Rediscovering the Monodispersity of Sulfonatocalix[4]arene-Based Micelles

When the micellar aggregation number (<i>N</i>_agg) is small enough (<30), the <i>N</i>_agg matches the value of vertexes of a regular polyhedron: Platonic solids, and demonstrates perfect monodispersity. These micelles are named Platonic micelles and are particularly found in the system of calix[4]­arene-based micelles due to the rigid structure of the backbone molecule. Although sulfonatocalix[4]­arene-based micelles are among the most studied host molecules in supramolecular chemistry, their micellar properties as Platonic micelles have thus far been overlooked. In this study, we prepared various sulfonatocalix[4]­arene-based amphiphiles bearing alkyl chains with different lengths and investigated their aggregation behavior. When the amphiphiles formed spherical micelles, they demonstrated monodispersity in terms of <i>N</i>_agg, whose value changed from 4 to 17, and then to 24, upon increasing the carbon number in each alkyl chain from C5 to C6, and then to C7, respectively. Although the numbers 17 and 24 do not match the vertices of regular polyhedra, these values can be reasonably explained by the Thomson problem, which considers the Coulomb potential for calculating the best packing on a sphere with multiple identical spherical caps. This study describes rediscovery of the monodispersity of sulfonatocalix[4]­arene-based micelles, which is consistent with the idea of Platonic micelles

A benzothiazole-based receptor-immobilised silica nanoparticle as chemosensor for Hg²⁺

<div><p>Fluorogenic benzothiazole-based receptor has been easily immobilised onto filter paper and silica nanoparticle by sol-gel reaction. The sensing ability of the benzothiazole-immobilised thin layer filter paper chromatography (<b>TLC-1</b>) was evaluated on the basis of fluorescent changes caused by metal ions that were dropped onto the TLC plate. The <b>TLC-1</b> exhibited a high affinity and selectivity for Hg²⁺ over other competing metal ions. Therefore, the <b>TLC-1</b> holds promise as a portable sensor for the detection of Hg²⁺ in aqueous solution. Furthermore, the adsorption capacity of a column packed with <b>SiO</b>_<b>2</b><b>-1</b> was evaluated by the application of metal ions under various experimental conditions, such as pH, flow rate and concentration. The <b>SiO2-1</b> column removed 98% of Hg²⁺ from drinking water containing 10 ppb of Hg²⁺. The adsorption capacity of the <b>SiO</b>_<b>2</b><b>-1</b> column was not strongly affected by pH and flow rates.</p></div

Reinforcement of a Sugar-Based Bolaamphiphile/Functionalized Graphene Oxide Composite Gel: Rheological and Electrochemical Properties

A sugar-based bolaamphiphile/graphene oxide composite hydrogel has been prepared using simple mixing. Unlike the corresponding sugar-based native gel, the composite gel exhibits a fibrillar structure with a 10–20 nm fiber diameter. The composite gel forms an interdigitated bilayer structure incorporating intermolecular hydrogen-bonding interactions. The composite gel formation did not change the beneficial electrical properties of graphene offering the potential for integration of this new material into electronic systems. Interestingly, the mechanical and electrochemical properties of the composite gel are both dramatically enhanced when compared to the native gel, thereby reflecting that the functionalized graphene oxide layers are efficiently intercalated within the composite gel structure

Luminescent Calix[4]arene-Based Metallogel Formed at Different Solvent Composition

We have synthesized a calix[4]­arene derivative (<b>1</b>) containing terpyridine and showed that gelation occurred in the presence of Pt²⁺ in DMSO/H₂O of varying compositions. Gelation was presumably mediated by the Pt–Pt and π–π stacking interactions. The scanning electron microscopy image of the xerogel showed a spherical structure with diameter of 1.8–2.1 μm. Interestingly, the metallogel showed strong luminescence enhancement, which was dependent on the DMSO/H₂O ratio of the solvent. We examined the effects of concentration, temperature, and time resolution on the luminescence emission of both the gel <b>1</b>-Pt²⁺ and the sol <b>1</b>-Pt²⁺. The luminescence lifetimes of the metallogel were particularly long, on the order of several microseconds. The luminescence lifetimes were also strongly dependent on the solvent composition. We also determined the thermodynamic parameters for the self-assembly of the gel by the Birks kinetic scheme. Furthermore, the rheological properties of the metallogels in the presence of more than 4.0 equiv of Pt²⁺ were independent of the concentration of Pt²⁺ applied

Metallogel of bis(tetrazole)-appended pyridine derivative with CoBr₂ as a chemoprobe for volatile gases containing chloride atom

<p>A bis(tetrazole)-appended ligand <b>1</b> formed the metallogel efficiently by mixing with Co²⁺ ion. Interestingly, the metallogel <b>1</b> with CoBr₂ showed the orange yellow colour, which has octahedral structure. The rheological properties of metallogel obtained with CoBr₂ were ca. 1.5-fold larger than that for the metallogel obtained with CoCl₂. Upon addition of HCl, SOCl₂, (COCl)₂ and COCl₂ containing chloride atoms in the metallogel <b>1</b> prepared with CoBr₂ changed from orange yellow to blue-green colour. These results indicate that the octahedral structure of metallogel was converted into the tetrahedral structure. On the other hand, no significant colour changes were observed in the presence of an excess of other anions, namely HF, HBr, HI, HNO₃ and H₂SO₄. These findings indicate that the metallogel <b>1</b> with CoBr₂ is useful as a chemoprobe for gases containing chloride atom.</p

Chiral Supramolecular Gels with Lanthanide Ions: Correlation between Luminescence and Helical Pitch

We report the correlation between the fluorescence intensity and the helical pitch of supramolecular hydrogels with Tb­(III) and Eu­(III) as well as their inkjet printing patterning as an application. The luminescent gels, which exhibited three different emissions of red, green, and blue, could be prepared without and with Eu­(III) and Tb­(III). The luminescence intensity of supramolecular gels (gel-Tb and gel-Eu) composed of Tb­(III) and Eu­(III) was ca. 3-fold larger than that of the sol (<b>1</b>+Tb­(III) or <b>1</b>+Eu­(III)), which was attributed to large tilting angles between molecules. By AFM observations, these gels showed well-defined right-handed helical nanofibers formed by coordination bonds in which the helical pitch lengths were strongly dependent on the concentrations of lanthanide ions. In particular, the large luminescence intensity of gel-Tb exhibited a smaller helical pitch length than that of gel-<b>1</b> due to relatively weak π–π stacking with large tilting angles between molecules. The luminescence intensities were enhanced linearly with increasing concentrations of lanthanide ions. This is the first example of the correlation between the helical pitch length and the luminescence intensity of supramolecular materials. The coordination bonding in supramolecular hydrogels had a strong influence on rheological properties. We also developed a water-compatible inkjet printing system to generate luminescent supramolecular gels on A4-sized paper. The images of a logo and the text were composed of three different emissions and were well-printed on A4 sized paper coated with gel-<b>1</b>

Core–Shell–Corona Micelles from a Polyether-Based Triblock Terpolymer: Investigation of the pH-Dependent Micellar Structure

Core–shell-corona micelles featuring a pH-responsive shell have been characterized in dilute aqueous solution at different pH values (4–8) by using dynamic light scattering (DLS), field-flow fractionation coupled with multiangle light scattering detector (FFF-MALS), steady-state fluorescence, small-angle X-ray scattering (SAXS), and cryogenic transmission electron microscopy (cryo-TEM). The micelles are formed by self-assembly of a polyether-based triblock terpolymer consisting of a hydrophobic poly­(<i>tert</i>-butyl glycidyl ether) block (P<i>t</i>BGE), a pH-responsive modified poly­(allyl glycidyl ether) segment (PAGE_COOH), and a neutral hydrophilic poly­(ethylene oxide) block (PEO). Because of the side-chain carboxylic acids in the middle block, the micellar structure and size depends on the solution pH. Hereby, we show that an increase in pH induces a decrease in the aggregation number (<i>N</i>_agg). In addition, the combination of the above measurements revealed an unexpected morphological change from spherical to ellipsoidal micelles by increasing pH

Self-Assembled Coumarin Nanoparticle in Aqueous Solution as Selective Mitochondrial-Targeting Drug Delivery System

The development of specifically targeted nanoparticles for subcellular organelles modified with a low-molecular-weight organic compound as drug nanocarriers can bring about wide applications in cancer therapy. However, their utility has been hampered by low selectivity, poor biodistribution, and limited efficiency. Herein, we report the aggregation behavior of a triphenylphosphonium-appended coumarin probe (<b>TPP-C</b>) in an aqueous solution and its applications as a mitochondria-targeting probe, and drug delivery carrier, which is a rare example for a low molecular-weight organic compound. The <b>TPP-C</b> formed homogeneous nanoparticles with small diameters in water as well as in mixtures of organic solvents and water. In pure water, the homogeneous nanoparticles induced J-aggregation, whereas in mixed solvents, the homogeneous nanoparticles induced H-aggregation. The luminescence intensities of nanoparticles originated from the aggregation-induced emission (AIE) effect in pure water and also in mixtures of organic solvents and water. These findings indicate that the AIE effect of <b>TPP-C</b> was dependent on the solvent. More interestingly, the <b>TPP-C</b> nanoparticles selectively accumulated in mitochondria. The <b>TPP-C</b> nanoparticles alone exhibited noncytotoxicity toward cancer cells. However, with the encapsulation of the anticancer drug doxorubicin (DOX) into the <b>TPP-C</b> nanoparticles, the DOX was efficiently delivered to the mitochondria. These results indicated that the proposed system demonstrates promise as a platform for future clinical medication, particularly for specific suborganelle-targeted drug delivery systems for cancer therapy

Enhanced NIR Radiation-Triggered Hyperthermia by Mitochondrial Targeting

Mitochondria are organelles that are readily susceptible to temperature elevation. We selectively delivered a coumarin-based fluorescent iron oxide nanoparticle, <b>Mito-CIO</b>, to the mitochondria. Upon 740 nm laser irradiation, the intracellular temperature of HeLa cells was elevated by 2.1 °C within 5 min when using <b>Mito-CIO</b>, and the treatment resulted in better hyperthermia and a more elevated cytotoxicity than HeLa cells treated with coumarin iron oxide (<b>CIO</b>), which was missing the mitochondrial targeting unit. We further confirmed these results in a tumor xenograft mouse model. To our knowledge, this is the first report of a near-infrared laser irradiation-induced hyperthermic particle targeted to mitochondria, enhancing the cytotoxicity in cancer cells. Our present work therefore may open a new direction in the development of photothermal therapeutics