The Structure of the First Supramolecular α-Cyclodextrin Complex with an Aliphatic Monofunctional Carboxylic Acid

Evidence of the Disassembly of α-Cyclodextrin-octylamine Inclusion Compounds Conjugated to Gold Nanoparticles via Thermal and Photothermal Effects

Cyclodextrin (CD) molecules form inclusion compounds (ICs), generating dimers that are capable of encapsulating molecules derived from long-chain hydrocarbons. The aim of this study is to evaluate the structural changes experienced by ICs in solution with increasing temperatures. For this, a nuclear magnetic resonance (¹H-NMR) titration was performed to determinate the stoichiometric α-cyclodextrin (α-CD):octylamine (OA) 2:1 and binding constant (k = 2.16 M⁻²) of ICs. Solution samples of α-CD-OA ICs conjugated with gold nanoparticles (AuNPs) were prepared, and ¹H-NMR spectra at different temperatures were recorded. Comparatively, ¹H-NMR spectra of the sample irradiated with a laser with tunable wavelengths, with plasmons of conjugated AuNPs, were recorded. In this work, we present evidence of the disassembly of ICs conjugated with AuNPs. Thermal studies demonstrated that, at 114 °C, there are reversible rearrangements of the host and guests in the ICs in a solid state. Migration movements of the guest molecules from the CD cavity were monitored via temperature-dependent ¹H-NMR, and were verified comparing the chemical shifts of octylamine dissolved in deuterated dimethylsulfoxide (DMSO-d₆) with the OA molecule included in α-CD dissolved in the same solvent. It was observed that, at 117 °C, OA exited the α-CD cavity. CD IC dimer disassembly was also observed when the sample was irradiated with green laser light.

Selective nanodecoration of modified cyclodextrin crystals with gold nanorods

Gold nanorods (AuNRs) stabilized by cetyltrimethylammonium bromide (CTAB) were deposited onto crystals of α-cyclodextrin (α-CD) inclusion compounds (ICs) that contained octanethiol (OT) as guest molecules. The nanodecoration was produced specifically at the {001} crystal planes through interaction between the -SH groups of the ICs and the AuNRs.

Synthesis and biological evaluation of multivalent carbohydrate ligands obtained by click assembly of pseudo-rotaxanes

Multivalent carbohydrate ligands have been prepared by assembling alpha-cyclodextrin-based pseudo-rotaxanes through "click chemistry". The inclusion complex formed by a lactosyl-alpha-CD conjugate and a decane axle carrying a lactosyl stopper at one extremity and an azido group at the other end was dimerized by bis-propargyl spacers of different lengths to provide oligorotaxanes having adjustable threading ratios. For the first time, saccharidic ligands have been introduced on rotaxanes both as a biological recognition element and as a capping group. The supramolecular species have been isolated and characterized by mass spectrometry as well as by 1D and DOSY NMR experiments. Their ability to inhibit the binding of Arachis hypogaea agglutinin to asialofetuin, assayed by enzyme linked lectin assays (ELLA), was shown to be valency-dependent.