摘要A series of branched polyethylenimine(PEI)modifications including PEGylation(PEG2k-PEI)for steric shielding,redox-sensitive crosslinking for synthesis PEG2k-PEI-ss nanogels and subsequent carboxymethylation(PEG2k-CMPEI-ss)for modulation of the polymer pka have been introduced for cellular delivery of Anti-miR-21.The synthesis was characterized us-ing 1H NMR,FTIR,TNBS,potentiometric titration,particle size and ζ potential.Loading of Anti-miR-21 at various N/P ratios was investigated by gel retardation,ethidium bromide dye exclusion,heparin sulfate competition and DNase I digestion experiments.The miR-21 si-lencing was measured by stem-loop RT PCR in A2780 ovarian cancer cell lines whether it is sensitive to resistant to cisplatin.It has been shown that PEG2k-CMPEI-ss was well suited for delivery of Anti-miR-21 in terms of nucleic acid loading,preservation against extracellu-lar matrix and nucleases and sequence-specific silencing of miRNA-21 in vitro.Moreover,it has been demonstrated that pre-treating cells with Anti-miR-21 loaded nanogels can sensi-tize them to cis-Pt even at non-toxic concentraions.The results indicate that PEG2k-CMPEI-ss mediated microRNA delivery can be considered as a novel strategy for ovarian cancer therapy.