Construction Of A Serum-resistant Vector For Gene Delivery Based On ε-Ply-DMA-MPD Brushes

Serum stability is one of the key factors influencing the transfection efficiency ofcationic vector mediated gene delivery in vivo. In this work, we used an atomictransfer radical polymerization （ATRP） method to construct p（2-（dimethylamino）ethyl methacrylate）-b-p（N-（3-（methacryloylamino）propyl）-N,N-dimethyl-N-（3-sulfopropyl） ammonium hydroxide）（PDMAEMA-b-PMPDSAH） diblock copolymer brushes-modified ε-polylysine（ε-Ply-DMA-MPD） non-viral vectors. The agarose gel electrophoresis assay indicatedthat conjugation of sulfobetaine only slightly decreased the DNA condensation abilityof PDMAEMA homopolymer brushes-modified-polylysine (ε-Ply-DMA₇₀), butincreased the stability of complexes in heparin sodium due to the anti-polyelectrolyteeffect of polysulfobetaine. The transfection efficiencies of PEI25k and ε-Ply-DMA₇₀vectors under the serum conditions from0%to50%were shown to decreasedramatically; while ε-Ply-DMA₇₀-MPDpvectors remained more stable for genetransfection in concentrated serum, and the efficiency of ε-Ply-DMA₇₀-MPD₂₀wasmore than10-fold higher than that of PEI25k. PDMAEMA-r-PMPDSAH randomcopolymer brushes-modified-polylysine (ε-Ply-DMA₇₀-r-MPD₂₀) showed noimproved serum tolerant gene transfection. The MTT assays revealed that thecytotoxicity of ε-Ply-DMA₇₀-MPDp vectors was much lower than that of ε-Ply-DMA₇₀due to the shielding of positive charges by polysulfobetaine. Theexpression of red fluorescence protein （RFP） was evaluated by a small animal in vivofluorescence imaging system and the results showed that the expression of RFP wasmuch higher in the mice injected with ε-Ply-DMA₇₀-MPD₂₀/pDNA-RFP than with ε-Ply-DMA₇₀/pDNA-RFP. We believed that this kind of serum-resistant non-viralvector will be promising as a systemic gene vector in gene therapy.