A block copolymer containing PEG and histamine-like segments: well-defined functions for gene delivery

Abstract

The delivery of genetic materials to cells provides a promising treatment approach to many genetic diseases. The rational structural design for reducing the toxicity while improving transfection efficiency is an important strategy for the development of safe and highly efficient polycation gene vectors. In this study, a novel block copolymer composed of PEG and cationic histamine-like segments was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization and subsequently the potential of its gene vector was explored in vitro. The block copolymer showed a lower cytotoxicity to three cell lines. After complexation with pEGFP-C1, the resulting DNA-encapsulated micelles possessed uniform small size, high salt and serum tolerance which were confirmed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Highly efficient gene transfection was further obtained in human liver carcinoma (HepG2) in vitro. The low cytotoxicity and high transfection stem from the well-defined functions of different moieties, PEG segments, imidazolium and amine groups on histamine-like pendants contributing to the different steps of gene delivery, including colloid stability, highly effective DNA condensation and endosomal escape respectively.

Block copolymer conjugated Au-coated Fe3O4 nanoparticles as vectors for enhancing colloidal stability and cellular uptake

“…Our previous reports demonstrated that polyplexes [45] and nanoplexes [24] with a PEG shell, and which condense DNA via PAMPImB, are highly stable in physiological media. We assessed magnetic nanoplex stability in different media by DLS (Table 1).…”

“…The cytotoxicity of composite nanoparticles often depends on their size and surface properties [46]. PEG- b -PAMPImB is a low cytotoxic polymer because PEG and the cationic histamine-like segment have high biocompatibility, as shown in our previous report [45]. The formation of micelle-like core–shell structures upon attachment to Fe 3 O 4 @Au further decreases cytotoxicity, as the PEG outer corona shields the inner shell of the cationic histamine-like segment.

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“…Vector stability under physiological conditions has significant effects on gene expression in vitro and on further applications in vivo [ 44 ]. Our previous reports demonstrated that polyplexes [ 45 ] and nanoplexes [ 24 ] with a PEG shell, and which condense DNA via PAMPImB, are highly stable in physiological media. We assessed magnetic nanoplex stability in different media by DLS (Table 1 ).…”

“…Second, we designed a neutral-cationic block copolymer as external coating polymer rather than only cationic polymer monolayer. The outer neutral PEG can provide high colloidal stability of vector in physiological conditions [ 45 ]. Moreover, the magnetic agglomeration of transfected cells has been proven to be feasible.…”

“…PEG 112 - b -PAMPImB 96 was synthesized by RAFT polymerization by using PEG-CTA (Mw 5000) as macromolecular chain transfer agent and AMPImB as monomer. The detailed synthesis and characterization of this polymer was previously described [ 45 ]. Dulbecco’s modified Eagle’s medium (DMEM), penicillin–streptomycin, trypsin, fetal bovine serum (FBS), 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT), and Dubelcco’s phosphate buffered saline (DPBS) were purchased from Thermo Fisher Scientific.…”