Biomedical Applications of Supramolecular Systems Based on Host–Guest Interactions

A Hybrid Supramolecular Polymeric Nanomedicine for Cascade-Amplified Synergetic Cancer Therapy

Supramolecular nanomedicines have shown great merits in cancer therapy, but their clinical translation is hampered by monotonous therapeutic modality and unsatisfactory antitumor performance. Herein, a hybrid supramolecular polymeric nanomedicine (SNPs) is developed based on β-cyclodextrin/camptothecin (CPT) host-guest molecular recognition and iron-carboxylate coordination. Iron ions stabilizing SNPs catalyze the conversion of intracellular hydrogen peroxide into highly toxic hydroxyl radical through a Fenton reaction, which further cleaves the thioketal linker of the supramolecular monomer to release potent CPT, thus amplifying the therapeutic efficacy by combining chemodynamic therapy and chemotherapy. The combination therapy stimulates antitumor immunity and promotes intratumoral infiltration of cytotoxic T lymphocytes by triggering immunogenic cell death. In synergy with PD-L1 checkpoint blockade, SNPs enables enhanced immune therapy and a long-term tumor remission.

Visualizing the Entire Range of Noncovalent Interactions in Nanocrystalline Hybrid Materials Using 3D Electron Diffraction

Noncovalent interactions are essential in the formation and properties of a diverse range of hybrid materials. However, reliably identifying the noncovalent interactions in nanocrystalline materials remains challenging using conventional methods such as X-ray diffraction and spectroscopy. Here, we demonstrate that accurate atomic positions including hydrogen atoms can be determined using three-dimensional electron diffraction (3D ED), from which the entire range of noncovalent interactions in a nanocrystalline aluminophosphate hybrid material SCM-34 are directly visualized. The protonation states of both the inorganic and organic components in SCM-34 are determined from the hydrogen positions. All noncovalent interactions, including hydrogen-bonding, electrostatic, π–π stacking, and van der Waals interactions, are unambiguously identified, which provides detailed insights into the formation of the material. The 3D ED data also allow us to distinguish different types of covalent bonds based on their bond lengths and to identify an elongated terminal P=O π-bond caused by noncovalent interactions. Our results show that 3D ED can be a powerful tool for resolving detailed noncovalent interactions in nanocrystalline materials. This can improve our understanding of hybrid systems and guide the development of novel functional materials.

Bimodal Treatment of Hepatocellular Carcinoma by Targeted Minimally Interventional Photodynamic/Chemotherapy Using Glyco-Covalent-Organic Frameworks-Guided Porphyrin/Sorafenib

Very limited treatment options are available to fight hepatocellular carcinoma (HCC), a serious global health concern with high morbidity and mortality. The integration of multiple therapies into one nanoplatform to exert synergistic therapeutic effects offers advantages over monotherapies. Here, we describe the construction of the nanoplatform Sor@GR-COF-366 for synergistic chemotherapy and photodynamic therapy (PDT) for HCC using a porphyrin-based covalent organic framework (COF-366) coated with N-acetyl-galactosamine (GalNAc) and rhodamine B (RhB), and loaded with the first-line agent, Sorafenib (Sor). The nanoplatform is targeted towards ASGPR-overexpressed HCC cells and liver tissues by GalNAc and observed by real-time imaging of RhB in vitro and in vivo. The nanoplatform Sor@GR-COF-366 exerts an enhanced synergistic tumor suppression effect in a subcutaneous HCC mouse model with a tumor inhibition rate (TGI) of 97% while significantly prolonging survival at very low toxicity. The potent synergistic therapeutic outcome is confirmed in an orthotopic mouse model of HCC with the TGI of 98% with a minimally invasive interventional PDT (IPDT). Sor@GR-COF-366 is a promising candidate to be combined with chemo-IPDT for the treatment of HCC. STATEMENT OF SIGNIFICANCE: This work describes the construction of covalent-organic frameworks (COFs) modified with glyco-moieties to serve as hepato-targeted multitherapy delivery systems. They combine minimally invasive interventional photodynamic therapy (IPDT) triggered synergism with chemotherapy treatment for hepatocellular carcinoma (HCC). With the aid of minimally invasive intervention, PDT can elicit potent anti-cancer activity for deep solid tumors. This platform shows strong therapeutic outcomes in both subcutaneous and orthotopic mouse models, which can significantly prolong survival. This work showed an effective combination of a biomedical nano-formulation with the clinical operational means in cancer treatment, which is greatly promising in clinical translation.

Colorimetric detection of Salmonella typhimurium based on hexadecyl trimethyl ammonium bromide-induced supramolecular assembly of β-cyclodextrin-capped gold nanoparticles

We developed an effective and specific colorimetric strategy to detect Salmonella typhimurium (S. typhimurium) based on hexadecyl trimethyl ammonium bromide (CTAB)-induced supramolecular assembly of β-cyclodextrin-capped gold nanoparticles (β-CD-AuNPs). In this study, ssDNA aptamer of S. typhimurium could combine with CTAB to form the supramolecular ssDNA-CTAB composite, so the ssDNA aptamer was applied to control the concentration of CTAB. In the presence of S. typhimurium, ssDNA aptamers selectively bound to S. typhimurium but not to CTAB, leading to the host-guest chemistry reaction of CTAB and β-CD resulting in β-CD-AuNP supramolecular assembly aggregation with an obvious color change. The ratio of absorption at 650 and 520 nm (A_650nm/A_520nm) has a linear correlation to the log scale of the concentration of the bacteria (1 × 10²-1 × 10⁷ CFU/mL) with a low limit of detection (LOD) of 13 CFU/mL. In addition, this optical sensor has good selectivity and practicability. In milk samples, the recovery was 93.55-111.32%, which suggested its potential application in real samples.

Noninvasive and Individual-Centered Monitoring of Uric Acid for Precaution of Hyperuricemia via Optical Supramolecular Sensing

Characterized by an excessively increased uric acid (UA) level in serum, hyperuricemia induces gout and also poses a great threat to renal and cardiovascular systems. It is urgent and meaningful to perform early warning by noninvasive diagnosis, thus conducing to blockage of disease aggravation. Here, guanidinocalix[5]arene (GC5A) is successfully identified from the self-built macrocyclic library to specifically monitor UA from urine by the indicator displacement assay. UA is strongly bound to GC5A at micromolar-level, while simultaneously excluding fluorescein (Fl) from the GC5A·Fl complex in the "switch-on" mode. This method successfully differentiates patients with hyperuricemia from volunteers except for those with kidney dysfunction and targets a volunteer at high risk of hyperuricemia. In order to meet the trend from hospital-centered to individual-centered testing, visual detection of UA is studied through a smartphone equipped with a color-scanning feature, whose adaptability and feasibility are demonstrated in sensing UA from authentic urine, leading to a promising method in family-centered healthcare style. A high-throughput and visual detection method is provided here for alarming hyperuricemic by noninvasive diagnosis.

A host-guest strategy for converting the photodynamic agents from a singlet oxygen generator to a superoxide radical generator

Type-I photosensitizers (PSs) generate cytotoxic oxygen radicals by electron transfer even in a hypoxic environment. Nevertheless, the preparation of type-I PSs remains a challenge due to the competition of triplet-triplet energy transfer with O2 (type-II process). In this work, we report an effective strategy for converting the conventional type-II PS to a type-I PS by host-guest complexation. Electron-rich pillar[5]arenes are used as an electron donor and macrocyclic host to produce a host-guest complex with the traditional electron-deficient type-II PS, an iodide BODIPY-based guest. The host-guest complexation promotes intermolecular electron transfer from the pillar[5]arene moiety to BODIPY and then to O2 by the type-I process upon light-irradiation, leading to efficient generation of the superoxide radical (O2 -˙). The results of anti-tumor studies indicate that this supramolecular PS demonstrates high photodynamic therapy efficacy even under hypoxic conditions. This work provides an efficient method to prepare type-I PSs from existing type-II PSs by using a supramolecular strategy.

Multicharged cyclodextrin supramolecular assemblies

Multicharged cyclodextrin (CD) supramolecular assemblies, including those based on positively/negatively charged modified mono-6-deoxy-CDs, per-6-deoxy-CDs, and random 2,3,6-deoxy-CDs, as well as parent CDs binding positively/negatively charged guests, have been extensively applied in chemistry, materials science, medicine, biological science, catalysis, and other fields. In this review, we primarily focus on summarizing the recent advances in positively/negatively charged CDs and parent CDs encapsulating positively/negatively charged guests, especially the construction process of supramolecular assemblies and their applications. Compared with uncharged CDs, multicharged CDs display remarkably high antiviral and antibacterial activity as well as efficient protein fibrosis inhibition. Meanwhile, charged CDs can interact with oppositely charged dyes, drugs, polymers, and biomacromolecules to achieve effective encapsulation and aggregation. Consequently, multicharged CD supramolecular assemblies show great advantages in improving drug-delivery efficiency, the luminescence properties of materials, molecular recognition and imaging, and the toughness of supramolecular hydrogels, in addition to enabling the construction of multistimuli-responsive assemblies. These features are anticipated to not only promote the development of CD-based supramolecular chemistry but also contribute to the rapid exploitation of these assemblies in diverse interdisciplinary applications.

Calixarene-mediated host-guest interactions leading to supramolecular assemblies: visualization by microscopy

Host-guest chemistry, particularly of supramolecules, has been an intriguing topic for researchers for a long time due to its multiplicative applications ranging from chemical to biological to materials science. Supramolecules, such as calixarenes, are excellent host molecular systems due to their controllable cavity along with the ease of functionalization both at the lower and upper rims. The host-guest interactions involving calixarenes have been primarily studied using physical methods, such as absorption, fluorescence and nuclear magnetic resonance spectroscopy, isothermal titration calorimetry and mass spectrometry. The corresponding literature as disseminated through review articles triggered broadening of the spectrum of research. Depending upon the nature of the derivatization, the supramolecular conjugates of calixarenes have been shown to form different morphologies of micro and nanometric size as reported in the literature. Pertinent research performed in our own group was based on atomic force microscopy, transmission electron microscopy and scanning electron microscopy studies. The literature reveals that such morphologies are modified in the presence of guest species. Thus, the supramolecular host-guest complexation of calixarenes leading to the formation of various architectures has been studied using both spectroscopy and microscopy techniques to obtain complimentary data. However, there are no review articles that provide discussions on this exciting area of supramolecular science involving microscopy. Therefore, in the present article, for the first time, we have brought together the research reported in the literature during the past decade, including ours, in demonstrating the supramolecular architectures formed from the host-guest interactions extended by the conjugates of calixarenes, and their applications using microscopy. The scope of this article spans across various features of interaction in these systems: (i) in solution, (ii) at the air-water interface and (iii) on solid surfaces. The application domain includes sensing of organic explosives and drugs, exhibiting antibacterial activity, supramolecular self-assembly or co-assembly resulting in gels, micelles and vesicles, and the consequent aggregation-induced emission and a few others.

Unveiling host-guest-solvent interactions in solution by identifying highly unstable host-guest configurations in thermal non-equilibrium gas phase

We propose a novel scheme of examining the host-guest-solvent interactions in solution from their gas phase structures. By adopting the permethylated β-cyclodextrin (perm β-CD)-protonated L-Lysine non-covalent complex as a prototypical system, we present the infrared multiple photon dissociation (IRMPD) spectrum of the gas phase complex produced by electrospray ionization technique. In order to elucidate the structure of perm β-CD)/LysH⁺ complex in the gas phase, we carry out quantum chemical calculations to assign the two strong peaks at 3,340 and 3,560 cm^-1 in the IRMPD spectrum, finding that the carboxyl forms loose hydrogen bonding with the perm β-CD, whereas the ammonium group of L-Lysine is away from the perm β-CD unit. By simulating the structures of perm β-CD/H⁺/L-Lysine complex in solution using the supramolecule/continuum model, we find that the extremely unstable gas phase structure corresponds to the most stable conformer in solution.

Supramolecular Detoxification of Macromolecular Biotoxin through the Complexation by a Large-Sized Macrocycle

Biotoxins are diverse, complex, and hypertoxic, ultimately serving as grave and lasting menaces to humanity. Here, it is aimed to introduce a new detoxification methodology for macromolecular biotoxin through complexation by a very large macrocycle. A 25-mer peptide isolated from Lycosa erythrognatha spider venom (LyeTxI) is selected as the model macromolecular biotoxin. Quaterphen[4]arene, with a side length of ≈1.6 nm, has a sufficient cavity to bind LyeTxI. Hence, the water-soluble derivative of Quaterphen[4]arene (H) is designed and synthesized. H exhibits an overall host-guest complexation toward LyeTxI, resulting in a considerably high association constant of (7.01 ± 0.18) × 10⁷  m^-1 . This encapsulation of peptide is interesting as traditional macrocycles can only engulf the amino acid residues of peptides due to their limited cavity size. In vitro assay verifies that complexation by H inhibits the interactions of LyeTxI with cell membranes, thereby reducing its cytotoxicity, suppressing hemolysis, and decreasing the release of lactate dehydrogenase. Notably, the intravenous administration of H has a significant therapeutic effect on LyeTxI-poisoned mice, alleviating inflammation and tissue damage, and markedly improving the survival rate from 10% to 80%. An efficient and potentially versatile approach is provided to detoxify macromolecular biotoxins, with giant macrocycle serving as an antidote.

Comprehensive step-by-step procedure to setup a molecular communication through liquid experiment

Molecular communication allows information to be exchanged in environments where electromagnetic waves are prohibited. It employs the exchange of information particles travelling through fluids. The transmitter releases several chemical messengers inside the communication channel, encoding the message it intends to send in an appropriate way. These messengers will be propagated in the communication channel according to the laws that determine their movement in the environment, until they reach the receiver, which then captures their presence and decodes their content.

To set up an experiment of molecular communication through liquid, the following are required:•

The simulation of the experiment by means of numerical resolution of the differential equations governing the process, in order to select the proper modulation technique.

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The synthesis of the carbon nanoparticles to serve as the information nanoparticles.

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The arrangement of the bench prototype for the experiments.

Supramolecular Self-Assembly in Living Cells

Supramolecular interactions rely on non-covalent forces, such as hydrophobic effects, hydrogen-bonding, and electrostatic interactions, which govern many intracellular biological pathways. In cellulo supramolecular self-assembly is mainly based on host-guest interactions, changes in pH, enzymes, and polymerization-induced self-assembly to accurately induce various unnatural reactions without disturbing natural biological processes. This process can produce synthetic biocompatible macromolecules to control cell properties and regulate biological functions, such as cell proliferation and differentiation. This Minireview focuses on the latest reports in the field of in cellulo supramolecular self-assembly and anticipates future advances regarding its activation in response to internal and external stimuli, such as pH changes, reactive oxygen species, and enzymes, as well as external light illumination.

New Calix[4]arene—Fluoresceine Conjugate by Click Approach—Synthesis and Preparation of Photocatalytically Active Solid Lipid Nanoparticles

New fluorescent systems for photocatalysis, sensors, labeling, etc., are in great demand. Amphiphilic ones are of special interest since they can form functional colloidal systems that can be used in aqueous solutions. A new macrocycle platform for click chemistry and its adduct with o-propargylfluoresceine was synthesized and characterized using modern physical techniques. Nanosized solid lipid nanoparticles (SLNs) from the calixarene—fluoresceine adduct were synthesized through the solvent injection technique and well-characterized in the solution and in solid state using light-scattering and microscopy methods. The maximum fluorescence intensity of the SLNs was found to be in the pH range from 7 to 10. The Förster resonance energy transfer (FRET) efficiency from SLNs to rhodamine 6g was found to be 97.8%. Finally, pure SLNs and the FRET system SLNs—Rh6G were tested in model photocatalytic ipso oxidative hydroxylation of phenylboronic acid under blue LED light. The SLNs—Rh6G system was found to be the best, giving an almost qualitative phenol yield, which was shown by HPLC-UV analysis.

A Review of the Application of Resorcinarenes and SBA-15 in Drug Delivery

Due to the diseases that people face today, scientists dedicate a part of their research to the synthesis, characterization, and study of functional compounds for controlled drug delivery. On the one hand, resorcinarenes are macrocycles obtained by condensation reactions of resorcinol and aldehyde. They include an upper and a lower rim functioning with different groups that confer solubility to the macrocycle and favor interactions with other compounds, therefore the hydroxyl groups on the upper rim improve the formation of hydrogen bonds. Additionally, resorcinarenes feature a cavity studied for forming host-guest complexes. SBA-15, on the other hand, is a mesoporous silica characterized by ordered pores in its structure and a large surface area. As a result of its properties, it has been used for several purposes, including absorbents, drug delivery, catalysis, and environmental processes. This review shows the recent advances in synthesis methods, characterization, micelle formation, interaction with other compounds, and host-guest procedures, as well as techniques for evaluating toxicity, drug retention, and their preliminary uses in pharmacology for macrocycles, such as resorcin[4]arenes and SBA-15.

Monitoring Methionine Decarboxylase by Supramolecular Tandem Assay

Methionine is an essential amino acid involved in many physiological and pathological processes. Methionine starvation caused by methionine decarboxylase ( MetDC) degradation becomes a promising strategy for cancer treatment. Multistep colorimetric method, the present approach to monitor the MetDC activity, possesses drawbacks of the complicated process, low accuracy, and poor anti-interference due to indirect detecting. Herein, we report a facile and easy-to-use supramolecular tandem assay (STA) with cucurbit[7]uril and acridine orange reporter pair for the direct and real-time monitoring of MetDC activity. The applicability of this strategy for measuring enzyme-kinetic parameters and screening of inhibitors are also demonstrated. The STA for MetDC activity detection not only provides a feasible method for methionine-related disease diagnosing but also opens a perspective for cancer therapy.

C60-β-cyclodextrin conjugates for enhanced nucleus delivery of doxorubicin

We demonstrate the use of water-soluble C₆₀-β-cyclodextrin conjugates to encapsulate and deliver doxorubicin to the cell nucleus. The behaviour of the fullerene aggregates inside cells is dictated by the functionalization of the C₆₀ cage. While both the C₆₀ conjugates are taken up by lysosomes upon cellular entry, only the one with a hydroxylated cage rapidly escaped the lysosome. The drug delivery system (DDS) with a hydroxylated C₆₀ cage showed significantly enhanced doxorubicin delivery to the cell nucleus, whereas the DDS with a hydrophobic C₆₀ cage was trapped in the lysosome for a longer time and showed significantly reduced doxorubicin delivery to the nucleus. This study opens new paths towards advanced fullerene-based DDSs for small molecule drugs.

Single-Molecule Junction: A Reliable Platform for Monitoring Molecular Physical and Chemical Processes

Monitoring and manipulating the physical and chemical behavior of single molecules is an important development direction of molecular electronics that aids in understanding the molecular world at the single-molecule level. The electrical detection platform based on single-molecule junctions can monitor physical and chemical processes at the single-molecule level with a high temporal resolution, stability, and signal-to-noise ratio. Recently, the combination of single-molecule junctions with different multimodal control systems has been widely used to explore significant physical and chemical phenomena because of its powerful monitoring and control capabilities. In this review, we focus on the applications of single-molecule junctions in monitoring molecular physical and chemical processes. The methods developed for characterizing single-molecule charge transfer and spin characteristics as well as revealing the corresponding intrinsic mechanisms are introduced. Dynamic detection and regulation of single-molecule conformational isomerization, intermolecular interactions, and chemical reactions are also discussed in detail. In addition to these dynamic investigations, this review discusses the open challenges of single-molecule detection in the fields of physics and chemistry and proposes some potential applications in this field.

Enhanced antibacterial function of a supramolecular artificial receptor-modified macrophage (SAR-Macrophage)

Bacterial infection has become a global concern owing to the significant morbidity and mortality. Although the phagocytosis of bacteria by immune cells acts as the front line to protect human body from invading pathogens, the relatively slow encounter and insufficient capture of bacteria by immune cells often lead to an inefficient clearance of pathogens. Herein, a supramolecular artificial receptor-modified macrophage (SAR-Macrophage) was developed to enhance the recognition and latch of bacteria in the systemic circulation, mediated via strong and multipoint host-guest interactions between the artificial receptors (cucurbit[7]uril) on the macrophage and the guest ligands (adamantane) selectively anchored on Escherichia coli (E. coli). As a result, the SAR-Macrophage could significantly accelerate the recognition of E. coli, catch and internalize more pathogens, which subsequently induced the M1 polarization of macrophages to generate ROS and effectively kill the intracellular bacteria. Therefore, the SAR-Macrophage represents a simple, yet powerful anti-bacterial approach.

Drug Delivery Strategies and Biomedical Significance of Hydrogels: Translational Considerations

Hydrogels are a promising and attractive option as polymeric gel networks, which have immensely fascinated researchers across the globe because of their outstanding characteristics such as elevated swellability, the permeability of oxygen at a high rate, good biocompatibility, easy loading, and drug release. Hydrogels have been extensively used for several purposes in the biomedical sector using versatile polymers of synthetic and natural origin. This review focuses on functional polymeric materials for the fabrication of hydrogels, evaluation of different parameters of biocompatibility and stability, and their application as carriers for drugs delivery, tissue engineering and other therapeutic purposes. The outcome of various studies on the use of hydrogels in different segments and how they have been appropriately altered in numerous ways to attain the desired targeted delivery of therapeutic agents is summarized. Patents and clinical trials conducted on hydrogel-based products, along with scale-up translation, are also mentioned in detail. Finally, the potential of the hydrogel in the biomedical sector is discussed, along with its further possibilities for improvement for the development of sophisticated smart hydrogels with pivotal biomedical functions.

Highly Bright AIE Nanoparticles by Regulating the Substituent of Rhodanine for Precise Early Detection of Atherosclerosis and Drug Screening

Fluorescent probes capable of precise detection of atherosclerosis (AS) at an early stage and fast assessment of anti-AS drugs in animal level are particularly valuable. Herein, a highly bright aggregation-induced emission (AIE) nanoprobe is introduced by regulating the substituent of rhodanine for early detection of atherosclerotic plaque and screening of anti-AS drugs in a precise, sensitive, and rapid manner. With dicyanomethylene-substituted rhodanine as the electron-withdrawing unit, the AIE luminogen named TPE-T-RCN shows the highest molar extinction coefficient, the largest photoluminescence quantum yield, and the most redshifted absorption/emission spectra simultaneously as compared to the control compounds. The nanoprobes are obtained with an amphiphilic copolymer as the matrix encapsulating TPE-T-RCN molecules, which are further surface functionalized with anti-CD47 antibody for specifically binding to CD47 overexpressed in AS plaques. Such nanoprobes allow efficient recognition of AS plaques at different stages in apolipoprotein E-deficient (apoE^-/- ) mice, especially for the recognition of early-stage AS plaques prior to micro-computed tomography (CT) and magnetic resonance imaging (MRI). These features impel to apply the nanoprobes in monitoring the therapeutic effects of anti-AS drugs, providing a powerful tool for anti-AS drug screening. Their potential use in targeted imaging of human carotid plaque is further demonstrated.

Recent Advances of Self-Healing Polymer Materials via Supramolecular Forces for Biomedical Applications

Noncovalent interactions can maintain the three-dimensional structures of biomacromolecules (e.g., polysaccharides and proteins) and control specific recognition in biological systems. Supramolecular chemistry was gradually developed as a result, and this led to design and application of self-healing materials. Self-healing materials have attracted attention in many fields, such as coatings, bionic materials, elastomers, and flexible electronic devices. Nevertheless, self-healing materials for biomedical applications have not been comprehensively summarized, even though many reports have been focused on specific areas. In this Review, we first introduce the different categories of supramolecular forces used in preparing self-healing materials and then describe biological applications developed in the last 5 years, including antibiofouling, smart drug/protein delivery, wound healing, electronic skin, cartilage lubrication protection, and tissue engineering scaffolds. Finally, the limitations of current biomedical applications are indicated, key design points are offered for new biological self-healing materials, and potential directions for biological applications are highlighted.

Thermo/pH dual-responsive micelles based on the host-guest interaction between benzimidazole-terminated graft copolymer and β-cyclodextrin-functionalized star block copolymer for smart drug delivery

Novel temperature and pH dual-sensitive amphiphilic micelles were fabricated exploiting the host-guest interaction between benzimidazole-terminated PHEMA-g-(PCL-BM) and β-CD-star-PMAA-b-PNIPAM. The fabricated graft copolymer had a brush-like structure with star side chains. The micelles were utilized as dual-responsive nanocarriers and showed the LCST between 40 and 41 °C. The acidic pH promoted the dissociation of the PHEMA-g-(PCL-BM: β-CD-star-PMAA-b-PNIPAM) micelles. DOX.HCl was loaded into the core of the micelles during self-assembly in an aqueous solution with a high encapsulation efficacy (97.3%). The average size of the amphiphilic micelles was about 80 nm, suitable size for the enhanced permeability and retention effect in tumor vasculature. In an aqueous environment, these micelles exhibited very good self-assembly ability, low CMC value, rapid pH- and thermo-responsiveness, optimal drug loading capacity, and effective release of the drug. The biocompatibility was confirmed by the viability assessment of human breast cancer cell line (MCF-7) through methyl tetrazolium assay. DOX-loaded micelles displayed excellent anti-cancer activity performance in comparison with free DOX.

Membrane-Active Antibacterial Agents Based on Calix[4]arene Derivatives: Synthesis and Biological Evaluation

Bacteria have developed increasing resistance to currently used antimicrobial agents. New classes of antimicrobial drugs are urgently required to fight drug-resistant pathogens. Here, we designed and synthesized a series of calix[4]arene derivatives as antibacterial agents by biomimicking the structural properties and biological functions of antibacterial peptides. After introducing cationic hydrophilic moieties and preliminary structural optimization, we obtained a lead compound (16) that exhibited excellent antibacterial activity against Gram-positive bacteria, low toxicity toward mammalian cells and poor hemolytic activity. The antibacterial mechanism studies showed that compound 16 can destroy bacterial cell membrane directly, leading to bacterial death and a low tendency to develop bacterial resistance.

Bioinspired tunable hydrogels: An update on methods of preparation, classification, and biomedical and therapeutic applications

Hydrogels exhibit water-insoluble three-dimensional polymeric networks capable of absorbing large amounts of biological fluids. Both natural and synthetic polymers are used for the preparation of hydrogel networks. Such polymeric networks are fabricated through chemical or physical mechanisms of crosslinking. Chemical crosslinking is accomplished mainly through covalent bonding, while physical crosslinking involves self-healing secondary forces like H-bonding, host-guest interactions, and antigen-antibody interactions. The building blocks of the hydrogels play an important role in determining the mechanical, biological, and physicochemical properties. Hydrogels are used in a variety of biomedical applications like diagnostics (biodetection and bioimaging), delivery of therapeutics (drugs, immunotherapeutics, and vaccines), wound dressing and skin materials, cardiac complications, contact lenses, tissue engineering, and cell culture because of the inherent characteristics like enhanced water uptake and structural similarity with the extracellular matrix (ECM). This review highlights the recent trends and advances in the roles of hydrogels in biomedical and therapeutic applications. We also discuss the classification and methods of hydrogels preparation. A brief outlook on the future directions of hydrogels is also presented.

Controlled, Sunlight-Driven Reversible Cycloaddition of Multiple Singlet Oxygen Molecules to Anthracene-Containing Trianglimine Macrocycles

Controlled release of singlet oxygen is of interest not only to chemists, but also to biologists and medics involved in cancer therapy. Two chiral polyaza macrocyclic compounds and their corresponding endoperoxides have been synthesized. These peroxides exhibit high temperature stability, up to 80 °C. Detailed studies on their structure, including X-ray analysis as well as NMR, UV-VIS ECD spectroscopy and theoretical calculations, combined with photochemical measurements indicate that their high stability is related to the arrangement of oxygen atoms in a conformationally stable macrocyclic ring. Despite the change of carbon hybridization from sp2 to sp3 at the 9 and 10 positions of the anthracene units, the macrocyclic skeleton of the obtained compounds does not change its conformation. The obtained endoperoxides can be formed and release singlet oxygen by irradiation with UV light of 365 and 275 nm, respectively. Release of the oxygen does not degrade the macrocyclic structure.

An amphiphilic water-soluble biphen[3]arene with a tunable lower critical solution temperature behavior

The first amphiphilic water-soluble thermoresponsive biphen[3]arene with a tunable lower critical solution temperature behavior is reported.

Supramolecular topological hydrogels: from material design to applications

Supramolecular topological hydrogels are constructed by introducing different dynamic topological structures into polymeric networks and thus exhibit a wide variety of stimuli-responsive properties and versatile applications.

Analyte sensing with unselectively binding synthetic receptors: virtues of time-resolved supramolecular assays

Time-resolved supramolecular assays probe analyte-characteristic complexation and decomplexation rates. Consequently, even unselectively binding synthetic receptors can be used for analyte identification and quantification.

Tunable Supramolecular Cavities Molecularly Homogenized in Polymer Membranes for Ultraefficient Precombustion CO2 Capture

Processable molecular-sieving membranes are important materials for realizing energy-efficient precombustion CO₂ capture during industrial-scale hydrogen production. However, the promising design of mixed matrix membranes (MMMs) that aims to integrate the molecular-sieving properties of nanoporous architectures with industrial processable polymers still faces performance and fabrication issues due to the formation of segregated nanofiller domains in their polymer matrices. Here, an unconventional nanocomposite membrane design is proposed using soluble organic macrocyclic cavitands (OMCs) with tunable open cavity sizes that not only mitigate the formation the discrete nanofiller phases but also deliver distinct molecular-sieving separations. The versatile organic-solvent solubility coupled with highly interactive functionalities of OMCs allows them to obtain molecularly homogeneous mixing with matrix polymers and form only one integral continuous phase crucial to the robust processability of polymers. A series of polybenzimidazole-based molecularly mixed composite membranes (MMCMs) are fabricated via the incorporation of a soluble and thermally stable OMC choice, sulfocalixarenes, with various cavity sizes. These membranes achieve outstanding high-temperature mixed-gas H₂ /CO₂ separation performances comparable with several state-of-the-art molecular-sieving membranes owing to effective size-sieving gas passages through the open or partially-intruded supramolecular cavities. The broadly tunable structures and functionalities of OMCs would make their MMCMs attractive for other energy-intensive molecular separations.

Metal-ion-mediated synergistic coordination: construction of AIE-metallogel sensor arrays for anions and amino acids

Metallogel-based six membered sensor arrays show applications in multi-analyte detection and fluorescence encryption.

Effective taste masking of alkaloids by a water-soluble terphen[3]arene

The synthesis of first water-soluble 2,2’’,4,4’’-terphen[3]arene bearing sulphonatopropoxy moieties (STP3), and its effective alleviation of aversive response to alkaloids in vitro and in vivo by forming supramolecular complexes has been...

An electron-deficient supramolecular macrocyclic host for the selective separation of aromatics and cyclic aliphatics

Host 1 with an electron-deficient nanometer-sized cavity were synthesized in two steps. Moreover, 1 has been successfully used as a gas chromatographic stationary phase to prepare a packed column for the separation of PhH/Cy and Tol/MCy.

Frustrated Behavior of Lewis/Brønsted Pairs inside Molecular Cages

Different endohedrally functionalized cages were designed to investigate the effects of the size and shape of molecular cavities on the frustrated behavior of Lewis/Brønsted acid-base pairs and on catalytic activities....

“The red cage”: implementation of pH-responsiveness within a macrobicyclic pyridinium-based molecular host

The “red cage”, a new pyridinium-based macrobicyclic host, has been found to complex model aromatic substrates in aqueous media in a pH-responsive fashion.

Recent advances of 3D hydrogel culture systems for mesenchymal stem cell-based therapy and cell behavior regulation

Mesenchymal stem cells (MSCs) have been increasingly recognized as resources for disease treatments and regenerative medicine. Meanwhile, the unique chemical and physical properties of hydrogels provide innate advantages to achieve...

Molecular Recognition by Pillar[5]arenes: Evidence for Simultaneous Electrostatic and Hydrophobic Interactions

The formation of inclusion complexes between alkylsulfonate guests and a cationic pillar[5]arene receptor in water was investigated by NMR and ITC techniques. The results show the formation of host-guest complexes stabilized by electrostatic interactions and hydrophobic effects with binding constants of up to 10⁷ M⁻¹ for the guest with higher hydrophobic character. Structurally, the alkyl chain of the guest is included in the hydrophobic aromatic cavity of the macrocycle while the sulfonate groups are held in the multicationic portal by ionic interactions.