Orthogonal Design of a Water-Soluble meso-Tetraphenylethene-Functionalized Pillar[5]arene with Aggregation-Induced Emission Property and Its Therapeutic Application

Bionic Artificial Leaves Based on AIE-Active Supramolecular Hydrogel for Efficient Photocatalysis

A novel hydrogel-based biomimetic artificial leaf is fabricated by integrating host-guest interactions with covalent bonding. Specifically, a water-soluble tetraphenylethylene-embedded pillar[5]arene (m-TPEWP5), which exhibits aggregation-induced emission (AIE) property, is synthesized as the host molecule. An amphiphilic guest G is introduced to form a stable complex (HGSM) via non-covalent interactions. Subsequent copolymerization of HGSM with gelatin methacryloyl (GelMA) yields a hydrogel network (HGGelMA), which not only exhibits AIE characteristics but also enables encapsulation of the acceptor eosin Y (ESY), thereby resulting in the construction of an artificial light-harvesting system HGGelMA⊃ESY that serves as a biomimetic leaf. To emulate natural photosynthesis more closely and optimize the utilization of the collected energy, two organic reactions are performed within this artificial leaf: dehalogenation of bromoacetophenone derivatives and coupling of benzylamine. These reactions demonstrate remarkable catalytic activity and recycling ability during the photocatalytic process.

Supramolecular artificial light-harvesting systems incorporating aggregation-induced emissive components: from fabrication to efficient energy conversion

The harvesting and utilization of light energy have increasingly captivated researchers. The construction of artificial light harvesting systems (ALHSs) through supramolecular assemblies has emerged as a prominent approach. Following the discovery of the aggregation-induced emission (AIE) phenomenon, AIE luminogens (AIEgens) have been extensively employed to develop ALHSs, in which these molecules are assembled into nanoparticles or nanoaggregates to enhance energy transfer efficiency. In this review, we summarize recent research advances in supramolecular ALHSs based on AIEgens, including some representative examples reported by our research group and others. In particular, different design strategies for ALHSs formed by self-assembly of host-guest complexes and other building blocks such as macrocyclic and amphiphilic molecules have been discussed over the past three years. For host-guest complexes with AIE activity, we analyze the design principles of AIE-active hosts or guests, and how their self-assembly influences the efficiency of ALHSs. For AIE-active macrocycles or amphiphiles that do not form host-guest complexes, we discuss how they can independently self-assemble into ALHSs. Finally, future research directions for the utilization of AIEgens in the development of ALHSs are discussed.

Calixarene Modification Strategy for Efficient Intracellular Protein Delivery

Efficient intracellular protein delivery is of great importance for the development of protein-based therapy and modern biotechnologies. However, the hydrophilic and macromolecular nature of proteins greatly hinders their ability to cross cell membranes. Herein, a calixarene modification strategy for the intracellular delivery of protein drugs is developed. The decoration of sulfonate azocalix[4]arene (SAC4A) on proteins results in a nano-multivalent effect between Protein-S and amino acids on the cell surface, leading to efficient intracellular delivery of the protein via the clathrin-mediated endocytic pathway. By using SAC4A as a novel ligand, this calixarene modification strategy efficiently delivers 7 proteins, bovine serum albumin (BSA), trypsin (TRY), horseradish peroxidase (HRP), α-chymotrypsin (α-Chyt), lysozyme (LYZ), cytochrome C (Cyt C) and ribonuclease A (RNase A), into cells and significantly enhances the cytotoxicity of Cyt C and RNase A. Moreover, SAC4A-modified Cyt C demonstrates markedly enhanced antitumor efficacy in 4T1-bearing mice without notable side effects. Considering that these proteins are varied in molecular weight and isoelectric point, this calixarene modification strategy provides a platform technology for intracellular protein delivery and the development of protein drugs targeting intracellular pathways.

Review of advancement in aggregation-induced emission-based fluorescent biosensors for enzyme detection: Mechanisms and biomedical applications

BACKGROUND

Enzymes, primarily proteins produced by living organisms, exhibit high substrate selectivity and catalytic efficiency. Many are crucial for normal biological processes and are closely associated with the onset of various diseases. As such, developing methods for detecting disease-related enzymes is essential. Biosensors based on aggregation-induced emission (AIE) have gained significant attention due to their outstanding properties, including excellent photostability, high luminescence efficiency in the aggregated state, large Stokes shift, and favorable biocompatibility. This has led researchers to design a variety of fluorogens with AIE characteristics (AIEgens).

RESULTS

This review provides an overview of the luminescence mechanism behind AIE and the key properties of AIEgens. It focuses on the physiological roles of disease-related enzymes and outlines various AIE-based fluorescent biosensors developed for enzyme recognition and detection. These biosensors are categorized according to their mechanisms, including hydrolysis, electrostatic adsorption, biological redox reactions, and pH-response. Additionally, this review explores the application of enzymes in disease progression, highlighting their value in inhibitor screening, traditional Chinese medicine research, sensing, bioimaging, and disease diagnosis and therapy. It also discusses the current limitations of AIEgens and explores emerging opportunities for their application.

SIGNIFICANCE AND NOVELTY

Enzyme activity and levels are closely linked to the development of specific diseases, underscoring the importance of advancing methods for enzyme detection in disease diagnosis and treatment. This review provides valuable insights for the development of innovative AIEgens for enzyme detection, expands the options for detection mechanisms, and offers a theoretical foundation for clinical diagnostics and therapeutic applications.

A Pillar[5]arene-Based π-Conjugated Organic Small Molecule Emitter: Synthesis, Self-Assembly, and Selective Sensing of Cr2O7 2- Anion

A triphenylamine-containing π-conjugated pillar[5]arene luminescent small organic molecule has been synthesized via Suzuki-coupling reaction. This molecule can self-assemble to form linear supramolecular polymers in both solution and solid state. The molecule shows enhanced emission compared with parent pillar[5]arene in dilute solution. Based on the bright luminescent behavior, its sensing ability for Cr2O7 2- anion was studied.

Fluorescent Macrocyclic Arenes: Synthesis and Applications

Fluorescent macrocyclic arenes have attracted increasing interest in macrocyclic and supramolecular chemistry due to their exceptional photophysical properties and versatile applications. Classical macrocyclic arenes modified with fluorescent groups at the upper or bottom rims have long provided valuable platforms across various fields. Recently, a large number of novel fluorescent macrocyclic arenes directly composed of polycyclic aromatic or heteroaromatic building blocks including naphthalene, anthracene, tetraphenylethene, pyrene, fluorene, carbazole, acridan, phenothiazine, coumarin, triphenylamine, benzothiadiazole and so on, have been reported, and they have shown specific fluorescent property, and also exhibited broad applications in molecular recognition, sensing, bioimaging and functional materials. In this review, we focus on the recent advances in the synthesis and applications of fluorescent macrocyclic arenes containing polycyclic aromatic or heteroaromatic skeletons emerged in the past decade. By categorizing these fluorescent macrocyclic arenes based on the different building blocks, this review provides a comprehensive summary of their synthesis, properties and applications.

Novel supramolecular artificial light-harvesting systems based on AIE-active macrocycles for efficient white-light photocatalysis in water

Constructing supramolecular artificial light-harvesting systems (ALHSs) based on the Förster resonance energy transfer (FRET) mechanism provides an optimal platform for understanding natural photosynthesis and simulating natural light-harvesting systems. In the present work, rigid macrocycle K-1 with a nonplanar conformation and aggregation-induced emission (AIE) properties was selected as an energy donor in ALHSs, while the non-cyclic AIEgen K-2 was used for a comparative study. In aqueous solution, an efficient one-step energy-transfer process was established between blue-emitting K-1 and an acceptor (namely PBTB) with orange fluorescence to afford a high energy-transfer efficiency (Φ ET) of up to 82.6%. Notably, bright white light emission can be readily realized. Moreover, the triad FRET system was fabricated through energy transfer from the AIEgens to PBTB, then further transferring the captured energy to the final red-emitting acceptor (namely as Z1), achieving an efficient two-step sequential energy transfer. When the ratio of K-1/PBTB/Z1 assemblies reached 1000 : 40 : 14, the optimal Φ ET was 66.4%. More importantly, it was found that the ALHS based on macrocycle K-1 showed much higher photocatalytic activity for the cross-dehydrogenative coupling (CDC) reaction. Therefore, the flexibility of this novel supramolecular strategy renders the macrocyclic AIEgen a promising candidate to construct efficient ALHSs for photocatalysis.

Recent developments in pillar[5]arene-based nanomaterials for cancer therapy

Nanomaterials possess unique size characteristics, enabling them to cross tissue gaps, penetrate the blood-brain barrier and endothelial cells, and release drugs at the cellular level. Additionally, the surface of nanomaterials is readily functionalized, endowing them with good biocompatibility, low biotoxicity, and specific targeting. All these advantages render nanomaterials broad application prospects in tumor therapy. Pillar[5]arenes are a new category of macrocyclic host compounds featuring rich host-guest properties and diverse environmental responses. In recent years, by combining the advantages of pillar[5]arenes and nanomaterials, the application of pillar[5]arene-based nanomaterials in tumor therapy has drawn extensive attention from scientists. In this review, we summarize five distinct types of pillar[5]arene-based nanomaterials: (1) pillar[5]arene-modified inorganic nanomaterials; (2) pillar[5]arene-modified organic porous materials; (3) pillar[5]arene-modified organic/inorganic hybrid materials; (4) nanomaterials self-assembled from pillar[5]arene-based host-guest complexes; (5) nanomaterials self-assembled from amphiphilic pillar[5]arenes. Moreover, the different tumor treatment modes of these nanomaterials, including chemotherapy, photodynamic therapy, photothermal therapy, gene therapy, and multimodal synergistic therapy, are also elaborated in detail.

Hydrogen-bonded macrocycle-mediated dimerization for orthogonal supramolecular polymerization

Orthogonal self-assembly represents a useful methodology to construct supramolecular polymers with AA- and AB-type monomers, as commonly used for covalently linked polymers. So far, the design of such monomers has relied heavily on three-dimensional macrocycles, and the use of two-dimensional shape-persistent macrocycles for this purpose remains rather rare. Here, we demonstrate a dimerization motif based on a hydrogen-bonded macrocycle that can be effectively applied to form orthogonal supramolecular polymers. The macrocycle-mediated connectivity was confirmed by single-crystal X-ray diffraction, which revealed a unique 2:2 binding motif between host and guest, bridged by two cationic pyridinium end groups through π-stacking interactions and other cooperative intermolecular forces. Zinc ion-induced coordination with the macrocycle and a terpyridinium derivative enabled orthogonal polymerization, as revealed by 1H NMR, DLS, and TEM techniques. In addition, viscosity measurements showed a transition from oligomers to polymers at the critical polymerization concentration of 17 μM. These polymers were highly concentration-dependent. Establishing this new dimerization motif with shape-persistent H-bonded macrocycles widens the scope of noncovalent building blocks for supramolecular polymers and augurs well for the future development of functional materials.

The Versatile Applications of Calix[4]resorcinarene-Based Cavitands

The advancement of synthetic host-guest chemistry has played a pivotal role in exploring and quantifying weak non-covalent interactions, unraveling the intricacies of molecular recognition in both chemical and biological systems. Macrocycles, particularly calix[4]resorcinarene-based cavitands, have demonstrated significant utility in receptor design, facilitating the creation of intricately organized architectures. Within the realm of macrocycles, these cavitands stand out as privileged scaffolds owing to their synthetic adaptability, excellent topological structures, and unique recognition properties. So far, extensive investigations have been conducted on various applications of calix[4]resorcinarene-based cavitands. In this review, we will elaborate on their diverse functions, including catalysis, separation and purification, polymeric materials, sensing, battery materials, as well as drug delivery. This review aims to provide a holistic understanding of the multifaceted roles of calix[4]resorcinarene-based cavitands across various applications, shedding light on their contributions to advancing the field of supramolecular chemistry.

Detecting Pb2+ in aqueous environment and live cells by amphiphilic pillar[5]arene-assembled supramolecular sensor based on host-guest charge transfer mechanism

Water-soluble fluorescent chemosensors for lead ion are highly desirable in environmental detection and bioimagery. Based on a water-soluble pillar[5]arene WP5 and imidazolium terminal functionalized 2,2'-bibenzimidazole derivative BIHB, we report a host-guest charge transfer assembly BIHB-2WP5 for sensitive and selective detection of Pb2+ in pure aqueous media. As a result of its high electron-rich cavity, WP5 can bind electron-deficiency guest BIHB with various host/guest stoichiometry to easily tune the microtopography of assembly from nanoparticle to nanocube. In view of the good biocompatibility and sensitivity, the supramolecular assembly BIHB-2WP5 was used as a fluorescent probe for the detection of Pb2+ in living cells and a smartphone Pb2+ detection device was constructed for the in situ test.

Extended Sulfo-Pillar[6]arenes ─ a New Host Family and Its Application in the Binding of Direct Oral Anticoagulants

Herein, we report the synthesis of extended sulfo-pillar[6]arenes (sP6), a new host class with a pedigree in salt tolerance and ultrahigh binding affinity toward multiple drug classes. The parent sulfo-pillar[6]arene is a high-affinity host with the potential to act as a supramolecular reversal agent. However, it lacks synthetic diversification of the core scaffold. The new extended sulfo-pillar[6]arenes have either a monodirectional (A1sP6) or bidirectional (A1A2sP6) extension of the hydrophobic cavity. This new functionality enables more noncovalent interactions and strong affinity toward guests, which we demonstrate using the direct oral anticoagulants (DOACs) dabigatran, betrixaban, and edoxaban. DOACs are highly prescribed therapeutics that are underexplored in host-guest chemistry. These agents prevent the formation of blood clots and are prime targets for supramolecular sequestration. This functionalization also introduces new fluorescent properties to the sulfo-pillar[6]arene family via an incorporated p-terphenyl (A1A2sP6). We show that these new hosts have ultrahigh affinity toward dabigatran (Kd = 27 nM, A1A2sP6) in salty solutions and that the A1A2sP6 analogue can bind betrixaban in bovine plasma with a physiologically relevant Kd (7 μM).

A nanoplatform based on allylthiopurine bio-MOF and glycosylated AIE PARP inhibitor for cancer synthetic lethal therapy

A biological nanoplatform (Gal-ANI@ZnAP NPs) was constructed based on a prodrug-skeletal metal-organic framework (MOF) using purine nucleobase analogue prodrug 6-allylthiopurine as a bioactive ligand, and functionalized with AIE fluorescent PARP inhibitor glycoconjugate for visualization therapy and synthetic lethal cancer therapy. This nanoplatform could actively target cancer cells, selectively release drugs in response to esterase/pH, and visualize drug uptake. In vitro studies revealed that Gal-ANI@ZnAP NPs increased the synthetic lethality in cancer cells by inducing DNA repair failure with the simultaneous targeting of PARP and nucleotide metabolism, thereby exhibiting a significant cancer-killing effect. The study presents a novel strategy to construct an AIE nanoplatform using pharmaceutical molecules for drug uptake visualization and boosting synthetic lethality in cancer.

Quinoxaline-based azamacrocycles: synthesis, AIE behavior and acidochromism

The development of luminescent molecular materials has advanced rapidly in recent decades, primarily driven by the synthesis of novel emissive compounds and a deeper understanding of excited-state mechanisms. Herein, we report a streamlined synthetic approach to light-emitting diazapolyoxa- and polyazamacrocycles N2CnOxQ and NyCnQ (n = 3-10; x = 2, 3; y = 2-5), incorporating a 2,3-diphenylquinoxaline residue (DPQ). This synthetic strategy based on macrocyclization through Pd-catalyzed amination reaction yields the target macrocycles in good or high yields (46-92%), enabling precise control over their structural parameters. A key role of the PhPF-tBu ligand belonging to the JosiPhos series in this macrocyclization was elucidated through DFT computation. This macrocyclization reaction eliminates the need for complex protecting-deprotecting procedures of secondary amine groups, offering a convenient and scalable method for the preparation of target compounds. Moreover, it boasts a potentially broad substrate scope, making it promising for structure-properties studies within photophysics, sensor development, and material synthesis. Photophysical properties of representative macrocycles were investigated, employing spectroscopic techniques and DFT computation. It was demonstrated that DPQ-containing macrocycles display aggregation-induced emission in a DCM-hexane solvent mixture despite the presence of flexible tethers within their structures. Single-crystal X-ray diffraction analysis of a representative compound N2C8O3Q allowed us to gain deeper insight into its molecular structure and AIE behaviour. The emissive aggregates of the N2C10O3Q macrocycle were immobilized on filter paper yielding AIE-exhibiting test strips for measuring acidity in vapors and in aqueous media.

Recent Progress of Supramolecular Chemotherapy Based on Host-Guest Interactions

Chemotherapy is widely recognized as an effective approach for treating cancer due to its ability to eliminate cancer cells using chemotherapeutic drugs. However, traditional chemotherapy suffers from various drawbacks, including limited solubility and stability of drugs, severe side effects, low bioavailability, drug resistance, and challenges in tracking treatment efficacy. These limitations greatly hinder its widespread clinical application. In contrast, supramolecular chemotherapy, which relies on host-guest interactions, presents a promising alternative by offering highly efficient and minimally toxic anticancer drug delivery. In this review, an overview of recent advancements in supramolecular chemotherapy based on host-guest interactions is provided. The significant role it plays in guiding cancer therapy is emphasized. Drawing on a wealth of cutting-edge research, herein, a timely and valuable resource for individuals interested in the field of supramolecular chemotherapy or cancer therapy, is presented. Furthermore, this review contributes to the progression of the field of supramolecular chemotherapy toward clinical application.

Pillararene-Based Stimuli-Responsive Supramolecular Delivery Systems for Cancer Therapy

Cancer poses a significant challenge to global public health, seriously threatening human health and life. Although various therapeutic strategies, such as chemotherapy (CT), radiotherapy, phototherapy, and starvation therapy, are applied to cancer treatment, their limited therapeutic effect, severe side effects, and unsatisfactory drug release behavior need to be carefully considered. Thus, there is an urgent need to develop efficient drug delivery strategies for improving cancer treatment efficacy and realizing on-demand drug delivery. Notably, pillararenes, as an emerging class of supramolecular macrocycles, possess unique properties of highly tunable structures, superior host-guest chemistry, facile modification, and good biocompatibility, which are widely used in cancer therapy to achieve controllable drug release and reduce the toxic side effects on normal tissues under various internal/external stimuli conditions. This review summarizes the recent advance of stimuli-responsive supramolecular delivery systems (SDSs) based on pillararenes for tumor therapy from the perspectives of different assembly methods and hybrid materials, including molecular-scale SDSs, supramolecular nano self-assembly delivery systems, and nanohybrid SDSs. Moreover, the prospects and critical challenges of stimuli-responsive SDSs based on pillararenes for cancer therapy are also discussed.

Precise molecular engineering for the preparation of pyridinium photosensitizers with efficient ROS generation and photothermal conversion

Organic photosensitizers (PSs) with aggregation-induced emission properties have great development potential in the integrated application of multi-mode diagnosis and treatment of photodynamic therapy (PDT) and photothermal therapy (PTT). However, preparing high-quality PSs with both optical and biological properties, high reactive oxygen species (ROS) and photothermal conversion ability are undoubtedly a great challenge. In this work, a series of pyridinium AIE PSs modified with benzophenone have been synthesized. A wide wavelength range of fluorescent materials was obtained by changing the conjugation and donor-acceptor strength. TPAPs5 has a significant advantage over similar compounds, and we have also identified the causes of high ROS generation and high photothermal conversion in terms of natural transition orbitals, excited state energy levels, ground-excited state configuration differences and recombination energy. Interestingly, migration of target sites was also found in biological imaging experiments, which also provided ideas for the design of double-targeted fluorescent probes. Therefore, the present work proposed an effective molecular design strategy for synergistic PDT and PTT therapy.

Silapillar[n]arenes: Their Enhanced Electronic Conjugation and Conformational Versatility

During recent decades, methylene-bridged macrocyclic arenes have been widely used in supramolecular chemistry. However, their π-conjugations are very weak, as the methylene bridges disrupt the electronic communication between π orbitals of the aromatic units. Herein, we successfully synthesized a series of silapillar[n]arenes (n = 4, 6, and 8) using silylene bridging. These showed enhanced electronic conjugation compared with the parent pillar[n]arenes because of σ*-π* conjugation between σ* (Si-C) orbitals and π* orbitals of the benzenes. Owing to the longer Si-C bond compared with the C-C bond, silylene-bridging provides additional structural flexibility into the pillar[n]arene scaffolds; a strained silapillar[4]arene was formed, which is unavailable in the parent pillar[n]arenes because of the steric requirements. Furthermore, silapillar[n]arenes displayed interesting size-dependent structural and optical properties.

Friedel-Crafts Acylation for Accessing Multi-Bridge-Functionalized Large Pillar[n]arenes

Pillar[n]arenes can be constructed using a Friedel-Crafts alkylation process. However, due to the reversible nature of the alkylation, mixture of large pillar[n]arenes (n≥7) are obtained as minor products, and thus laborious purification are necessary to isolate the larger pillar[n]arenes. Moreover, inert methylene bridges are introduced during the alkylation process, and the multi-functionalization of the bridges has never been investigated. Herein, an irreversible Friedel-Crafts acylation is used to prepare pillar[n]arenes. Due to the irreversible nature of the acylation, the reaction of precursors bearing carboxylic acids and electron-rich arene rings results in a size-exclusive formation of pillar[n]arenes, in which the ring-size is determined by the precursor length. Because of this size-selective formation, laborious separation of undesired macrocycles is not necessary. Moreover, the bridges of pillar[n]arenes are selectively installed with reactive carbonyl groups using the acylation method, whose positions are determined by the precursor used. The carbonyl bridges can be easily converted into versatile functional groups, leading to various laterally modified pillar[n]arenes, which cannot be accessed by the alkylation strategy.

Stereoselective Single Step Cyclization to Give Belt-Functionalized Pillar[6]arenes

Two macrocycles were synthesized through cyclization reactions of secondary benzylic alcohols, giving pillar[6]arenes with a methyl substituent at each belt position. These macrocycles form stereoselectively with only the rtctct isomer with alternating up and down orientations of the belt methyl groups definitively identified. Isolated yields were modest (7 and 9%), but the macrocycles are prepared in a single step from either a commercially available alcohol or a very readily prepared precursor. X-ray crystal structures of the macrocycles indicate they have a capsule-like structure, which is far from the conventional pillar shape. Density functional theory calculations reveal that the energy barrier required to obtain the pillar conformation is significantly higher for these belt-functionalized macrocycles than for conventional belt-unfunctionalized pillar[6]arenes.

Polydopamine modified by pillar[5]arene in situ for targeted chemo-photothermal cancer therapy

A pillar[5]arene-modified polydopamine (PDA-P[5]OH) displaying pH/NIR dual-responsive properties was constructed successfully in situ for targeted chemo-photothermal cancer therapy.

Macrocyclic-Albumin Conjugates for Precise Delivery of Radionuclides and Anticancer Drugs to Tumors

Precise delivery of radionuclides and anticancer drugs to tumor tissue is crucial to ensuring drug synergism and optimal therapeutic effects in radionuclide-based combination radio-chemotherapy. However, current codelivery vectors often rely on physical embedment/adsorption to load anticancer drugs, which lacks precise mechanisms for drug loading and release, resulting in unpredictable combination effects. Herein, a macrocyclic-albumin conjugate (MAC) that enables precise loading and controlled release of anticancer drugs is presented. By conjugating multiple macrocyclic hosts (sulfonate azocalix[4]arenes, SAC4A) to albumin molecules, the MAC facilitates the precise loading of anticancer drugs through host-guest interactions and site-specific labeling of radionuclides. Furthermore, the MAC degrades under hypoxic conditions, enabling the release of loaded drugs upon reaching tumor tissues. Through precise loading and targeted delivery of radionuclides and anticancer drugs, MAC achieves efficient cancer diagnosis and combined radio-chemotherapy in breast cancer cell (4T1)-bearing mice. Considering that SAC4A can load many anticancer drugs, MAC may provide a promising platform for effective combination radio-chemotherapy.

Water-soluble phosphate-pillar[5]arene (WPP5)-based artificial light-harvesting system for photocatalytic cross-coupling dehydrogenation

A novel water-soluble phosphate-pillar[5]arene (WPP5)-based artificial light-harvesting system (LHS) was successfully fabricated through the supramolecular assembly of phenyl-pyridyl-acrylonitrile derivative (PBT), WPP5, and organic pigment Eosin Y (ESY). Initially, after host-guest interaction, WPP5 could bind well with PBT and form WPP5 ⊃ PBT complexes in water, which further assembled into WPP5 ⊃ PBT nanoparticles. WPP5 ⊃ PBT nanoparticles performed an outstanding aggregation-induced emission (AIE) capability because of the J-aggregates of PBT in WPP5 ⊃ PBT nanoparticles, which were appropriate as fluorescence resonance energy transfer (FRET) donors for artificial light-harvesting. Moreover, due to the emission region of WPP5 ⊃ PBT overlapped well with the UV-Vis absorption of ESY, the energy of WPP5 ⊃ PBT (donor) could be significantly transferred to ESY (acceptor) via FRET process in WPP5 ⊃ PBT-ESY nanoparticles. Notably, the antenna effect (AE_{WPP5⊃PBT-ESY}) of WPP5 ⊃ PBT-ESY LHS was determined to be 30.3, which was much higher than that of recent artificial LHSs for photocatalytic cross-coupling dehydrogenation (CCD) reactions, suggesting a potential application in photocatalytic reaction. Furthermore, through the energy transfer from PBT to ESY, the absolute fluorescence quantum yields performed a remarkable increase from 14.4% (for WPP5 ⊃ PBT) to 35.7% (for WPP5 ⊃ PBT-ESY), further confirming their FRET processes in WPP5 ⊃ PBT-ESY LHS. Subsequently, in order to output the harvested energy for catalytic reactions, WPP5 ⊃ PBT-ESY LHSs were used as photosensitizers to catalyze the CCD reaction of benzothiazole and diphenylphosphine oxide. Compared to free ESY group (21%), a significant cross-coupling yield of 75% in WPP5 ⊃ PBT-ESY LHS was observed, because more UV region energy of PBT was transferred to ESY for CCD reaction, which suggested more potential in improving the catalytic activity of organic pigment photosensitizers in aqueous systems.

Structural Modification Endows Small-Molecular SN38 Derivatives with Multifaceted Functions

As a camptothecin derivative, 7-ethyl-10-hydroxycamptothecin (SN38) combats cancer by inhibiting topoisomerase I. SN38 is one of the most active compounds among camptothecin derivatives. In addition, SN38 is also a theranostic reagent due to its intrinsic fluorescence. However, the poor water solubility, high systemic toxicity and limited action against drug resistance and metastasis of tumor cells of SN38 indicates that there is great space for the structural modification of SN38. From the perspective of chemical modification, this paper summarizes the progress of SN38 in improving solubility, increasing activity, reducing toxicity and possessing multifunction and analyzes the strategies of structure modification to provide a reference for drug development based on SN38.

Pillar[5]arene based water-soluble [3]pseudorotaxane with enhanced fluorescence emission for cell imaging and both type I and II photodynamic cancer therapy

Water-soluble [3]pseudorotaxane with enhanced fluorescence emission was successfully constructed and applied in cell imaging and photodynamic cancer therapy.

Erlotinib-Loaded Dendrimer Nanocomposites as a Targeted Lung Cancer Chemotherapy

Lung cancer is the main cause of cancer-related mortality globally. Erlotinib is a tyrosine kinase inhibitor, affecting both cancerous cell proliferation and survival. The emergence of oncological nanotechnology has provided a novel drug delivery system for erlotinib. The aims of this current investigation were to formulate two different polyamidoamine (PAMAM) dendrimer generations-generation 4 (G4) and generation 5 (G5) PAMAM dendrimer-to study the impact of two different PAMAM dendrimer formulations on entrapment by drug loading and encapsulation efficiency tests; to assess various characterizations, including particle size distribution, polydispersity index, and zeta potential; and to evaluate in vitro drug release along with assessing in situ human lung adenocarcinoma cell culture. The results showed that the average particle size of G4 and G5 nanocomposites were 200 nm and 224.8 nm, with polydispersity index values of 0.05 and 0.300, zeta potential values of 11.54 and 4.26 mV of G4 and G5 PAMAM dendrimer, respectively. Comparative in situ study showed that cationic G4 erlotinib-loaded dendrimer was more selective and had higher antiproliferation activity against A549 lung cells compared to neutral G5 erlotinib-loaded dendrimers and erlotinib alone. These conclusions highlight the potential effect of cationic G4 dendrimer as a targeting-sustained-release carrier for erlotinib.

Supramolecular nanoprodrug based on a chloride channel blocker and glycosylated pillar[5]arenes for targeted chemoresistance cancer therapy

A supramolecular nanoprodrug (DOX@GP5⊃Pro-NFA) was constructed based on the host-guest complexation of chloride channel blocker prodrug (Pro-NFA) and glycosylated pillar[5]arene (GP5), which could target tumor cells via galactose and release DOX/NFA responsively under esterase stimulation. In vitro studies revealed that this supramolecular nanoprodrug can overcome drug resistance through inhibiting chloride channels as well as inhibiting the migration of HepG2/ADR cells. This strategy can therefore achieve enhanced potency in chemotherapy through reverse chemoresistance.

An L-arginine-functionalized pillar[5]arene-based supramolecular photosensitizer for synergistically enhanced cancer therapeutic effectiveness

An L-arginine-functionalized pillar[5]arene-based supramolecular photosensitizer LAP5⊃NBSPD was constructed by host-guest interactions, which could self-assemble into nano-micelles to achieve effective delivery and selective release of LAP5 and NBS in cancer cells. In vitro studies revealed that LAP5⊃NBSPD NPs exhibited excellent cancer cell membrane disruption and ROS generation properties, which provides a novel route for synergistically enhanced cancer therapeutic effectiveness.

A rational design of polymers through donor modulation to weaken the aggregation-caused quenching effect for NIR-II fluorescence imaging

The great tissue penetration depth and low tissue autofluorescence of NIR-II fluorescence imaging make it attractive for in vivo diagnosis. However, the aggregation-caused quenching (ACQ) effect is among the dominant obstacles that weaken NIR-II imaging and restrict its application. Herein, the donor unit, 2,8-dibromo-6H,12H-5,11-methanodibenzo[b,f] [1,5]diazocine with a V-configuration, was introduced to prepare the donor-acceptor (D-A) polymer P-TB with a twisted backbone, while the planar D-A polymer P-TP was used as a control. P-TB and P-TP were prepared by Stille Coupling with DPP as the acceptor. The main absorption peaks of P-TB and P-TP are located at 610 nm and 640 nm, and the emission peaks of P-TB and P-TP are 1060 nm and 930 nm, respectively. Significantly, the V-shaped P-TB showed no obvious ACQ effect within 600 μM, and the same phenomenon was demonstrated during in vivo NIR-II imaging in mice, which proves that the introduction of V-configuration donor units is beneficial for weakening the ACQ effect. This work outlines a prospective tactic for the design of conventional NIR-II fluorescent polymers by modulating the configuration of the donor units.

Dimeric Pillar[5]arene as a Novel Fluorescent Host for Controllable Fabrication of Supramolecular Assemblies and Their Photocatalytic Applications

A dimeric fluorescent macrocycle m-TPE Di-EtP5 (meso-tetraphenylethylene dimeric ethoxypillar[5]arene) is synthesized based on the meso-functionalized ethoxy pillar[5]arene. Through the connectivity of two pillar[5]arenes by CC double bond, the central tetraphenylethylene (TPE) moiety is simultaneously formed. The resultant bicyclic molecule not only retains the host-guest properties of pillararenes but also introduces the interesting aggregation-induced emission properties inherent in the embedded TPE structure. Three dinitrile derivatives with various linkers are designed as guests (G1, G2, and G3) to form host-guest assemblies with m-TPE Di-EtP5. The morphological control and fluorescence properties of the assemblies are successfully realized. G1 with a shorter alkyl chain as the linker completely threads into the cavities of the host. G2, due to its longer chain length, forms a linear supramolecular polymer upon binding to m-TPE Di-EtP5. G3 differs from G2 by possessing a bulky phenyl group in the middle of the chain, which can be further assembled with m-TPE Di-EtP5 to form supramolecular layered polymer and precipitated out in solution, and can be efficiently applied to photocatalytic reactions.

Photoresponsive reversible self-assembly of rod-coil amphiphiles containing spiropyran groups

Stimuli-responsive assembly deformation is a key feature in constructing smart soft materials, which makes them versatile and autonomous. In this study, rod-coil amphiphilic compounds containing spiropyran (SP) groups were developed and synthesized to investigate their stimuli-responsive assembly in a solution system with 99% water content. In addition to photochromic phenomena, reversible light-mediated morphological alterations occurred in these molecular aggregates. Based on the different flexible chain segments of rod-coil amphiphiles, the initial assemblies underwent a dissociation-reassembly process under ultraviolet (UV) irradiation, whereupon they deformed or disassembled to assemblies. Furthermore, as the UV source was removed, the original nanostructures were gradually recovered again via the ring-closing reaction process. These compounds, interestingly, can selectively combine with copper ions to produce cross-linked co-assembled nanostructures. The copper ion complex solution of rod-coil amphiphilic compounds emitted unique bright blue fluorescence, which allowed for the specific visual identification of copper ions in aqueous solutions.

Pillar[5]arene Derivatives Embedded with Aggregation-Induced Emission Luminogens and Their Fluorescence Regulation

Through McMurry coupling reaction, three meso-position functionalized pillar[5]arene derivatives (H-1, H-2, and H-3) have been successfully prepared by embedding aggregation-induced emission luminogens (AIEgens, diphenyldibenzofulvene (DPDBF) and tetraphenylethylene (TPE)) into the skeleton of supramolecular macrocycles. H-1, bearing [1₅ ]paracyclophane ([1₅ ]PCP) and DPDBF moiety, exhibits yellow emission and demonstrates obvious AIE effect. In order to further improve the host-guest properties of this type of structure, H-2 and H-3 are prepared by replacing the [1₅ ]PCP moiety with pillar[5]arene backbone, both of which show significant AIE effect and excellent host-guest complexation properties with pyrazine salt guest G-1 and 1,4-dicyanobutane G-2. Our findings indicate that G-1 can decrease the fluorescence intensity of the AIE macrocycles, while G-2 can increase their fluorescence intensity in solution.

Supramolecular Biopharmaceutical Carriers Based on Host-Guest Interactions

Traditional drugs have the disadvantages of poor permeability and low solubility, which makes the utilization of pesticides lower and brings many side effects. With the continuous development of supramolecular chemistry in recent years, it has also played an irreplaceable role in the field of pharmaceutical science. Supramolecular macrocycles, such as crown ethers, cyclodextrins, calixarenes, pillararenes and cucurbiturils, are potentially good candidates for drug carriers due to their biocompatibility, hydrophobic cavity and ease of derivatization. The encapsulation of drugs based on host-guest interaction has the advantage of being adjustable and reversible as well as improving the low availability of drugs. Here, the recent advances in methods and strategies for drug encapsulation and release based on supramolecular macrocycles with host-guest interactions have been systematically summarized, laying a bright foundation for the development of novel nanopesticide preparations in the future and pointing out future directions of novel biopesticide research.

Dynamic combinatorial libraries of a dimercapto-pillar[5]arene

We report the synthesis and dynamic covalent chemistry (DCvC) of an A1/A2-dimercapto-functionalized pillar[5]arene (Di-SH-P5). The introduction of thiol moieties into this macrocyclic host makes it an effective building block for making a dynamic combinatorial library (DCL), giving rise to a set of cyclic trimers with intriguing host-guest properties as the dominant constituents.

Tetraphenylethylene-embedded [15]paracyclophanes: AIEgen and macrocycle merged novel supramolecular hosts used for sensing Ni2+ ions

Transformation of [1₅]paracyclophanes ([15]PCP) into fluorophores has been achieved by embedding tetraphenylethene (TPE) units into their skeletons at the meso-positions. The obtained two hosts demonstrated distinct aggregation-induced emission (AIE) properties and their fluorescence could be selectively quenched by Ni²⁺ ions.

Orthogonal Design of Supramolecular Prodrug Vesicles via Water-Soluble Pillar[5]arene and Betulinic Acid Derivative for Dual Chemotherapy

Supramolecular prodrug vesicles with efficient property for dual chemotherapy have been successfully constructed based on the orthogonal self-assembly between a water-soluble pillar[5]arene host (WP5) and a betulinic acid guest (BA-D) as well as doxorubicin (DOX). Under the acidic microenvironment of cancer cells, both the encapsulated anticancer drug DOX and prodrug BA-D can be effectively released from DOX-loaded WP5⊃BA-D prodrug vesicles for combinational chemotherapy. Furthermore, bioexperiments indicate that DOX-loaded prodrug vesicles can obviously enhance the anticancer efficiency based on the cooperative effect of DOX and BA-D, while remarkably reducing the systematic toxicity in tumor-mice, displaying great potential applications in combinational chemotherapy for cancer treatments.

Tetraphenylethylene-embedded pillar[5]arene-based orthogonal self-assembly for efficient photocatalysis in water

Herein, we have designed and fabricated a simple and efficient supramolecular self-assembled nanosystem based on host-guest interactions between water-soluble tetraphenylethylene-embedded pillar[5]arene ( m -TPEWP5) and ammonium benzoyl-ʟ-alaninate (G) in an aqueous medium. The obtained assembly of m -TPEWP5 and G showed aggregation-induced emission (AIE) via the blocking of intramolecular phenyl-ring rotations and functioned as an ideal donor. After the loading of eosin Y (EsY) as acceptor on the surface of the assembly of m -TPEWP5 and G, the worm-like nanostructures changed into nanorods, which facilitates a Förster resonance energy transfer (FRET) from the m -TPEWP5 and G assembled donor to the EsY acceptor present in the nanorod assembly. The system comprising m -TPEWP5, G and EsY displayed moderate FRET efficiency (31%) at a 2:1 molar ratio of donor-to-acceptor. Moreover, the obtained supramolecular nanorod assembly could act as a nanoreactor mimicking natural photosynthesis and exhibited a high catalytic efficiency for the photocatalytic dehalogenation reaction of various bromoketone derivatives with good yields in short reaction time in water.

A disulfide-induced supra-amphiphilic co-assembly for glycosylated pro-drug-photosensitizer nanoparticles in combination therapies

We reported an intermolecular chalcogen bonding interaction (S⋯S contacts) induced supra-amphiphilic co-assembly strategy to construct glycosylated pro-drug-photosensitizer nanoparticles (BG-L NPs) in combination therapies.

Construction of a pillararene-based supramolecular polymer network and its application in efficient removal of dyes from water

An AB-type monomer based on a pillar[5]arene host and an imidazolium salt guest was successfully synthesized through a facile way. This monomer can self-assemble into linear supramolecular polymers in chloroform. After the addition of silver ions, the imidazolium salt group coordinated with silver ions to crosslink the linear supramolecular polymers at their ends, resulting in the formation of supramolecular polymer networks. Meanwhile, after further adding iodide ions, the supramolecular polymer network changed back to the linear supramolecular polymer. As a result, the topological structure of the system can be reversibly tuned. Furthermore, this supramolecular polymer network can be applied to remove organic dyes in water, suggesting its great potential in the treatment of waste water.

Step-Growth Cyclo-Oligomerization for the Preparation of Functionalized Pillar[6]arenes with Alternating Methylene Bridge Substitutions

Methylene-bridge-substituted pillar[6]arenes (PA[6]) are synthesized by step-growth cyclo-oligomerization. Dimers, trimers, tetramers, and hexamers with substituted methylene bridges are synthesized. Hexamers are converted to PA[6] derivatives with alternating methylene bridge substitutions by ring-closing reactions. PA[6] derivatives are further modified with pyrene groups or carboxylate groups by Suzuki-Miyaura coupling reactions. The modifications render PA[6] fluorescent or water-soluble. A host-guest chemistry study confirms that the water-soluble PA[6] derivative is a high-affinity host toward suitable guests in water.