293T and HeLa cells, respectively, which were approximately 4-fold and 2-fold higher than that of 25 kDa PEI control. The superior transfection activity of 1.8 kDa PEI-(TMB-THME)10.1 polyplexes was also confirmed by confocal laser scanning microscopy (CLSM), which showed efficient delivery of DNA into the nuclei of 293T cells following 4 h transfection. Modification of low molecular weight PEI with pH-sensitive degradable hydrophobe has appeared to be highly promising in the development of “artificial viruses” for safe and efficient gene transfer.
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Zhu, Caihong,Jung, Sooyeon,Si, Guoying,Cheng, Ru,Meng, Fenghua,Zhu, Xiulin,Park, Tae Gwan,Zhong, Zhiyuan Wiley Subscription Services, Inc., A Wiley Company 2010 Journal of polymer science Part A, Polymer chemist Vol.48 No.13
<P>A versatile family of cationic methacrylate copolymers containing varying amounts of primary and tertiary amino side groups were synthesized and investigated for in vitro gene transfection. Two different types of methacrylate copolymers, poly(2-(dimethylamino)ethyl methacrylate)/aminoethyl methacrylate [P(DMAEMA/AEMA)] and poly(2-(dimethylamino)ethyl methacrylate)/aminohexyl methacrylate [P(DMAEMA/AHMA)], were obtained by reversible addition-fragmentation chain transfer (RAFT) copolymerization of dimethylaminoethyl methacrylate (DMAEMA) with N-(tert-butoxycarbonyl)aminoethyl methacrylate (Boc-AEMA) or N-(tert-butoxycarbonyl)aminohexyl methacrylate (Boc-AHMA) followed by acid deprotection. Gel permeation chromatography (GPC) measurements revealed that Boc-protected methacrylate copolymers had M<SUB>n</SUB> in the range of 16.1–23.0 kDa and low polydispersities of 1.12–1.26. The copolymer compositions were well controlled by monomer feed ratios. Dynamic light scattering and agarose gel electrophoresis measurements demonstrated that these PDMAEMA copolymers had better DNA condensation than PDMAEMA homopolymer. The polyplexes of these copolymers revealed low cytotoxicity at an N/P ratio of 3/1. The in vitro transfection in COS-7 cells in serum free medium demonstrated significantly enhanced (up to 24-fold) transfection efficiencies of PDMAEMA copolymer polyplexes as compared with PDMAEMA control. In the presence of 10% serum, P(DMAEMA/AEMA) and P(DMAEMA/AHMA) displayed a high transfection activity comparable with or better than 25 kDa PEI. These results suggest that cationic methacrylate copolymers are highly promising for development of safe and efficient nonviral gene transfer agents. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2869–2877, 2010</P> <B>Graphic Abstract</B> <P>A versatile family of cationic PDMAEMA copolymers containing varying amounts of primary and tertiary amine groups were designed and synthesized by controlled RAFT copolymerization. These novel copolymers showed improved DNA condensation and dramatically enhanced gene transfection as compared with the PDMAEMA homopolymer. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.] <img src='wiley_img_2010/0887624X-2010-48-13-POLA24064-gra001.gif' alt='wiley_img_2010/0887624X-2010-48-13-POLA24064-gra001'> </P>
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