Anisotropic Self-Assembly of Organic–Inorganic Hybrid Microtoroids

Macrocyclic Diacetylene / Sulfonate Fluorophore Hierarchical Multifunctional Nanotoroids

Functional supramolecular materials exhibit important features including structural versatility and versatile applications. Here, this study reports the construction of unique hierarchically organized nanotoroids exhibiting fluorescence, photocatalytic, and sensing properties. The nanotoroids comprise of macrocyclic diacetylenes (MCDA) and 8-anilino-1-naphthalene sulfonate (ANS), a negatively charged aromatic fluorescent dye. This study shows that the hierarchical structure of the nanotoroids consist of MCDA nanofibers formed by stacked diacetylene monomers as the basic units, which are further bent and aligned into toroidal organization by electrostatic and hydrophobic interactions with the ANS molecules. The amine moieties on the nanotoroids surface are employed for deposition of gold nanostructures - Au nanoparticles or Au nanosheets - which constitute effective platforms for photocatalysis and surface enhanced Raman scattering (SERS)-based sensing.

Self-assembled multiprotein nanostructures with enhanced stability and signal amplification capability for sensitive fluorogenic immunoassays

Fundamentally improving the sensing sensitivity of immunoassay remains a huge challenge, which limited further critical applications. Herein we designed a new immunoprobe by integrating biometric unit (antibody) and signal amplification element (enzyme) to form urease-antibody-CaHPO₄ hybrid nanoflower (UAhNF) via the biomineralization process. The dual-functional UAhNF enhances the stability of urease in NaCl (10 mmol L^-1) and high temperature (60 °C), and also maintains the ability of antibody recognition, fitting greatly well with the need for immunosensor. Using imidacloprid as a model target, the fixed coating antigens are competed with imidacloprid to capture primary antibodies, and the secondary antibody of UAhNF was linked to construct the competitive-type fluorogenic immunoassays. An in-situ etching process of copper nanoparticles initiated by urease is integrated with UAhNF-based immune response for further improving the detection sensitivity. The proposed immunosensor possessed a 50% inhibition concentration value of 0.72 ng mL^-1, which is 30-fold lower than conventional enzyme-linked immunosorbent assay. This presented approach provided a versatile sensing tool by varying building blocks, making it practically functional for a variety of bioassay applications.

Metallic Oxide-Induced Self-Assembly of Block Copolymers to Form Polymeric Hybrid Micelles with Tunable Stability for Tumor Microenvironment-Responsive Drug Delivery

Since block copolymers are able to self-assemble into various polymeric architectures, it is intriguing to explore a unique self-assembly strategy for polymers. Two different metallic oxides [manganese dioxide (MnO2) and zinc oxide (ZnO)] are displayed herein to demonstrate this self-assembly mechanism of polymers. In situ generation of metallic oxides induces self-assembly of block copolymers to form polymeric hybrid micelles with tunable stability in aqueous solutions. These final ZnO-cross-linked polymeric micelles exhibited a high drug loading capacity of 0.41 mg mg-1 toward doxorubicin (DOX), whereas DOX-loaded ZnO-cross-linked polymeric micelles could be broken down into Zn2+ and polymer scraps, which facilitated drug release in tumor microenvironments. Both in vitro and in vivo investigations showed that the drug-loaded ZnO-cross-linked polymeric micelles effectively suppressed tumor growth. Accordingly, the present study demonstrates a novel strategy of polymer self-assembly for fabricating polymeric architectures that can potentially provide insight for developing other polymeric architectures.

Supramolecular cyclization of semiflexible cylindrical micelles assembled from rod-coil graft copolymers

Uniform toroidal micelles can be constructed via the supramolecular cyclization of semiflexible cylindrical micelles, but revealing the conditions under which the cyclization occurs and the mechanism underlying the cyclization remains a challenge. In this study, we performed Brownian dynamics simulations of the supramolecular cyclization of semiflexible cylindrical micelles formed by rod-coil graft copolymers to obtain the cyclization conditions and understand the cyclization mechanism. It was found that the balance of the bending energy of the polymer backbones with the self-attraction energy between the pendant groups on the polymer backbones plays an important role in the cyclization process. A theoretical model based on this balance is developed to explain the cyclization mechanism, and the conditions required for realizing the supramolecular cyclization are obtained. The proposed mechanism is supported by our experimental findings regarding the supramolecular cyclization of polypeptide cylindrical micelles. The cyclization conditions and the revealed mechanism can guide further preparation of uniform toroidal micelles from semiflexible cylindrical micelles in an end-to-end closure manner.

Systematic study on evolution of self-assembly morphologies of CABC tetrablock terpolymers with varied segment lengths

The self-assembly structures of PEEA-PMMA-PGLMMA-PEEA CABC-type tetrablock terpolymers with a fixed length of the PGLMMA (red colour) segment and varied lengths of the PMMA (blue) and PEEA (green) segments were systematically studied.

A comparative study of the self-assembly of achiral and chiral hairy nanoparticles with polystyrene cores and poly(2-hydroxyethylmethacrylate) hairs

Hairy nanoparticles with polystyrene cores (PS cores) and poly(2-hydroxyethylmethacrylate) (PHEMA) shells were synthesized by combining living anionic polymerization and atom transfer radical polymerization (ATRP). The structural characterization was carried out by FT-IR and NMR spectroscopy (¹H NMR, ¹³C NMR, APT ¹³C NMR and ¹H ¹³C HMQC). The thermal stability of the PS cores was not affected by grafting PHEMA on their surfaces. A differential scanning calorimetry (DSC) thermogram of the HNPs showed two distinct transition temperatures indicating microphase separation. Chiral HNPs were prepared by inducing chirality in the achiral HNPs by complexation with R- or S-mandelic acid. The circular dichroism (CD) spectroscopy of complexes of the HNPs/R- or S-mandelic acid indicated the formation of enantiomeric chiral structures. The self-assembled structures formed from the achiral HNPs show different surface morphologies, porous and zigzag, dependent on the solvents used. Blends of polystyrene functionalized with hydroxyl groups and PHEMA show different morphology and thermal properties compared with the core–shell HNP system. The chiral HNPs self-assembled into donut like structures or toroids with sizes in the range between 200 to 5000 nm. The study suggests that chirality can be utilized to develop interesting self-assembled structures.

Chiral hairy nanoparticles (HNP), prepared by complexation of achiral HNPs with R- or S-mandelic acid, self-assemble into toroidal or donut like structures.

Acenes beyond organic electronics: sensing of singlet oxygen and stimuli-responsive materials

Although they are often detrimental in organic electronics, the cycloaddition reactions of acenes, especially with singlet oxygen, are useful in a range of responsive materials.

Sonochemically-Promoted Preparation of Silica-Anchored Cyclodextrin Derivatives for Efficient Copper Catalysis

Silica-supported metallic species have emerged as valuable green-chemistry catalysts because their high efficiency enables a wide range of applications, even at industrial scales. As a consequence, the preparation of these systems needs to be finely controlled in order to achieve the desired activity. The present work presents a detailed investigation of an ultrasound-promoted synthetic protocol for the grafting of β-cyclodextrin (β-CD) onto silica. Truly, ultrasound irradiation has emerged as a fast technique for promoting efficient derivatization of a silica surface with organic moieties at low temperature. Three different β-CD silica-grafted derivatives have been obtained, and the ability of β-CD to direct and bind Cu when CD is bonded to silica has been studied. A detailed characterization has been performed using TGA, phenolphthalein titration, FT-IR, diffuse reflectance (DR), DR UV-Vis, as well as the inductively-coupled plasma (ICP) of the β-CD silica-grafted systems and the relative Cu-supported catalysts. Spectroscopic characterization monitored the different steps of the reaction, highlighting qualitative differences in the properties of amino-derivatized precursors and final products. In order to ensure that the Cu-β-CD silica catalyst is efficient and robust, its applicability in Cu(II)-catalyzed alkyne azide reactions in the absence of a reducing agent has been explored. The presence of β-CD and an amino spacer has been shown to be crucial for the reactivity of Cu(II), when supported.

Polymer Amphiphiles for Photoregulated Anticancer Drug Delivery

We report the synthesis of amphiphilic polymers featuring lipophilic stearyl chains and hydrophilic poly(ethylene glycol) polymers that are connected through singlet oxygen-cleavable alkoxyanthracene linkers. These amphiphilic polymers assembled in water to form micelles with diameters of ∼20 nm. Reaction of the alkoxyanthracene linkers with light and O₂ cleaved the ether C-O bonds, resulting in formation of the corresponding 9,10-anthraquinone derivatives and concomitant disruption of the micelles. These micelles were loaded with the chemotherapeutic agent doxorubicin, which was efficiently released upon photo-oxidation. The drug-loaded reactive micelles were effective at killing cancer cells in vitro upon irradiation at 365 nm, functioning through both doxorubicin release and photodynamic mechanisms.

Hierarchical Self-Assembly of Toroidal Micelles into Multidimensional Nanoporous Superstructures

Materials with controlled porosity play a prominent role in industrial and domestic applications. Although a rich array of methods has been developed to tune the pore size over a broad range (from <1 nm to >1 μm), the fabrication of functional materials with a fully open porous structure with sub-100 nm pore size has remained a significant challenge. Herein, we report the hierarchical assembly of block copolymer toroidal micelles with an intrinsic cavity into multidimensional nanoporous superstructures (pore size 85-90 nm) by modulation of interparticle interactions. The toroids aggregate into oligo-supermicelles or 2D hexagonal arrays through van der Waals interactions upon drying on a substrate, while synergistic hydrogen bonding interactions further promote the formation of 3D nanoporous superstructures directly in solution. Thus, toroidal micelles can be manipulated as a type of distinctive building block to construct nanoporous materials.

A novel flurophore-cyano-carboxylic-Ag microhybrid: Enhanced two photon absorption for two-photon photothermal therapy of HeLa cancer cells by targeting mitochondria

In this study, a novel two-photon photothermal therapy (TP-PTT) agent based on an organic-metal microhybrid with surface Plasmon resonance (SPR) enhanced two-photon absorption (TPA) characteristic was designed and synthesized using a fluorescent cyano-carboxylic derivative 2-cyano-3-(9-ethyl-9H-carbazol-3-yl) -acrylic acid (abbreviated as CECZA) and silver nanoparticles through self-assembly process induced by the interfacial coordination interactions between the O/N atom of CECZA and Ag⁺ion at the surface of Ag nanoparticles. The coordination interactions caused electron transfer from the Ag nanoparticles to CECZA molecules at the excited state, resulting in a decreased fluorescence quantum yield. The interfacial coordination interactions also enhanced the nonlinear optical properties, including 13 times increase in the TPA cross-section (δ). The decreased fluorescence quantum yield and increased two photon absorption caused by the SPR effect led excellent two-photon photothermal conversion, which was beneficial for the TP-PTT effect on HeLa cancer cells.

Bundle formation of supramolecular fibers of amphiphilic diarylethene by depletion force

Supramolecular nanofibers composed of the closed-ring isomer of a diarylethene formed bundles in a methylcellulose aqueous solution and showed a photoinduced shrinking of more than 100 μm under visible light irradiation.