Stable Inclusion Complexes Research Articles

Screening and inclusion of luteolin for β-cyclodextrin: molecular simulations and experiments

In this study, we first established a guest small molecule screening mechanism by molecular simulation, and then screened lignans from 10 polyphenolic compounds to identify the most suitable guest molecule for encapsulation with β-cyclodextrin (β-CD). Subsequently, the subject-guest interactions and encapsulation mechanisms of lignans with β-CD, 2-hydroxypropyl-cyclodextrin (HP-β-CD) and 2,6-dimethyl-cyclodextrin (DM-β-CD) were investigated using a combination of molecular simulation and experimental methods, respectively. Molecular simulations were performed to calculate the microstructural parameters, including solubility parameters, binding energies, and mean square displacements. The simulation results demonstrated that DM-β-CD exhibited the strongest interaction with luteolin and formed the most stable inclusion complex. The inclusion complexes of luteolin with the three cyclodextrins were prepared by freeze-drying method, and the formation of the inclusion complexes was demonstrated using infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and ultraviolet-visible spectroscopy (UV). Phase solubility studies confirmed the formation of 1:1 stoichiometric inclusion complexes of lignans with cyclodextrins. Furthermore, 2,2-diphenyl-1-pyridine hydrazine (DPPH) free radical scavenging experiments demonstrated that the inclusion complexes exhibited enhanced antioxidant capacity. In light of these findings, it can be concluded that among the three cyclodextrins, DM-β-CD was optimally encapsulated with luteolin.

Deep Eutectic Solvents for Next-generation Cyclodextrin Science

Abstract In cyclodextrin science, water has been almost exclusively employed as solvent, and this imposes non-negligible limitations to the scope of applications. Accordingly, deep eutectic solvents, constructed from hydrogen-bonding donors and acceptors, have been attracting much interest as important substitutes of water. This review comprehensively covers chemical and physicochemical features of cyclodextrins in these eco-friendly solvents. In one category, cyclodextrins or their derivatives are dissolved as solutes in conventional deep eutectic solvents. All of α-, β-, and γ-cyclodextrins efficiently form inclusion complexes with various guest molecules, exactly as observed in water. Notably, chemically modified cyclodextrins (e.g., 2-hydroxypropyl-cyclodextrins) form still more stable inclusion complexes than native cyclodextrins. Alternatively, deep eutectic solvents are prepared by combining cyclodextrins with other hydrogen-bonding components. The cyclodextrin units in these mixtures also form inclusion complexes with guest molecules. It has been proposed that enhanced flexibility of cylindrical structures of cyclodextrins allows effective induced-fit to stabilize inclusion complexes. The applications of these systems widely range from catalysis for organic synthesis to extraction, analysis, pharmaceutics, and many other fields. High solubilities of CDs and various chemicals in these solvents guarantee high productivity of target transformation, and unprecedentedly novel functions are promising for these unique systems.

Conformations of α-cyclodextrin and its role on the stability of inclusion complexes in aqueous solution

α-Cyclodextrin (αCD), a cyclic carbohydrate polymer, presents a wealth of opportunities for drug delivery and various industrial applications. Its high affinity and selectivity in encapsulating target molecules have been well-documented. However, the influence of αCD's conformational variations on its encapsulation capacity remains a promising area for further exploration. This study explores the conformational dynamics of αCD and its relationship with the formation of inclusion complexes (ICs) in aqueous solutions, focusing on understanding the forces driving these dynamics and the formation of stable ICs. Classical molecular dynamics (CMD) demonstrate that αCD solvated in water can adopt two conformations: a truncated cone shape with a suitable cavity for encapsulation and a distorted cone shape with a collapsed cavity. The predominant conformation observed in the CMD trajectory of pristine αCD is the distorted cone. However, under complexation conditions with aliphatic molecules, the guest molecule's size dictates the ICs' stability, forcing αCD to maintain the truncated cone conformation. Quantum chemistry methods and electron density analyses (Quantum Theory of Atoms in Molecules and Non-Covalent Interactions index) support CMD observations by characterizing and quantifying non-covalent interactions. Findings indicate that the shift from the truncated to the distorted cone conformation in αCD is primarily driven by intramolecular non-covalent interactions and the reconfiguration of water molecules surrounding αCD. The ICs' analysis displays a significant correlation between the size of the aliphatic chain and the intensity of intermolecular interactions. The strength of these interactions can effectively disrupt the αCD intramolecular non-covalent interactions that lead to a conformational change and, consequently, the loss of the inclusion complex. In conclusion, although αCD's conformational change can affect encapsulation, guest molecules can manipulate the conformational preference. The systematic analysis of non-covalent interactions offers a way to characterize and quantify these forces, enhancing our ability to understand and predict the stability of inclusion complexes.

Inclusion Complexation of Flavonoids with Cyclodextrin: Molecular Docking and Experimental Study

AbstractIn our work, the inclusion ability and binding pattern of flavonoids (catechin, iso‐liquiritigenin, luteolin, puerarin, rutin, and curcumin) with β‐cyclodextrin (β‐CD) and curcumin (CUR) with CDs (α‐CD, β‐CD, γ‐CD, dimethyl‐β‐CD, Hydroxypropyl‐β‐CD, and glucosyl‐β‐CD) were studied by molecular docking. The results showed that CUR among the six flavonoids was more likely to form stable inclusion complexes with β‐CD, and the HP‐β‐CD is the most suitable for CUR inclusion among the 6 types of CD. Phase solubility studies showed that CUR with β‐CD or HP‐β‐CD, respectively, could form stable inclusion complexes in a stoichiometric ratio of 1 : 1. The CUR/β‐CD and CUR/HP‐β‐CD inclusion complexes (ICs) were prepared by freeze‐drying method. The successful preparation of IC was confirmed by SEM images, FT‐IR spectra, and TG‐DSC. The results of in vitro release showed that the release of CUR from IC prepared with β‐CD or HP‐β‐CD could be improved significantly, and the release effect of HP‐β‐CD was better than that of β‐CD. The inclusion with CD could be used to improve the solubility and bioavailability of CUR.

Sustained-Release Microspheres of Cyclodextrin-Resveratrol Complex Using Fenugreek Galactomannan Hydrogels: A Green Approach to Phytonutrient Delivery.

Food matrices are becoming increasingly complex with the impregnation of phytonutrients with health-beneficial pharmacological effects. Herein, we report the preparation, characterization, and functional application of soluble and stable microspheres of trans-resveratrol (t-RES) developed through a water-based green process involving cyclodextrin (CD) and fenugreek galactomannan (FG). Spectroscopic and thermodynamic calculations identified γ-CD as the best CD to form a stable cyclodextrin-resveratrol inclusion complex (CD-R, 49-fold enhanced solubility); however, it exhibited a burst release profile. The sustained release of resveratrol was achieved by further encapsulating the inclusion complex within the fenugreek galactomannan hydrogel scaffold by a gel-phase dispersion process, resulting in an amorphous powder (FG-CD-R) as evident from powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) studies. Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) studies confirmed the formation of the inclusion complex with no chemical alterations. When dissolved in water, FG-CD-R swelled and released stable cuboid structures with an average particle size of 500 ± 53 nm with a zeta potential of -52 ± 5.3 mV. FG-CD-R demonstrated a sustained-release profile upon in vitro release studies. Accelerated study demonstrated its stability for a shelf-life of two years. Further it was shown to be suitable for the preparation of transparent gummies with improved sensory attributes compared to unformulated t-RES. In summary, FG-CD-R is simple to prepare and easily scalable, providing a sustained-release t-RES with a natural, food-grade, and clean label status (non-genetically modified, allergen-free, vegan, and free from residual solvents) for nutritional applications.

Recognition of monoamine neurotransmitters by cucurbiturils

Neurological disorders are linked to deficiencies in monoamine neurotransmitters (NTs) in the brain, and their inability to cross the blood–brain barrier (BBB) prevents their use as treatments. Encapsulating them within an appropriate host could present a potential remedy. Molecular dynamics (MD) simulations are employed to investigate the molecular recognition of protonated and neutral forms of five NTs and two dopamine (DP) analogs by cucurbit[n]urils (CBn). Binding free energies (ΔG), computed with the molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) method, reveal CB7 forms stable inclusion complexes with all studied NTs, driven by ion–dipole/dipole–dipole interactions between and the ammonium/amine in the NT with the carbonyl portal of CB7, as well as van der Waals interactions of the included catechol/heterocyclic ring. ΔG was more favorable (by ∼2–3 kcal.mol−1) for the DP analogs. MD simulations performed to study complexation between DP and CB6 and CB8 revealed 1:1 and 2:1 stoichiometries, respectively.

Host-Guest Complexes of Flavanone and 4'-Chloroflavanone with Naturals and Modified Cyclodextrin: A Calorimetric and Spectroscopy Investigations.

The aim of the research was to investigate and compare the interaction between flavanones (flavanone, 4-chloro-flavanone) with potential anticancer activity and selected cyclodextrins. Measurements were made using calorimetric (ITC, DSC) and spectrophotometric (UV-Vis spectroscopy, FT-IR, 1H NMR) methods. The increase in the solubility in aqueous medium caused by the complexation process was determined by the Higuchi-Connors method. As a result of the study, the stoichiometry and thermodynamics of the complexation reaction were determined. The formation of stable inclusion complexes at a 1:1 M ratio between flavanone and 4-chloroflavanone and the cyclodextrins selected for research was also confirmed.

Integrative approach for improved dofetilide solubility using β-cyclodextrin and two its substituted derivatives: Solutions and solid dispersions

The complexation an anti-arrhythmia drug dofetilide (DFT) with β-cyclodextrin (β-CD), 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) and sulfobutylether-β-cyclodextrin (SBE-β-CD) were studied using two main approaches: phase solubility diagrams and solid dispersions technique. The phase solubility diagrams were constructed in buffer solutions with physiological values рН 2.0 и 7.4. In accordance with the protolytic properties of the drug, the solubilizing effect of cyclodextrins turned out to be more effective in a neutral environment (buffer pH 7.4): the solubility improvement of DFT in the presence of β-CD, HP-β-CD and SBE-β-CD was 3.6, 11.8 and 18.1 times, respectively. In buffer pH 2.0, the tendency for an increase in the solubilizing effect, depending on the chemical nature of the CDs used, is maintained, but the solubility of the drug almost does not grow. The binding constants for the DFT/HP-β-CD and DFT/SBE-β-CD complexes equal to 344 L·mol−1 and 429 L·mol−1 in buffer pH 7.4 indicate the formation of stable inclusion complexes and belong to the optimal range for refinement bioavailability and stability of hydrophobic drugs. Amorphous solid dispersions DFT/β-CD, DFT/HP-β-CD and DFT/SBE-β-CD with stoichiometry 1:1 were obtained by grinding method. The combination FTIR, PXRD, DSC, TGA and SEM methods confirmed the inclusion complexes formation of the drug with cyclodextrins used. Dissolution profiles of solid dispersions DFT/β-CD, DFT/HP-β-CD and DFT/SBE-β-CD were graphing in buffer solutions рН 2.0 and 7.4. Enlargement factor of DFT solubility in the composition of solid dispersions DFT/β-CD, DFT/HP-β-CD and DFT/SBE-β-CD in the neutral medium are 3.4, 4.1 and 5.2, respectively. Whereas the formation of solid inclusion complexes DFT/CDs in an acidic buffer has virtually no effect on the increase in the equilibrium concentration of the active substance in the solution. Findings have demonstrated that the use of SBE-β-CD shows the best solubilization potential for DFT both in solution and as a solid dispersion.

Formation of Inclusion Complexes of 2-Hydroxypropyl β-Cyclodextrin with 2-Hydroxychalcone: Experimental and Theoretical Study

The formation of inclusion complexes of 2-hydroxypropyl-β-cyclodextrin (HP β-CD) with 2-hydroxychalcone (2HOCH) in solution and solid state was investigated using UV–Visible, fluorescence, Fourier transform-infrared (FT-IR) spectroscopy, powder X-ray diffraction (PXRD), scanning electron microscope (SEM) techniques. The results obtained confirmed that 2HOCH formed the stable inclusion complex with HP β-CD. Moreover, the spectral data and Benesi–Hildebrand plots results indicated that the stoichiometry of the inclusion complex was 1:1. Theoretically, the structure of the inclusion complexes and the physical parameters such as complexation energy, highest occupied molecular orbital–lowest unoccupied molecular orbital, and energy gap were obtained using the DFT/B3LYP/6-311G method. It was found that the complexation energy for orientation B was lower than that for orientation A as evidenced by the theoretical calculations. Moreover, the carbonyl group of molecules was located outside of the cyclodextrin cavity while the hydroxyl group was located inside the cavity. The antioxidant capacity and antibacterial responses of the inclusion complexes and, for comparison, the parent compounds were also carried out.

Polyaromatic Hydrocarbon Inclusion Complexes with 2-Hydroxylpropyl-β/γ-Cyclodextrin: Molecular Dynamic Simulation and Spectroscopic Studies.

In aqueous and solid media, 2-HP-β/γ-CD inclusion complexes with poly aromatic hydrocarbon (PAH) Phenanthrene (PHN), Anthracene (ANT), Benz(a)pyrene (BaP), and Fluoranthene (FLT) were investigated for the first time. The inclusion complexes were characterized and investigated using fluorescence and 1HNMR spectroscopy. The most prevalent complexes consisting of both guests and hosts were those with a 1:1 guest-to-host ratio. The stability constants for the complexes of PHN with 2-HP-β-CD and 2-HP-γ-CD were 85 ± 12 M-1 and 49 ± 29 M-1, respectively. Moreover, the stability constants were found to be 502 ± 46 M-1 and 289 ± 44 M-1 for the complexes of ANT with both hosts. The stability constants for the complexes of BaP with 2-HP-β-CD and 2-HP-γ-CD were (1.5 ± 0.02) × 103 M-1 and (9.41 ± 0.03) × 103 M-1, respectively. The stability constant for the complexes of FLT with 2-HP-β-CD was (1.06 ± 0.06) × 103 M-1. However, FLT was observed to form a weak complex with 2-HP-γ-CD. Molecular dynamic (MD) simulations were used to investigate the mechanism and mode of inclusion processes, and to monitor the atomic-level stability of these complexes. The analysis of MD trajectories demonstrated that all guests formed stable inclusion complexes with both hosts throughout the duration of the simulation time, confirming the experimental findings. However, the flexible Hydroxypropyl arms prevented the PAHs from being encapsulated within the cavity; however, a stable exclusion complex was observed. The main forces that influenced the complexation included van der Waals interactions, hydrophobic forces, and C-H⋯π interaction, which contribute to the stability of these complexes.

Room-temperature stable Perillaldehyde—Natural cyclodextrin inclusion complexes: Preparation, characterization, thermal stability, water solubility, antioxidant activity and slow–release performance

The compound Perillaldehyde (PA) is a bioactive constituent found in natural Perilla oil, exhibiting remarkable antibacterial and antioxidant activity. However, the instability of this compound caused by the easy oxidation of its aldehyde and olefin groups imposes limitations on its extensive applications. Therefore, it is crucial to develop effective strategies for enhancing the stability of PA. This study focuses on utilizing a series of natural cyclodextrins (CDs) to synthesize inclusion complexes (ICs) with PA, aiming to improve water solubility and achieve exceptional stability at room temperature, which is essential for their potential applications in biomedicine or food industries. The hydrophobic cavity of CDs can accommodate the hexatomic ring and hydrophobic chains of PA based on the well-known size-matching effect and hydrophobic interaction, thereby forming stable ICs. Additionally, the hydrophilic outer wall of CDs imparts excellent water solubility to ICs. Phase solubility investigations demonstrate successful construction of α-CD-PA IC and β-CD-PA IC with an inclusion ratio of 1:1. Their respective stability constant (KC) are determined as 342 L/mol and 180 L/mol, indicating superior stability for α-CD-PA IC compared to β-CD-PA IC. Conversely, γ-CD with a larger cavity fails to form a stable inclusion complex with PA due to inadequate size matching. Nuclear Magnetic Resonance Hydrogen Spectroscopy (1H and 2D NMR) studies reveal that PA enters the CDs cavity (α-CD or β-CD) from its wide rim with almost the entire molecule being obliquely embedded within it. Thermogravimetry Analysis (TGA) confirm that after inclusion with CDs, PA exhibits expected stability at 25 ℃. Furthermore, CDs-PA ICs demonstrate significantly improved water solubility compared to pure PA along with enhanced antioxidant activity and slow-release performance, rendering them highly favorable for various applications.

Enhancing the bioavailability of clozapine through microwave-assisted formulation of a stable β-cyclodextrin inclusion complex

The low oral bioavailability of clozapine due to its poor aqueous solubility, poor dissolution rate, and extensive hepatic first-pass metabolism poses a challenge to the effective treatment of psychiatric disorders. The objective of the current research was to address the above issues by developing a clozapine inclusion complex (CLZ-IC) using the microwave irradiation method. To optimize the formulation and processing variables, namely the molar ratio of CLZ to β-CD (X1) and the irritation reaction time (X2), a 32 factorial design was performed. The phase solubility study revealed the formation of a stable inclusion complex with a stoichiometry of 1:1, suggesting that β-cyclodextrin could effectively solubilize clozapine. The characterization data confirmed the formation of the inclusion complex of clozapine in β-cyclodextrin. The optimized inclusion complex showed a solubility of 342 ± 26 µg/ml and a percentage dissolution of 91.1 ± 3.4% after four hours. The inclusion-complex tablets exhibited excellent physical properties and showed an improved in vitro dissolution profile, with 80% of the drug being released within 100 minutes, compared to marketed tablets (80% release in 300 min). In vivo pharmacokinetic studies conducted in a rat model demonstrated an increase in Cmax, area under the curve (AUC), and relative bioavailability by a factor of 2.26 with the optimized formulation, indicating a significant improvement in drug absorption compared to the marketed tablet. The techno-economic analysis suggests a cost-benefit ratio of 25.08 after 7 years, indicating the suitability for large-scale production. Overall, using Design of Experiment, in silico, and in vivo studies proved effective in optimizing the inclusion-complex formation and enhancing the bioavailability of clozapine. In conclusion, the optimized clozapine-β-cyclodextrin inclusion complex prepared using a time-saving (90 sec) and cost-effective microwave irradiation method exhibited excellent physical properties and demonstrated significant improvements in the drug's solubility, dissolution rate, and pharmacokinetic performance.

Structure and activity of amphiphilic PEO-PPO-based polymeric micelles and gels incorporating host–guest complexes of miltefosine as novel formulations for the treatment of leishmaniasis

Hypothesis: Poloxamines are amphiphilic block copolymers that self-assemble forming polymeric micelles (PMs) and hydrogels. They have emerged as promising colloidal carriers for their potential in improving drug delivery and controlled release through their multi-responsive properties. Tetronic® 1307 (T1307) PMs and gels have been used herein as vehicles of host–guest complexes of cyclodextrins (CDs) and miltefosine (MF), an amphiphilic, anti-parasitic drug effective against leishmaniasis.Experiments: The association of MF to αCD, βCD, and HPβCD and the topology of the complexes have been fully characterized by NMR spectroscopy. Then, the structure of the complex-loaded PMs and hydrogels investigated using diffusion nuclear magnetic resonance (DOSY), small angle neutron scattering (SANS), and dynamic light scattering (DLS). The antileishmanial activity of the constructs was evaluated against Leishmania major promastigotes and amastigotes, as well as their cytotoxicity in macrophages.Findings: All the CDs investigated form highly stable inclusion complexes with MF in a 2CD:1MF stoichiometry that lead to considerable proportions of complexed drug at high dilution, the HPβCD providing the highest stability and compatibility with the poloxamine. The complex incorporates preferentially into the hydrophilic shell of the PMs, inducing the elongation of the aggregates and the dehydration of the micellar core, formed mainly by the PPO blocks. At high concentration of polymer and physiological temperature, the complex-loaded PMs pack in a BCC-type paracrystal network. The micellar formulations of the CD-complexed MF reduced the cytotoxicity of the drug, while enhancing its antileishmanial activity. This approach could improve the currently available treatments, facilitating the administration of MF at lower concentrations and achieving relevant therapeutic effects, not only through the intravenous route, but also as topical formulations through injectable thermogels for the treatment of the cutaneous and mucocutaneous forms of the disease.

Photo-Controlled Reversible Uptake and Release of a Modified Sulfamethoxazole Antibiotic Drug from a Pillar[5]arene Cross-Linked Gelatin Hydrogel.

Pillararene cross-linked gelatin hydrogels were designed and synthesized to control the uptake and release of antibiotics using light. A suite of characterization techniques ranging from spectroscopy (FT-IR, 1H and 13C NMR, and MAS NMR), X-ray crystallographic analysis, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) was employed to investigate the physicochemical properties of hydrogels. The azobenzene-modified sulfamethoxazole (Azo-SMX) antibiotic was noncovalently incorporated into the hydrogel via supramolecular host-guest interactions to afford the A-hydrogel. While in its ground state, the Azo-SMX guest has a trans configuration structure and forms a thermodynamically stable inclusion complex with the pillar[5]arene motif in the hydrogel matrix. When the A-hydrogel was exposed to 365 nm UV light, Azo-SMX underwent a photoisomerization reaction. This changed the structure of Azo-SMX from trans to cis, and the material was released into the environment. The Azo-SMX released from the hydrogel was effective against both Gram-positive and Gram-negative bacteria. Importantly, the A-hydrogel exhibited a striking difference in antibacterial activity when applied to bacterial colonies in the presence and absence of UV light, highlighting the switchable antibacterial activity of A-hydrogel aided by light. In addition, all hydrogels containing pillar[5]arenes have demonstrated biocompatibility and effectiveness as scaffolds for biological and medical purposes.

Molecular Insight into the Ternary Complex Formation between Ethambutol, Isoniazid and β‐Cyclodextrin

AbstractLong term intake of antituberculosis drugs will lead to severe adverse reactions that will ultimately deteriorate a patient's health and well‐being. With that, the ternary inclusion complex was explored, whereby β‐cyclodextrin (β‐CD) was chosen as the supramolecular host carrier to accommodate two kinds of first line antituberculosis guest drug molecules simultaneously, namely isoniazid (INH) and ethambutol (ETB) which would provide many therapeutic benefits. The inclusion complex of β‐CD/INH/ETB was prepared using solvent evaporation method. Fourier transform infrared spectroscopy (FT‐IR), proton nuclear magnetic resonance spectroscopy (1H‐NMR), and 2‐dimensional nuclear Overhauser effect spectroscopy (2D‐NOESY) NMR were used to investigate the functional groups and structure of the complex. Scanning electron microscopy (SEM) and X‐ray diffraction (XRD) were employed to study the surface morphology and crystallinity changes during complex formation. Thermogravimetric analysis (TGA) was performed to investigate the thermal properties of the complex. FT‐IR and both types of NMR results had revealed the successful penetration of both the drug molecules into the β‐CD cavity. SEM images and XRD spectra had shown a drastic change in surface structure and reduction in crystallinity during complex formation, which had indicated successful formation of a new compound. TGA had proven that the complex had significantly greater thermal stability as compared to the pure components. Molecular dynamics (MD) and molecular docking simulations were also performed to understand the molecular interaction between β‐CD, INH, and ETB. Through precise calculations of interaction and binding energies, β‐CD/INH/ETB was found to be a more stable inclusion complex compared to the binary β‐CD/INH and β‐CD/ETB complexes.

Tetracationic macrocycles form highly stable inclusion complexes with uric acid enabling solution-phase and paper-strip bicolor colorimetric detection of hyperuricemia

Uric acid can be detected using a bicolor colorimetric system of tetracationic macrocycles and rhodamine B in solution or a paper assay.

Complexes between 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AAPH) and cucurbit[n]uril hosts modulate the yield and fate of photolytically-generated AAPH radicals.

Using theoretical and experimental tools we investigated the recognition of AAPH (2,2'-azobis(2-methylpropionamidine) dihydrochloride), a well-known water-soluble azo-compound employed as a source of peroxyl radicals, by cucurbit[6]uril (CB[6]), and cucurbit[8]uril (CB[8]). Density functional theory calculations and isothermal titration calorimetry experiments demonstrated that AAPH was not included in the cavity of CB[6], however, an exclusion complex was generated. Inclusion of AAPH in the CB[8] cavity was favored, forming stable inclusion complexes at 1 : 1 and 2 : 1 stoichiometries; AAPH@CB[8] and 2AAPH@CB[8], respectively. Radical formation upon photolytic cleavage of AAPH was examined theoretically, and by spin trapping with electron paramagnetic resonance. The radical yields detected with uncomplexed (free) AAPH and the AAPH-CB[6] (exclusion) complex were identical, whereas a marked decrease was shown for AAPH@CB[8]. Lower decreases were seen with a bimolecular (2 : 1) AAPH-CB[8] inclusion complex (2AAPH@CB[8]). This modulation was corroborated by the consumption of pyrogallol red (PGR), an oxidizable dye that does not associate with CB[6] or CB[8]. AAPH-CB[6] and 2AAPH@CB[8] did not significantly modify the initial consumption rate (Ri) of PGR, whereas AAPH@CB[8] decreased this. The oxidative consumption of free Trp, Gly-Trp and Trp-Gly by radicals derived from AAPH in the presence of CB[8] showed a dependence on the association of the targets with CB[8].

Synthesis of responsive microcapsule (4H7MC-ECH-g-β-CD) and preparation of UV-responsive controlled-release packaging film

The synthesis of green UV-controlled release active packaging films using 4-hydroxy-7-methoxycoumarin as photosensitizing factor, β-cyclodextrin as main molecule and PLA-PVA as film-making base solution was reported. Firstly, 4-hydroxy-7-methoxycoumarin and β-cyclodextrin reacted to obtain 4H7MC-ECH-g-β-CD. 4H7MC-ECH-g-β-CD can undergo reversible photodimerization reaction at 365/256 nm in solid state. Then p-methoxybenzaldehyde/4H7MC-ECH-g-β-CD inclusion complex was prepared, investigated the loading capacity and found to be maximum at 40 ℃ and 3 h. Molecular docking proved that they formed stable inclusion complex. In the study of UV-controlled release of inclusion complex and film, it was found that the release rate of p-methoxybenzaldehyde was as follows: the release rate of samples irradiated with 365 nm < the release rate of samples irradiated with 256 nm < the release rate of samples without any treatment. This suggested that UV light can be used as a condition to control the release of p-methoxybenzaldehyde to regulate the release from inclusion complex and film.

Dual-functionalization of fluorescent carbon dots via cyclodextrin and aminosilane for visual detection of β-glucuronidase and bioimaging

A sensitive method for the detection of β-glucuronidase was established using functionalized carbon dots (β-CD-SiCDs) as fluorescent probes. The β-CD-SiCDs were found to be obtained through in situ autopolymerization by mixing the solutions of methyldopa, mono-6-ethylenediamine-β-cyclodextrin and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane at room temperature. The method has the characteristics of low energy consumption, simple and rapid. β-CD-SiCDs exhibited green fluorescence at 515 nm emission with a quantum yield of 7.9 %. 4-nitrophenyl-β-D-glucuronide was introduced as a substrate for β-glucuronidase to generate p-nitrophenol. Subsequently, p-nitrophenol self-assembled with β-CD-SiCDs through host-guest recognition to form a stable inclusion complex, resulting in the fluorescence quenching of β-CD-SiCDs. The linear range of β-CD-SiCDs for detecting β-glucuronidase activity was 0.5–60 U L−1 with a detection limit of 0.14 U L−1. For on-site detection, gel reagents were prepared by a simple method and the images were visualized and quantified by taking advantage of smartphones, avoiding the use of large instrumentation. The constructed fluorescence sensing platform has the benefits of easy operation and time saving, and has been successfully used for the detection of β-glucuronidase activity in serum and cell imaging.

Acyclic Cucurbit[n]urils: Effective Taste Masking Nanocontainers for Cationic Bitter Compounds.

New acyclic cucurbit[n]urils (ACBs) with eight carboxylate groups were synthesized. These hosts are highly soluble in water, and can form stable inclusion complexes with cationic bitter compounds. ACBs are confirmed to be non-toxic and biocompatible. Two-bottle preference (TBP) tests on mice show that all ACBs are tasteless to mammals. ACBs are discovered to mask the bitterness of berberine and denatonium benzoate, but not quinine hydrochloride, due to different binding modes.