Cucurbit[10]uril-Encapsulated Cationic Porphyrins with Enhanced Fluorescence Emission and Photostability for Cell Imaging

Water-Soluble Rotaxane-Type Porphyrin Dyes as a Highly Membrane-Permeable and Durable Photosensitizer Suitable for Photodynamic Therapy

Porphyrins have emerged as highly effective photosensitizers in the field of photodynamic therapy (PDT) because of their high singlet oxygen generation efficiency. However, most porphyrin derivatives do not have adequate water solubility and cell membrane permeability suitable for use in PDT. In addition, they frequently suffer from low durability under photoirradiation. Here, we propose rotaxane-type photosensitizers, in which a porphyrin axle is irreversibly encapsulated within cyclodextrins (CDs), to overcome the drawbacks of porphyrins for PDT. The rotaxane-type photosensitizers were synthesized in high yields by employing a cooperative capture strategy. The CD derivatives worked as a transparent shell to impart a porphyrin axle not only with water solubility but also with photostability. These rotaxanes showed higher cell membrane permeability and photoinduced cytotoxic abilities than talaporfin sodium, presently used as a clinical photosensitizer. The rotaxane-based photosensitizer could have potential for being ideal PDT drugs.

Expanding the Color Range of Photoresponsive Multicolor Luminescent System Through Host-Guest Interaction

Photoresponsive multicolor luminescent systems offer interesting functions, which have led to applications in anticounterfeiting and biological imaging. However, expanding the color range of these materials remains a challenging task. Herein, a carbazole-modified dithienylethene derivative (DTE-CZ) that exhibits modulated fluorescence color changes through the photocyclization reaction and photolysis reaction is synthesized. DTE-CZ emits orange fluorescence, and it can release a fluorophore which emits blue fluorescence by the photolysis reaction, resulting in the color change. Upon complexation of DTE-CZ with cucurbit[10]uril (CB[10]), the fluorescence wavelength will have a blue shift and the photolysis reaction will be inhibited. Benefiting from the influence of CB[10] and the photolysis reaction of free guests, the color range of the photoresponsive system which is composed of free guests and host-guest complexes is further extended. White light emission along with a color shift from yellow-green to blue was achieved by adjusting the ratio of free guests to host-guest complexes. Finally, the photoresponsive multicolor systems are utilized to construct a photostimulated PVA film and an information encryption system. This work provides an alternative strategy for the preparing of photoresponsive multicolor luminescent system and modulation of its color range.

Perphenazine modified pillar[5]arene based nano-assemblies for synergistic photothermal and photodynamic cancer therapy

Nano-assemblies based on perphenazine modified pillar[5]arene were constructed successfully for synergistic photothermal and photodynamic (I&II) cancer therapy.

Acyclic cucurbit[n]uril-based nanosponges significantly enhance the photodynamic therapeutic efficacy of temoporfin in vitro and in vivo

Acyclic cucurbit[n]uril-based nanosponges are prepared based on supramolecular vesicle-templated cross-linking. The nanosponges are capable of encapsulating the clinically approved photodynamic therapeutic (PDT) drug temoporfin. When loaded with nanosponges, the PDT bioactivity of temoporfin is enhanced 7.5-fold for HeLa cancer cells and 20.8 fold for B16-F10 cancer cells, respectively. The reason for the significant improvement in PDT efficacy is confirmed to be an enhanced cell uptake by confocal laser scanning microscopy and flow cytometry. Animal studies show that nanosponges could dramatically increase the tumor suppression effect of temoporfin. In vitro and in vivo experiments demonstrate that nanosponges are nontoxic and biocompatible.

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.

Supramolecular Chemotherapy with Cucurbit[n]urils as Encapsulating Hosts

The cucurbit[n]urils (CB[n]) belong to the field of relatively young supramolecules which act as containers for a large variety of guests and are being explored extensively for their numerous biomedical applications. This includes drug formulation and delivery, controlled drug release, photodynamic therapy, sensing for bioanalytical purposes, etc. These supramolecular host-guest systems have distinctive recognition properties and have successfully been shown to enhance the in vitro and in vivo utility of various chemotherapeutic agents. The CB[n]s are tailored to optimize their application in payload delivery and diagnostics and in lowering the toxicity of existing drugs. This review has listed the recent studies on working mechanisms and host-guest complexation of the biologically vital molecules with CB[n] and highlighted their implementation in anticancer therapeutics. Various modifications in CB-drug inclusion compounds like CB supramolecular nanoarchitectures along with application in photodynamic therapy, which has shown potential as targeted drug delivery vehicles in cancer chemotherapy, have also been discussed.

Fluorophore-based host-guest assembly complexes for imaging and therapy

Recently, supramolecular chemistry with its unique properties has received considerable attention in many fields. Supramolecular fluorescent systems constructed on the basis of macrocyclic hosts are not only effective in overcoming the limitations of imaging and diagnostic reagents, but also in enhancing their performances. This paper summarizes the recent advances in supramolecular fluorescent systems based on host-guest interactions and their application in bioimaging and therapy as well as the challenges and prospects in developing novel supramolecular fluorescent systems.

Cucurbit[10]uril-based supramolecular radicals: Powerful arms to kill facultative anaerobic bacteria

Two water-soluble supramolecular complexes (CB[10]⊃PSA and CB[10]⊃TPE-cyc) are constructed based on the host-guest interaction between cucurbit[10]uril (CB[10]) and perylene diimide derivative (PSA) or tetracationic cyclophane (TPE-cyc). Attributing to the matched redox potential, both supramolecular complexes can be specifically reduced into corresponding supramolecular radical cations or anions by facultative anaerobic E. coli. Benefiting from the strong near-infrared (NIR) absorption, CB[10]⊃PSA radical anions and CB[10]⊃TPE-cyc radical cations act as efficient NIR photosensitizers and perform an excellent antimicrobial activity (close to 100%) via PTT. In addition, the biocompatibility of TPE-cyc is notably improved under the protection of CB[10], guaranteeing its biosafety for in vivo application. CB[10]⊃PSA radical anions and CB[10]⊃TPE-cyc radical cations are in situ generated in the E. coli-infected abscess of mice and effectively inhibit the bacterial infection without obvious system toxicity. It is anticipated that this supramolecular strategy may pave a new way for the selective bacteria inhibition to regulate the balance of different bacterial flora.

Cucurbit[10]uril-Based Orthogonal Supramolecular Polymers with Host-Guest and Coordination Interactions and Its Applications in Anion Classification

A novel orthogonal supramolecular polymer (Q[10]-TPDPB-Lu³⁺) in a host-guest ratio of 2:1 was successfully constructed utilizing the specificity and excellent cavity matching of Q[10] with the tripyridine derivatives (TPDPB). Significantly, non-covalent interactions between Q[10]'s hydrophobic cavities and Lu³⁺ were used to induce charge transfer of TPDPB to TPDPB and TPDPB to Lu³⁺, resulting in the construction of structurally interesting orthogonal assemblies with excellent fluorescence properties. Finally, the Q[10]-TPDPB-Lu³⁺ assemblies were shown to have good recognition and classification of strong and weak acid anions as well as iodide anions, and the classification was accompanied by a clear fluorescence emission change allowing visual observation.

Morpholine-Functionalized Multicomponent Metallacage as a Vector for Lysosome-Targeted Cell Imaging

Metallacages with suitable cavities and specific functions are promising delivery vectors in biological systems. Herein, we report a morpholine-functionalized metallacage for lysosome-targeted cell imaging. The efficient host-guest interactions between the metallacage and dyes prevent them from aggregation, so their emission in aqueous solutions is well maintained. The fluorescence quantum yield of these host-guest complexes reaches 74.40%. Therefore, the metallacage is further employed as a vector to deliver dyes with different emission colors (blue, green, and red) into lysosomes for targeted imaging. This research affords a type of vector for the delivery of various cargos toward biological applications, which will enrich the usage of metallacages in biomedical engineering.

A Bacteria-Responsive Porphyrin for Adaptable Photodynamic/Photothermal Therapy

We report a cationic porphyrin 5,10,15,20-tetrakis-(4-N-methylpyridyl)-porphyrin (TMPyP) that can respond to specific bacteria, followed by adaptable photodynamic/photothermal therapy processes. TMPyP could be reduced to phlorin by facultative anaerobes with a strong reducing ability such as E. coli and S. typhimurium in hypoxic environments, possessing strong NIR absorption and remarkable photothermal conversion capacity, thus demonstrating excellent antimicrobial activity (>99 %) by photothermal therapy. While in an aerobic environment with aerobic bacteria, TMPyP functioned as a typical photosensitizer that killed bacteria effectively (>99.9 %) by photodynamic therapy. By forming a host-guest complex with cucurbit[7]uril, the biocompatibility of TMPyP significantly improved. This kind of bacteria-responsive porphyrin shows specificity and adaptivity in antimicrobial treatment and holds potential in non-invasive treatments of bacterial infections.

Assembly and Applications of Macrocyclic-Confinement-Derived Supramolecular Organic Luminescent Emissions from Cucurbiturils

Cucurbit[n]urils (Q[n]s or CB[n]s), as a classical of artificial organic macrocyclic hosts, were found to have excellent advantages in the fabricating of tunable and smart organic luminescent materials in aqueous media and the solid state with high emitting efficiency under the rigid pumpkin-shaped structure-derived macrocyclic-confinement effect in recent years. This review aims to give a systematically up-to-date overview of the Q[n]-based supramolecular organic luminescent emissions from the confined spaces triggered host-guest complexes, including the assembly fashions and the mechanisms of the macrocycle-based luminescent complexes, as well as their applications. Finally, challenges and outlook are provided. Since this class of Q[n]-based supramolecular organic luminescent emissions, which have essentially derived from the cavity-dependent confinement effect and the resulting assembly fashions, emerged only a few years ago, we hope this review will provide valuable information for the further development of macrocycle-based light-emitting materials and other related research fields.

A hypoxia-responsive supramolecular formulation for imaging-guided photothermal therapy

Photothermal agents (PTAs) based on organic small-molecule dyes emerge as promising theranostic strategy in imaging and photothermal therapy (PTT). However, hydrophobicity, photodegradation, and low signal-to-noise ratio impede their transformation from bench to bedside. In this study, a novel supramolecular PTT formulation by a stimuli-responsive macrocyclic host is prepared to overcome these obstacles of organic small-molecule PTAs. Methods: Sulfonated azocalix[4]arene (SAC4A) was synthesized as a hypoxia-responsive macrocyclic host. Taking IR780 as an example, the supramolecular nanoformulation IR780@SAC4A was constructed by grinding method, and its solubility, photostability, and photothermal conversion were evaluated. The hypoxia tumor-selective imaging and supramolecular PTT of IR780@SAC4A were further evaluated in vitro and in vivo. Results: IR780@SAC4A is capable of enhancing the solubility, photostability, and photothermal conversion of IR780 significantly, which achieve this supramolecular formulation with good imaging-guided PTT efficacy in vitro and in vivo. Conclusions: This study demonstrates that the supramolecular PTT strategy is a promising cancer theranostic method. Moreover, this supramolecular approach is applicative to construct kinds of supramolecular PTAs, opening a general avenue for extending smart PTT formulations.

Targeted Delivery and Site-Specific Activation of β-Cyclodextrin-Conjugated Photosensitizers for Photodynamic Therapy through a Supramolecular Bio-orthogonal Approach

Targeted delivery of photosensitizers using hydrophilic and tumor-directing carriers and site-specific activation of their photocytotoxicity are two common strategies to enhance the specificity of anticancer photodynamic therapy. We report herein a novel supramolecular bio-orthogonal approach to integrate these two functions. A β-cyclodextrin-substituted aza-boron-dipyrromethene-based photosensitizer was first complexed with a ferrocene-substituted black-hole quencher to inhibit its photosensitizing ability. Upon encountering the adamantane moieties that had been delivered to target cancer cells through specific binding of the conjugated peptide to the overexpressed epidermal growth factor receptor, the ferrocene-based guest species were displaced due to the stronger binding interactions between β-cyclodextrin and adamantane, thereby restoring the photodynamic activity of the photosensitizer. Hence, this two-step process enabled targeted delivery and site-specific activation of the photosensitizer, as demonstrated through a series of experiments in aqueous media, in a range of cancer cell lines and in tumor-bearing nude mice.

Single-crystal structures of cucurbituril-based supramolecular host-guest complexes for bioimaging

Two single-crystal structures of cucurbit[n]uril mediated supramolecular complexes were obtained in which [1+3] and [2+3] self-assembly modes are adopted due to the different sizes of cucurbit[7]uril and cucurbit[8]uril. An obvious red-shift in absorption and emission was observed compared to the guest molecule itself which makes them good biolabels.