PDMAEMA-b-polysulfobetaine brushes-modified ε-polylysine as a serum-resistant vector for highly efficient gene delivery

Abstract

Serum stability is one of the key factors influencing the transfection efficiency of cationic vector-mediated gene delivery in vivo. In this work, we used an atomic transfer 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 indicated that conjugation of sulfobetaine only slightly decreased the DNA condensation ability of PDMAEMA homopolymer brushes-modified ε-polylysine (ε-Ply-DMA₇₀), but increased the stability of complexes in heparin sodium due to the anti-polyelectrolyte effect of polysulfobetaine. The transfection efficiencies of PEI25K and ε-Ply-DMA₇₀ vectors under the serum conditions from 0% to 50% were shown to decrease dramatically; while ε-Ply-DMA₇₀-MPD_p vectors remained more stable for gene transfection in concentrated serum, and the efficiency of ε-Ply-DMA₇₀-MPD₂₀ is more than 10-fold higher than that of PEI25K. PDMAEMA-r-PMPDSAH random copolymer brushes-modified ε-polylysine (ε-Ply-DMA₇₀-r-MPD₂₀) showed no improved serum tolerant gene transfection. The MTT assays revealed that the cytotoxicity of ε-Ply-DMA₇₀-MPD_p vectors was much lower than that of ε-Ply-DMA₇₀ due to the shielding of positive charges by polysulfobetaine. The expression of red fluorescence protein (RFP) was evaluated by a small animal in vivo fluorescence imaging system and the results showed that the expression of RFP was much higher in the mice injected with ε-Ply-DMA₇₀-MPD₂₀/pDNA-RFP than with ε-Ply-DMA₇₀/pDNA-RFP.