Tangxin Xiao

pH-Responsive Supramolecular Vesicles Based on Water-Soluble Pillar[6]arene and Ferrocene Derivative for Drug Delivery

The drug delivery system based on supramolecular vesicles that were self-assembled by a novel host-guest inclusion complex between a water-soluble pillar[6]arene (WP6) and hydrophobic ferrocene derivative in water has been developed. The inclusion complexation between WP6 and ferrocene derivative in water was studied by (1)H NMR, UV-vis, and fluorescence spectroscopy, which showed a high binding constant of (1.27 ± 0.42) × 10(5) M(-1) with 1:1 binding stoichiometry. This resulting inclusion complex could self-assemble into supramolecular vesicles that displayed a significant pH-responsive behavior in aqueous solution, which were investigated by fluorescent probe technique, dynamic laser scattering, and transmission electron microscopy. Furthermore, the drug loading and in vitro drug release studies demonstrated that these supramolecular vesicles were able to encapsulate mitoxantrone (MTZ) to achieve MTZ-loaded vesicles, which particularly showed rapid MTZ release at low-pH environment. More importantly, the cellular uptake of these pH-responsive MTZ-loaded vesicles by cancer cells was observed by living cell imaging techniques, and their cytotoxicity assay indicated that unloaded vesicles had low toxicity to normal cells, which could dramatically reduce the toxicity of MTZ upon loading of MTZ. Meanwhile, MTZ-loaded vesicles exhibited comparable anticancer activity in vitro as free MTZ to cancer cells under examined conditions. This study suggests that such supramolecular vesicles have great potential as controlled drug delivery systems.

Pillar[5]arene-based polymeric architectures constructed by orthogonal supramolecular interactions

Ureidopyrimidinone functionalized pillar[5]arene (UPyP5) was synthesized and employed to complex with a bisparaquat derivative (G) to form supramolecular polymers at relatively high concentration. The orthogonal binding interactions including quadruple hydrogen bonding and host-guest interaction should play vital roles in the construction of this linear assembly.

Dynamic Supramolecular Complexes Constructed by Orthogonal Self-Assembly

CONSPECTUS: Supramolecular complexes, including various low-molecular-mass structures and large molecular aggregates that are assembled by reversible and highly directional noncovalent interactions, have attracted more and more attention due to their fascinating and unconventional chemical and physical properties that are different from those of traditional architectures encountered by covalently linked backbones. Supramolecular complexes are by nature dynamic architectures considering the reversibility of noncovalent interactions by which small molecular monomers can assemble into specific architectures that are able to be repeatably reorganized through the assembly/disassembly processes under certain environmental factors such as temperature, concentration, and solvent conditions. The construction of supramolecular complexes by orthogonal self-assembly with different types of highly specific, noninterfering interactions is currently attracting considerable interest since they not only can dynamically self-assemble, but also can be tuned by various external stimuli through addressing each type of noncovalent interaction separately. Therefore, these dynamic supramolecular complexes, especially with external responsiveness, represent the most outstanding candidates for the future development of functional and smart materials, and even mimic the assembling process of natural systems. In this Account, we will summarize the recent advances of dynamic supramolecular complexes constructed by orthogonal self-assembly in soluiton in two sections: (1) Construction strategies for supramolecular complexes based on orthogonal self-assembly, whose dynamic behaviors with external responsiveness were not experimentally investigated but potentially existed due to the intrinsic reversibility of noncovalent bonds; (2) dynamic behaviors of multiresponsive supramolecular complexes, which were experimentally reported to exhibit reversible multi-responsiveness to external stimuli. Dynamic nature is one of intrinsic properties of supramolecular complexes constructed by self-assembly. Therefore, in the first section, we will describe the dynamic self-assembly in the construction of supramolecular complexes, but will focus on their external responsive dynamic behaviors in the second section. In addition, considering that an increasing number of supramolecular complexes constructed by biological building blocks through bio-orthogonal assembly as mimics of biological systems have been reported in recent years, in the second section we will also present some typical examples on such special dynamic biological supramolecular complexes. The final part of this Account is devoted to foreseeing the rapid development of dynamic supramolecular complexes toward applications in functional and smart materials and fundamental questions facing dynamic supramolecular complexes in the future.

Pillar[5]arene-based supramolecular polypseudorotaxanes constructed from quadruple hydrogen bonding

Novel linear supramolecular polypseudorotaxanes constructed from bifunctional ureidopyrimidinone (UPy) pillar[5]arene as the wheel and alkyl diamine as the axle were successfully prepared. This supramolecular polymer was stabilized by the combination of two different non-covalent interactions: quadruple hydrogen bonding and pillararene-based host–guest interactions.

Novel self-assembled dynamic [2]catenanes interlocked by the quadruple hydrogen bonding ureidopyrimidinone motif

Novel dynamic [2]catenanes interlocked by the quadruple hydrogen bonding ureidopyrimidinone (UPy) motif have been developed. The dynamic catenation process was due to the selective cyclization of bifunctional UPy molecules over a wide concentration range with the assistance of the cyclobis(paraquat-p-phenylene) (CBPQT4+4+) macrocycle. The self-assembled [2]catenanes were stabilized by a combination of different non-covalent interactions comprising quadruple hydrogen bonding and host–guest interactions. This type of non-covalent bonded catenane is the first one interlocked by multiple hydrogen bonding interactions instead of metal–ligand interactions.

Warm/cool-tone switchable thermochromic material for smart windows by orthogonally integrating properties of pillar[6]arene and ferrocene

Functional materials play a vital role in the fabrication of smart windows, which can provide a more comfortable indoor environment for humans to enjoy a better lifestyle. Traditional materials for smart windows tend to possess only a single functionality with the purpose of regulating the input of solar energy. However, different color tones also have great influences on human emotions. Herein, a strategy for orthogonal integration of different properties is proposed, namely the thermo-responsiveness of ethylene glycol-modified pillar[6]arene (EGP6) and the redox-induced reversible color switching of ferrocene/ferrocenium groups are orthogonally integrated into one system. This gives rise to a material with cooperative and non-interfering dual functions, featuring both thermochromism and warm/cool tone-switchability. Consequently, the obtained bifunctional material for fabricating smart windows can not only regulate the input of solar energy but also can provide a more comfortable color tone to improve the feelings and emotions of people in indoor environments.Materials for smart windows usually possess single functionality, thus developing materials that regulate solar energy whilst changing color to affect human emotion is desirable. Here the authors combine pillar[6]arenes and ferrocene/ferrocenium groups to produce warm/cool tone-switchable thermochromic materials.

Hydrogen-Bonded Supramolecular Polymers

Supramolecular polymers constructed by different kinds of low-molecular-weight monomers or high-molecular-weight conventional polymeric species based on hydrogen bonding interactions have attracted more and more attention due to their fascinating and unconventional chemical and physical properties. A series of multiple hydrogen-bonding building blocks are described herein, which make the expansion of the research field of hydrogen-bonded supramolecular polymers and allow the fabrication of more new and functional supramolecular polymers. This chapter focuses on linear hydrogen-bonded supramolecular polymers and networks which are described in three parts. The first part is the main-chain supramolecular polymers, in which the polymeric backbone is constructed by noncovalently bonded low-molecular-weight monomers. The second part is the conventional polymer-based supramolecular polymers, in which the main polymeric backbone part is constructed by covalently bonded conventional polymer, but functionalized by hydrogen-bonding motifs. The last part is supramolecular polymers constructed by orthogonal hydrogen bonding-driven self-assembly and other noncovalent interactions.