Self-assembled cyclodextrin (CD)-DNA nanoparticles (CDplexes) exhibiting transfection efficiencies significantly higher than PEI-based polyplexes have been prepared from homogeneous seven-fold symmetric polyaminothiourea amphiphiles constructed on a beta-cyclodextrin scaffold.

A molecular-diversity-oriented approach for the preparation of well-defined polycationic amphiphilic cyclodextrins (paCDs) as gene-delivery systems is reported. The synthetic strategy takes advantage of the differential reactivity of primary versus secondary hydroxyl groups on the CD torus to regioselectively decorate each rim with cationic elements and lipophilic tails, respectively. Both the charge density and the hydrophobic-hydrophilic balance can be finely tuned in a highly symmetrical architecture that is reminiscent of both cationic lipids and cationic polymers, the two most prominent types of nonviral gene vectors. The monodisperse nature of paCDs and the modularity of the synthetic scheme are particularly well suited for structure-activity relationship studies. Gel electrophoresis revealed that paCDs self-assemble in the presence of plasmid DNA (pDNA) to provide homogeneous, stable nanoparticles (CDplexes) of 70-150 nm that fully protect pDNA from the environment. The transfection efficiency of the resulting CDplexes has been investigated in vitro on BNL-CL2 and COS-7 cell lines in the absence and presence of serum and found to be intimately dependent on architectural features. Facial amphiphilicity and the presence of a cluster of cationic and hydrogen-bonding centers for cooperative and reversible complexation of the polyanionic DNA chain is crucial to attain high transgene expression levels with very low toxicity profiles. Further enhancement of gene expression, eventually overcoming that of polyplexes from commercial polyethyleneimine (PEI) polymers (22 kDa), is achieved by building up space-oriented dendritic polycationic constructs.

Fully homogeneous facial amphiphiles consisting in a cyclodextrin (CD) platform onto which a polycationic cluster and a multi-tail hydrophobic moiety have been installed (polycationic amphiphilic CDs; paCDs) self-organized in the presence of plasmid DNA to form nanometric complexes (CDplexes) which exhibit broad-range transfection capabilities. We hypothesized that biorecognizable moieties located at the hydrophilic rim in the CD scaffold would be exposed at the surface of the corresponding nanoparticles after DNA-promoted aggregation, endowing the system with molecular recognition abilities towards cell receptors. This concept has been demonstrated by developing an efficient synthetic strategy for the preparation of multivalent polycationic glyco-amphiphilic CDs (pGaCDs). Self-assembled nanoparticles obtained from mannosylated pGaCDs and pDNA (average hydrodynamic diameter 80 nm) have been shown to be specifically recognized by mannose-specific lectins, including concanavalin A (Con A) and the human macrophage mannose receptor (MMR). Further macrophage adhesion studies indicated that unspecific binding, probably due to electrostatic interactions with negatively charged cell membrane components, can also operate. The relative specific versus non-specific internalization is dependent on the pGaCD:pDNA proportion, being optimal at a protonable nitrogen/phosphate (N/P) ratio of 5. The resulting GlycoCDplexes were shown to specifically mediate transfection in Raw 264.7 (murine macrophage) cells expressing the mannose-fucose receptor in vitro. FACS experiments confirmed that transfection using these nanoparticles is mannose-dependent, supporting the potential of the approach towards vectorized gene delivery.

Monodisperse facial amphiphiles consisting of a β-cyclodextrin (βCD) platform exposing a multivalent display of cationic groups at the primary rim and bearing hydrophobic chains at the secondary oxygens have been prepared by implementing two very robust "click" methodologies, namely cuprous cation-catalyzed azide-alkyne cycloaddition (CuAAC) and thiourea-forming reaction. Most interestingly, the use of solid-supported Cu(I) catalysts was found to be very well suited for multiple CuAAC while facilitating purification of the C(7)-symmetric macromolecular triazole adducts. The strategy is compatible with molecular diversity-oriented approaches, which has been exploited to generate a small library of click polycationic amphiphilic CDs (paCDs) for assessing the influence of structural modifications in the ability to complex, compact, and protect pDNA and the efficiency of the resulting paCD:pDNA nanocomplexes (CDplexes) to deliver DNA into cells and promote transfection. The results indicate that fine-tuning the hydrophilic/hydrophobic balance is critical to achieve optimal self-assembling properties and stability of the resulting CDplexes in saline- and serum-containing media. Triazole-type paCDs were, in general, less efficient in promoting gene transfection than thiourea-type derivatives. Nevertheless, the current body of results support that the "dual click" approach implying sequential CuAAC and thiourea-forming reactions represents a versatile strategy to optimize the gene delivery capabilities of cyclodextrin-based facial amphiphiles.

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We describe the synthesis of a series of alpha-galacto-omega-polyamine double-chain bolaamphiphiles (Gal-CL) and report on the gene transfer mediated with lipoplexes they form either when used in conjunction with DOPE or with pcTG90:DOPE. Lipofection was investigated with human HepG2 and murine BNL-CL2 hepatocytes expressing the asialoglycoprotein (ASGP) receptor which displays a high affinity for galactosyl residues, and with A549 cells which do not express ASGP. Our results show that cationic N/P = 5 and 2.5 Gal-CL lipoplexes constitute very efficient nonspecific gene transfer systems. Lipofection experiments performed in the presence of asialofetuin (a high affinity ligand of ASGP) led us to evidence also the involvement of a specific receptor-mediated endocytosis pathway for the transfection of the ASGP(+) HepG2 or BNL-CL2 hepatocytes with some Gal-CL formulations. This work suggests that targetable lipopolyamines presenting a single galactose residue appear as promising synthetic vectors for specific gene delivery to ASGP(+) cells.

An efficient general strategy for the incorporation of functional elements onto the secondary hydroxyl rim of beta-cyclodextrin has been developed and applied to the synthesis of a novel series of C7-symmetric homogeneous macromolecular polycations with improved DNA complexing and delivery properties.

International audienceExperiments of magnetolysis, i.e., destruction of cells induced with magnetic particles (MPs) submitted to the application of a magnetic field, were conducted on HepG2 cancer cells. We herein demonstrate the usefulness of combining anisotropic MPs with an alternative magnetic field in magnetolysis. Thus, the application of an alternative magnetic field of low frequency (a few Hertz) in the presence of anisotropic, submicronic particles allowed the destruction of cancer cells "in vitro". We also show that a constant magnetic field is far less efficient than an oscillating one. Moreover, we demonstrate that, at equal particle volume, it is much more efficient to utilize spindle shaped particles rather than spherical ones. In order to get deeper insight into the mechanism of magnetolysis experiments, we performed a study by AFM, which strongly supports that the magnetic field induces the formation of clusters of particles becoming then large enough todamage cell membranes