Α-cyclodextrin Inclusion Complex Research Articles

Molecularly Imprinted Electrochemical Sensor Based on α-Cyclodextrin Inclusion Complex and MXene Modification for Highly Sensitive and Selective Detection of Alkylresorcinols in Whole Wheat Foods.

Authenticating whole wheat foods poses a significant challenge for both the grain industry and consumers. Alkylresorcinols (ARs), serving as biomarkers of whole wheat, play a crucial role in assessing the authenticity of whole wheat foods. Herein, we introduce a novel molecularly imprinted electrochemical sensor with modifications involving a molecularly imprinted polymer (MIP) and MXene nanosheets, enabling highly sensitive and selective detection of ARs. Notably, we specifically chose 5-heneicosylresorcinol (AR21), the predominant homologue in whole wheat, as the template molecule. α-Cyclodextrin and acrylamide served as dual functional monomers, establishing a robust multiple interaction between the MIP and AR21. As a result, the sensor exhibited a wide linear range of 0.005 to 100 μg·mL-1 and a low detection limit of 2.52 ng·mL-1, demonstrating exceptional selectivity and stability. When applied to commercial whole wheat foods, the assay achieved satisfactory recoveries and accuracy, strongly validating the practicality and effectiveness of this analytical technique.

Water-responsive supercontractile polymer films for bioelectronic interfaces.

Connecting different electronic devices is usually straightforward because they have paired, standardized interfaces, in which the shapes and sizes match each other perfectly. Tissue-electronics interfaces, however, cannot be standardized, because tissues are soft1-3 and have arbitrary shapes and sizes4-6. Shape-adaptive wrapping and covering around irregularly sized and shaped objects have been achieved using heat-shrink films because they can contract largely and rapidly when heated7. However, these materials are unsuitable for biological applications because they are usually much harder than tissues and contract at temperatures higher than 90 °C (refs. 8,9). Therefore, it is challenging to prepare stimuli-responsive films with large and rapid contractions for which the stimuli and mechanical properties are compatible with vulnerable tissues and electronic integration processes. Here, inspired by spider silk10-12, we designed water-responsive supercontractile polymer films composed of poly(ethylene oxide) and poly(ethylene glycol)-α-cyclodextrin inclusion complex, which are initially dry, flexible and stable under ambient conditions, contract by more than 50% of their original length within seconds (about 30% per second) after wetting and become soft (about 100 kPa) and stretchable (around 600%) hydrogel thin films thereafter. This supercontraction is attributed to the aligned microporous hierarchical structures of the films, which also facilitate electronic integration. We used this film to fabricate shape-adaptive electrode arrays that simplify theimplantation procedure through supercontraction and conformally wrap around nerves, muscles and hearts of different sizes when wetted for in vivo nerve stimulation and electrophysiological signal recording. This study demonstrates that this water-responsive material can play an important part in shaping the next-generation tissue-electronics interfaces as well as broadening the biomedical application of shape-adaptive materials.

New type polyrotaxanes based on polyethyleneimine and α-cyclodextrin

Functional polyrotaxanes of N-alkanoylpolyethyleneimine@ α-cyclodextrin type are synthesized by acylation of the polypseudorotaxane precursor, namely, a polyethylenimine@ α-cyclodextrin inclusion complex, with excess of carboxylic acid anhydrides. In the course of the processing, α-cyclo-dextrin moieties are also fully O-acylated. The introduction of acyl moieties into polyethyleneimine backbone prevents the expulsion of α-cyclodextrin rings from this backbone.

Inclusion complexation of chloroquine with α and β-cyclodextrin: Theoretical insights from the new B97-3c composite method

Inclusion complexes of α-cyclodextrin (α-CD) and β-cyclodextrin (β-CD) with chloroquine drug (CQ) have been explored using the recently developed B97-3c composite method. Calculated complexation energies were negatively higher for both CQ@α-CD and CQ@β-CD complexes indicating a thermodynamically favorable process. The inclusion mode involves the partial encapsulation of the fused aromatic ring of chloroquine in α- and β-CD cavities from the wider side, in agreement with proton NMR data. NCI-RDG, IGM and NBO analysis showed that weak Van der Waals intermolecular interactions and in particular strong intermolecular hydrogen bonding stabilize the inclusion of chloroquine that forms complex with β-CD more favorably than with α-CD.

Multi-spectroscopic investigation on the inclusion complexation of α-cyclodextrin with long chain ionic liquid

Host-guest interaction of ionic liquid (IL) 1-decyl-3-methylimidazolium tetrafluoroborate [Dmim][BF4] within α-cyclodextrin (α-CD) has been studied by different spectroscopic techniques and our investigated system is significant in the field of supramolecular chemistry and medicine. Benesi-Hildebrand correlation is used to study the stoichiometry of the host-guest complexation. Here concurrence with FT-IR and dynamic light scattering (DLS) results, it is shown that α-CD interacts with [Dmim][BF4], induces compositional and structural changes. Characterization of the [Dmim][BF4]-α-CD inclusion complex (IC) by 1H NMR spectroscopy provided information about the complexation among the [Dmim][BF4] and α-CD molecules and the structure of the ICs. 1H NMR results confirm the formation of inclusion complex (IC) while UV–vis spectroscopy, DLS and FTIR studies show development of IC with 1:1 stoichiometry. The present study can be highly applicable in the fields of pharmaceutical science, supra-molecular chemistry and material science.

Calorimetric studies of α-cyclodextrin inclusion complexes with carbendazim and thiabendazole

ABSTRACT Calorimetric titration studies of carbendazim and thiabendazole solutions with α-cyclodextrin solutions were performed. The study involved the determination stoichiometry of the resulting inclusion complexes, their formation constant values and thermodynamic parameters (molar enthalpy and molar entropy) characterising the ligand-receptor complexes. The ITC calorimetric measurements were supplemented with UV–VIS spectroscopic measurements to determine the increase in the water solubility of test fungicides in the presence of increasing concentration of α-cyclodextrin.

Prediction of correct intermolecular interactions in host-guest systems involving cyclodextrins

Investigations of intermolecular interactions are of great interest and many studies in this field focus on the use of theoretical computational chemistry. Commonly the systems of interest comprise molecules with hundreds of atoms, limiting the use of ab initio theoretical methods. In order to investigate the accuracy of different quantum chemical methods, a systematic study was carried out involving 15 inclusion complexes of α-cyclodextrin and 28 complexes of β-cyclodextrin. The accuracy of semiempirical methods in geometry prediction was evaluated in comparison to crystallographic data, with AM1 and PM3 showing the best results. Subsequently, the accuracy of semiempirical methods in predicting both geometry and interaction energy was studied using the results of DFT calculation as reference, with and without dispersion correction. The best method was B3LYP/6-31G(d,p) with D3 correction, followed by PM6 with D3 correction with similar accuracy. However, as the DFT method require a high computational cost for large systems, PM6-D3 is the method recommended for the systems studied here. The main conclusion is the need to develop a semiempirical method capable of correctly describing the interaction energy, which must correspond to an accurate geometry.

X-ray crystal structures of α-cyclodextrin–5-hydroxypentanoic acid, β-cyclodextrin–5-hydroxypentanoic acid, β-cyclodextrin–ε-caprolactone, and β-cyclodextrin–ε-caprolactam inclusion complexes

Inclusion complexes of α-cyclodextrin–5-hydroxypentanoic acid (αCD-5HPA) and β-cyclodextrin–5-hydroxypentanoic acid (βCD-5HPA) were respectively prepared from aqueous solutions of cyclodextrins (CDs) and δ-valerolactone (δVL). The solutions were allowed to stand at room temperature for 1 week to give single crystals preferable for X-ray crystallography. δVL was found to be hydrolyzed in the presence of αCD or βCD to give the inclusion complexes of CDs and the hydrolysate. On the contrary, inclusion complexes of βCD–e-caprolactone (βCD–eCL) and βCD–e-caprolactam (βCD–eCLm) were respectively obtained from the aqueous solution of βCD and eCL/eCLm without hydrolysis. Packing structure of the complexes showed that αCD-5HPA forms a layer-type structure of the αCD host molecules, and that βCD-5HPA, βCD–eCL and βCD–eCLm form cage-type structures of the βCDs molecules. In these crystal structures, the guest molecules are included in the CD cavity through the hydrogen bonds or hydrophobic interactions.

Effect of stepwise humidity change on the release rate constant of 1-methylcyclopropene (1-MCP) in a cyclodextrin inclusion complex powder

The release behaviour of 1-methylcyclopropene (1-MCP) is important during postharvest treatment of fruit and vegetable. Effect of humidity and temperature on the release rate of 1-MCP in an α-cyclodextrin (α-CD) inclusion complex powder were investigated on the potential of direct application of 1-MCP inclusion complex powder and developing of functional packaging. The aim of this research was to study the release behaviour of 1-MCP from an inclusion complex powder under a stepwise humidity change. 1-MCP release experiments were conducted using a dynamic vapour sorption (DVS) system at different temperatures (40, 50, and 60 °C) with stepwise humidity changes (20% RH for 2 h to 40, 50, 60, and 80% RH for 2 h, respectively). The results showed that the release rate constant of 1-MCP from inclusion complex powders increased linearly with moisture concentration at 40, 50, and 60% RH. The highest release rate constant of 1-MCP was 1.5 × 10−3 s−1 for 80% RH at 60 °C. The activation energy at the highest humidity condition of 80% RH was 27.5 kJ/mol. The release rate constant of 1-MCP from the inclusion complex powders was well correlated with a first-order release rate equation. The results obtained showed that 1-MCP inclusion complex in α-CD has a potential as an active compound that could be incorporated into active packaging systems where storage condition below 60% RH is needed.

α-Cyclodextrin concentration-controlled thermo-sensitive supramolecular hydrogels

Supramolecular hydrogels (SHGs) built from inclusion complex of macrocyclic compound α-cyclodextrin (α-CD) and poly(ethylene glycol) (PEG) have attracted much interest due to their excellent biocompatibility and great potential for biomedical applications. In this work, the hydrogen bond of nucleic acid was introduced into the above-mentioned SHG by syntheses of nucleobase guanine/cytosine (G/C)-terminated PEG (G-PEG-G/C-PEG-C). The base-pairing interaction between G and C as an additional network junction effectively enhanced storage moduli (G's) of the hydrogels. Moreover, the prepared hydrogels exhibited excellent cytocompatibility and property for controlled drug release, outlining the potential of thermo-sensitive construct for biomedical applications, such as local chemotherapy of cancers.

Inclusion Complex of α-Cyclodextrin with Poly(ethylene glycol) Brush

The inclusion complex (IC) of α-cyclodextrin (α-CD) with poly(ethylene glycol) (PEG) brush was investigated by neutron reflectometry and grazing-incidence wide-angle X-ray scattering. When the PEG brush was exposed to 10% aqueous α-CD solution, an IC consisting of randomly oriented α-CD polycrystals appeared. On the other hand, when the PEG brush was exposed to 5% aqueous α-CD solution, a uniform 10-nm-thick IC layer with α-CD stacked perpendicular to the substrate was formed. A 10-nm-thick IC was also found in the diluted PEG brush, even when exposed to the 10% α-CD solution. The characteristic 10-nm-thick layer is related to the folded crystalline structure of α-CD on the PEG brush.

Pickering emulsions with α-cyclodextrin inclusions: Structure and thermal stability

This paper explores structural, interfacial and thermal properties of two types of Pickering emulsions containing α-cyclodextrin inclusion complexes: on one hand, emulsions were obtained between aqueous solutions of α-cyclodextrin and different oils (fatty acids, olive oil, silicone oil) and on the other hand, emulsions were obtained between these oils, water and micro or nano-platelet suspensions with inclusion complexes of hydrophobically-modified polysaccharides. The emulsions exhibit versatile properties according to the molecular architecture of the oils. Experiments were performed by microcalorimetry, X-ray diffraction and confocal microscopy. The aptitude of oil molecules to be threaded in α-cyclodextrin cavity is a determining parameter in emulsification and thermal stability. The heat flow traces and images showed dissolution, cooperative melting and de-threading of inclusion complexes which take place progressively, ending at high temperatures, close or above 100°C. Another important feature observed in the emulsions with micro-platelets is the partial substitution of the guest molecules occurring at room temperature at the oil/water interfaces without dissolution, possibly by a diffusion mechanism of the oil. Accordingly, the dissolution and the cooperative melting temperatures of the inclusion crystals changed, showing marked differences upon the type of guest molecules. The enthalpies of dissolution of crystals were measured and compared with soluble inclusions.

Host-Guest Inclusion Complexation of α-Cyclodextrin and Triiodide Examined Using UV-Vis Spectrophotometry.

The historically relevant host-guest complexation of α-cyclodextrin (α-CD) and triiodide (I3(-)) in aqueous solution was examined using a systematic UV-vis spectrophotometric approach. This particular system is experimentally challenging because of the coupled equilibria, namely, I2 + I(-) ⇌ I3(-) and α-CD + I3(-) ⇌ α-CD·I3(-). We therefore developed a unique experimental approach that allowed us to determine the concentration of all iodine species. This enabled us to unequivocally demonstrate that the large increase in the UV absorbance with added α-cyclodextrin is due to an increase in the overall triiodide concentration as α-CD essentially converts iodine to triiodide according to the coupled equilibria. Herein we report (a) the complexation stoichiometry is 1:1 (i.e., the host-guest complex is α-CD·I3(-)), (b) the binding constant is KH-G = (1.35 ± 0.05) × 10(5) M(-1) at room temperature, and

An injectable, dual pH and oxidation-responsive supramolecular hydrogel for controlled dual drug delivery

A novel pH and oxidation dual-responsive and injectable supramolecular hydrogel was developed, which was formed from multi-block copolymer poly(ether urethane) (PEU) and α-cyclodextrin (α-CD) inclusion complexes (ICs). The PEU copolymer was synthesized through a simple one-pot condensation polymerization of poly(ethylene glycol), di(1-hydroxyethylene) diselenide, dimethylolpropionic acid and 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate. In aqueous solution, the amphiphilic PEU copolymers could self-assemble into nanoparticles with dual pH and oxidation sensitivities, which can efficiently load and controllably release a hydrophobic drug indomethacin (IND). Then a dual-drug loaded supramolecular hydrogel was obtained by addition of α-CD and hydrophilic model drug (rhodamine B, RB) into the resulting IND-loaded PEU nanoparticle solution. The rheology studies showed that the supramolecular hydrogels with good injectability underwent a pH-induced reversible sol–gel transition and an oxidation-triggered degradation behavior. The in vitro drug release results demonstrated that the hydrogels showed dual drug release behavior and the release rates could be significantly accelerated by addition of an oxidizing agent (H2O2) or increasing the environmental pH. Therefore, this injectable and dual stimuli-responsive supramolecular hydrogel based codelivery systems could potentially be a promising candidate for controlled drug delivery systems.

Controlled Atmosphere in Food Packaging Using Ethylene−α-Cyclodextrin Inclusion Complexes Dispersed in Photocured Acrylic Films

Waste of fruits in their supply chain is an issue that is drawing increasing interest. Postharvest ripening processes enable better control of the ripening and diminish the loss of produce. Many of these techniques consist of exposure of fruits to controlled concentrations of ethylene, which acts as a phytohormone and trigger the ripening process. In this work, a new way to control the ethylene administration is studied. Inclusion complexes of ethylene in α-cyclodextrin are produced by molecular encapsulation and the crystals obtained are dispersed in thermosetting films made of Poly(ethylene glycol)diacrylate polymerized by UV-curing. The samples are then characterized with respect to thermal behavior, complex crystalline structure and ethylene release kinetics both from the loose crystals and those embedded into the polymeric films.

Structural Elucidation of α-Cyclodextrin-Succinic Acid Pseudo Dodecahydrate: Expanding the Packing Types of α-Cyclodextrin Inclusion Complexes

This paper reports a new packing type of α-cyclodextrin inclusion complexes, obtained here with succinic acid under low-temperature crystallization conditions. The structure of the 1:1 complex is characterized by heavy disorder of the guest, the solvent, and part of the host. The crystal packing belongs to the known channel-type structure; the basic structural unit is composed of cyclodextrin trimers, as opposed to the known isolated molecular or dimeric constructs, packed along the c-axis. Each trimer is made of crystallographically independent molecules assembled in a stacked vase-like cluster. A multi-temperature single-crystal X-ray diffraction analysis reveals the presence of dynamic disorder.

Ultrasonic Investigations of Inclusion Complexation of α-Cyclodextrin by DMSO in Pseudo-Binary Aqueous System

Abstract The paper reports the study of the complexation processes in aqueous solution of α-CD and DMSO. Cyclodextrins (CDs) (sometimes called cycloamyloses) are cyclic oligosaccharides formed by glucose units interconnected by α-(1,4) linkages; α-CD is one of three the most common CDs. It consists of six glucopyranose units. The speed of ultrasonic waves has been measured by the resonance method on ResoscanTM System apparatus. Some collateral data, such as density and heat capacity of the system, have also been measured. On the basis of the experimental data the excess adiabatic compressibility was determined. The extremes of the excess adiabatic compressibility function for different mixture compositions allowed us to establish the composition of molecular complexes formed in the solution. The obtained results suggest the formation of the α-CD with DMSO inclusion complexes with chemical stoichiometric ratio value of 1:1.

Enhanced mechanical properties of poly (ε-caprolactone) nanofibers produced by the addition of non-stoichiometric inclusion complexes of poly (ε-caprolactone) and α-cyclodextrin

A unique nanofibrous structure consisting of poly (ε-caprolactone) (PCL) and non-stoichiometric α-cyclodextrin-poly (ε-caprolactone) inclusion complexes [(n-s)-PCL-α-CD-ICs] was produced by electrospinning. For electrospinning experiments, stoichiometric ratios of the (n-s)-PCL-α-CD-ICs, their percentage loading, and the concentration of the PCL solutions were varied. With their partially un-included guest PCL chain portions, the effects of the (n-s)-PCL-α-CD-ICs on the thermal behavior and mechanical properties of the PCL nanofibers have been investigated. SEM indicated that at lower PCL concentrations (12%), loading of up to 15% (n-s)-PCL-α-CD-ICs resulted in bead-free fibers. However, at 14% PCL concentration, bead-free fibers were obtained only until 10% loading; beyond this loading, some beads were observed. DSC analyses indicated, compared to neat PCL nanowebs, there were significant increases in the melting and the crystallization temperatures of the PCL/(n-s)-PCL-α-CD-IC nanowebs. Absence of water loss and enhanced thermal stability of α-CDs was observed by TGA analyses, which indicated the presence of α-CDs threaded by PCL chains. Mechanical properties of the composite webs indicated, with the addition of the ICs, the tensile modulus and ultimate tensile strength of the composite fibers increased significantly (200–400% for the modulus) over those of neat PCL or uncomplexed PCL/α-CD nanofibers. At the same time, their extensions at break were reduced by factors of ∼ (2–3). With better mechanical and stiffness properties, these novel nanocomposite fibers, which are non-toxic, but biodegradable and biocompatible, would be potential candidates as scaffolds for various applications.

Star-pseudopolyrotaxane organized in nanoplatelets for poly(ε-caprolactone)-based nanofibrous scaffolds with enhanced surface reactivity.

Herein, it is demonstrated that star pseudopolyrotaxanes (star-pPRs) obtained from the inclusion complexation of α-cyclodextrin (CD) and four-branched star poly(ε-caprolactone) (star-PCL) organize into nanoplatelets in dimethyl sulfoxide at 35 °C. This peculiar property, not observed for linear pseudopolyrotaxanes, allows the processing of star-pPRs while preserving their supramolecular assembly. Thus, original PCL:star-pPR core:shell nanofibers are elaborated by coaxial electrospinning. The star-pPR shell ensures the presence of available CD hydroxyl functions on the fiber surface allowing its postfunctionalization. As proof of concept, fluorescein isothiocyanate is grafted. Moreover, the morphology of the fibers is maintained due to the star-pPR shell that acts as a shield, preventing the fiber dissolution during chemical modification. The proposed strategy is simple and avoids the synthesis of polyrotaxanes, i.e., pPR end-capping to prevent the CD dethreading. As PCL is widely used for biomedical applications, this strategy paves the way for simple functionalization with any bioactive molecules.

Multistimuli-responsive supramolecular assembly of cucurbituril/cyclodextrin pairs with an azobenzene-containing bispyridinium guest.

A linear supramolecular architecture was successfully constructed by the inclusion complexation of α-cyclodextrin with azobenzene and the host-stabilized charge-transfer interaction of naphthalene and a bispyridinium guest with cucurbit[8]uril in water, which was comprehensively characterized by (1)H NMR spectroscopy, UV/Vis absorption, fluorescence, circular dichroism spectroscopy, dynamic laser scattering, and microscopic observations. Significantly, because it benefits from the photoinduced isomerization of the azophenyl group and the chemical reduction of bispyridinium moiety with noncovalent connections, the assembly/disassembly process of this supramolecular nanostructure can be efficiently modulated by external stimuli, including temperature, UV and visible-light irradiation, and chemical redox.