The affinity of hexakis(2-O-methyl-3,6-anhydro)-alpha-cyclodextrin (3,6-alpha-CDM) for Ba2+, Pb2+, Ca2+ and Sr2+ has been tested by H-1 NMR. It was shown that 3,6-alpha-CDM forms strong complexes in water with Pb2+ and Ba2+. The comparison with the parent hexakis (3, 6-anhydro)-alpha-cyclodextrin bearing hydroxyl groups instead of methoxy groups reveals that the O-CH3 substitution significantly improves the anhydro-cyclodextrin selectivity.

Using per(3,6-anhydro)cyclodextrin derivatives [per(3,6-anhydro)CD], it was possible to produce new lanthanide chelates by careful choice of the size and functional groups. Heptakis(3,6-anhydro-2-O-methyl)cyclomaltoheptaose fulfils the best criteria for complexation of lanthanide ions. Nuclear magnetic resonance was used to derive the association constants and the stoichiometries of these new complexes. Finally, a three-dimensional structure of these complexes consistent with the NMR data is proposed, to ascertain the position of lanthanide in the cavity of the per(3,6-anhydro)CD. For the present purposes, heptakis(2-O-acetyl-3,6-anhydro)cyclomaltoheptaose, octakis(2-O-acetyl-3,6-anhydro)cyclomaltooctaose, heptakis(3,6-anhydro-2-O-methyl)cyclomaltoheptaose and octakis(3,6-anhydro-2-O-methyl)cyclomaltooctaose have been synthesized and purified.

Propionate of vitamin A (PVA) is a highly instable and poorly water-soluble molecule which is of real interest for therapeutics. 1:1 γCD/PVA and 2:1 βCD/PVA inclusion complexes are formed. A stability study using NMR and HPLC indicated that βCD induced an accelerated degradation of PVA but, conversely γCD could protect it efficiently for many months. A very stable and soluble complex can be formed between heptakis(2,6-di- O-methyl)cyclomaltoheptaose (Dimeb) and vitamin A propionate. This solution was used to form an aqueous gel. The skin absorption of PVA and Dimeb through the stratum corneum, epidermis and the dermis of human skin were assayed by HPLC and by specific immunoassays, respectively. In presence of Dimeb, the amounts of PVA inside the different skins were significantly higher. It was also demonstrated that Dimeb penetrated in every cutaneous layer and showed no significant difference between free and bound forms.

Two methods usually used in the literature to determine stability constant values (Kc) of cyclodextrin complexes were compared: the phase solubility diagram and NMR spectroscopy. Two model drugs were used to determine limitations of both techniques: betamethasone and miconazole, with three cyclodextrins: fi-cyclodextrine (fiCD), dimethylated-fiCD (Dimeb) and trimethylated-fiCD (Trimeb). This study shows that both techniques can give the same Kc value if they are used in exactly the same conditions with well defined cyclodextrins. As a matter of fact, if the degree of substitution of cyclodextrin is not well defined (as it is often the case with Dimeb), results are biased. This study also shows that when interactions between both molecules are weak (<1000 M−1), stability constants can not be determined by NMR due to low chemical shift variations. The limitations of the phase solubility diagram method are an oversimplification of the solubility data which can lead to large errors in the calculation of the stability constant values. Moreover, this method is time and material consuming

We investigate the interfacial behavior of a new type of amphiphilic cyclic oligosaccharide obtained by grafting a phospholipid onto a methylated cyclodextrin. These compounds are able to form stable black foam films, the structure of which can be determined using X-ray reflectivity. These films consist of a highly hydrated bilayer of modified cyclodextrins which are remarkably thick due to their abundant hydration core. In the present paper, we explore the influence of cyclodextrin hydration on the film structure. The hydration rate of the films is tuned by changing the cyclodextrin methylation, by binding the modified cyclodextrins to various molecules (complex formation) and by exposing the films to IR radiation. In addition, we show that the gas permeability of these phospholipidyl-cyclodextrin films is governed by their central layer of bound water, which is an efficient barrier against gas permeation.

Few studies have been performed to assess the risk of skin damage by cyclodextrins (CD) and they have yielded contradictory results. The present study was conducted using the corneoxenometry bioassay on human stratum corneum to compare the skin compatibility of CD currently used in pharmaceutical preparations (βCD, γCD, Rameb, Dimeb, Trimeb, HP-βCD and HP-γCD) and that of new amphiphilic CD derivatives, namely, the phospholipidyl-CD (DMPE-Dimeb and DMPE-Trimeb). All the tested CD were well tolerated by the stratum corneum at a concentration of 5%. However, inter-individual reactivity was larger for DMPE-Dimeb, suggesting a more aggressive trend for this compound. Cutaneous Index of Mildness values obtained confirm that Dimeb is able to extract some skin components and shows that DMPE-Dimeb performs similarly.

Rameb (randomized dimethyl-β-cyclodextrin) was mixed with vitamin A propionate (PVA) (molar ratio 10/1 in water) and a water soluble complex was formed and studied by HPLC and NMR (structure, concentration and stability of PVA). Then solution was used to form an aqueous gel. The skin absorption of PVA through stratum corneum, epidermis and dermis of human skin (on modified Franz cells) was assayed by HPLC and was compared to that of a reference gel (or oil) without cyclodextrin. The solution obtained contains a maximum of 10 mg/mL PVA (if saturated with Rameb) and the PVA can remain stable up to 90 days in solution, and up to 1 year if freeze-dried (storage at 4 °C, in the dark). The results of the different experiments of skin distribution were statistically analyzed and show that when complexed with Rameb, the amount of PVA that penetrates each skin layer is significantly higher than pure PVA. The results also show that PVA cannot pass through the dermis and enter the circulation.

Recently, new cyclodextrin derivatives were synthesized and shown to exhibit strong amphiphilic properties. In this paper, we study the action of these new amphiphilic cyclodextrins on phospholipids. Mixed phospholipid/cyclodextrin derivative films were prepared and studied using X-ray reflectivity for various phospholipid/cyclodextrin ratios. A molar ratio of 3 provides a highly stable film the molecular structure of which has been investigated in detail. The cholesterol tail of the cyclodextrin molecule was found to be anchored into the phospholipid film. The cyclodextrin moieties exposed to the aqueous medium are prone to the addition of the guest molecule Dosulepin, making them of high interest for drug delivery. For this purpose and as an example of a potential application, this cyclodextrin molecular carrier property is also addressed to this complex film architecture.

Cholesteryl cyclodextrins, obtained by grafting a cholesterol moiety on the oligosaccharide core, combine the size selectivity of the cyclodextrin cavity with the carrier properties of model membrane systems such as micelles or liposomes. The cholesteryl cyclodextrins were incorporated as guests in chain perdeuterated dimyristoyl phosphatidylcholine (DMPC-d54) membranes. The deuterium nuclear magnetic resonance (NMR) spectra obtained with the A form of cholesteryl-beta-cyclodextrin (beta CC(A)), with a succinyl spacer inserted between the cholesterol moiety and the cyclodextrin headgroup, indicated that this compound induces a lateral phase separation of DMPC-d54, into a pure lipid phase and a cholesteryl cyclodextrin-rich phase. The lipid exchange rate between the two phases was slow on the NMR timescale (>10(-5) s), and two well-resolved spectral components could be detected. The laterally segregated mixed phase was observed at various membrane concentrations of cholesteryl cyclodextrin, even with dispersions containing only 5% of the derivative. The dePaked spectra allowed the determination of the relative amount of DMPC-d54 molecules contained in each phase, giving approximately 1 to 1.5 DMPC molecules per unit of beta CC(A). This ratio was found to be independent of the total membrane concentration of beta CC(A). The cholesteryl cylodextrin-rich phase was detected on a large range of temperature from -12 degrees C to 25 degrees C and exhibits a smooth transition from a fluid environment to a more ordered state, occurring approximately 0 degrees C. A boundary phase between the pure lipid and cyclodextrin-rich phase was detected at 19 degrees C just below the fluid-to-gel transition. The average orientational order was reduced in the cholesteryl cyclodextrin-rich phase, and quasi-independent of temperature, as opposed to the order parameters measured for the NMR signals of the pure lipid phase. However, the NMR data obtained with beta CC(A) deuterated on the cyclodextrin headgroup indicated that the latter was quasistatic, with very large order parameters (approximately 120 kHz) at all temperatures, suggesting strong interactions between neighboring cyclodextrin headgroups. The interactions of DMPC-d54 membranes with the B form of cholesteryl-beta-cyclodextrin, lacking the succinyl spacer, was also investigated in a parallel study. No lateral phase separation was found with this compound, indicating that the spatial location and a precise positioning (allowed by the spacer) of the cyclodextrin headgroup at the membrane interface was crucial for the stability of the cholesteryl cyclodextrin lamellar phase.

Isothiocyanates are natural products extracted from plants. These molecules which exhibit very interesting antifungal properties, are insoluble in water. To increase their solubility, we have prepared inclusion complexes with different cyclodextrins. Among all the isothiocyanates studied, we have investigated in more detail the structure of one complex: butyl-isothiocyanate and alpha-cyclodextrin, using two different techniques. Firstly, 1H NMR experiments were performed and revealed the inclusion phenomenon. In parallel, crystals of butyl-isothiocyanate–alpha-cyclodextrin were grown and their crystallographic structure determined. This confirmed the inclusion of the ITC molecules and allowed us to determine the exact position of the guest. Finally, we showed that even though the complex structure was determined separately in solution and in the solid state, the structural characterisations obtained with these two techniques are complementary, enhancing the respective benefits of X-ray crystallography and NMR.

The association of guest molecules in aggregates of a modified cyclodextrin, 6(I)-(cholest-5-en-3 alpha -ylamido)succinylamido-6'-deoxy-per(2,6-di-O-methyl)cyclomaltoheptaose, was investigated for four different sparingly water-soluble molecules and an anionic surfactant (sodium dodecyl sulfate). The binding and spatial proximities were demonstrated for these different guests by NMR (nuclear Overhauser effect pumping). By use of small-angle X-ray and neutron scattering, the microstructure at the supramolecular scale of the modified cyclodextrin micelle, i.e., aggregation number, charge, and volume, in the presence of guest molecules could be defined. From the analysis of the variations in terms of aggregation number and charge induced by the presence of the guest molecule, the cavity of the cyclodextrin was shown to remain available for solubilization and transport. The stability and specificity of the mixed micelle involving target molecules demonstrated here make these hydrophobically modified cyclodextrins good candidates as molecular carriers.

Some biological properties of new bifunctional conjugates designed for drug targeting were evaluated through in vitro experiments. Eight peptidylcyclodextrin compounds were used, which correspond to modified beta- or gamma-cyclodextrin (CD) grafted on neuropeptide substance P (SP) or a shorter derivative (SP(4-11)). Using anti-SP and anti-CD antibodies as molecular probes, we showed that the main structural features of the two moieties of these adducts were preserved. Binding experiments, using CHO cells expressing the human SP-specific NK1 receptor, demonstrated the functionality of all peptidylcyclodextrin derivatives, which exhibited IC50 values in a 10(-9)-10(-7) M range. All compounds were able to induce a pharmacological response, triggering phosphatidylinositol turnover with EC50 values in the same range as the natural ligand. Moreover, autoradiography analysis of rat spinal corn sections proved that [125I]SP binding was dose-dependently displaced by one selected compound (a gamma-CD-SP), showing a similar affinity of this adduct for the rat neurokinin 1 receptor. Our observations demonstrate that these peptidylcyclodextrins efficiently target NK1 receptor-expressing cells.

The grafting of a cholesterol derivative onto a methylated cyclodextrin through a spacer arm produces an amphiphilic compound exhibiting high solubility in water. This new molecule was fully characterized in terms of chemical and optical purities by high resolution NMR and mass spectrometry. An analysis of its behavior in aqueous solution using surface tension measurements and light, small-angle X-ray, and neutron scattering techniques proved that it self-assembles into monodisperse spherical micelles with an average aggregation number of 24. The micelles can be described as two-shell objects, the cyclodextrin moieties being exposed to the aqueous medium, making them prone to include guest molecules in the cavities. These objects can therefore be of high interest for the targeting of biologically important molecules and especially for the delivery of drugs.

The affinity of hexakis(2-O-methyl-3,6-anhydro)-α-cyclodextrin (3,6-α-CDM) for Ba2+, Pb2+, Ca2+ and Sr2+ has been tested by 1H NMR. It was shown that 3,6-α-CDM forms strong complexes in water with Pb2+ and Ba2+. The comparison with the parent hexakis(3,6-anhydro)-α-cyclodextrin bearing hydroxyl groups instead of methoxy groups reveals that the O-CH3 substitution significantly improves the anhydro-cyclodextrin selectivity.

Both (-)-geosmin and (+)-2-methyl-isoborneol are the main compounds responsible for the unpleasand smells found in the vicinity of water-processing plant. Attempts to eliminate them using oxidation, filtration and/or biologic degradation processes are only partly efficient. The use of cage molecules could provide an alternative solution. In this respect, cyclodextrins and derivatives have demonstrated their role as candidates as hosts for these highly hydrophobic compounds. In this paper, we evidence the complexation of above mentionned pollutants by cyclodextrins using high-resolution proton Nuclear Magnetic Resonance spectroscopy. The latter method is also used to afford a three-dimensional structure of inclusion complexes in solution and to show that cyclodextrins can as well discriminate between the optical isomers of synthetic geosmin and methyl-isoborneol. Finally, a solution to the problem of waste waters is proposed.

Nuclear magnetic resonance of proton (1H-NMR) is a powerfull tool to study “host-guest” interactions. Classical “NOESY-type” experiments and especially the ROESY sequence are useful to determine interactions in cyclodextrins domain. But, due to intrinsic problems, the basic ROESY sequence can lead to misinterpretations. We investigate in this work alternative 2D 1H- NMR “ROESY-type” experiments, and estimate their relative advantages on the well-known case of β-CD/PGE2 complex.

The cation chelating properties of per(3,6 anhydro) α-cyclodextrin, [A36] and of per(3,6 anhydro, 2-O methyl) α-cyclodextrin, [A36M] were investigated by mass and NMR spectroscopy. A36 forms 1: 1 complexes with lead (K=2500 M -1), and also with strontium and potassium with a fast exchange rate kinetics. However, the formation of A36-Pb complex results in a dramatic enhancement of the haemolytic properties. Permethylation at the position 2 (A36M) confers an extreme affinity for Ba2+, Pb2+, Sr2+ and Ca2+ following a slow rate exchange process and a 1: 1 stoichiometry. Besides, a weak 1:1 A36M-K complex is also found, with a fast exchange rate. By opposition with A36. A36M complexes showed no haemolytic properties.

La RMN constitue l'outil idéal pour la mise en évidence, en solution aqueuse, de complexes d'inclusion de cyclodextrine ainsi que pour la détermination fine de leurs structures. Ainsi des méthodes RMN spécifiques sont utilisées pour obtenir les caractéristiques thermodynamiques et structurales d'un complexe d'inclusion β-cyclodextrine/ prostaglandine E2 en milieu aqueux. De plus, les expériences de type NOESY et ROESY sont souvent utilisées pour mettre en évidence les intéractions hôte-invité. Mais pour des problèmes intrinsèques, la séquence de base de ROESY peut conduire à des erreurs d'interprétation. Nous avons évalué des séquences ROESY modifiées et estimé leur avantages respectifs sur le complexe β-CD/PGE2.

Cyclodextrins are natural cyclic oligosaccharides and behave as cage molecules. Since their internal cavity is relatively hydrophobic compared to the highly hydrophilic external face, the cyclodextrins and their derivatives exhibit the capacity to incorporate hydrophobic guests in their internal cavity leading to a wealth of applications. NMR appears as the most efficient approach to investigate and evidence the formation of inclusion complexes in aqueous solution. Dedicated experiments are used to derive thermodynamic properties as well as "molecular model" for the solution structure of inclusion complexes as beta-cyclodextrin/Prostaglandin E-2 complex. Classical "NOESY-type" experiments and especially the ROESY sequence are used to proove interactions in cyclodextrin domain. But, due to intrinsic problems, the basic ROESY sequence can lead to misinterpretations. We investigate in this work alternative 2D 1H-NMR ROESY-type experiments and estimated their relative advantages.