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We previously reported that polyamidoamine STARBURST dendrimer (generation 3, G3) (dendrimer) conjugate with α-cyclodextrin (α-CyD) having an average degree of substitution of 2.4 of α-CyD (α-CDE) provided remarkable aspects as novel carriers for DNA and small-interfering RNA. To develop novel α-CDE derivatives with tumor cell specificity, we prepared folate-appended α-CDEs (Fol-α-CDEs) and folate-polyethylene glycol (PEG)-appended α-CDEs (Fol-PαCs) with the various degrees of substitution of folate (DSF), and evaluated in vitro and in vivo gene transfer activity, cytotoxicity, cellular association and physicochemical properties. In vitro gene transfer activity of Fol-α-CDEs (G3, DSF 2, 5 or 7) was lower than that of α-CDE (G3) in KB cells, folate receptor (FR)-overexpressing cancer cells. Of the three Fol-PαCs (G3, DSF 2, 5 or 7), Fol-PαC (G3, DSF 5) had the highest gene transfer activity in KB cells. The activity of Fol-PαC (G3, DSF 5) was significantly higher than that of α-CDE (G3) in KB cells, but not in A549 cells, FR-negative cells. Negligible cytotoxicity of the plasmid DNA (pDNA) complex with Fol-PαC (G3, DSF 5) was observed in KB cells or A549 cells up to a charge ratio of 100/1 (carrier/pDNA). The cellular association of the pDNA complex with Fol-PαC (G3, DSF 5) could be mediated by FR on KB cells, resulting in its efficient cellular uptake. Fol-PαC (G3, DSF 5) had a higher binding affinity with folate-binding protein than α-CDE (G3), although the physicochemical properties of pDNA complex with Fol-PαC (G3, DSF 5) were almost comparable to that with α-CDE (G3), although the onset charge ratio and the compaction ability of Fol-PαC (G3, DSF 5) were slightly different. Fol-PαC (G3, DSF 5) tended to show a higher gene transfer activity than α-CDE (G3) 12 h after intratumoral administration in mice. These results suggest that Fol-PαC (G3, DSF 5), not Fol-α-CDEs, could be potentially used as a FR-overexpressing cancer cell-selective DNA carrier.

We previously reported that glucuronylglucosyl-β-cyclodextrin (GUG-β-CyD) conjugate with polyamidoamine starburst dendrimer (GUG-β-CDE conjugate) with the average degree of substitution (DS) of cyclodextrin (CyD) of 1.8 (GUG-β-CDE conjugate (DS 1.8)), showed remarkably higher gene transfer activity than α-CyD/dendrimer conjugate (α-CDE conjugate (DS 1.2)) and β-CyD/dendrimer conjugate (β-CDE conjugate (DS 1.3)) in vitro and in vivo. In this study, to clarify the enhancing mechanism for high gene transfer activity of GUG-β-CDE conjugate (DS 1.8), we investigated the physicochemical properties, cellular uptake, endosomal escape and nuclear translocation of the plasmid DNA (pDNA) complexes as well as pDNA release from the complexes. The particle size, ζ-potential and cellular uptake of GUG-β-CDE conjugate (DS 1.8)/pDNA complex were mostly comparable to those of α-CDE conjugate (DS 1.2) and β-CDE conjugate (DS 1.3). Meanwhile, GUG-β-CDE conjugate (DS 1.8)/pDNA complex was likely to have high endosomal escaping ability and nuclear localization ability in A549 and RAW264.7 cells. In addition, the pDNA condensation and decondensation abilities of GUG-β-CDE conjugate (DS 1.8) were lower and higher than that of α-CDE conjugate (DS 1.2) or β-CDE conjugate (DS 1.3), respectively. These results suggest that high gene transfer activity of GUG-β-CDE conjugate (DS 1.8) could be, at least in part, attributed to high endosomal escaping ability, nuclear localization ability and suitable pDNA release from its complex., (Copyright © 2012 Elsevier B.V. All rights reserved.)

The purpose of this study is to evaluate in vitro and in vivo gene delivery efficiency of polyamidoamine (PAMAM) starburst dendrimer (generation 2, G2) conjugates with alpha-cyclodextrin (alpha-CDE (G2)) bearing lactose (Lac-alpha-CDE) with various degrees of substitution of the lactose moiety (DSL) as a novel hepatocyte-selective carrier in hepatocytes. Lac-alpha-CDE (DSL 2.6) was found to have much higher gene transfer activity than dendrimer, alpha-CDE, Lac-alpha-CDE (DSL 1.2, 4.6, 6.2 and 10.2) and lactosylated dendrimer (Lac-dendrimer, DSL 2.4) in HepG2 cells, which are dependent on the expression of cell-surface asialoglycoprotein receptor (ASGP-R), reflecting the cellular association of the plasmid DNA (pDNA) complexes. The physicochemical properties of pDNA complex with Lac-alpha-CDE (DSL 2.6) were almost comparable to that with alpha-CDE. Lac-alpha-CDE (DSL 2.6) provided negligible cytotoxicity up to a charge ratio of 150 in HepG2 cells. Lac-alpha-CDE (DSL 2.6) provided gene transfer activity higher than jetPEI-Hepatocyte to hepatocytes with much less changes of blood chemistry values 12h after intravenous administration in mice. These results suggest the potential use of Lac-alpha-CDE (DSL 2.6) as a non-viral vector for gene delivery toward hepatocytes., (Copyright 2010 Elsevier B.V. All rights reserved.)

The potential of starburst polyamidoamine dendrimer (dendrimer, generation 3, G3) conjugate with alpha-cyclodextrin (alpha-CyD) having an average degree of substitution of 2.4 (alpha-CDE) as a novel carrier of short hairpin RNA (shRNA) expressing plasmid DNA (shpDNA) was evaluated and the shpDNA transfer activity of alpha-CDE was compared with that of dendrimer (G3). Alpha-CDE formed a stable and condensed complex with shpDNA and induced a conformational transition of shpDNA in solution even in the low charge ratios. In addition, alpha-CDE markedly inhibited the enzymatic degradation of shpDNA by DNase I. The shpDNA complex with alpha-CDE at the charge ratio of 20/1 (alpha-CDE/shpDNA) elicited the most potent RNAi effects in cells transiently and stably expressing the GL3 and GL2 luciferase genes without cytotoxicity among the complexes with the various charge ratios. Besides, the RNAi effects were strikingly enhanced by the further addition of the adequate amounts of siRNA to the shpDNA complex with alpha-CDE. Taken together, the prominent RNAi effects of the shpDNA complex with alpha-CDE could be attributed to the stabilizing effect of alpha-CDE on enzymatic degradation of shpDNA and negligible cytotoxicity. These results suggest that alpha-CDE possesses the potential to be a novel carrier for shpDNA and siRNA.

To improve gene transfer activity of a new nonviral vector, a polyamidoamine dendrimer (G2) conjugate with alpha-cyclodextrin (alpha-CDE conjugate (G2)), we prepared alpha-CDE conjugates with dendrimer having different generations (G3 and G4), and their gene transfer activities were compared with those of alpha-CDE conjugate (G2) and TransFast, a novel transfection reagent. alpha-CDE conjugates (G2, G3, and G4) formed the complexes with pDNA, changing the zeta-potential and particle size of pDNA complexes and the protection of pDNA from DNase I in a charge ratio-dependent manner, although their differences at higher charge ratios (vector/pDNA) were small. The gene transfer activity of alpha-CDE conjugates (G2, G3, and G4) was higher than that of the corresponding dendrimer alone in NIH3T3 and RAW264.7 cells. Of these CDE conjugates, alpha-CDE conjugate (G3) had a superior gene transfer activity which was comparable to that of TransFast in NIH3T3 cells. The intracellular distribution of pDNA after application of the pDNA complex with alpha-CDE conjugate (G3) to NIH3T3 cells was different from that with dendrimer alone (G3), although the cellular association of pDNA was almost comparable among all vectors. alpha-CDE conjugate (G3) strongly interacted with a fluorescence probe, 2-(p-toluidinyl)-naphthalene-6-sulfonate (TNS), suggesting that the conjugate possesses the inclusion ability with biomembrane constituents such as phospholipids after transfection. These results suggest that alpha-CDE conjugates, particularly the G3 conjugate, could be novel nonviral gene transfer agents.

To improve the transfection efficiency of nonviral vector, we synthesized the starburst polyamidoamine dendrimer conjugates with alpha-, beta-, and gamma-cyclodextrins (CDE conjugates), expecting the synergistic effect of dendrimer and cyclodextrins (CyDs). The (1)H NMR spectroscopic data indicated that alpha-, beta-, and gamma-CyDs are covalently bound to dendrimer in a molar ratio of 1:1. The agarose gel electrophoretic studies revealed that CDE conjugates formed the complexes with plasmid DNA (pDNA) and protected the degradation of pDNA by DNase I in the same manner as dendrimer. CDE conjugates showed a potent luciferase gene expression, especially in the dendrimer conjugate with alpha-CyD (alpha-CDE conjugate) which provided the greatest transfection activity (approximately 100 times higher than those of dendrimer alone and of the physical mixture of dendrimer and alpha-CyD) in NIH3T3 and RAW264.7 cells. In addition, the gene transfer activity of alpha-CDE conjugate was superior to that of Lipofectin. The enhancing gene transfer effect of alpha-CDE conjugate may be attributable to not only increasing the cellular association, but also changing the intracellular trafficking of pDNA. These findings suggest that alpha-CDE conjugate could be a new preferable nonviral vector of pDNA.