Supramolecular Assembly Based on Calix(4)arene and Aggregation-Induced Emission Photosensitizer for Phototherapy of Drug-Resistant Bacteria and Skin Flap Transplantation

Photodynamic therapy as a burgeoning and non-invasive theranostic technique has drawn great attention in the field of antibacterial treatment but often encounters undesired phototoxicity of photosensitizers during systemic circulation. Herein, a supramolecular substitution strategy is proposed for phototherapy of drug-resistant bacteria and skin flap repair by using macrocyclic p-sulfonatocalix(4)arene (SC4A) as a host, and two cationic aggregation-induced emission luminogens (AIEgens), namely TPE-QAS and TPE-2QAS, bearing quaternary ammonium group(s) as guests. Through host-guest assembly, the obtained complex exhibits obvious blue fluorescence in the solution due to the restriction of free motion of AIEgens and drastically inhibits efficient type I ROS generation. Then, upon the addition of another guest 4,4'-benzidine dihydrochloride, TPE-QAS can be competitively replaced from the cavity of SC4A to restore its pristine ROS efficiency and photoactivity in aqueous solution. The dissociative TPE-QAS shows a high bacterial binding ability with an efficient treatment for methicillin-resistant Staphylococcus aureus (MRSA) in dark and light irradiation. Meanwhile, it also exhibits an improved survival rate for MRSA-infected skin flap transplantation and largely accelerates the healing process. Thus, such cascaded host-guest assembly is an ideal platform for phototheranostics research.

2D MOF-enhanced SPR detector based on tunable supramolecular probes for direct and sensitive detection of DOX in serum

Therapeutic drug monitoring of doxorubicin (DOX) is important to study pharmacokinetics in patients undergoing chemotherapy for reduction of side effects and improve patient survival by rationally controlling the dose of DOX. A fast and ultra-sensitive surface plasmon resonance (SPR) detector without sample pre-handling was developed for DOX monitoring. First, the two-dimensional metal-organic framework was modified on the Au film to enhance SPR, and then, the supramolecular probes with tunable cavity structure were self-assembled at the sensing interface for direct detection of DOX through specific host-guest interactions with a low detection limit of 60.24 pM. The precise monitoring of DOX in serum proved the possibility of clinical application with recoveries in the range 102.86-109.47%. The mechanisms of host-guest interactions between supramolecular and small-molecule drugs were explored in depth through first-principles calculations combined with SPR experiments. The study paves the way for designing facile and sensitive detectors and provides theoretical support and a new methodology for the specific detection of small molecules through calixarene cavity modulation.

Novel biotin-linked amphiphilic calix[4]arene-based supramolecular micelles as doxorubicin carriers for boosted anticancer activity

Supramolecular carrier-mediated chemotherapy is a highly attractive strategy for targeted drug delivery. In this study, four novel biotin-linked calix[4]arenes BPCA1-BPCA4 have been rationally designed to construct nano-complex with doxorubicin. The in vitro and in vivo assessments reveal that BPCA4-DOX with excellent stability are capable of affording significantly superior anti-tumor activity and lower side effects.

Supramolecular Modulation of Tumor Microenvironment through Pillar[5]arene-Based Host-Guest Recognition to Synergize Cancer Immunotherapy

Despite the tremendous breakthrough of immunotherapy, the low response rate and resistance of immune checkpoint inhibitors (ICIs) toward solid tumors occur frequently. A highly hypoxic tumor microenvironment (TME) provides tumor cells with high concentrations of HIF-1α and polyamines to evade immune cell destruction. Reprogramming of an immunogenic TME has exhibited a brilliant future to boost immunotherapeutic performances. Herein, a supramolecular nanomedicine (TAPP) is developed on the basis of host-guest molecular recognition and metal coordination, showing the capability to remodel the immunosuppressive TME. Tamoxifen (Tmx) and Fe3+ are encapsulated into TAPP to achieve the combination of chemotherapy and chemodynamic therapy (CDT). Tmx directly downregulates HIF-1α, and a pillar[5]arene-based macrocyclic host successfully eliminates polyamines in tumors. Enhanced immunogenic cell death is achieved by Tmx and Fe3+, and the therapeutic efficacy is further synergized by immune checkpoint blockade (ICB) therapy. This supramolecular reprogramming modality encourages cytotoxic T lymphocyte infiltration, achieving pre-eminent immune response and long-term tumor suppression.

Sulfonate-modified calixarene-based porous organic polymers for electrostatic enhancement and efficient rapid removal of cationic dyes in water

Developing of fast and efficient adsorbents for removal of low concentration refractory organics in water is significant. Herein, a novel calix[4]arene-based porous organic polymer CaPy is constructed through Sonogashira-Hagihara cross-coupling polycondensation. The strong polar sulfonate is further anchored onto the polymer skeleton of CaPy and three sulfonate-modified anionic polymers CaPy-S1, CaPy-S2, and CaPy-S3 were obtained and fully characterized. The adsorption isotherms showed that the maximum adsorption capacities of CaPy, CaPy-S1, CaPy-S2, and CaPy-S3 toward methylene blue (MB) were 270, 1454, 558 and 1381 mg g^-1, whereas those for Rhodamine B (RhB) were 183, 2653, 1132, and 1796 mg g^-1, respectively. The maximum adsorption capacity toward RhB was the highest reported vale among the currently used synthetic adsorbents. In addition, the pseudo-second-order rate constants of CaPy, CaPy-S1, CaPy-S2, and CaPy-S3 toward MB were 0.00572, 0.488, 2.24, and 0.192 g mg^-1 min^-1, respectively, and those toward RhB were 0.000234, 0.138, 0.0819, and 0.203 g mg^-1 min^-1, respectively. The pseudo-second-order rate constant of CaPy-S2 toward MB was 2.24 g mg^-1 min^-1 indicating one of the highest adsorption speeds. The activation energy of CaPy-S1 for RhB and MB were 121 and 109 kJ mol^-1, respectively, demonstrating that the adsorption of both dyes on CaPy-S1 was chemisorption process. Further, the obtained values of Gibbs free energy were negative, revealing that the adsorption process was spontaneous. This work provides an effective approach for improving adsorption performance via post-modification.

Stability of composite polymeric beads containing a calix[4]arene-mono-crown-6 ligand for radio-cesium separation

Bis-octyloxy-calix[4]arene-mono-crown-6 (BOCMC) is a selective ligand for Cs(I) cation, and has been used in solvent extraction method for its separation from acidic feed. Looking at the various advantages and ease of extraction chromatography separation method, an attempt was made to prepare stable composite beads containing BOCMC entrapped in a suitable polymeric matrix. Therefore, an attempt was made to prepare a series of composite polymeric beads containing BOCMC in polysulfone (PS), polyether sulfone (PES) and sodium alginate polymeric matrix. Preparations of the beads were attempted by dissolving the solid BOCMC in the polymer solution, and also by using the ligand solution in isodecanol/dodecane and ionic liquids and then mixing in the polymeric solution. Every attempt failed to get the desired quality of beads in PES and sodium alginate matrix. However, very good quality and stable beads were obtained when 25 mM ligand solution dissolved in C₈mim.Tf₂N ionic liquid was used in PS matrix. Detail study for the extraction chromatography separation of Cs(I) was studied with BOCMC/C₈mim.Tf₂N/PS composite beads. Detail investigations on the preparation, characterization, reusability and radiation stability of these beads have been studied and reported in details.

Bifunctional Calix[4]arene-Coated Gold Nanoparticles for Orthogonal Conjugation

Gold nanoparticles (AuNPs) are currently intensively exploited in the biomedical field as they possess interesting chemical and optical properties. Although their synthesis is well-known, their controlled surface modification with defined densities of ligands such as peptides, DNA, or antibodies remains challenging and has generally to be optimized case by case. This is particularly true for applications like in vivo drug delivery that require AuNPs with multiple ligands, for example a targeting ligand and a drug in well-defined proportions. In this context, we aimed to develop a calixarene-modification strategy that would allow the controlled orthogonal conjugation of AuNPs, respectively, via amide bond formation and copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC). To do this, we synthesized a calix[4]arene-tetradiazonium salt bearing four PEG chains ended by an alkyne group (C1) and, after optimization of its grafting on 20 nm AuNPs, we demonstrated that CuAAC can be used to conjugate an azide containing dye (N₃-cya7.5). It was observed that AuNPs coated with C1 (AuNPs-C1) can be conjugated to approximately 600 N₃-cya7.5 that is much higher than the value obtained for AuNPs decorated with traditional thiolated PEG ligands terminated by an alkyne group. The control over the number of molecules conjugated via CuAAC was even possible by incorporating a non-functional calixarene (C2) into the coating layer. We then combined C1 with a calix[4]arene-tetradiazonium salt bearing four carboxyl groups (C3) that allows conjugation of an amine (NH₂-cya7.5) containing dye. The conjugation potential of these bifunctional AuNPs-C1/C3 was quantified by UV-vis spectroscopy: AuNPs decorated with equal amount of C1 and C3 could be conjugated to approximately 350 NH₂-dyes and 300 N₃-dyes using successively amide bond formation and CuAAC, demonstrating the control over the orthogonal conjugation. Such nanoconstructs could benefit to anyone in the need of a controlled modification of AuNPs with two different molecules via two different chemistries.

Green, Efficient Detection and Removal of Hg2+ by Water-Soluble Fluorescent Pillar[5]arene Supramolecular Self-Assembly

Developing a water-soluble supramolecular system for the detection and removal of Hg²⁺ is extremely needed but remains challenging. Herein, we reported the facile construction of a fluorescent supramolecular system (H⊃G) in 100% water through the self-assembly of carboxylatopillar[5]arene sodium salts (H) and diketopyrrolopyrrole-bridged bis(quaternary ammonium) guest (G) by host–guest interaction. With the addition of Hg²⁺, the fluorescence of H⊃G could be efficiently quenched. Since Hg²⁺ showed synergistic interactions (coordination and Hg²⁺- cavity interactions with G and H, respectively), crosslinked networks of H⊃G@Hg²⁺ were formed. A sensitive response to Hg²⁺ with excellent selectivity and a low limit of detection (LOD) of 7.17 × 10⁻⁷ M was obtained. Significantly, the quenching fluorescence of H⊃G@Hg²⁺ can be recovered after a simple treatment with Na₂S. The reusability of H⊃G for the detection of Hg²⁺ ions was retained for four cycles, indicating the H⊃G could be efficiently used in a reversible manner. In addition, the H⊃G could efficiently detect Hg²⁺ concentration in real samples (tap water and lake water). The developed supramolecular system in 100% water provides great potential in the treatment of Hg²⁺ detection and removal for environmental sustainability.

Effects of the Calix[4]arene Derivative Compound OTX008 on High Glucose-Stimulated ARPE-19 Cells: Focus on Galectin-1/TGF-β/EMT Pathway

Diabetic retinopathy (DR) is a neurovascular disease characterized by the reduction of retina integrity and functionality, as a consequence of retinal pigment epithelial cell fibrosis. Although galectin-1 (a glycan-binding protein) has been associated with dysregulated retinal angiogenesis, no evidence has been reported about galectin-1 roles in DR-induced fibrosis. ARPE-19 cells were cultured in normal (5 mM) or high glucose (35 mM) for 3 days, then exposed to the selective galectin-1 inhibitor OTX008 (2.5–5–10 μM) for 6 days. The determination of cell viability and ROS content along with the analysis of specific proteins (by immunocytochemistry, Western blotting, and ELISA) or mRNAs (by real time-PCR) were performed. OTX008 5 μM and 10 μM improved cell viability and markedly reduced galectin-1 protein expression in cells exposed to high glucose. This was paralleled by a down-regulation of the TGF-β/, NF-kB p65 levels, and ROS content. Moreover, epithelial–mesenchymal transition markers were reduced by OTX008 5 μM and 10 μM. The inhibition of galectin-1 by OTX008 in DR may preserve retinal pigment epithelial cell integrity and functionality by reducing their pro-fibrotic phenotype and epithelial–mesenchymal transition phenomenon induced by diabetes.

Fluorescence switchable sensor enabled by a calix[4]arene-Cu(II) complex system for selective determination of itraconazole in human serum and aqueous solution

A switchable fluorescence sensor based on a calix (Monapathi et al., 2021) [4]arene:Cu²⁺ complex (FLCX/Cu) has been developed for the detection of itraconazole (ITZ) with high sensitivity and specificity. For the development of the sensor, the selective complexation of a fluorescent calix (Monapathi et al., 2021) [4]arene derivative (FL-CX) with the Cu²⁺ ion causing fluorescence quenching was utilized. In addition, the sensor properties of the FLCX/Cu prepared were investigated. For this purpose, various substances (selected anions, cations, and drugs) with which ITZ can be found together were studied in an aqueous solution. Limit of detection (LOD) and limit of quantification (LOQ) values were determined in the range of 1.00-60.0 μg/L as 3.34 μg/L and 11.1 μg/L for ITZ, respectively. Moreover, the real sample analyses were performed in human serum and tablet form. Furthermore, the effect of some possible serum contents on sensor performance was also studied. All these studies confirmed the development of a simple, precise, accurate, reproducible, highly sensitive, and very stable fluorescence sensor.

Sulfonated calixarene modified Poly(methyl methacrylate) nanoparticles:A promising adsorbent for Removal of Vanadium Ions from aqueous media

The poly (methyl methacrylate) (PMMA)-based nanoparticle was synthesized by surfactant-free emulsion polymerization method and then post modified with Calixarene using (3-Aminopropyl)triethoxysilane organo-silane as a linker after OH-treatment. The prepared structure was applied for efficient adsorption of Vanadium ions in the aqueous solution after characterization by FT-IR, SEM, TEM, DLS, and EDX. Additional investigations discovered that the prepared adsorbent has a good capacity to adsorb vanadium ions. The effect of key experimental factors was studied to find the optimal point of adsorbent efficiency including the initial concentration of analyte, sorbent dosage, pH of the solution, contact time, and type/quantity of the eluents. It was specified, the maximum adsorption capacity for the synthesized nanoparticles was obtained about 322 mg g^-1. The adsorption mechanism was revealed that the model of Langmuir isotherm well-matched compared to the others due to the calculated equilibrium data. Besides, the kinetics of the adsorption process was fitted with pseudo-second-order. Eventually, the prepared adsorbent was successfully applied in vanadium adsorption from real water media.

Ultrastable Silver Nanoparticles for Rapid Serology Detection of Anti-SARS-CoV-2 Immunoglobulins G

Dipstick assays using silver nanoparticles (AgNPs) stabilized by a thin calix[4]arene-based coating were developed and used for the detection of Anti-SARS-CoV-2 IgG in clinical samples. The calixarene-based coating enabled the covalent bioconjugation of the SARS-CoV-2 Spike Protein via the classical EDC/sulfo-NHS procedure. It further conferred remarkable stability to the resulting bioconjugated AgNPs, as no degradation was observed over several months. In comparison with lateral-flow immunoassays (LFIAs) based on classical gold nanoparticles, our AgNP-based system constitutes a clear step forward, as the limit of detection for Anti-SARS-CoV-2 IgG was reduced by 1 order of magnitude and similar signals were observed with 10 times fewer particles. In real clinical samples, the AgNP-based dipstick assays showed impressive results: 100% specificity was observed for negative samples, while a sensitivity of 73% was determined for positive samples. These values match the typical sensitivities obtained for reported LFIAs based on gold nanoparticles. These results (i) represent one of the first examples of the use of AgNP-based dipstick assays in the case of real clinical samples, (ii) demonstrate that ultrastable calixarene-coated AgNPs could advantageously replace AuNPs in LFIAs, and thus (iii) open new perspectives in the field of rapid diagnostic tests.

Synchronous Imaging in Golgi Apparatus and Lysosome Enabled by Amphiphilic Calixarene-Based Artificial Light-Harvesting Systems

Artificial supramolecular light-harvesting systems have expanded various properties on photoluminescence, enabling promising applications on cell imaging, especially for imaging in organelles. Supramolecular light-harvesting systems have been used for imaging in some organelles such as lysosome, Golgi apparatus, and mitochondrion, but developing a supramolecular light-harvesting platform for imaging two organelles synchronously still remains a great challenge. Here, we report a series of lower-rim dodecyl-modified sulfonato-calix[4]arene-mediated supramolecular light-harvesting platforms for efficient light-harvesting from three naphthalene diphenylvinylpyridiniums containing acceptors, Nile Red, and Nile Blue. All of the constructed supramolecular light-harvesting systems possess high light-harvesting efficiency. Furthermore, when the two acceptors are loaded simultaneously in a single light-harvesting donor system for imaging in human prostate cancer cells, organelle imaging in lysosome and Golgi apparatus can be realized at the same time with distinctive wavelength emission. Nile Red receives the light-harvesting energy from the donors, reaching orange emissions (625 nm) in lysosome while Nile Blue shows a near-infrared light-harvesting emission at 675 nm in Golgi apparatus in the same cells. Thus, the light harvesting system provides a pathway for synchronously efficient cell imaging in two distinct organelles with a single type of photoluminescent supramolecular nanoparticles.

Calixarene-modified albumin for stoichiometric delivery of multiple drugs in combination-chemotherapy

Rationale: In combination chemotherapy, the molar ratio of drugs is a critical parameter that determines the synergistic effects. However, most co-delivery vectors are incapable of maintaining the optimal molar ratio of drugs throughout the delivery process. Herein, a calixarene-modified albumin (CaMA), which can co-deliver multiple drugs with precise control of the drug ratio, is presented. Methods: CaMA was prepared by chemically conjugating multiple sulfonate azocalix[4]arenes (SAC4A) onto the surface of bovine serum albumin (BSA). The precise drug loading and synchronous drug release were measured using fluorescence spectroscopy. Mouse tumor cell 4T1 and 4T1-bearing mice were used to evaluate the combined effects of mitomycin C (MMC) and doxorubicin (DOX) in vitro and in vivo. Results: With multiple hypoxia-responsive calixarenes conjugated onto a single albumin molecule, CaMA achieved precise drug loading and synchronous release of multiple drugs into the tumor microenvironment. This unique drug loading and release mechanism ensures that CaMA maintains the drug ratio from the initial drug loading to the release site, providing a solid foundation for multi-drug combination therapy with the goal of achieving predictable therapeutic outcomes in vivo. The delivery of the model drug combination MMC and DOX at a prescreened ratio via CaMA achieved significantly enhanced tumor suppression and reduced systemic toxicity. Conclusions: This stoichiometric delivery feature makes CaMA a powerful tool for the development of combination chemotherapy and personalized medications for cancer treatment.

New Calix[4]arene—Fluoresceine Conjugate by Click Approach—Synthesis and Preparation of Photocatalytically Active Solid Lipid Nanoparticles

New fluorescent systems for photocatalysis, sensors, labeling, etc., are in great demand. Amphiphilic ones are of special interest since they can form functional colloidal systems that can be used in aqueous solutions. A new macrocycle platform for click chemistry and its adduct with o-propargylfluoresceine was synthesized and characterized using modern physical techniques. Nanosized solid lipid nanoparticles (SLNs) from the calixarene—fluoresceine adduct were synthesized through the solvent injection technique and well-characterized in the solution and in solid state using light-scattering and microscopy methods. The maximum fluorescence intensity of the SLNs was found to be in the pH range from 7 to 10. The Förster resonance energy transfer (FRET) efficiency from SLNs to rhodamine 6g was found to be 97.8%. Finally, pure SLNs and the FRET system SLNs—Rh6G were tested in model photocatalytic ipso oxidative hydroxylation of phenylboronic acid under blue LED light. The SLNs—Rh6G system was found to be the best, giving an almost qualitative phenol yield, which was shown by HPLC-UV analysis.

Synthesis, Crystal Structure and Separation Performance of p-tert-butyl(tetradecyloxy)calix[6]arene

This work describes the investigation of separation performance of the p-tert-butyl(tetradecyloxy)calix[6]arene (C6A-C10-OH) as stationary phase for gas chromatography (GC) separations. Its structure was characterized by IR, 1H NMR, 13C NMR, MS and single-crystal X-ray diffraction analysis. The C6A-C10-OH column shows good separation capacity for aliphatic, aromatic and cis-/trans- isomers. Especially, it exhibits multiple molecular recognition interactions for the analytes with a wide range of polarity, including dispersion, π-π, H-bonding and dipole-dipole interactions. The present work provides experimental and theoretical basis for the designing of the new calixarene stationary phases in GC analyses.

Synthesis and Application of Silica Supported Calix[4]arene Derivative as a New Processing Aid Agent for Reducing Hysteresis of Tread Rubber Compounds Used in Low Rolling Resistance Tires

Rolling resistance is one of the most important properties of a tire which is highly dependent on the viscoelastic properties of its rubber compounds. There are a lot of ways to reduce this parameter both in construction improvement of the tire and changing in rubber compound formulation especially in tire tread formulation. Rubber scientists have been trying to introduce new processing aid agents beyond the traditional tire components for reducing the rolling resistance. In this study, a unique structure of silica-supported calix[4]arene (SS-CSC[4]A) has been synthesized and applied as a processing aid agent in tire tread formulation. Fourier-transform infrared spectroscopy (FTIR), Nuclear Magnetic Resonance (1HNMR and 13CNMR), 29Si CP/MAS spectroscopy, thermal gravimetric analysis (TGA), elemental analysis, and acid-base titration were used to characterize its structure. Scanning Electron Microscopy (SEM) use to investigate the effect of prepared material on qualification of filler dispersion in the rubber matrix. The viscoelastic properties of the prepared rubber compound were measured by Dynamic Mechanical Thermal Analysis (DMTA) which showed the great decrease in rolling resistance of rubber compound based on SS-CSC[4]A as a processing aid agent. The mechanical and rheological properties of obtained tread rubber compound measured by tensometer and MDR rheometer showed no sensible changes in these properties.

Azo-methoxy-calix[4]arene complexes with metal cations for chemical sensor applications: Characterization, QTAIM analyses and dispersion-corrected DFT- computations

In this work, the structures, quantum chemical descriptors, morphologic characterization of the azo-methoxy-calix[4]arene were investigated. The analyses and interpretation of the theoretical and the experimental IR spectroscopy results for the corresponding compounds was performed. The complexation of the azo-methoxy-calix[4]arene with Zn²⁺,Hg²⁺ , Cu²⁺ , Co²⁺, Ni²⁺ , Pb²⁺ and Cd²⁺metal cations has been calculated by the dispersion corrected density functional theory (DFT-D3). The values of the interaction energies show that the specific molecule is more selective to the Cu²⁺ cation. The study of the reactivity parameters confirms that the azo-methoxy-calix[4]arene molecule is more reactive and sensitive to the Cu²⁺ cation than that Co²⁺ and Cd²⁺. In addition, the investigation of the electrophilic and nucleophilic sites has been studied by the molecular electrostatic potential (MEP) analysis. The Hirshfeld surface (HS) analysis of the azo-methoxy-calix[4]arene-Cu²⁺ interaction have been used to understand the Cu⋯hydrogen-bond donors formed between the cation and the specific compound. The Quantum Theory of Atoms in Molecules (QTAIM) via Non covalent Interaction (NCI) analysis was carried out to demonstrate the nature, the type and the strength of the interaction formed between the Cu²⁺ cation and the two symmetrical ligands and the cavity. Finally, the chemical sensor properties based on the Si/SiO₂/Si₃N₄/Azo-methoxy-calix[4]arene for detection of Cu²⁺ cation were studied. Sensing performances are determined with a linear range from 10^-5.2 to 10^-2.2 M. The Si/SiO₂/Si₃N₄/azo-methoxy-calix[4]arene structure is a promoter to have a good performance sensor.

Uncommon Supramolecular Phosphorescence-Capturing Assembly Based on Cucurbit[8]uril-Mediated Molecular Folding for Near-Infrared Lysosome Imaging

The construction of highly effective phosphorescence energy transfer capturing system still remains great challenge in aqueous phase. Herein, a high-efficiency supramolecular purely organic room temperature phosphorescence (RTP)-capturing system via a secondary assembly strategy by taking advantage of cucurbit[8]uril (CB[8]) and amphiphilic calixarene (SC4AH) is reported. Comparing with free bromonaphthalene-connected methoxyphenyl pyridinium salt (G), G⊂CB[8] exhibits an emerging RTP emission peak at 530 nm. Moreover, G⊂CB[8] further interacts with SC4AH to form the ternary assembly G⊂CB[8]  @  SC4AH accompanied by remarkably enhanced RTP emission. Interestingly, RTP-capturing systems with delayed near-infrared (NIR) emissive performance (635, 675 nm) are feasibly acquired by introducing Nile Red (NiR) or Nile Blue (NiB) as the acceptor into hydrophobic layer of G⊂CB[8] @ SC4AH, possessing ultrahigh antenna effects (352.9, 123.5) at a high donor/acceptor ratio (150:1, 300:1). More importantly, cell experiments indicate that G⊂CB[8]  @  SC4AH/NiB not only hold low cytotoxicity but also can successfully realize NIR lysosome-targeted imaging of A549 cancer cells. This RTP-capturing system of delayed NIR emission via multistage assembly strategy offers a new approach for NIR imaging in living cells.

Antibacterial and Antibiofilm Formation Activities of Pyridinium-Based Cationic Pillar[5]arene Against Pseudomonas aeruginosa

An omnipresent pathogenic bacterium, Pseudomonas aeruginosa (P. aeruginosa PAO1), is easy to contaminate environmental water or foods, causing daily food spoilage and infections. The biofilm-forming ability and bacterial resistance of P. aeruginosa PAO1 make it difficult to be eradicated by traditional bacteriostatic agents. In this work, we designed and synthesized a pyridinium-based pillar[5]arene (PP5), while trimethylammonium-based pillar[5]arene (TP5) was used as a control compound. After clear characterization, the antibacterial and antibiofilm activities as well as the microbial resistance of TP5 and PP5 against P. aeruginosa PAO1 were extensively examined. It was revealed that PP5 exhibited good inhibition activity with the minimum inhibitory concentration (MIC) of 0.051 mmol/L, while no significant antibacterial and biofilm formation activity for TP5 against P. aeruginosa PAO1 was observed. More importantly, PP5 had negligible antimicrobial resistance even after 18th passages. A transmission electron microscope (TEM) showed that PP5 could physically disrupt the cell membranes, causing the leakage of internal constituents, which is possibly ascribed to the synergistic penetrability and π-π interactions of strain, thus greatly reduced the development of bacterial resistance. Overall, the presented studies indicated that pyridinium moieties could facilitate the cationic pillar[5]arene to generate surprising antibacterial and antibiofilm formation ability against P. aeruginosa PAO1.

Nano-scale selective and sensitive optical sensor for metronidazole based on fluorescence quenching: 1H-Phenanthro[9,10-d]imidazolyl-calix[4]arene fluorescent probe

It is crucial to determine and control the metronidazole (MET) ingredient in food and pharmaceuticals for human health and food safety. Even though many sensors have been previously reported to detect MET, there is still a need for a highly selective and sensitive, easy, fast, cost-effective sensor in this area. Herein, we report a fluorescent calix[4]arene derivative (PIMC) for highly selective and sensitive and facile and rapid MET detection based on fluorescence (FL) quenching. The highest FL quenching occurs when PIMC is exposed to MET solution at 400 nm (λ_ex = 340). Owing to the quenching efficacy of MET linearly up to 5.5 × 10⁴ nM was obtained a detection limit of 2.44 nM. Besides, interferences of other pharmaceuticals and ions on probe performance were investigated. The FL probe was successful in MET detection without the assistance of any separation techniques in a pharmaceutical sample (tablet) with an acceptable recovery of 101.3%. The applicability of the current probe as a paper-based sensor to MET detection has been successfully tested. As a result, the proposed probe presents a fast and suitable strategy to sensitive and selective detect MET and proves a good potential for practical applications, especially pharmaceutical preparations.

Nitrile-calixarene grafted magnetic graphene oxide for removal of arsenic from aqueous media: Isotherm, kinetic and thermodynamic studies

A novel adsorbent was developed based on nitrile functionalized calix [4]arene grafted onto magnetic graphene oxide (N-Calix-MGO) for remediation of arsenic (III) ions from aqueous media. The nanocomposite was characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The effective parameters on adsorption efficiency such as pH, adsorbent dosage, contact time, initial concentration, and temperature were studied. The adsorption process was provided with a high removal efficiency up to (90%) at pH 6 which followed by IUPAC Type II pattern. The mathematical models of kinetics and isotherm validated the experimental process. The adsorption kinetic is followed pseudo-first-order model with R² > 0.9. The adsorption equilibrium was well fitted on the Freundlich model (R² ∼ 0.96) as compared Langmuir model (R² ∼ 0.75). Hence, the Freundlich model suggested a multilayer sorption pattern with a physisorption mechanism for arsenic (III) uptake ono developed nanocomposite with a sorption capacity of 67 mg/g for arsenic. The Gibbs free energy (ΔG° < -20 kJ/mol) showed As(III) uptake ono N-Calix-MGO nanocomposite was the physical adsorption mechanism.

Sulfonated calix[4]arene functionalized SiO2@TiO2 for recognition of lysine methylation

Lysine methylations are common protein post-translational modifications (PTMs), that play significant roles in regulating gene activities. Studies of their functions and connections with diseases have important values. However, due to the small variations from their native structures and very low component proportions, it is very difficult to extract methylated peptides from biological mixtures. In this research, a new material that utilizes sulfonated calix[4]arene (SC4A) as the recognition unit and silica coated with TiO₂ as carrier, denoted as SiO₂@TiO₂@SC4A, was synthesized. The equilibrium binding experiments demonstrated that SiO₂@TiO₂@SC4A can identify lysine and arginine methylation and peptides with these methylated residues. The maximum isotherm binding capacities are 70.0, 55.9, 31.4 and 24.8 μmol g^-1 for Lys(Me₃), Lys(Me)₂, Lys(Me) and Lys, respectively. It demonstrated that the higher the degree of methylation, the stronger the interactions. In addition, the analyses of high performance liquid chromatography (HPLC) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) demonstrated that peptides with methylated lysine or arginine can be selectively extracted from spiked histone trypsin digestion. The recoveries for the spiked GGAK(Me)R, GGAKR(Me)₂ and GGAK(Me)₃R are 83%, 78%, and 84% respectively. The experiments from the nuclear extracts of HeLa cells also illustrated that SiO₂@TiO₂@SC4A holds a potential in the enrichment and identification of lysine methylations.

Calixarene-Embedded Nanoparticles for Interference-Free Gene-Drug Combination Cancer Therapy

Combination therapy based on molecular drugs and therapeutic genes provides an effective strategy for malignant tumor treatment. However, effective gene and drug combinations for cancer treatment are limited by the widespread antagonism between therapeutic genes and molecular drugs. Herein, a calixarene-embedded nanoparticle (CENP) is developed to co-deliver molecular drugs and therapeutic genes without compromising their biological functions, thereby achieving interference-free gene-drug combination cancer therapy. CENP is composed of a cationic polyplex core and an acid-responsive polymer shell, allowing CENP loading and delivering therapeutic genes with improved circulation stability and enhanced tumor accumulation. Moreover, the introduction of carboxylated azocalix[4]arene, which is a hypoxia-responsive calixarene derivatives, in the polyplex core endows CENP with the capability to load molecular drugs through the host-guest complexation as well as inhibit the interference between the drugs and genes by encapsulating the drugs into its cavity. By loading doxorubicin and a plasmid DNA-based CRISPR interference system that targets miR-21, CENP exhibits the significantly enhanced anti-tumor effects in mice. Considering the wide variety of calixarene derivatives, CENP can be adapted to deliver almost any combination of drugs and genes, providing the potential as a universal platform for the development of interference-free gene-drug combination cancer therapy.

Novel integrated sensing system of calixarene and rhodamine molecules for selective colorimetric and fluorometric detection of Hg2+ ions in living cells

Three novel and facile calixarene derivatives (5, 6 and 7), which were appended with four rhodamine units at the upper rim of calixarene skeleton, were firstly prepared and evaluated for selective detection of metal ions in solution. Receptors (5) and (7) indicated immediate turn on fluorescence output toward Hg²⁺ ions over other most competitive metal ions with the ultralow detection limits, indicating their high efficiency and reliability. The binding response to Hg²⁺ ions in solution was also observed through a chromogenic change (from colorless to pale pink). Furthermore, in vitro and bio-imaging studies with MCF-7 or MIA PaCa-2 cell lines were also performed to investigate the use of receptors in biological systems in order to monitor of mercury ions. Results showed that new receptors (5) or (7) were cell permeable and suitable for real-time imaging of Hg²⁺ in living cells (MCF-7) or (MIA PaCa-2) without any damage to healthy cell lines (HEK 293).

A pillar[5]arene-based fluorescent sensor for sensitive detection of L-Met through a dual-site collaborative mechanism

L-Methionine (L-Met) is one of the essential amino acids in human health, efficiently detect L-Met is a significant issue. Herein, a concept "dual-site collaborative recognition" had been successfully introduced into the design and achieved high selective and sensitive recognition of L-Met. In order to realize the "dual-site collaborative recognition", we rationally designed and synthesized an ester functionalized pillar[5]arene-based fluorescent sensor (SP5). And it shows blue Aggregation-induced emission (AIE) fluorescence. In the SP5, the pillar[5]arene group act as C-H···π interactions site, and ester group serve as multi hydrogen bonding acceptor. Interestingly, the SP5 exhibited high selectivity and sensitivity (2.84 × 10^-8 M) towards L-Met based on the collaboration of electron-rich cavernous pillar[5]arene group and ester group through C-H···π and H-bond interactions, respectively. This "dual-site collaborative recognition" mechanism has been investigated by ¹H NMR, ESI-MS and theoretical calculation including frontier orbital (HOMO and LUMO), electrostatic potential (ESP) and the noncovalent interaction (NCI). These theoretical calculations not only support the proposed host-guest recognition mechanism, but also provided visualized information on the "dual-site collaborative recognition" mode. Furthermore, the concept "dual-site collaborative recognition" is an effective strategy for easily detecting biological molecules.

Tunable nanogels by host-guest interaction with carboxylate pillar[5]arene for controlled encapsulation and release of doxorubicin

Nanogels have become one of the most attractive systems for application as delivery vectors or for theragnostic approaches in nanomedicine, which is mainly related to the ease of their synthesis by precipitation polymerization. However, only a few suitable monomers have been reported so far and stabilization of the nanogels requires the incorporation of rather defined amounts of in most cases charged co-monomers, such as acrylic acid, which limits the flexibility in their design. Here, we present an alternative approach using a pyridinium based monomer, which not only provides stability due to the positive charge, but also allows the attachment of functional carboxylate-pillar[5]arene by the formation of a host-guest complex. This approach is tested on pH-sensitive nanogels based on the monomer N-[(2,2-dimethyl-1,3-dioxolane)methyl]acrylamide (DMDOMA) featuring an acetal group, which is hydrolysed under acidic conditions. As carboxylates are known to catalyze this hydrolysis, we tested different amounts of carboxylate-pillar[5]arenes to tune the hydrolysis rate of the acetal group and found a direct correlation. Additional encapsulation studies with doxorubicin (DOX) revealed that surface potential and charge density represent additional key factors not only for the loading capacity, but also for the release profile of the nanogels. The option to tune such properties simply by the addition of a co-factor, in this case, the carboxylate-pillar[5]arenes provides a powerful tool to optimize characteristics of functional nanogels for drug delivery or other applications.

t-Butyl calixarene/Fe2O3@MWCNTs composite-based potentiometric sensor for determination of ivabradine hydrochloride in pharmaceutical formulations

Ivabradine hydrochloride (IVB) has shown high medical importance as it is a medication for lowering the heart rate for the symptomatic chronic heart failure and symptomatic management of stable angina pectoralis. The high dose of IVB may cause severe and prolonged bradycardia, uncontrolled blood pressure, headache, and blurred vision. In this study, a highly sensitive carbon-paste electrode (CPEs) was constructed for the potentiometric determination of IVB in pharmaceutical formulations. t-Butyl calixarene (t-BCX) was used as an ionophore due to its ability to mask IVB in the cavity via multiple H-bonding at the lower rim, as estimated quantitatively by the sandwich membrane method (Log β_ILn = 8.62). Besides, the use of multi-walled carbon nanotubes decorated with Fe₂O₃ nanoparticles (Fe₂O₃@MWCNTs) as an additive for the paste electrode significantly improved the detection limit of the sensor up to 36 nM, with Nernstian response of 58.9 mV decade^-1 in the IVB linear dynamic range of 10^-3-10^-7 M in aqueous solutions. The constructed sensors showed high selectivity against interfering species that may exist in physiological fluids or pharmaceutical formulations (e.g. Na⁺, K⁺, NH₄⁺, Ca²⁺, Mg²⁺, Ba²⁺, Fe³⁺, Co²⁺, Cr³⁺, Sr²⁺, glucose, lactose, maltose, glycine, dopamine, and ascorbic acid). The sensors were successfully employed for IVB determination in the pharmaceutical formulations (Savapran®).

Regioselectivity in nonsymmetric methyl pentyl Pillar[5]arene bound to non-symmetric axles

The present work illustrates regioselective binding of nonsymmetric axle BuX (X = F, Cl, Br, CN) and 5-bromovaleronitrile (BVN) to the non-symmetric methyl pentyl pillar[5]arene (MPP5). Theoretical calculations reveal that the guest encapsulation within MPP5 is spontaneous and the conformer showing X weakly bound to pentyl rim of MPP5 is favoured over its other conformer wherein it interacts with methyl rim of the host. The noncovalent interactions namely C-H---π, C-H---X and H-H prevail over C-H⋯O hydrogen bonding in the complexes of MPP5. The manifestations of these to vibrational spectra obtained from the present theory are discussed. The strength of host-guest binding further is shown to correlate well with weakening of the C-X bond through natural bond orbital analyses.

Fabrication of calixarene-grafted magnetic nanocomposite for the effective removal of lead(II) from aqueous solution

Magnetic nanocomposites adorned with calixarene were successfully prepared by immobilizing diethanolamine functionalized p-tert-butylcalix[4]arene (DEA-Calix) onto silica-coated magnetic nanoparticles (MNPs). The synthesis, surface morphology, purity, elemental composition and thermal stability of newly prepared nanocomposites were analyzed using FT-IR spectroscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX), X-ray diffractometer (XRD), thermal gravimetric analysis (TGA) and vibrating sample magnetometer (VSM). Magnetic solid-phase adsorption (MSPA) was employed to explore the adsorption behavior of DEA-Calix-MNPs towards Pb(II) from water samples prior to its flame atomic absorption spectrometric analysis. The essential analytical factors governing the adsorption efficiency such as solution pH, mass of adsorbent, concentration and contact time have been investigated and optimized. The results depict that DEA-Calix-MNPs has excellent adsorption efficiency 97% (at pH 5.5) with high adsorption capacity of 51.81 mg g^-1 for Pb(II) adsorption. Additionally, kinetic and equilibrium studies suggested that Pb(II) adsorption process follows a pseudo-second-order model and Langmuir isotherms, respectively. Real sample analysis also confirmed field applicability of the new DEA-Calix-MNPs adsorbent.

Fabrication of Calixarene Based Protein Scaffold by Electrospin Coating for Tissue Engineering

In this study, calixarene was synthesized by using different functional groups as p-tert-butyl-Calix[4]arene ester and amides. Calixarene nanofibers were produced by electrospin coating. Protein immobilization onto the calixarene nanofibers was carried out with human serum albumin (HSA). The maximum amount of binding on produced three different calixarene nanofibers (DE, 2-AMP and 3-AMP) was compared by using a fluorescence technique for protein analysis. Result showed that maximum binding amount was found to be as 177.85 mg cm-2 for 3-AMP surface. The protein binding was also characterized by using SEM, TEM, AFM and FT-IR. From obtained results, calixarene-albumin nanofiber was also fabricated by spin coating using 3-AMP which has ability max binding of protein.

Reductive-Responsive, Single-Molecular-Layer Polymer Nanocapsules Prepared by Lateral-Functionalized Pillar[5]arenes for Targeting Anticancer Drug Delivery

Herein, a new reductive-responsive pillar[5]arene-based, single-molecule-layer polymer nanocapsule is constructed for drug delivery. The functionalized system shows good biocompatibility, efficient internalization into targeted cells and obvious triggered release of entrapped drugs in a reducing environment such as cytoplasm. Besides, this smart vehicle loaded with anticancer drug shows excellent inhibition for tumor cell proliferation and exhibits low side effect on normal cells. This work not only demonstrates the development of a new reductive-responsive single molecular layer polymer nanocapsule for anticancer drug targeting delivery but also extends the design of smart materials for biomedical applications.

Phosphonated Pillar[5]arene-Valved Mesoporous Silica Drug Delivery Systems

To explore the diversity and promising applications of pillararene-based molecular machines, phosphonated pillar[5]arenes (PPA[5]) were synthesized to construct novel supramolecular nanovalves for the first time, based on mesoporous silica nanoparticles (MSNs) functionalized with choline and pyridinium moieties, respectively. PPA[5] encircled the choline or pyridinium stalks to construct supramolecular nanovalves for encapsulation of drugs within the MSN pores. PPA[5] showed a high binding affinity for the quaternary ammonium stalks through the host-guest interactions primarily via ion pairing between the phosphonate and quaternary ammonium moieties, in comparison with carboxylated pillar[5]arene (CPA[5]), to minimize premature drug release. The specific ion pairing between the phosphonate and quaternary ammonium moieties was elaborated for the first time to construct supramolecular nanovalves. The supramolecular nanovalves were activated by low pH, Zn²⁺ coordination, and competitive agents for controlled drug release, and release efficiency and antitumor efficacy were further enhanced when gold nanorod (GNR)-embedded MSNs (GNR@MSNs) were used instead under illumination of near-infrared (NIR) light, attributed to the synergistic effect of photothermo-chemotherapy. The constructed PPA[5]-valved GNR@MSN delivery system has promising applications in tumor photothermo-chemotherapy.

Determination of dopamine hydrochloride by host-guest interaction based on water-soluble pillar[5]arene

The supramolecular interaction between the water-soluble pillar[5]arene (WP[5]) as host and dopamine hydrochloride (DH) as guest was studied by spectrofluorometry. The fluorescence intensity of DH gradually decreased with increasing WP[5] concentration, and the possible interaction mechanism between WP[5] and DH was confirmed by ¹H NMR, 2D NOESY, and molecular modelling. Based on significant DH fluorescence, a highly sensitive and selective method for DH determination was developed for the first time. The fluorescence intensity was measured at 312nm, with excitation at 285nm. The effects of pH, temperature, and reaction time on the fluorescence spectra of the WP[5]-DH complex were investigated. A linear relationship between fluorescence intensity and DH concentration in the range of 0.07-6.2μgmL^-1 was obtained. The corresponding linear regression equation is ΔF=25.76 C+13.56 (where C denotes the concentration in μgmL^-1), with the limit of detection equal to 0.03μgmL^-1 and the correlation coefficient equal to 0.9996. This method can be used for the determination of dopamine in injection and urine samples. In addition, the WP[5]-DH complex has potential applications in fluorescent sensing and pharmacokinetics studies of DH.

A Bimodal, Cationic, and Water-Soluble Calix[4]arene Conjugate: Design, Synthesis, Characterization, and Transfection of Red Fluorescent Protein Encoded Plasmid in Cancer Cells

A new bimodal fluorescent cationic calix[4]arene (L1) conjugate has been synthesized in multiple steps and well characterized by NMR and electrospray ionization-mass spectrometry (ESI-MS) techniques. L1 has been investigated for its DNA binding ability by various spectroscopy techniques like absorption, fluorescence, and circular dichroism (CD). The formation of L1-DNA complex has been confirmed by the gel electrophoresis in the presence of incremental concentration of L1. To visualize the packing of the plasmid (pBR322), detailed tapping mode atomic force microscopy study has been performed, which revealed blob-like structure of plasmid upon addition of the incremental amount of L1. Concentration dependent transfection ability of L1 has been established in MCF-7 cells by confocal microscopy by carrying the red fluorescent protein (RFP) encoded plasmid pCMV-tdTomato-N1 to emit both intrinsic fluorescence of L1 as well as that from RFP. All this has been possible in the absence of any adjuvant phospholipids (DOPE) that are commonly used as helper. Further transfection efficiency of L1 has been compared with the commercially available lipofectamine (LTX) in two cancer cell lines, MCF 7 and SH-SY5Y, and found that the L1 is as efficient as that of LTX. Hence, L1 is an efficient and effective cargo to transport genetic material into the cells.

Highly fluorescent resorcinarene cavitand nanocapsules with efficient renal clearance

Nanomaterial based imaging approaches hold substantial promise in addressing current diagnostic and therapeutic challenges. One of the key requirements for the successful clinical translation of nanomaterials is their complete clearance from the body within a reasonable time period preferably via the renal filtration route. This article describes the synthesis of highly fluorescent, water soluble, resorcinarene cavitand nanocapsules and demonstrates their effective renal clearance in mice. The synthesis and functionalization of nanocapsules was accomplished in a one-pot operation via thiol-ene reactions without involving self-assembly, sacrificial templates or emulsions. Water soluble resorcinarene cavitand nanocapsules obtained by this approach were covalently functionalized with Alexa Fluor 750. Highly fluorescent nanocapsules with hydrodynamic diameters of 122 nm and 68 nm and extinction coefficients of 1.3 × 10(9) M(-1) cm(-1) and 1.5 × 10(8) M(-1) cm(-1) respectively were prepared by varying the reaction conditions. The in vivo biodistribution and clearance of these nanocapsules in mice followed by whole-body fluorescence imaging showed that they were both cleared renally within a few hours. Given the inherent encapsulation capabilities of nanocapsules, the renal clearance demonstrated in this work opens up new opportunities for their theranostic applications especially for targeting and treating the urinary tract.

Calixarene Assisted Rapid Synthesis of Silver-Graphene Nanocomposites with Enhanced Antibacterial Activity

Demonstrated herein is a single rapid approach employed for synthesis of Ag-graphene nanocomposites, with excellent antibacterial properties and low cytotoxicity, by utilizing a continuous hydrothermal flow synthesis (CHFS) process in combination with p-hexasulfonic acid calix[6]arene (SCX6) as an effective particle stabilizer. The nanocomposites showed high activity against E. coli (Gram-negative) and S. aureus (Gram-positive) bacteria. The materials were characterized using a range of techniques including transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, UV-vis spectrophotometry, FT-IR, and X-ray powder diffraction (XRD). This rapid, single step synthetic approach not only provides a facile means of enabling and controlling graphene reduction (under alkaline conditions) but also offers an optimal route for homogeneously producing and depositing highly crystalline Ag nanostructures into reduced graphene oxide substrate.

Stimulus-responsive light-harvesting complexes based on the pillararene-induced co-assembly of β-carotene and chlorophyll

The locations and arrangements of carotenoids at the subcellular level are responsible for their designated functions, which reinforces the necessity of developing methods for constructing carotenoid-based suprastructures beyond the molecular level. Because carotenoids lack the binding sites necessary for controlled interactions, functional structures based on carotenoids are not easily obtained. Here, we show that carotene-based suprastructures were formed via the induction of pillararene through a phase-transfer-mediated host-guest interaction. More importantly, similar to the main component in natural photosynthesis, complexes could be synthesized after chlorophyll was introduced into the carotene-based suprastructure assembly process. Remarkably, compared with molecular carotene or chlorophyll, this synthesized suprastructure exhibits some photocatalytic activity when exposed to light, which can be exploited for photocatalytic reaction studies of energy capture and solar conversion in living organisms.

Bio-Applications of Calix[n]arene Capped Silver Nanoparticles

During the 10 last years, there has been a growing interest in calix[n]arene capped silver nanoparticles for their uses in biosensing and much more recently for their intrinsic therapeutic properties. Cost effective, portable and ultra-sensitive analytical tools are one of the major expectations of silver nanoparticles capped with calix[n]arenes. Their uses for detecting a wide range of hazardous molecules and biological compounds by different physical approaches (optical or electrical) are reviewed in depth here. A second part deals with their biological activities. These hybrid nanoparticles have been shown to possess antibacterial properties, and to reach antiviral and anti-cancer targets.

[Research progress of the drug delivery system of antitumor platinum drugs with macrocyclic compounds]

Platinum-based anticancer drugs have been becoming one of the most effective drugs for clinical treatment of malignant tumors for its unique mechanism of action and broad range of anticancer spectrum. But, there are still several problems such as side effects, drug resistance/cross resistance and no-specific targeting, becoming obstacles to restrict its expanding of clinical application. In recent years, supramolecular chemistry drug delivery systems have been gradually concerned for their favorable safety and low toxicity. Supramolecular macrocycles-platinum complexes increased the water solubility, stability and safety of traditional platinum drugs, and have become hot focus of developing novel platinum-based anticancer drugs because of its potential targeting of tumor tissues/organs. This article concentrates in the research progress of the new drug delivery system between platinum-based anticancer drugs with three generations of macrocycles: crown ether, cyclodextrin, cucurbituril and calixarene.

Magnetic-responsive supramolecular vesicles from self-organization of amphiphilic pillar[5]arene and application in controlled release

A new amphiphilic pillar[5]arene (AP5-glycol) with five oligomeric glycol groups and five alkyl chains was prepared. AP5-glycol spontaneously formed bilayer vesicles in water, and these vesicles were still stable after several weeks. Additionally, when they were exposed to external physical stimuli, these vesicles also showed reversible thermal and dynamic properties. Interestingly, oleic-acid-stabilized magnetic iron oxide nanoparticles could be incorporated into the bilayer of the AP5-glycol vesicles to form hybrid magnetic-responsive supramolecular vesicles.

Improved measurements of Na+ fluxes in plants using calixarene-based microelectrodes

Ion-selective microelectrodes are a powerful tool in studying adaptive responses of plant cells and tissues to various abiotic stresses. However, application of this technique in Na(+) flux measurements was limited due to poor selectivity for Na(+) ions of commercially available Na(+) cocktails. Often, these cocktails cannot discriminate between Na(+) and other interfering ions such as K(+) and Ca(2+), leading to inaccurate measurements of Na(+) concentration and, consequently, inaccurate Na(+) flux calculations. To overcome this problem, three Na(+)-selective cocktail mixtures were prepared using tetramethoxyethyl ester derivative of p-t-butyl calix[4]arene. These cocktail mixtures were compared with commercially available ETH 227-based Na(+) cocktail for selectivity for Na(+) ions over other ions (particularly K(+) and Ca(2+)). Among the three calixarene-based Na(+) cocktails tested, cocktail 2 [in % w/w: Na(+) ionophore (4-tert-butylcalix[4]arene-tetra acetic acid tetraethyl ester) 3.5, the plasticizer (2-nitrophenyl octyl ether) 95.9 and lipophilic anion (potassium tetrakis (4-chlorophenyl) borate) 0.6] showed the best selectivity for Na(+) ions over K(+) and Ca(2+) ions and was highly stable over time (up to 10h). Na(+) flux measurements under a wide range of NaCl concentrations (25-150 mM) using Na(+) cocktail 2 established a clear dose-response relationship between severity of salt stress and magnitude of Na(+) influx at the distal elongation and mature zones of Arabidopsis thaliana roots. Furthermore, Na(+) cocktail 2 was compared with commercially available ETH 227-based Na(+) cocktail by measuring Na(+) fluxes at the two Arabidopsis root zones in response to 100mM NaCl treatment. With calixarene-based Na(+) cocktail 2, a large decreasing Na(+) influx (0-15 min) followed by small Na(+) influx (15-45 min) was measured, whereas with ETH-based Na(+) cocktail Na(+) influx was short-lived (1-3 min) and was followed by Na(+) efflux (3-45 min) that might have been due to K(+) and Ca(2+) efflux measured together with Na(+) influx. In conclusion, Na(+)-selective calixarene-based microelectrodes have excellent potential to be used in real-time Na(+) flux measurements in plants.

Paraquat detoxification with p-sulfonatocalix-[4]arene by a pharmacokinetic study

The p-sulfonatocalix[n]arenes are supposed to show potential application in the clinical treatment of viologen poisoning. In the present study, p-sulfonatocalix[4]arene (C4AS), the most common derivative of p-sulfonatocalix[n]arenes, is used to study the antidotic mechanism for paraquat (PQ) by pharmacokinetics in vivo. A high-performance liquid chromatography (HPLC) method was established to determine the concentration of PQ in rat plasma. The results showed that the peak plasma concentration (C(max)) and area under the plasma concentration-time curve (AUC(0-t)) were significantly lower after C4AS intervention than in the PQ intoxication group. It was considered that C4AS has great effective detoxication to PQ poisoning, and the results of in vitro intestinal absorption studies showed that C4AS can inhibit the absorption of PQ via oral administration by forming a stable inclusion constant.

Potentiometric polymeric membrane electrodes for mercury detection using calixarene ionophores

It is here established that potentiometric polymeric membrane electrodes based on electrically neutral ionophores are a useful analytical tool for the detection of heavy metal ions from environmental and industrial waste water. PVC based membrane containing p-tert-butyl-calix[4]arenethioether derivative as active material along with sodiumtetraphenylborate (NaTPB) as solvent mediator and dibutylphthalate as a plasticizer in the ratio 45:9:460:310 (w/w%) (I:NaTPB:DBP:PVC) exhibits good properties with a Nernstian response of 29.50+/-1.0 mV per decade of activity and a working concentration range of 7.2 x 10(-8)-1.0 x 10(-1) M. The electrode gave more stable potential readings when used around pH 2.5-6.8 and exhibits fast response time of 14 s. The sensors were found to work satisfactorily in partially non-aqueous media up to 40% (v/v) content of acetone, methanol or ethanol and could be used over a period of 7-9 months. Excellent selectivity for Hg(2+) ions is indicated by match potential method and fixed interference method. The sensors could be used successfully in the estimation of mercury in different sample.

Preconcentration-separation of Co2+, Ni2+, Cu2+ and Cd2+ in real samples by solid phase extraction of a calix[4] resorcinarene modified Amberlite XAD-16 resin

A new method is described for the simultaneous preconcentration of trace metal ions. The method is based on the adsorption of Co(2+), Ni(2+), Cu(2+) and Cd(2+) ions on 2,4,6,8-tetra(2-hydroxyphenyl)-1,3,5,7(1,3)tetrabenzenzcyclooctaphane-14,16,34,36,54, 56,74,76-octol (salicylaldehyde calix[4] resorcinarenes) (new resorcinarenes derivative) modified on Amberlite XAD-16. The adsorbed analyte ions were eluted with 6 mL 3M HCl in acetone solution, which then were determined by atomic absorption spectroscopy. The influences of the analytical parameters including pH, ligand amount and solid phase ingredient, eluting solution conditions and sample volume were investigated. Common coexisting ions did not interfere with the separation and determination. The preconcentration factor is 208. The sorbent exhibited excellent stability and its sorption capacity under optimum conditions has been found to be more than 60 microg of ions per gram of sorbent. The relative standard deviation under optimum conditions is lower than 4.10%. The accuracy of the method was estimated by using different real samples.

Chiral recognition of amino acids by use of a fluorescent resorcinarene

The spectroscopic properties of a chiral boronic acid based resorcinarene macrocycle employed for chiral analysis were investigated. Specifically, the emission and excitation characteristics of tetraarylboronate resorcinarene macrocycle (TBRM) and its quantum yield were evaluated. The chiral selector TBRM was investigated as a chiral reagent for the enantiomeric discrimination of amino acids using steady-state fluorescence spectroscopy. Chiral recognition of amino acids in the presence of the macrocycle was based on diastereomeric complexes. Results demonstrated that TBRM had better chiral discrimination ability for lysine as compared to the other amino acids. Partial least squares regression modeling (PLS-1) of spectral data for macrocycle-lysine guest-host complexes was used to correlate the changes in the fluorescence emission for a set of calibration samples consisting of TBRM in the presence of varying enantiomeric compositions of lysine. In addition, validation studies were performed using an independently prepared set of samples with different enantiomeric compositions of lysine. The results of multivariate regression modeling indicated good prediction ability of lysine, which was confirmed by a root mean square percent relative error (RMS%RE) of 5.8%.

Conversion of the surface property of oleic acid stabilized silver nanoparticles from hydrophobic to hydrophilic based on host-guest binding interaction

This paper describes a general method to change the surface property of the oleic acid stabilized silver nanoparticles and successful tranferring of the silver nanoparticles from the organic phase into the aqueous phase. By vigorous shaking of a biphasic mixture of the silver organosol protected with oleic acid and p-sulfonated calix[4]arene (pSC4) aqueous solution, it is believed that an inclusion complex is formed between oleic acid molecules and pSC4, and the protective layer of the silver nanoparticles shifts from hydrophobic to hydrophilic in nature, which drives the transfer of silver nanoparticles from the organic phase into the aqueous phase. The efficiency of the phase transfer to the aqueous solution depends on the initial pSC4 concentration. The pSC4-oleic acid inclusion complex stabilized nanoparticles can be stable for long periods of time in aqueous phase under ambient atmospheric conditions. The procedure of phase transfer has been independently verified by UV-vis, transmission electron microscopy, Fourier transform infrared, and 1H nuclear magnetic resonance techniques.

Experimental and Computational Probes of a Self-Assembled Capsule

[reaction: see text] This research was undertaken to explore the interior surface of a synthetic receptor 1.1 with arylpyridines as guests. The interior surface differentiates the guests through the recognition of their nitrogen atoms. Experimental and computational analyses revealed that there is a delicate balance of attractions and repulsions between the host and the lone pairs of guests.

Experimental and computational probes of the space in a self-assembled capsule

Self-assembled capsules are hosts that recognize and surround smaller molecule guests of appropriate size, shape, and chemical surfaces. The space available inside is a cage of fixed solvent molecules, many of which are aromatic. These aromatics provide anisotropic shielding to guests, and a map of induced magnetic shielding for the inner space can be obtained through nucleus-independent chemical shift calculations. Experimental values of the magnetic environment can be determined by NMR spectra of the guests inside. We describe here the environment in a cylindrical capsule with tapered ends. A series of terminal acetylenes -- the narrowest of organic structures -- was synthesized and used to probe the magnetic shielding of the capsule's ends. Their NMR spectra showed that the acetylenic hydrogen experiences deshielding as it is forced deeper into the tapered end of the capsule where four benzene rings converge. Modeling and density functional theory calculations provided excellent agreement with the experimental values and established a molecular ruler to explore steric and magnetic environments inside the capsule.