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.
The presence of a doubly-linked naphthylene clip at the O -2 I and O -3 II positions in the secondary ring of β-cyclodextrin (βCD) derivatives promoted their self-assembly into head-to-head supramolecular dimers in which the aromatic modules act either as cavity extension walls (if the naphthalene moiety is 1,8-disubstituted) or as folding screens that separate the individual βCD units (if 2,3-disubstituted). Dimer architecture is governed by the conformational properties of the monomer constituents, as determined by NMR, fluorescence, circular dichroism, and computational techniques. In a second supramolecular organization level, the topology of the assembly directs host-guest interactions and, reciprocally, guest inclusion impacts the stability of the supramolecular edifice. Thus, inclusion of adamantane carboxylate, a well-known βCD cavity-fitting guest, was found to either preserve the dimeric arrangement, leading to multicomponent species, or elicit dimer disruption. The ensemble of results highlights the potential of the approach to program self-organization and external stimuli responsiveness of CD devices in a controlled manner while keeping full diastereomeric purity.
Original molecular vectors that ensure broad flexibility to tune the shape and surface properties of plasmid DNA (pDNA) condensates are reported herein.T he prototypic design involves ac yclodextrin (CD) platform bearing a polycationic cluster at the primary face and ad oubly linked aromatic module bridging two consecutive monosaccharide units at the secondary face that behaves as at opology-encoding element.S ubtle differences at the molecularl evel then translate into disparatem orphologies at the nanoscale, including rods, worms, toroids, globules, ellipsoids, and spheroids. In vitro evaluation of the transfection capabilities revealedm arked selectivity differences as af unction of nanocomplexm orphology. Remarkably high transfection ef-ficiencies were associatedw ith ellipsoidal or spherical shapesw ith al amellar internal arrangemento fp DNA chains and CD bilayers. Computational studies support that the stability of such supramolecular edifices is directly related to the tendency of the molecular vectort of orm noncovalent dimers upon DNA templating.B ecause the stabilityo ft he dimers depends on the protonation state of the polycationic clusters,t he coaggregates display pH responsiveness, which facilitates endosomal escapea nd timely DNA release, ak ey step in successful transfection. The results provide av ersatile strategy for the construction of fully synthetic and perfectly monodispersen onviral gene delivery systems uniquely suitedf or optimizations chemes.
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β-cyclodextrin (βCyD) derivatives equipped with aromatic appendages at the secondary face exhibit tailorable self-assembling capabilities. The aromatic modules can participate in inclusion phenomena and/or aromatic–aromatic interactions. Supramolecular species can thus form that, at their turn, can engage in further co-assembling with third components in a highly regulated manner; the design of nonviral gene delivery systems is an illustrative example. Endowing such systems with stimuli responsiveness while keeping diastereomeric purity and a low synthetic effort is a highly wanted advancement. Here, we show that an azobenzene moiety can be “clicked” to a single secondary O-2 position of βCyD affording 1,2,3-triazole-linked βCyD-azobenzene derivatives that undergo reversible light-controlled self-organization into dimers where the monomer components face their secondary rims. Their photoswitching and supramolecular properties have been thoroughly characterized by UV–vis absorption, induced circular dichroism, nuclear magnetic resonance, and computational techniques. As model processes, the formation of inclusion complexes between a water-soluble triazolylazobenzene derivative and βCyD as well as the assembly of native βCyD/βCyD-azobenzene derivative heterodimers have been investigated in parallel. The stability of the host–guest supramolecules has been challenged against the competitor guest adamantylamine and the decrease of the medium polarity using methanol–water mixtures. The collective data support that the E-configured βCyD-azobenzene derivatives, in aqueous solution, form dimers stabilized by the interplay of aromatic–aromatic and aromatic-βCyD cavity interactions after partial reciprocal inclusion. Photoswitching to the Z-isomer disrupts the dimers into monomeric species, offering opportunity for the spatiotemporal control of the organizational status by light.
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