Guest Inclusion Research Articles

Viscoelastic behaviors for optimizing self-healing of gels with host–guest inclusion complexes

Viscoelastic behaviors for optimizing self-healing of gels with host–guest inclusion complexes

Synergistic thickening mechanism of surfactants and supramolecular inclusion systems

The effectiveness of conventional polymer flooding systems for improving oil recovery (IOR) in high-temperature and high-salt reservoirs is greatly limited. The polymer inclusion system forms a spatial network structure through host–guest inclusion, which can achieve the goal of low concentration and high viscosity in high-temperature and high-salt environments. However, there are few reports on further enhancing the performance of polymer flooding systems based on the inclusion system. In this study, the optimal ratio of erucamide propyl betaine (EDAB) to polymer inclusion system (ABMN) was first investigated. The results showed that the optimal formulation for the synergistic enhanced inclusion system was 2000 mg/L ABMN+2000 mg/L EDAB, which could reach 95.7 mPa·s under 85 ℃ and salinity of 32868 mg/L, and the viscosity was more than twice that of the ABMN system. The wormlike micelles (WLMs) formed by EDAB synergistically interacted with the ABMN, resulting in a larger hydrodynamic radius and a denser spatial network structure. Due to the synergistic effect of supramolecular forces, the system has significantly improved its temperature resistance, salt resistance, and shear resistance, with a viscosity recovery rate of up to 98.9 %. This provides a new oil displacement system for IOR in high-temperature and high-salt reservoirs.

Impacts of CSR autonomy, self-expressiveness and hedonic value of CSR activity on guest citizenship and hotel brand preference

Recruiting guests to participate in corporate social responsibility (CSR) activities during a vacation presents a dilemma for hotel managers – will such requests spoil a holiday? The study is significant because of increased investment by hotels in CSR activities and greater inclusion of hotel guests in CSR activities. We extend psychological wellbeing theory to evaluate the relative importance of CSR autonomy in enhancing guest engagement. A scenario based on a guest’s return to an actual hotel recently visited was designed and a convenience sample of 249 survey respondents analyzed using structural equation modeling. While hedonic value of the CSR activity provided the greatest effect on brand preference, both self-expressiveness and CSR autonomy significantly impacted brand preference. Effects for all constructs were mediated through cocreated citizenship behavior. The study has substantial theoretical implications for scholars and practical implications for CSR marketing communication campaigns to guests conducted by hotel managers and non-governmental organizations.

Discrete Quadruple Stacks Formed in a Nanosized Metallorectangle.

An iridium-cornered nanosized metallorectangle was obtained by combining a quinoxalinophenanthrophenazine-connected Janus-di-imidazolylidene ligand and 4,4'-bipyridine. This metallorectangle was used as host for a series of planar molecules, including pyrene, triphenylene, perylene, coronene, and N,N'-dimethyl-naphthalenetetracarboxy-diimide (NTCDI). The binding of coronene and NTCDI followed a strongly positive cooperative 1:2 stoichiometric binding model, as the inclusion of the first guest generates the geometrical requirements for the optimum encapsulation of the second planar molecule. The simultaneous encapsulation of coronene and NTCDI produces a heteroguest inclusion system, whose exchange dynamics was studied by means of variable temperature 1H NMR spectroscopy.

Dynamic control of His-hemin coordination and catalysis by reversible host–guest inclusion in peptide assemblies

Dynamic self-assembly has significant implications in the regulation of the enzyme activities. In this study, we present a histidine-based enzyme-mimicking catalyst, formed by the self-assembly of carefully-engineered FH-based short peptides with hemin, showcasing switchable catalytic activity of hemin due to externally induced reversible inclusion of a cucurbit[7]uril-peptide hybrid. 1H NMR, ITC and theoretical simulation are employed to examine the binding affinity between the guest and host components, and UV–vis spectra are used to investigate changes in the hemin coordination environment. The histidine segment of the short peptide can be partially shielded by the cucurbituril and released following addition of the azo compound, leading to a decrease and subsequent restoration of the histidine-hemin coordination affinity and hemin activity. The photoisomeriziable nature of the azo compound enabled the activation of FHH/hemin activity to be switched on and off by exposure to different wavelengths of light. During the operation, the Phe residue remained within the cucurbituril, allowing reversible inclusion and exposure of the histidine residues. The hemin stayed connected to FHH/cucurbit[7]uril hybrid, preventing the severe aggregation of hemin and irreversible deactivation. This work may provide insights into engineering the dynamic behaviors of the cofactor-dependent catalytic assemblies.

Designing green and recyclable switchable supramolecular deep eutectic solvents for efficient extraction of flavonoids from Scutellariae Radix and mechanism exploration

A green and recyclable switchable supramolecular deep eutectic solvent (SS-DES) was designed and prepared for effective extraction of flavonoids from Scutellariae Radix. The novel SS-DES has both excellent extraction performance of DES and the host guest inclusion of cyclodextrin, thereby showing superior extraction efficiency and selectivity. The characteristic of polarity switching can endow the SS-DES with achieving homogeneous extraction and rapid two-phase separation, shorting per-treatment time largely. Parameters affecting the extraction performance were investigated by the response surface methodology. The results indicated that the SS-DES showed better extraction yield of total flavonoids (157.95 mg/g) compared with pure DES (135 mg/g) and traditional organic solvent (60 % ethanol, 104.87 mg/g). Moreover, the switching mechanism of SS-DES was characterized by FT-IR and 1H NMR, and the extraction mechanism was studied by density functional theory and molecular docking analysis. After evaluating the ecological impact of the method, the cytotoxicity of SS-DES was investigated and the result displayed that its toxicity was very low or even negligible with the EC50>2000 mg/L. After being adsorbed by macroporous AB-8 resin, the regenerated SS-DES was recycled 5 times and the extraction efficiency still remained above 90 %, indicating the desirable reusability. Therefore, the proposed method was efficient and sustainable, and revealed favorable application prospect for the extraction of bio-active compounds from plant materials.

Study on 2D Molecular Networks of Flexible Pentacarboxylic Acid Ligands Induced by Ether Bonds in Response to Selective Guest Inclusion.

The flexibility of ligands allows for their bending, twisting, or rotation to adopt various conformations, leading to distinct symmetries during the self-assembled process. Flexible aromatic acid ligands modified by ether bonds are a promising type of self-assembled module when it comes to surfaces. Here, two pentacarboxylic acid ligands (H5L1 and H5L2) with minor skeleton differences have successfully self-assembled into disparate porous networks on the graphite surface and demonstrated excellent potential for the inclusion of guest molecules. The H5L1 molecule's network structure only accommodates coronene (COR) molecules. With fewer COR molecules, H5L1 molecules act as a host template to accommodate the COR molecules. When there are too many COR molecules, COR molecules will induce H5L1 molecules to transform into a new host-guest nanostructure. Additionally, H5L2 molecules showed the ability to capture C70 molecules and exhibited cavity selectivity. However, the assembled network of H5L2 was slightly deformed in attempts to trap the COR molecules. To understand these phenomena more deeply, various assembled mechanisms were analyzed in combination with building theoretical models and energy analysis. These results reveal the great potential of flexible aromatic acid ligands in two-dimensional self-assembly and host-guest systems for their application in related fields.

Chiral Induction in a Self-Assembled Pd4 Coordination Cage with Chiral Guests.

The dynamic interplay of coordination bonds within metal-organic cages offers a unique avenue for structural evolution in response to external stimuli, presenting a promising strategy for the construction of chiral assemblies. This adaptability is crucial for the selective synthesis of homochiral assemblies and advancement of asymmetric catalysis. In this study, we report the self-assembly of an achiral square-planar Pd(II) acceptor with a C2-symmetric tetrapyridyl donor resulted in the formation of a racemic mixture of the chiral octahedral cage Pd4L2. The existence of this racemic mixture was confirmed using circular dichroism spectroscopy as well as single crystal X-ray diffraction analysis. We encoded chiral information into the asymmetric cavity of the cage by encapsulating chiral aromatic guests through efficient π-π stacking and hydrophobic interactions in aqueous media. The inclusion of a chiral guest induces a preference for one enantiomeric conformation of the cage over the other, effectively shifting the equilibrium towards a single, enantiopure host-guest complex. While the concept of chiral guest recognition by a chiral host is well-established, this work constitutes a remarkable example of guest-mediated chirality transfer leading to the formation of a single enantiopure coordination complex from achiral building blocks.

Perylenediimide‐Derived Nonmacrocyclic Host–Guest Donor–Acceptor Assemblies for Long‐Wavelength Emissions and Low‐Threshold Microlasers

AbstractMacrocyclic hosts can bind appropriate guests in endo‐cavity or exo‐wall modes to yield Host–Guest cocrystals via weak intermolecular forces. Contrary, it remains challenging to achieve their nonmacrocyclic partners with high‐efficiency fluorescence even lasing due to profound adaptive behaviors during guest inclusion. Here, a variety of low dispersity 1D and 2D assemblies made of a sterically demanding perylenediimide derivative (PDI) host and diverse aromatic guests are realized. Depending on the types and the substituted groups of aromatic guests, these Host–Guest microcrystals show high‐efficiency solid‐state emissions ranging from orange to near‐infrared (NIR). Interestingly, either electron‐deficient or electron‐rich guests can adapt to the cavity of the nonmacrocyclic PDI host in diverse geometries and orientations. Theoretical analysis indicates that the long‐wavelength emissions stem from local or charge‐transfer excited states and the Host–Guest Donor–Acceptor cocrystals are stabilized largely by dispersion forces. The binding of appropriate π‐electron guests makes the PDI‐derived Host–Guest microcrystals function as microscale lasers with low lasing thresholds. The rational creation of these nonmacrocyclic Host–Guest Donor–Acceptor cocrystals offers new insights for developing new crystal structures and high‐efficiency optoelectronic devices.

Guest Author and Ghost Author: My Experience as an Editor of a Medical Journal

The author (s) of a scientific article should have contributed to a research article in a meaningful and substantive way. A person who contributes to the research but whose name is excluded from the authors’ list is known as a ghost author. Whereas a guest author doesn’t contribute in a meaningful way to the research and preparation of the manuscript, however, appears on the author's byline. Often, guest authors are influential persons invited by the principal author to get favours later. Gift authorship often involves mutual authorship among the articles of colleagues and vice-versa. The Inclusion of ghost authors, guests, or gift authors is common in the district town’s journal of Noakhali. This article was written to express my ten years of experience regarding the malpractices of authorship of a medical journal as an editor of a medical journal. It is a common phenomenon that after a few days of submitting an article to the editor’s office, the principal author requests to insert another author or to change the order of the author’s position. Members of the editorial board and reviewer of the article insert their names as authors violating the ICMJE (International Committee of Medical Journal Editors) guidelines. Course on authorship should be almost important to change the trend of our current culture in publishing articles, especially district medical college Journals.

Supramolecular Nano‐Grid Platform to Load and Deliver Liposomes and Exosomes

In general, carriers are designed to deliver pharmaceutical (featuring small drug‐molecules) and biopharmaceutical (featuring large‐molecule drugs, e.g., antibodies, proteins, etc.) active ingredients and platform that is capable of transporting nanoparticles is rare. Herein, the fabrication of a supramolecular carrier with a nano‐grid structure for the entrapment of liposomes and exosomes is reported. The nano‐grid particles (NGP) are made of cyclodextrins as elementary units which are widely used to load drugs through host–guest inclusion complexes, whilst its secondary structure further formed the NGP tertiary architectures, enabling the entrapment of nanoparticles. The NGP features stimuli responsiveness, tunable surface charge, and good biocompatibility. The entrapped liposomes in NGP present enhanced distribution in lungs and extended duration of action in mice. And elongated release profiles for over 14 days is obtained for exosomes—making one‐of‐its‐kind unique platform to load and deliver nanoparticles.

New Polymorph of β-Cyclodextrin with a Higher Bioavailability

A new polymorph of anhydrous β-cyclodextrin (polymorph III) was obtained and characterized for the first time using powder X-ray diffraction, infrared spectroscopy, and thermal analysis. The solution enthalpy and time of dissolution in water were determined using solution calorimetry for this polymorph and compared with those of the dried commercial form of β-cyclodextrin (polymorph I), its amorphous form, and 2-hydroxypropyl-β-cyclodextrin. The specific heat capacities of polymorphs I and III were determined using differential scanning calorimetry across a wide range of temperatures, providing enthalpy and Gibbs energy values for the polymorphic transition at 298 K. The affinities of polymorph III and 2-hydroxypropyl-β-cyclodextrin for water were characterized by determining their hydration isotherms, which provided values of hydration Gibbs energy. Being energy-rich, the new-found polymorph of β-cyclodextrin has a significantly higher dissolution rate and an increased affinity for water compared with the dried commercial form of β-cyclodextrin. These properties render the new polymorph promising in industrial applications for guest inclusion in aqueous solutions and pastes, and may be a desirable alternative for water-soluble β-cyclodextrin derivatives.

A detection system for serum cholesterol based on the fluorescence color detection of beta-cyclodextrin-capped gold nanoclusters

Cholesterol is one of the major markers for cardiovascular diseases. Herein, a portable cholesterol measurement system based on fluorescence color detection was constructed by combining the high sensitivity of fluorescence analysis with the ease of color sensing to determine low levels of serum cholesterol. Cyclodextrin capping gold nanoclusters with blue-green emission were used as fluorescent probes because cholesterol exposure induced fluorescence enhancement of the probe due to the host–guest inclusion interaction between cholesterol and the cavity of cyclodextrin. The integrated sensing system consisted of modules including a microprocessor, a power supply, an LED light with a constant current source, an RGB color sensor, a display, and a darkroom. All the modules except the display screen were placed in a 3D printing darkroom to avoid interference from ambient light. An RGB color sensor TCS230 was applied to capture the RGB signals of the fluorescent color of the probe solution before and after cholesterol addition. Then the obtained RGB signals were converted into the signals in Hue, Saturation, and Value (HSV) color space with a central control chip STM32F407. The Hue value of the fluorescent color of the solution can discriminate the concentration change of cholesterol. Experimental results demonstrate that the system responds linearly to cholesterol in the concentration range of 20.00 ∼ 150.00 μmol·L-1 with a detection limit of 16.07 μmol·L-1 (3σ, n = 3). The detection of the system has good consistency and accuracy compared with the standard instrument, showing potential for the detection of low levels of serum cholesterol.

Impostorization in the ivory tower: less discussed but more vexing than impostor syndrome

PurposeGiven the lack of research on the lived experiences of racially minoritized women in academia, this paper provides primary accounts of their experience with impostorization. Impostorization refers to the policies, practices and seemingly innocuous interactions that make or intend to make individuals (i.e. women of color) question their intelligence, competence and sense of belonging.Design/methodology/approachTo explore experiences with impostorization and identify effective coping strategies to counter the debilitating effects of impostorization, 17 semi-structured interviews were conducted with women of color PhD students and faculty at universities throughout the USA and across disciplines.FindingsWhile impostor syndrome, which refers to feelings of inadequacy that individuals experience and a fear that they will be discovered as fraud, has garnered much attention, the present accounts suggest that the more vexing issue in academia is impostorization, not impostor syndrome. Forms of impostorization include microaggressions, grateful guest syndrome, invisibility and inclusion taxation.Originality/valueThe interviews reveal the implicit and explicit ways in which academia impostorizes racially minoritized women scholars and the coping strategies that they use to navigate and survive within academia. The accounts demonstrate the pernicious effects of labeling feelings of inadequacy and unbelonging as impostor syndrome rather than recognizing that the problem is impostorization. This is a call to change the narrative and go from a fix-the-individual to a fix-the-institution approach.

A comparative study of green solid contact ion selective electrodes for the potentiometric determination of Letrozole in dosage form and human plasma

Analysis of drugs clinically and their identification in biological samples are of utmost importance in the process of therapeutic drug monitoring, also in pharmacokinetic investigations and tracking of illicit medications. These investigations are carried out using a variety of analytical methods, including potentiometric electrodes. Potentiometric electrodes are a wonderful solution for researchers because they outperform other methods in terms of sustainability, greenness, and cost effectiveness. In the current study, ion-selective potentiometric sensors were assembled for the aim of quantification of the anticancer drug Letrozole (LTZ). The first step was fabrication of a conventional sensor based on the formation of stable host–guest inclusion complex between the cationic drug and 4-tert-butylcalix-8-arene (TBCAX-8). Two additional sensors were prepared through membrane modification with graphene nanocomposite (GNC) and polyaniline (PANI) nanoparticles. Linear responses of 1.00 × 10–5–1.00 × 10–2, 1.00 × 10–6–1.00 × 10–2 and 1.00 × 10–8–1.00 × 10–3 with sub-Nernstian slopes of 19.90, 20.10 and 20.30 mV/decade were obtained for TBCAX-8, GNC, and PANI sensors; respectively. The developed sensors were successful in determining the drug LTZ in bulk powder and dosage form. PANI modified sensor was used to determine LTZ in human plasma with recoveries ranging from 88.00 to 96.30%. IUPAC recommendations were followed during the evaluation of the electrical performance of the developed sensors. Experimental conditions as temperature and pH were studied and optimized. Analytical Eco-scale and Analytical GREEness metric were adopted as the method greenness assessment tools.

Electrochemical sensor for simultaneous determination of antiviral favipiravir drug, paracetamol and vitamin C based on host–guest inclusion complex of β-CD/CNTs nanocomposite

Favipiravir (FVI) is extensively used as an effective medication against several diverse infectious RNA viruses. It is widely administered as an anti-influenza drug. Combination therapy formed from FVI, paracetamol (PAR) and vitamin C (VC) is needed for treating patients diseased by RNA viruses. Thus, an efficient electrochemical sensor is developed for detecting FVI in human serum samples. The sensor is fabricated by casting a thin layer of carbon nanotubes (CNTs) over a glassy carbon (GC) electrode surface followed by electrodeposition of another layer of β-cyclodextrin (β-CD). Under optimized conditions, the sensor shows excellent catalytic effect for FVI, PAR and VC oxidation in the concentration ranges (0.08 µM → 80 µM), (0.08 µM → 50 µM) and (0.8 µM → 80 µM) with low detection limits of 0.011 μM, 0.042 μM and 0.21 μM, respectively. The combined effect of host–guest interaction ability of β-CD for the drugs, and a large conductive surface area of CNTs improves the sensing performance of the electrode. The sensor exhibits stable response over 4 weeks, good reproducibility, and insignificant interference from common species present in serum samples. The reliability of using the sensor in serum samples shows good recovery of FVI, PAR and VC.

Tuning cyclopropanecarboxaldehyde clathrate hydrates for enhancement of methane storage

This study investigates the tuning behavior of guest molecules in gas hydrates to achieve an optimal balance between the storage capacity and moderate formation conditions for CH4 gas storage. A new structure II hydrate-forming agent, cyclopropanecarboxaldehyde (CPCAld), was examined, and the guest inclusion behavior, crystal structure, and tuning behavior of the binary (CPCAld + CH4) clathrate hydrate were analyzed using 13C solid-state nuclear magnetic resonance (NMR), Raman spectroscopy, and synchrotron powder X-ray diffraction (PXRD). The phase equilibria and CH4 storage capacity of the binary (CPCAld + CH4) clathrate hydrates were also investigated. The experimental results provide insights into the design and optimization of gas hydrate storage systems for CH4 gas and other applications. The study demonstrates the potential for tuning CH4 content in clathrate hydrates by adjusting the concentration of CPCAld from 0.5 mol% to 5.56 mol%, which enhanced the storage and transportation of CH4 gas. The CH4 storage capacity of the binary (CPCAld + CH4) clathrate hydrate at 3.0 mol% CPCAld concentration was approximately 25 % higher than that of (CPCAld + CH4) hydrate at 5.56 mol% of CPCAld concentration. Overall, the exploration of a new hydrate former, CPCAld, and the understanding of the tuning behaviors of the binary (CPCAld + CH4) hydrate provide important insights into enhancing the storage capacity and contribute to the development of efficient and safe CH4 gas storage technologies using gas hydrates.

Transitions between Nanoporous crystalline α and β forms of poly(2,6-dimethyl-1,4-phenylene) oxide (PPO)

Nanoporous-crystalline (NC) α and β forms of Poly(2,6-dimethyl-1,4-phenylene) oxide (PPO), exhibit two different large helix conformations, both being suitable for intrahelical low-molecular-mass guest inclusion. α → β and β → α transitions can be achieved by sorption of liquid β-guests and α-guests (i.e., of guest inducing β and α forms by solution casting and by sorption in amorphous PPO), respectively. Both α → β and β → α transitions occur with complete loss of possibly present crystalline phase orientations (both axial and planar). Moreover, the reported data show that transitions between the two phases and the associated loss of crystalline phase orientation occur only for guests being good PPO solvents. These observations rule out the possibility of solid–solid transitions while can be rationalized by mechanisms involving a local dissolution of the NC phases. This local polymer dissolution is followed by host/guest co-crystallization with the helical conformation being different from the starting one and more suitable to host the used guest. These data fully confirm complete separation between the two NC phases while rule out the hypothesis of a continuum of NC phases between two limit ones.

Strong thickening performance and mechanism of supramolecular system constructed by β-cyclodextrin polymer included adamantane polymer

Introducing supramolecular interactions into polymer systems to improve their properties has recently become a hot topic. However, the formation of supramolecular polymers through host–guest interactions using two types of polymers is rarely reported. In this paper, a novel supramolecular system (ABMN) is prepared by host–guest inclusion of β-cyclodextrin polymer (PAAB) and adamantane polymer (PAMN). Subsequently, the thickening ability and viscoelasticity of ABMN are investigated. The microstructure of ABMN is studied by dynamic light scattering (DLS), atomic force microscopy (AFM), and field emission scanning electron microscopy (FE-SEM). The results show that at the molar ratio of PAAB: PAMN = 1:1 the optimal inclusion is observed with the binding constant between β-cyclodextrin group and adamantane group of 575.33 L/mol. The thickening ability of ABMN is greatly improved when compared to the original polymers. At 90℃ and 32868 mg/L, the viscosity of the ABMN system at 2000 mg/L can reach 38.5 mPa s. The microstructure results evidence that a larger hydrodynamic radius and denser spatial network structures in the ABMN system are formed through the host–guest inclusion interactions. Therefore, the supramolecular system exhibits strong thickening properties and demonstrates exceptional resistance to both temperature and salt, rendering it an optimal candidate for employment in EOR in high-temperature and high-salinity reservoirs.

Different Conformational Properties and Frequencies of Periodic Motion in the β‐ and γ‐Cyclodextrin

AbstractCyclodextrins (CDs) are cyclic oligosaccharides with application in different fields. These systems can encapsulate hydrophobic molecules and allow their solubilization in water. CDs and CD complexes can self‐associate forming aggregate or micelle‐like structures. Theoretical studies based on molecular mechanics (MM) and molecular dynamics (MD) simulations are demonstrated to be a useful tool for understanding the conformational properties, the stability, their host–guest inclusion complexes in the solid state or in aqueous solution in a good agreement with experimental data. The aim of this work is to compare at atomistic level the conformational properties, the flexibility of the native β‐ and γ‐CD. The β‐CD shows very slightly deviation from C7 symmetry, and its glycosidic oxygens are on a flat plane, while in the γ‐CD they are in different arrangement on a curved plane. From the variation of the distance between opposite glycosidic oxygens in these CDs, the frequencies of motion due to periodic motions are calculated during MD run. These frequencies indicate faster periodic motion for the β‐CD and slower for the γ‐CD having larger dimension and less symmetrical structure. MD simulations are an interesting tool for investigating the flexibility of these systems, their possible periodic motion, and their frequencies of motion.