title: Functionalization of lignin through ATRP grafting of poly(2-dimethylaminoethyl methacrylate) for gene delivery.
abstract: The biomass kraft lignin was modified into lignin-based macroinitiators (LnMI) through esterification of the alcohol and phenol functional groups on lignin backbone with 2-bromo-isobutyric bromide under mild condition. Then a series of cationic amphiphilic lignin-based graft copolymers were synthesized by atom transfer radical polymerization (ATRP) of 2-(dimethylamino)ethyl methacrylate (DMAEMA) starting from the lignin-based macroinitiators. These copolymers, denoted as LnPDMAEMA, had a hyperbranched structure with a hydrophobic backbone of lignin and multiple cationic hydrophilic arms of PDMAEMA. The LnPDMAEMA copolymers were characterized by (1)H NMR and elemental analysis (EA), and studied in terms of their DNA binding capability, formation of nanoparticles with plasmid DNA (pDNA), cytotoxicity, and gene transfection in cultured cells. It was found that all the copolymers could efficiently compact pDNA into nanoparticles with sizes ranging from 100 to 200 nm at N/P ratios of 5 or higher. The cytotoxicity of these copolymers depends greatly on the chain length of PDMAEMA arms, the longer the PAMAEMA chain the higher the cytotoxicity. Luciferase assay was used to study the in vitro gene transfection for the LnPDMAEMA copolymers in different cell lines. The gene transfection efficiency of these copolymers was dependent on the grafted PDMAEMA chain length and N/P ratio. Generally, the transfection efficiency decreased with the increase of PAMAEMA length at N/P ratio of 20 or higher. It is very interesting that one of the LnPDMAEMA copolymers with very short arm length (degree of average DMAEMA units=5.5) showed excellent in vitro transfection efficiency that was comparable or even higher than that of branched PEI (25K). These novel biomass-based LnPDMAEMA hyperbranched copolymers can be a promising nonviral gene vectors for future gene delivery application.
authors.affiliation: Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, 7 Engineering Drive 1, Singapore 117574, Singapore.
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Liu
authors.affiliation: Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, 7 Engineering Drive 1, Singapore 117574, Singapore.
authors.forename: Hui
authors.initials: H
authors.lastname: Yin
authors.affiliation: Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602, Singapore. Electronic address: zhangzx@imre.a-star.edu.sg.
authors.forename: Zhongxing
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, 7 Engineering Drive 1, Singapore 117574, Singapore.
authors.forename: Bishuo
authors.initials: B
authors.lastname: Diao
authors.affiliation: Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, 7 Engineering Drive 1, Singapore 117574, Singapore; Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602, Singapore; NUS Graduate School for Integrative Sciences & Engineering, National University of Singapore, 28 Medical Drive, Singapore 117456, Singapore. Electronic address: jun-li@nus.edu.sg.
authors.forename: Jun
authors.initials: J
authors.lastname: Li
mesh_terms: D000818:Animals; D001965:Bromides; D019556:COS Cells; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D004247:DNA / Q000737:chemistry / Q000235:genetics; D015870:Gene Expression; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008031:Lignin / Q000737:chemistry*; D008156:Luciferases / Q000235:genetics* / Q000378:metabolism; D008689:Methacrylates / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D009757:Nylons / Q000737:chemistry*; D010316:Particle Size; D010957:Plasmids / Q000737:chemistry / Q000378:metabolism; D058105:Polymerization; D014162:Transfection / Q000379:methods*
chemical_list: D001965:Bromides; D008689:Methacrylates; D009757:Nylons; C407037:poly(2-(dimethylamino)ethyl methacrylate); C076151:Kraft lignin; D008031:Lignin; D004247:DNA; D008156:Luciferases
keywords: ATRP; Biomass; Gene delivery; Graft copolymer; Lignin; PDMAEMA