Lithiated Polycalix[4]arenes for Efficient Adsorption of Iodine from Solution and Vapor Phases

Lithiated Polycalix[4]arenes for Efficient Adsorption of Iodine from Solution and Vapor Phase

Sequential Delivery of Doxorubicin and Zoledronic Acid to Breast Cancer Cells by CB[7]-Modified Iron Oxide Nanoparticles

Drug-loaded magnetic nanoparticles were synthesized and used for the sequential delivery of the antiresorptive agent zoledronic acid (Zol) and the cytotoxic drug doxorubicin (Dox) to breast cancer cells (MCF-7). Zol was attached to bare iron oxide nanoparticles (IONPs) via phosphonate coordination to form <b>Z-NPs</b>. The unbound imidazole of Zol was then used to complex the organic macrocycle CB[7] to obtain <b>CZ-NPs</b>. Dox was complexed to the <b>CZ-NPs</b> to form the fully loaded particles (<b>DCZ-NPs</b>), which were stable in solution at 37 °C and physiological pH (7.4). Fluorescence spectroscopy established that Dox is released in solution from <b>DCZ-NPs</b> suddenly (i) when the particles are subjected to magnetically induced heating to 42 °C at low pH (5.0) and (ii) in the presence of glutathione (GSH). Mass spectrometry indicated that Zol is released slowly in solution at low pH after Dox release. Magnetic measurements with a magnetic reader revealed that <b>DCZ-NPs</b> are internalized preferentially by MCF-7 cells versus nonmalignant cells (HEK293). Zol and Dox acted synergistically when delivered by the particles. <b>DCZ-NPs</b> caused a decrease in the viability of MCF-7 cells that was greater than the net decrease caused when the drugs were added to the cells individually at concentrations equivalent to those delivered by the particles. MCF-7 cells were treated with <b>DCZ-NPs</b> and subjected to an alternating magnetic field (AMF) which, with the nanoparticles present, raised the temperature of the cells and triggered the intracellular release of Dox, as indicated by fluorescence activated cell sorting (FACS). The cytotoxic effects of the <b>DCZ-NPs</b> on MCF-7 cells were enhanced 10-fold by AMF-induced heating. <b>DCZ-NPs</b> were also able to completely inhibit MCF-7 cell adhesion and invasion in vitro, indicating the potential of the particles to act as antimetastatic agents. Together these results demonstrate that <b>DCZ-NPs</b> warrant development as a system for combined chemo- and thermo-therapeutic treatment of cancer

Redox-Responsive Viologen-Mediated Self-Assembly of CB[7]-Modified Patchy Particles

Sulfonated surface patches of poly­(styrene)-based colloidal particles (CPs) were functionalized with cucurbit[7]­uril (CB[7]). The macrocycles served as recognition units for diphenyl viologen (DPV²⁺), a rigid bridging ligand. The addition of DPV²⁺ to aqueous suspensions of the particles triggered the self-assembly of short linear and branched chainlike structures. The self-assembly mechanism is based on hydrophobic/ion-charge interactions that are established between DPV²⁺ and surface-adsorbed CB[7]. DPV²⁺ guides the self-assembly of the CPs by forming a ternary DPV²⁺⊂(CB­[7])₂ complex in which the two CB[7] macrocycles are attached to two different particles. Viologen-driven particle assembly was found to be both directional and reversible. Whereas sodium chloride triggers irreversible particle disassembly, the one-electron reduction of DPV²⁺ with sodium dithionite causes disassembly that can be reversed via air oxidation. Thus, this bottom-up synthetic supramolecular approach allowed for the reversible formation and directional alignment of a 2D colloidal material

Redox-Responsive Viologen-Mediated Self-Assembly of CB[7]-Modified Patchy Particles

Sulfonated surface patches of poly­(styrene)-based colloidal particles (CPs) were functionalized with cucurbit[7]­uril (CB[7]). The macrocycles served as recognition units for diphenyl viologen (DPV²⁺), a rigid bridging ligand. The addition of DPV²⁺ to aqueous suspensions of the particles triggered the self-assembly of short linear and branched chainlike structures. The self-assembly mechanism is based on hydrophobic/ion-charge interactions that are established between DPV²⁺ and surface-adsorbed CB[7]. DPV²⁺ guides the self-assembly of the CPs by forming a ternary DPV²⁺⊂(CB­[7])₂ complex in which the two CB[7] macrocycles are attached to two different particles. Viologen-driven particle assembly was found to be both directional and reversible. Whereas sodium chloride triggers irreversible particle disassembly, the one-electron reduction of DPV²⁺ with sodium dithionite causes disassembly that can be reversed via air oxidation. Thus, this bottom-up synthetic supramolecular approach allowed for the reversible formation and directional alignment of a 2D colloidal material

Viologen-Based Conjugated Covalent Organic Networks via Zincke Reaction

Morphology influences the functionality of covalent organic networks and determines potential applications. Here, we report for the first time the use of Zincke reaction to fabricate, under either solvothermal or microwave conditions, a viologen-linked covalent organic network in the form of hollow particles or nanosheets. The synthesized materials are stable in acidic, neutral, and basic aqueous solutions. Under basic conditions, the neutral network assumes radical cationic character without decomposing or changing structure. Solvent polarity and heating method determine product morphology. Depending upon solvent polarity, the resulting polymeric network forms either uniform self-templated hollow spheres (<b>HS</b>) or hollow tubes (<b>HT</b>). The spheres develop via an inside-out Ostwald ripening mechanism. Interestingly, microwave conditions and certain solvent polarities result in the formation of a robust covalent organic gel framework (<b>COGF</b>) that is organized in nanosheets stacked several layers thick. In the gel phase, the nanosheets are crystalline and form honeycomb lattices. The use of the Zincke reaction has previously been limited to the synthesis of small viologen molecules and conjugated viologen oligomers. Its application here expands the repertoire of tools for the fabrication of covalent organic networks (which are usually prepared by dynamic covalent chemistry) and for the synthesis of viologen-based materials. All three materials<b>HT</b>, <b>HS</b>, and <b>COGF</b>serve as efficient adsorbents of iodine due to the presence of the cationic viologen linker and, in the cases of <b>HT</b> and <b>HS</b>, permanent porosity