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  • Title: pH-sensitive multi-PEGylated block copolymer as a bioresponsive pDNA delivery vector.
    Author: Lai TC, Bae Y, Yoshida T, Kataoka K, Kwon GS.
    Journal: Pharm Res; 2010 Nov; 27(11):2260-73. PubMed ID: 20300803.
    Abstract:
    PURPOSE: A reversibly-PEGylated diblock copolymer, poly(aspartate-hydrazide-poly(ethylene glycol))-block-poly(aspartate-diaminoethane) (p[Asp(Hyd-PEG)]-b-p[Asp(DET)]) was reported here for enhanced gene transfection and colloidal stability. The diblock copolymer possessed a unique architecture based on a poly(aspartamide) backbone. The first block, p[Asp(Hyd)], was used for multi-PEG conjugations, and the second block, p[Asp(DET)], was used for DNA condensation and endosomal escape. METHODS: p[Asp(Hyd-PEG)]-b-p[Asp(DET)] was synthesized and characterized by (1)H-NMR. Polyplexes were formed by mixing the synthesized polymers and pDNA. The polyplex size, ζ-potential, and in vitro transfection efficiency were determined by dynamic light scattering, ζ-potential measurements, and luciferase assays, respectively. pH-dependent release of PEG from the polymer was monitored by cationic-exchange chromatography. RESULTS: The polyplexes were 70-90 nm in size, and the surface charge was effectively shielded by a PEG layer. The transfection efficiency of the reversibly PEGylated polyplexes was confirmed to be comparable to that of the non-PEGylated counterparts and 1,000 times higher than that of the irreversibly PEGylated polyplexes. PEG release was demonstrated to be pH-sensitive. Fifty percent of the PEG was released within 30 min at pH 5, while the polymer incubated at pH 7.4 could still maintain 50% of PEG after 8 h. CONCLUSION: The reversibly PEGylated polyplexes were shown to maintain polyplex stability without compromising transfection efficiency.
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