β-Cyclodextrin/calix[4]arene hybrid porous organic polymer membrane for synergistic extraction of fluorescent whitening agents migrating from food contact materials

Acurate and sensitive determination of hazards from food contact materials is important to monitor food safety. It is necessary to excavate efficient adsorbent for simultaneous recognition and adsorption of food hazards of trace level for sample preparation. In this work, β-cyclodextrin and calix[4]arene were employed as hybrid functional monomers to prepare macrocyclic porous organic polymer (β-CD-CX4 POP). It was proved that the supramolecular cavities of β-CD-CX4 POP could form inclusion complexes with fluorescent whitening agents (FWAs) through host-guest recognition, which greatly improved the adsorption performance. The hydrophobic cavities of β-cyclodextrin and calix[4]arene of β-CD-CX4 POP exhibited synergistic effect for simultaneous recognition of FWAs. The high-throughput enrichment of FWAs was realized by β-CD-CX4 POP membranes coupled with a multiple-channel syringe pump. Based on membrane-based solid-phase extraction combined with UHPLC-MS/MS, a sensitive analytical method was established to determine six FWAs. The LODs was in range of 3-50 ng/L with the linear range of 0.02-100 μg/L. The developed method was used to quantify FWAs in bread wrapper and bread, and the spiked recoveries ranged from 78.1%-119% with RSD of 2.3%-9.7%. This work indicated that β-CD-CX4 POP was promising for the simultaneous recognition and adsorption of FWAs migrating from food contact materials.

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.

Flower-like calix[6]arene-based covalent organic framework for membrane extraction of sulfonamides in animal-derived food through host-guest interaction prior to determination with ultra-high performance liquid chromatography-tandem mass spectrometry

Supramolecular macrocycle-based covalent organic frameworks (COFs) are promising adsorbents for adsorption of hazards due to their host-guest recognition property. However, most supramolecular macrocycles are conformationally flexible, making them challenging to introduce into COFs. In this work, a calix[6]arene-based COF (CX6-BD COF) was fabricated with a unique flower-like morphology and high crystallinity. Especially, the cavity of CX6 exhibited host-guest inclusion interaction for sulfonamides (SAs), which was verified by quantum chemistry calculation. The integration of the porosity of COFs with the recognition cavity of CX6 made CX6-BD COF display excellent enrichment performance for SAs, with good enrichment factors (EFs) between 77 and 96. The material was employed as an adsorbent for COF membrane filter extraction, coupled with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) to simultaneously enrich and determine seven SAs in animal-derived food. The analytical method showed a wide linear range (0.01-100 µg/L and 0.05-100 µg/L) and low detection limits (3-10 ng/L). The established method was successfully applied to sensitively determine SAs in chicken, pork and beef samples, which achieved satisfactory recoveries (73.8-113%). These results demonstrated CX6-BD COF has good application potential in determination of trace and ultra-trace SAs in complex food matrices as an adsorbent.

Synthetically Tunable Suprahybrid Nanoparticle Platform for the Efficacious Delivery of Therapeutics

The discovery of lipid-hybrid nanosystems has offered potential solutions to various drug delivery and theranostic challenges. However, in many instances, the commonly used lipids and other components in these systems often pose challenges related to their solubility, physicochemical properties, immune compatibility, and limited synthetic tunability. In this work, we introduce a synthetically tunable supramolecular scaffold with amphiphilic characteristics based on the calix[4]arene macrocyclic system. We designed and synthesized two novel calix[4]arene-polyethylene glycol (PEG) conjugates, termed Cal-P1 and Cal-P2, and these were characterized utilizing a wide range of spectroscopic and analytical methods. The rational design of Cal-P1 and Cal-P2 demonstrates their utility in forming stable blended nanospheres with sustained drug release characteristics. The synergistic blending of PLGA and the calixarene scaffold (Cal-P1 and Cal-P2) in constructing long-lasting and controlled-release nanoparticles (NPs), which are optimized for encapsulating Nile Red dye, and their successful internalization and retention in HeLa cancer cells are demonstrated through in vitro assays. The potential of these NPs as sustained therapeutic carriers is investigated in vivo, showing improved retention compared to free dye with negligible toxicity. The successful design and construction of Cal-P1 and Cal-P2 nanosystems represent a new paradigm for addressing drug loading challenges, opening up opportunities for the development of highly efficient, synthetically tunable alternative adjuvants for drug encapsulation and delivery.

Multi-Responsive Molecular Encapsulation and Release Based on Hydrogen-Bonded Azo-Macrocycle

Research on stimuli-responsive host-guest systems is at the cutting edge of supramolecular chemistry, owing to their numerous potential applications such as catalysis, molecular machines, and drug delivery. Herein, we present a multi-responsive host-guest system comprising azo-macrocycle 1 and 4,4'-bipyridinium salt G1 for pH-, photo-, and cation- responsiveness. Previously, we reported a novel hydrogen-bonded azo-macrocycle 1. The size of this host can be controlled through light-induced E↔Z photo-isomerization of the constituent azo-benzenes. The host is found in this work to be capable of forming stable complexes with bipyridinium/pyridinium salts, and implementing guest capture and release with G1 under light in a controlled manner. The binding and release of the guest in the complexes can also be easily controlled reversibly by using acid and base. Moreover, the cation competition-induced dissociation of the complex 1a₂⊃G1 is achieved. These findings are expected to be useful in regulating encapsulation for sophisticated supramolecular systems.

Recent Advances in Supramolecular-Macrocycle-Based Nanomaterials in Cancer Treatment

Cancer is a severe threat to human life. Recently, various therapeutic strategies, such as chemotherapy, photodynamic therapy, and combination therapy have been extensively applied in cancer treatment. However, the clinical benefits of these therapeutics still need improvement. In recent years, supramolecular chemistry based on host-guest interactions has attracted increasing attention in biomedical applications to address these issues. In this review, we present the properties of the major macrocyclic molecules and the stimulus-response strategies used for the controlled release of therapeutic agents. Finally, the applications of supramolecular-macrocycle-based nanomaterials in cancer therapy are reviewed, and the existing challenges and prospects are discussed.

Macrocycle-Surfaced Polymer Nanocapsules: An Emerging Paradigm for Biomedical Applications

In the recent decade, macrocycle-surfaced polymer nanocapsules have been developed and studied as potential drug carriers. In particular, a unique group of these nanocapsules were constructed from a covalently self-assembled polymer network based on several classic macrocycles including cucurbituril, pillararene, and calixarene. The unique structure of these nanocapsules consists of a liquid or solid core and a shell laced with macrocycles in which the macrocycles not only act as the shell matrix of the nanocapsules but also allow further facile, modular functionalization via host-guest interactions with guest-tagged molecules. More interestingly, when a responsive cross-linker was introduced between the macrocycles, the payload inside the nanocapsules could be selectively released in the presence of typical hallmarks of certain diseases, which is of great interest for biomedical applications. In this Topical Review, macrocycle-surfaced polymer nanocapsules derived from covalently self-assembled polymer networks are introduced systemically with a focus on the molecular design and biomedical applications.

Synthesis of 6-Methyluracilpentylviologen Resorcinarene Cavitand

Resorcinarenes, as macrocyclic compounds, are widely used to recognize substrates and create supramolecular assemblies. Their bowl-like form organizes functional groups at the upper and lower rims, which has a substantial impact on the molecular recognition of various substrates. As a result, resorcinarenes make good drug nanocarrier candidates. This paper presents the synthesis of a new resorcinarene cavitand functionalized along the upper rim with methyluracil and viologen fragments for its potential use in drug delivery. Methyluracils and viologens are well-known receptor-targeted compounds capable of facilitating the vector transfer of drugs and increasing the effectiveness of their action on cells. The paper describes the synthesis of resorcinarene modified with methyluracil and viologen groups along with its structure determined by 1H-, 13C-NMR and IR spectroscopy.

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.

C60 Fullerene Clusters Stabilize the Biologically Inactive Form of Topotecan

There is a range of experimental proofs that biologically relevant compounds change their activity in the presence of C₆₀ fullerene clusters in aqueous solution, which most frequently act as a nanoplatform for drug delivery. Inspired by this evidence, we made an effort to investigate the interaction of fullerene clusters with the antibiotic topotecan (TPT). This study proceeded in three steps, namely, UV/vis titration to confirm complexation and in vitro assays on proliferating and nonproliferating cells to elucidate the role of C₆₀ fullerene in the putative change in TPT activity. Surprisingly, although the nonproliferating cell assay is consistent with the titration data and confirms complex formation, it contradicted the results of the proliferating cell assay. The latter showed that the mixture of TPT and fullerene affects the cells in the same way as pure TPT, as if there were no fullerenes in solution at all, whereas the action of TPT was expected to be enhanced. We explained this contradiction by the specific stabilization of the biologically inactive carboxylate form of the antibiotic adsorbed in the alkaline shell of large fullerene clusters, which leads to neutralization of the drug delivery function and almost zero net biological effect of the antibiotic in vitro. The practical outcome of the work is that fullerene clusters can be used for the selective delivery of pH-sensitive drug forms.

An efficient synthesis of furan-3(2H)-imine scaffold from alkynones

A novel efficient method to generate spiro furan-3(2H)-imine derivatives is established by the reaction between the α,β-unsaturated ketones and aniline derivatives. The reaction involves 1,4- addition of aniline followed by the subsequent intramolecular cyclization mediated by tertiary alcohol to produce the furan-3(2H)-imine. All the synthesized compounds are characterized using nuclear magnetic resonance and high-resolution mass spectrometry (HRMS).

Glycocalixarene with luminescence for Warburg effect-mediated tumor imaging and targeted drug delivery

Fluorescently labeled calix[4]arene glycoconjugates demonstrate multifunctional potential in both Warburg effect mediated tumor imaging and GLUT1 targeted drug delivery. Nitrobenzoxadiazole and mannose conjugated NBD-Man-CA was found to be selectively recognized by GLUT1 and act as a "molecular carrier" for selective tumor targeting.

Matrix Metalloproteinase Inspired Therapeutic Strategies for Bone Diseases

Matrix Metalloproteinases (MMPs), as a family of zinc-containing enzymes, show the function of decomposing Extracellular Matrix (ECM) and participate in the physiological processes of cell migration, growth, inflammation, and metabolism. Clinical and experimental studies have indicated that MMPs play an essential role in tissue injury and repair as well as tumor diagnosis, metastasis, and prognosis. An increasing number of researchers have paid attention to their functions and mechanisms in bone health and diseases. The present review focuses on MMPs-inspired therapeutic strategies for the treatment of bone-related diseases. We introduce the role of MMPs in bone diseases, highlight the MMPs-inspired therapeutic options, and posit MMPs as a trigger for smart cell/drug delivery.

Porous Polycalix[n]arenes as Environmental Pollutant Removers

A new and innovative class of calixarene-based polymers emerged as adsorbents for a variety of compounds and ions in solution and vapor media. These materials take advantage of the modifiable rims and hydrophobic cavities of the calixarene monomers, in addition to the porous nature of the polymeric matrix. With main-chain calixarenes' function as supramolecular hosts and the polymers' high surface areas, polycalixarenes can effectively encapsulate target analytes. This feature is particularly useful for environmental remediation as dangerous and toxic molecules reversibly bind to the macrocyclic cavity, which facilitates their removal and enables repeated use of the polymeric sorbent. This Spotlight touches on the unique characteristics of the calixarene monomers and discusses the synthetic methods of our reported calixarene-based porous polymers, including Sonogashira-Hagihara coupling, and diazo and imine bond formation. It then discusses the promising applications of these materials in adsorbing dyes, micropollutants, iodine, mercury, paraquat, and perfluorooctanoic acid (PFOA) from water. In most cases, these reports cover materials that outperform others in terms of recyclability, rates of adsorption, or uptake capacities of specific pollutants. Finally, this Spotlight addresses the current challenges and future aspects of utilizing porous polymers in pollution treatment.

Bifunctional Aptamer Drug Carrier Enabling Selective and Efficient Incorporation of an Approved Anticancer Drug Irinotecan to Fibrin Gels

We have previously developed a bifunctional aptamer (bApt) binding to both human thrombin and camptothecin derivative (CPT1), and showed that bApt acts as a drug carrier under the phenomenon named selective oligonucleotide entrapment in fibrin polymers (SOEF), which enables efficient enrichment of CPT1 into fibrin gels, resulting in significant inhibition of tumor cell growth. However, although the derivative CPT1 exhibits anticancer activity, it is not an approved drug. In this study, we evaluated the binding properties of bApt to irinotecan, a camptothecin analog commonly used for anticancer drug therapy, in addition to unmodified camptothecin (CPT). Furthermore, we have revealed that irinotecan binds to bApt like CPT1 and is selectively concentrated on fibrin gels formed around the tumor cells under the SOEF phenomenon to suppress cell proliferation.

Molecular Insight into the Interaction between Camptothecin and Acyclic Cucurbit[4]urils as Efficient Nanocontainers in Comparison with Cucurbit[7]uril: Molecular Docking and Molecular Dynamics Simulation

Cucurbit[n]urils (CB[n], n = 5, 6, 7, 8, 10, 14) and their derivatives due to the hydrophobic cavities and polar carbonyl portals have been considerably explored for their potential uses as drug delivery systems. It is important to understand how these macrocyclic compounds interact with guests. Camptothecin (CPT), as a natural alkaloid, is a topoisomerase inhibitor with antitumor activity against breast, pancreas, and lung cancers. The application of this drug in cancer therapy is restricted due to its low aqueous solubility and high toxicity. Recently, the complex formation between the cucurbit[7]uril (CB[7])/acyclic cucurbit[4]uril (aCB[4]) nanocontainers and CPT have been evaluated to overcome the potential drawbacks of the related drug. Herein, using computational methods, we identified the interaction mechanism of CPT with CB[7]/aCB[4]s, which consist of benzene and naphthalene sidewalls (aCB[4]_benzene and aCB[4]_naphthalene, respectively) since the experimental approaches have not completely provided information at the molecular level. Our molecular docking and molecular dynamics (MD) simulations show that CB[7] and its two acyclic derivatives form stable inclusion complexes with CPT especially through hydrophobic interactions. We also found that aCB[4]s with the aromatic sidewalls can attach to CPT through π-π interactions. This investigation highlights aCB[4]s due to the structural properties and flexible nature as better nanocontainers for controlled release delivery of pharmaceutical agents in comparison with the CB[7] nanocontainer.

In situ condensation of an anti-cancer drug into fibrin gel enabling effective inhibition of tumor cell growth

We show herein the highly effective inhibition of tumor cell growth using a gel consisting of a fibrin polymer formed with the in situ condensation of a camptothecin (CPT) derivative as an anti-cancer drug, which is efficiently conveyed with a carrier aptamer from a solution to the gel in a phenomenon, called selective oligonucleotide entrapment in fibrin polymers (SOEF).