γ-Cyclodextrin Forms a Highly Compressible Complex with 1-Adamantanecarboxylic Acid

Volumetric Properties of Four-Stranded DNA Structures

Four-stranded non-canonical DNA structures including G-quadruplexes and i-motifs have been found in the genome and are thought to be involved in regulation of biological function. These structures have been implicated in telomere biology, genomic instability, and regulation of transcription and translation events. To gain an understanding of the molecular determinants underlying the biological role of four-stranded DNA structures, their biophysical properties have been extensively studied. The limited libraries on volume, expansibility, and compressibility accumulated to date have begun to provide insights into the molecular origins of helix-to-coil and helix-to-helix conformational transitions involving four-stranded DNA structures. In this article, we review the recent progress in volumetric investigations of G-quadruplexes and i-motifs, emphasizing how such data can be used to characterize intra-and intermolecular interactions, including solvation. We describe how volumetric data can be interpreted at the molecular level to yield a better understanding of the role that solute-solvent interactions play in modulating the stability and recognition events of nucleic acids. Taken together, volumetric studies facilitate unveiling the molecular determinants of biological events involving biopolymers, including G-quadruplexes and i-motifs, by providing one more piece to the thermodynamic puzzle describing the energetics of cellular processes in vitro and, by extension, in vivo.

Effect of Dimethyl Sulfoxide on the Binding of 1-Adamantane Carboxylic Acid to β- and γ-Cyclodextrins

Most therapeutic targets are proteins whose binding sites are hydrophobic cavities. For this reason, the majority of drugs under development are hydrophobic molecules exhibiting low solubility in water. To tackle this issue, a few percent of cosolvent, such as dimethyl sulfoxide (DMSO), is usually employed to increase drug solubility during the drug screening process. However, the few published studies dealing with the effect of adding DMSO showed that the affinity of hydrophobic ligands is systematically underestimated. To better understand the effect of DMSO, there is a need of studying its effect on a large range of systems. In this work, we used β- and γ-cyclodextrins (made of 6 and 7 α-d-glucopyranoside units, respectively) as models of hydrophobic cavities to investigate the effect of the addition 5% DMSO on the affinity of 1-adamantane carboxylic acid (ADA) to these cyclodextrins. The two systems differ by the size of the cyclodextrin cavity. The evaluation of binding constants was performed using ultrasound velocimetry, nuclear magnetic resonance spectroscopy, and molecular simulations. All techniques show that the presence of 5% DMSO does not significantly modify the affinity of ADA for γ-cyclodextrin, while the affinity is dramatically reduced for β-cyclodextrin. The bias induced by the presence of DMSO is thus more important when the ligand volume better fits the cyclodextrin cavity. Our work also suggests that free energy calculations provide a sound alternative to experimental techniques when dealing with poorly water-soluble drugs.

Targeting ETS1 with RNAi-based supramolecular nanoassemblies for multidrug-resistant breast cancer therapy

Overexpression of erythroblastosis virus E26 oncogene homolog 1 (ETS1) gene is correlated with both tumor progression and poor response to chemotherapy in cancer treatment, and the exploitation of RNA interference (RNAi) technology to downregulate ETS1 seems to be a promising approach to reverse multidrug-resistant cancer cells to chemotherapy. Hence, the RNAi-based nanomedicine which is able to simultaneously downregulate ETS1 expression and to deliver chemotherapeutic agents may improve multidrug-resistant cancer therapy synergistically. In this study, we developed a supramolecular nanoassembly that could deliver siRNA targeting ETS1 (siETS1) and doxorubicin (DOX) as an effective nanomedicine to achieve successful chemotherapy towards multidrug-resistant breast cancer. The nanotherapeutic system was prepared by loading adamantane-conjugated doxorubicin (AD) into polyethyleneimine-modified (2-hydroxypropyl)-γ-cyclodextrin (HP) through the supramolecular assembly to form AD-loaded HP (HPAD), followed by electrostatically-driven self-assembly between siETS1 and HPAD. When the HPAD/siETS1 nanoassemblies were delivered into drug-resistant MCF-7/ADR cells, the drug efflux was significantly reduced as a result of simultaneous silencing of ETS1 and MDR1 genes. Importantly, the HPAD/siETS1 nanoassembly could enhance drug residence time at tumor site, and effectively inhibit drug-resistant tumor growth due to the inhibition of angiogenesis and necrosis in tumor tissues. Western blot analysis indicated that the gene expression of both ETS1 and MDR1 in vivo was considerably downregulated after the drug-resistant tumor-bearing mouse was treated with HPAD/siETS1 nanoassemblies. This study offers a new therapeutic delivery strategy targeting ETS1 for the effective multidrug-resistant chemotherapy.

Host-Guest-Mediated DNA Templation of Polycationic Supramolecules for Hierarchical Nanocondensation and the Delivery of Gene Material

Only a few examples of monodisperse molecular entities that can compact exogenous nucleic acids into nanocomplexes, protect the cargo from the biological environment, facilitate cell internalization, and promote safe transfection have been reported up to date. Although these species open new venues for fundamental studies on the structural requirements that govern the intervening processes and their application in nonviral gene-vector design, the synthesis of these moieties generally requires a relatively sophisticated chemistry, which hampers further development in gene therapy. Herein, we report an original strategy for the reversible complexation and delivery of DNA based on the supramolecular preorganization of a β-cyclodextrin-scaffolded polycationic cluster facilitated by bisadamantane guests. The resulting gemini-type, dual-cluster supramolecules can then undergo DNA-templated self-assembly at neutral pH value by bridging parallel DNA oligonucleotide fragments. This hierarchical DNA condensation mechanism affords transfectious nanoparticles with buffering capabilities, thus facilitating endosomal escape following cell internalization. Protonation also destabilizes the supramolecular dimers and consequently the whole supramolecular edifice, thus assisting DNA release. Our advanced hypotheses are supported by isothermal titration calorimetry, NMR and circular dichroism spectroscopic analysis, gel electrophoresis, dynamic light scattering, TEM, molecular mechanics, molecular dynamics, and transfection studies conducted in vitro and in vivo.