Low generation PAMAM dendrimer and CpG free plasmids allow targeted and extended transgene expression in tumors after systemic delivery.

Polyplexes consisting of a standard CMV promoter driven luciferase plasmid condensed with PAMAM starburst dendrimers (generation 4 and 5) efficiently transfected tumor cells in vitro. Tail vein injection of PAMAM polyplexes into immune competent mice bearing subcutaneous, well vascularized murine neuroblastoma tumors (Neuro2A) led to predominant luciferase reporter gene expression in the tumor, and negligible transgene expression levels in other organs. Repeated PAMAM polyplex applications were well tolerated and prolonged transgene expression in the tumor.

Synthesis and biological evaluation of a bioresponsive and endosomolytic siRNA-polymer conjugate.

Extracellular stability of electrostatically formed siRNA polyplexes is a significant concern in the delivery process. To overcome the risk of polyplex dissociation in the extracellular environment, siRNA was covalently incorporated into a pH- and redox-responsive polymer conjugate. The novel siRNA conjugate consists of polylysine (PLL) as RNA binding and protecting polycation, polyethylene glycol (PEG) as solubilizing and shielding polymer, the lytic peptide melittin masked by dimethylmaleic anhydride (DMMAn) removable at endosomal pH, and the siRNA attached at the 5'-end of the sense strand via a bioreducible disulfide bond.