Thais Carmona

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.

Binding of a neutral guest to cucurbiturils: photophysics, thermodynamics and molecular modelling

Steady-state and time-resolved fluorescence techniques were used to study the thermodynamics of binding of a neutral polarity-sensitive guest, the methyl 2-naphthalenecarboxylate (2MN), with three cucurbiturils (CBn; n = 6, 7 and 8) in water. Association constants (K) were obtained from nonlinear regression analysis of the fluorescence intensity against [CB] in the 5–45°C range. 2MN complexed with CB7 exhibited a 1:1 stoichiometry (K ≈ 103 M− 1 at 25°C); however, it hardly did with CB6 (K < 10 M− 1) and it did not with the larger CB8 macrocyclic ring. The (1:1) 2MN:CB7 complexation process was accompanied by a small unfavourable enthalpy change and was, therefore, entropically governed. Molecular mechanics and molecular dynamics calculations in the presence of water were also used to study the geometry of the complexes formed and the driving forces responsible for their formation. The results were compared with those previously obtained for the complexation of the same guest, 2MN, with natural α-, β- and γ-cyclodextrins.

Organisation and complexation of mono- and bis-β-cyclodextrins without chromophores with a fluorescence-sensitive probe in aqueous solutions

The behaviour of mono- and bis-β-cyclodextrin (CD) derivatives, namely 6I-deoxy-6I-[4-(hept-6-ynyl)-1H-1,2,3-triazolyl]-β-CD and 1,5-bis((1-(6I-deoxy-β-CD-6I-yl)-1H-1,2,3-triazol-4-yl)methoxy) pentyl, whose appended groups and inter-CD linkers, respectively, do not contain any chromophore, and their complexation with dimethyl-2,6-naphthalenedicarboxylate (DMN), a fluorescent polarity-sensitive probe in aqueous solutions, were investigated. Steady-state, time-resolved fluorescence, circular dichroism techniques, molecular mechanics (MM) and molecular dynamics (MD) simulations were employed. DMN appeared to slightly interact with the mono-β-CD and only unstable non-covalent dimers were formed. On the contrary, stable 1:1 and 2:1 stoichiometry complexes were obtained with bis-β-CD and DMN. A certain cooperativity due to the presence of both cavities and the linker favoured the formation of the complex 2:1 DMN:CD. DMN appeared to be axially oriented inside both CD cavities. MM and MD calculations also demonstrated the stability of the 1:1 and 1:2 stoichiometry complexes.

Predicting self-assembly and structure in diluted aqueous solutions of modified mono- and bis-β-cyclodextrins that contain naphthoxy chromophore groups

The water diluted solution behaviour of mono- and bis-β-cyclodextrin (mono- and bis-CD) derivatives, whose appended groups and inter-CD linkers contain a naphthoxy chromophore moiety, has been studied using steady-state and time-resolved fluorescence techniques, circular dichroism and molecular modelling. Mono-CD derivatives form non-covalent dimeric tail-to-tail supramolecular structures via the mutual partial penetration, through their primary sides, of axially oriented naphthoxy appended groups and the self-inclusion of the naphthoxy moiety is rather improbable. Non-covalent dimer formation may compete with any guest complexation. Nevertheless, these assemblies can be broken up by decreasing medium polarity or when the appended group is captured by macrorings such as cucurbit[7]urils or native βCDs. Bis-CD derivatives, however, do not exhibit self-association processes which were observed in the mono-derivatives. This is because the presence of the bulky naphthoxy group in the spacer keeps the βCD cavities, which are capable of accommodating an external guest, away from each other. The dinaphthoxy group, in the bis-NβCD, was located in a quasi-parallel plane conformation between both CDs.

Xylylene Clips for the Topology-Guided Control of the Inclusion and Self-Assembling Properties of Cyclodextrins

The topology of β-cyclodextrin can be molded, from toroidal to ovoid basket-shaped, by the installation of an o- or m-xylylene moiety connecting two consecutive d-glucopyranosyl units through the secondary O-2(I) and O-3(II) positions. This strategy can be exploited advantageously to precast the cavity for preferential inclusion of globular or planar guests as well as to privilege dimeric or monomeric species in water solution.