Stabilization of Antitumor Agent Busulfan through the Encapsulation within a Water-Soluble Pillar[5]arene

The complexation of antitumor agent busulfan by negatively charged carboxylatopillar[5]arenein water is reported. The encapsulation within carboxylatopillar[5]arenein reduces the hydrolytic degradation of busulfan from 90.7 % to 25.2 % after 24 days and accordingly enhances its stability by providing a hydrophobic shelter for busulfan in water. Moreover, the complexation result in 12 times improvement of water solubility for busulfan. Our result provides a supramolecular approach for stabilizing the anticancer agent busulfan.

Cancer-Mitochondria Dual-Targeting Glycol/Ferrocenium-Based Polydopamine Nanoparticles for Synergistic Photothermal and Photodynamic Therapy

A cancer-mitochondria dual-targeting nanoparticle based on lactose and ferrocenium derivatives conjugated polydopamine (PDA@Lac/Fc/Hyp) was constructed, which exhibited cancer-targeting and mitochondria-targeting ability deriving from lactose and ferrocenium derivatives due to the specific carbohydrate-protein interaction and cationic species properties, respectively. Moreover, PDA@Lac/Fc/Hyp showed great biocompatibility and phototherapeutic efficiency. This work displays a good example of constructing cancer-mitochondria dual-targeting nanoparticle for synergistic phototherapy.

A Modular Synthetic Strategy for Functional Macrocycles

Reported here is a molecule-Lego synthetic strategy for macrocycles with functional skeletons, involving one-pot and high-yielding condensation between bis(2,4-dimethoxyphenyl)arene monomers and paraformaldehyde. By changing the blocks, variously functional units (naphthalene, pyrene, anthraquinone, porphyrin, etc.) can be conveniently introduced into the backbone of macrocycles. Interestingly, the macrocyclization can be tuned by the geometrical configuration of monomeric blocks. Linear (180°) monomer yield cyclic trimers and pentamers, while V-shaped (120°, 90° and 60°) monomers tend to form dimers. More significantly, even heterogeneous macrocycles are obtained in moderate yield by co-oligomerization of different monomers. This series of macrocycles have the potential to be prosperous in the near future.

Asymmetric Hybrid Polyoxometalates: A Platform for Multifunctional Redox-Active Nanomaterials

Access to asymmetrically functionalized polyoxometalates is a grand challenge as it could lead to new molecular nanomaterials with multiple or modular functionality. Now, a simple one‐pot synthetic approach to the isolation of an asymmetrically functionalized organic–inorganic hybrid Wells–Dawson polyoxometalate in good yield is presented. The cluster bears two organophosphonate moieties with contrasting physical properties: a chelating metal‐binding group, and a long aliphatic chain that facilitates solvent‐dependent self‐assembly into soft nanostructures. The orthogonal properties of the modular system are effectively demonstrated by controlled assembly of POM‐based redox‐active nanoparticles. This simple, high‐yielding synthetic method is a promising new approach to the preparation of multi‐functional hybrid metal oxide clusters, supermolecular systems, and soft‐nanomaterials.

Precise Manipulation of Temperature-Driven Chirality Switching of Molecular Universal Joints through Solvent Mixing

Three chiral bicyclic pillar[5]arene derivatives termed as molecular universal joints (MUJs), were synthesized and separated enantiomerically. These MUJs showed temperature-driven chirality switching in certain solvents. Herein, it is demonstrated that temperature-driven chirality switching could also be realized by mixing two miscible organic solvents, in each of which chirality inversion is not accomplishable. Additionally, solvent mixing drastically varied the inversion temperature of the MUJs, for example, from far below zero to room temperature. Moreover, the temperature-driven S_p /R_p to R_p /S_p chirality switching direction could be reversed by the solvent mixing and it was critically controlled by the mixing ratios of the two solvents. These observations allowed precise manipulation of the chirality switching behavior of the MUJs. Such a chirality switching was ascribed to the influences of solvent and temperature on the in-out equilibrium of the side rings, which is delicately controlled by several processes, including the solvation/desolvation and the inclusion/exclusion of the side rings and solvent molecules. Crucially, the solvent mixing introduced new supramolecular processes, in particular the desolvation of solvent molecules from the mixed solvent system and the solvation of the side ring by the mixed solvent, which significantly disturbed the original in-out equilibrium of MUJs and drastically switched the entropy and enthalpy changes of conformational interconversion.

The siRNAsome: A Cation-Free and Versatile Nanostructure for siRNA and Drug Co-delivery

Nanoparticles show great potential for drug delivery. However, suitable nanostructures capable of loading a range of drugs together with the co-delivery of siRNAs, which avoid the problem of cation-associated cytotoxicity, are lacking. Herein, we report an small interfering RNA (siRNA)-based vesicle (siRNAsome), which consists of a hydrophilic siRNA shell, a thermal- and intracellular-reduction-sensitive hydrophobic median layer, and an empty aqueous interior that meets this need. The siRNAsome can serve as a versatile nanostructure to load drug agents with divergent chemical properties, therapeutic proteins as well as co-delivering immobilized siRNAs without transfection agents. Importantly, the inherent thermal/reduction-responsiveness enables controlled drug loading and release. When siRNAsomes are loaded with the hydrophilic drug doxorubicin hydrochloride and anti-P-glycoprotein siRNA, synergistic therapeutic activity is achieved in multidrug resistant cancer cells and a tumor model.

Pillar[5]-bis-thiacrown: An Adaptive Tricyclic Host Selectively Recognizing an Organic Guest by Dimetalation

Some biological receptors change their shapes and rigidity by metalation to recognize substrates precisely via adaptive guest binding process. Herein we present a semi-flexible tricyclic host molecule whose conformation is rigidified by dimetalation to uptake organic guests selectively. Considering two metal binding sites and an empty space between them, pillar[5]-bis-thiacrown (L) was synthesized. The tricyclic host L forms a disilver(I) complex [Ag₂ L(NO₃ )₂ ], with an Ag⋅⋅⋅Ag separation of 9.976 Å. Binding studies based on ¹ H NMR including 2D NOESY and DOSY experiments towards α,ω-dicyanoalkanes [CN(CH₂ )_n CN, n=2-6, shortly C2-C6] demonstrated that the dimetalated L, Ag₂ L preferentially recognizes C2 over other guests than that of free L. Furthermore, the dimetalated the host only uptakes C2 in the presence of other guests. Crystal structures support the idea that the space between two silver(I) centers plays a decisive role on the selective guest binding forming an Ag-C2-Ag@L arrangement via the length-selective recognition. This work demonstrates the chemical example of the adaptive guest binding and presents a new perspective on the metallosupramolecules of pillararenes.

Transformative Supramolecular Vesicles Based on Acid-Degradable Acyclic Cucurbit[n]uril and a Prodrug for Promoted Tumoral-Cell Uptake

Smart supramolecular vesicles constructed by host-guest interactions between "acid-degradable" acyclic cucurbit[n]uril (CB[n]) and a doxorubicin prodrug are reported. "Acid-degradable" acyclic CB[n] is a high-affinity host for several common antitumor drugs, and its degradation leads to a more dramatic decrease in binding affinity than that observed for "acid-sensitive" hosts. Supramolecular complexation between acid-degradable acyclic CB[n] and a doxorubicin prodrug resulted in the formation of negatively charged supramolecular vesicles. The prodrug strategy allowed doxorubicin to be conjugated to vesicles in a stable manner with a high drug-loading ratio of 20 %. The resulting supramolecular vesicles were responsive to tumor acidity (pH 6.5). Induced by mildly acidic conditions (pH 6.5-5.5), acid-degradable acyclic CB[n] could be degraded, and this led to a vesicle-to-micelle transition to form positively charged micelles. This transition resulted in a pH-dependent change in size and surface charge, which improved tumoral-cell uptake for doxorubicin.

Added-Value Surfactants

Surfactants are ubiquitous in cellular membranes, detergents or as emulsification agents. Due to their amphiphilic properties, they cannot only mediate between two domains of very different solvent compatibility like water and organic but also show fascinating self-assembly features resulting in micelles, vesicles, or lyotropic liquid crystals. The current review article highlights some approaches towards the next generation surfactants, for example, those with catalytically active heads. Furthermore, it is shown that amphiphilic properties can be obtained beyond the classical hydrophobic-hydrophilic interplay, for instance with surfactants containing one molecular block with a special shape. Whereas, classical surfactants are static, researchers have become more interested in species that are able to change their properties depending on external triggers. The article discusses examples for surfactants sensitive to chemical (e.g., pH value) or physical triggers (temperature, electric and magnetic fields).

Controlled and Tunable Loading and Release of Vesicles by Using Gigahertz Acoustics

Controllable exchange of molecules between the interior and the external environment of vesicles is critical in drug delivery and micro/nano‐reactors. While many approaches exist to trigger release from vesicles, controlled loading remains a challenge. Herein, we show that gigahertz acoustic streaming generated by a nanoelectromechanical resonator can control the loading and release of cargo into and from vesicles. Polymer‐shelled vesicles showed loading and release of molecules both in solution and on a solid substrate. We observed deformation of individual giant unilamellar vesicles and propose that the shear stress generated by gigahertz acoustic streaming induces the formation of transient nanopores, with diameters on the order of 100 nm, in the vesicle membranes. This provides a non‐invasive method to control material exchange across membranes of different types of vesicles, which could allow site‐specific release of therapeutics and controlled loading into cells, as well as tunable microreactors.

Plasmid-Templated Control of DNA-Cyclodextrin Nanoparticle Morphology through Molecular Vector Design for Effective Gene Delivery

Engineering self-assembled superstructures through complexation of plasmid DNA (pDNA) and single-isomer nanometric size macromolecules (molecular nanoparticles) is a promising strategy for gene delivery. Notably, the functionality and overall architecture of the vector can be precisely molded at the atomic level by chemical tailoring, thereby enabling unprecedented opportunities for structure/self-assembling/pDNA delivery relationship studies. Beyond this notion, by judiciously preorganizing the functional elements in cyclodextrin (CD)-based molecular nanoparticles through covalent dimerization, here we demonstrate that the morphology of the resulting nanocomplexes (CDplexes) can be tuned, from spherical to ellipsoidal, rod-type, or worm-like nanoparticles, which makes it possible to gain understanding of their shape-dependent transfection properties. The experimental findings are in agreement with a shift from chelate to cross-linking interactions on going from primary-face- to secondary-face-linked CD dimers, the pDNA partner acting as an active payload and as a template. Most interestingly, the transfection efficiency in different cells was shown to be differently impacted by modifications of the CDplex morphology, which has led to the identification of an optimal prototype for tissue-selective DNA delivery to the spleen in vivo.

Supramolecular Self-Assembly of Histidine-Capped-Dialkoxy-Anthracene: A Visible-Light-Triggered Platform for Facile siRNA Delivery

Supramolecular self-assembly of histidine-capped-dialkoxy-anthracene (HDA) results in the formation of light-responsive nanostructures. Single-crystal X-ray diffraction analysis of HDA shows two types of hydrogen bonding. The first hydrogen bond is established between the imidazole moieties while the second involves the oxygen atom of one amide group and the hydrogen atom of a second amide group. When protonated in acidic aqueous media, HDA successfully complexes siRNA yielding spherical nanostructures. This biocompatible platform controllably delivers siRNA with high efficacy upon visible-light irradiation leading up to 90 % of gene silencing in live cells.