Synchronous Imaging in Golgi Apparatus and Lysosome Enabled by Amphiphilic Calixarene-Based Artificial Light-Harvesting Systems

Amphiphilic Acyclic Cucurbit[n]uril: Synthesis, Self-Assembly, and Chemotherapeutic Delivery to Overcome Multidrug Resistance

A new amphiphilic acyclic cucurbit[n]uril (CB[n]) is designed and synthesized. This amphiphilic acyclic CB[n] could encapsulate pharmaceutical drugs via a host-guest interaction. Self-assembly of this acyclic CB[n] forms spherical nanoparticles with diameters of 91 nm in water. The self-assembled nanoparticles are capable of delivering doxorubicin with high efficiency. Cell experiments show that the doxorubicin-loaded nanoparticles can improve cellular uptake and cytotoxicity by using the MCF-7/ADR cell line. The A549 tumor-bearing mouse model shows that self-assembled nanoparticles help overcome multidrug resistance in vivo. Cell study and histological assays confirm the biocompatibility of self-assembled nanoparticles.

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.

Solvent-Free Artificial Light-Harvesting System in a Fluid Donor with Highly Efficient Förster Resonance Energy Transfer

Multi-step Förster resonance energy transfer (FRET) plays a vital role in photosynthesis. While the energy transfer efficiency (ΦET) of a naturally occurring system can reach 95%, that of most artificial light-harvesting systems (ALHSs) is still limited. Herein, we propose a strategy to construct highly efficient ALHSs using a blue-emitting, supercooled ionic compound of naphthalimide (NPI) as the donor, a green-emitting BODIPY derivate as a relay acceptor, and a commercially available, red-emitting dye [rhodamine B (RhB)] as the final acceptor. The broad emission of the fluid donor can overlap simultaneously with the absorption of BODIPY and RhB, enabling the occurrence of a sequential FRET from NPI to BODIPY to RhB as well as a parallel FRET directly from NPI to RhB. These two complementary energy transfer routes lead to an overall ΦET up to 97.4%, which is the champion among all of the reported ALHSs and is also higher than that found in plants and photosynthetic bacteria. This strategy is universal, and ΦET of the system could be further improved by optimizing the structures of the fluid donor and relay acceptor.

Discrete Macrocyclic Polymer Hosts-Induced Cascade Luminescence Enhancement and Application in Bioimaging

The integration of polymers, supramolecular macrocycles and aggregation-induced emission (AIE) molecules provides numerous possibilities for constructing various functional supramolecular systems. Herein, we constructed supramolecular assembled systems based on discrete macrocyclic polymer hosts via the cooperation of hydra-headed macrocycles containing two or three pillar[5]arene units (defined as P2, P3), the block polymer F127 and AIE molecules (alkyl-cyano modified tetraphenylethene, alkyl-triazole-cyano modified 9,10-distyrylanthracene, defined as TPE-(CN)4 and DSA-(TACN)2). Compared with the binary assembly between hydra-headed hosts or F127 and AIE molecules, cascaded supramolecular assembly-induced emission enhancement (SAIEE) in aqueous solution was achieved in discrete macrocyclic polymer-based supramolecular assembled systems. Considering the cascaded SAIEE performance, we have successfully applied discrete macrocyclic polymer-based supramolecular assembled systems to bioimaging and constructed an artificial light-harvesting system (LHs) to explore more potential applications. The supramolecular assembly form of discrete macrocyclic polymers hosts and AIE molecules proposed in this work provides new inspiration for the construction and application of high-performance supramolecular luminescent systems.

Recent Advances in Calixarene-Based Fluorescent Sensors for Biological Applications

Due to their structural features, macrocyclic compounds such as calixarenes, conjugated with a variety of fluorophores have led to the development of fluorescent probes for numerous applications. This review covers the recent advances (from 2009 to date) made in calixarene-based fluorescent sensors and their biological applications. In addition to the fluorescence mechanisms used to signal the analyte binding, this article focuses mainly on the detection of biological relevant ions, on the selective sensing of biomolecules, such as amino acids, enzymes, drugs and other organic compounds, and on intracellular imaging. Calixarene-containing fluorescent nanoparticles and nanoaggregates for imaging and drug delivery are also described. Finally, this review presents some conclusions and future perspectives in this field.

Selective delivery of imaging probes and therapeutics to the endoplasmic reticulum or Golgi apparatus: Current strategies and beyond

To maximize therapeutic effects and minimize unwanted effects, the interest in drug targeting to the endoplasmic reticulum (ER) or Golgi apparatus (GA) has been recently growing because two organelles are distributing hubs of cellular building/signaling components (e.g., proteins, lipids, Ca2+) to other organelles and the plasma membrane. Their structural or functional damages induce organelle stress (i.e., ER or GA stress), and their aggravation is strongly related to diseases (e.g., cancers, liver diseases, brain diseases). Many efforts have been developed to image (patho)physiological functions (e.g., oxidative stress, protein/lipid-related processing) and characteristics (e.g., pH, temperature, biothiols, reactive oxygen species) in the target organelles and to deliver drugs for organelle disruption using organelle-targeting moieties. Therefore, this review will overview the structure, (patho)physiological functions/characteristics, and related diseases of the organelles of interest. Future direction on ER or GA targeting will be discussed by understanding current strategies and investigations on targeting, imaging/sensing, and therapeutic systems.

High-Fidelity Spatiotemporal Recognition of Golgi ALP through an Initial-Accumulation and Postactivation Strategy

Various signal molecules mediate complex physiological processes collectively in the Golgi. However, most currently accessible probes are questionable in illuminating the functions of these reactive species in Golgi because of the inability to irradiate these probes only at the desired Golgi location, which compromises specificity and accuracy. In this study, we rationally designed the first photocontrollable and Golgi-targeted fluorescent probe to in situ visualize the Golgi alkaline phosphatase (ALP). The designed probe with natural yellow fluorescence can provide access into Golgi and monitor the exact timing of accumulation in Golgi. On-demand photoactivation at only the desired Golgi location affords a significant emission response to ALP with illuminating red fluorescence at 710 nm. Through the photocontrollable fluorescence responsiveness to ALP, precise spatiotemporal recognition of Golgi ALP fluctuations is successfully performed. With this probe, for the first time, we revealed the Golgi ALP levels during cisplatin-induced acute kidney injury (AKI), which will further facilitate and complement the comprehensive exploration of ALP kinetics during physiological and pathological processes.

Hypoxia and its effect on the cellular system

Eukaryotic cells utilize oxygen for different functions of cell organelles owing to cellular survival. A balanced oxygen homeostasis is an essential requirement to maintain the regulation of normal cellular systems. Any changes in the oxygen level are stressful and can alter the expression of different homeostasis regulatory genes and proteins. Lack of oxygen or hypoxia results in oxidative stress and formation of hypoxia inducible factors (HIF) and reactive oxygen species (ROS). Substantial cellular damages due to hypoxia have been reported to play a major role in various pathological conditions. There are different studies which demonstrated that the functions of cellular system are disrupted by hypoxia. Currently, study on cellular effects following hypoxia is an important field of research as it not only helps to decipher different signaling pathway modulation, but also helps to explore novel therapeutic strategies. On the basis of the beneficial effect of hypoxia preconditioning of cellular organelles, many therapeutic investigations are ongoing as a promising disease management strategy in near future. Hence, the present review discusses about the effects of hypoxia on different cellular organelles, mechanisms and their involvement in the progression of different diseases.

Three-step cascaded artificial light-harvesting systems with tunable efficiency based on metallacycles

It is still challenging to develop multi-step cascaded artificial light-harvesting systems (ALHSs) with tunable efficiency. Here, we designed novel cascaded ALHSs with AIE-active metallacycles as the light-harvesting antenna, Eosin Y (ESY) and sulforhodamine 101 (SR101) as conveyors, near-infrared emissive chlorin-e6 (Ce6) as the final acceptor. The close contact and fair spectral overlap between donor and acceptor molecules at each level ensured the efficient sequential three-step energy transfer. The excited energy was sequentially and efficiently funneled to Ce6 along the cascaded line MTPEPt1 → ESY → SR101 → Ce6. Additionally, a unique strategy for regulating the efficiency of ALHS was illustrated by adjusting hydrophilic and hydrophobic interactions.

Self-assembled supramolecular artificial light-harvesting nanosystems: construction, modulation, and applications

Artificial light-harvesting systems, an elegant way to capture, transfer and utilize solar energy, have attracted great attention in recent years. As the primary step of natural photosynthesis, the principle of light-harvesting systems has been intensively investigated, which is further employed for artificial construction of such systems. Supramolecular self-assembly is one of the feasible methods for building artificial light-harvesting systems, which also offers an advantageous pathway for improving light-harvesting efficiency. Many artificial light-harvesting systems based on supramolecular self-assembly have been successfully constructed at the nanoscale with extremely high donor/acceptor ratios, energy transfer efficiency and the antenna effect, which manifests that self-assembled supramolecular nanosystems are indeed a viable way for constructing efficient light-harvesting systems. Non-covalent interactions of supramolecular self-assembly provide diverse approaches to improve the efficiency of artificial light-harvesting systems. In this review, we summarize the recent advances in artificial light-harvesting systems based on self-assembled supramolecular nanosystems. The construction, modulation, and applications of self-assembled supramolecular light-harvesting systems are presented, and the corresponding mechanisms, research prospects and challenges are also briefly highlighted and discussed.

Light-Driven Aqueous Dissipative Pseudorotaxanes with Tunable Fluorescence Enabling Deformable Nano-Assemblies

Developing an artificial dynamic nanoscale molecular machine that dissipatively self-assembles far from equilibrium is fundamentally important but is significantly challenging. Herein, we report dissipatively self-assembling light-activated convertible pseudorotaxanes (PRs) that show tunable fluorescence and enable deformable nano-assemblies. A pyridinium-conjugated sulfonato-merocyanine derivative (EPMEH) and cucurbit[8]uril (CB[8]) form the 2EPMEH ⊂ CB[8] [3]PR in a 2:1 stoichiometry, which phototransforms into a transient spiropyran containing 1:1 EPSP ⊂ CB[8] [2]PR when exposed to light. The transient [2]PR thermally relaxes (reversibly) to the [3]PR in the dark accompanied by periodic fluorescence changes that include near-infrared emission. Moreover, octahedral and spherical nanoparticles are formed through the dissipative self-assembly of the two PRs, and the Golgi apparatus is dynamically imaged using fluorescent dissipative nano-assemblies.

Highly efficient Förster resonance energy transfer between an emissive tetraphenylethylene-based metal-organic cage and the encapsulated dye guest

The host-guest strategy presents an ideal way to achieve efficient Förster resonance energy transfer (FRET) by forcing close proximity between an energy donor and acceptor. Herein, by encapsulating the negatively charged acceptor dyes eosin Y (EY) or sulforhodamine 101 (SR101) in the cationic tetraphenylethene-based emissive cage-like host donor Zn-1, host-guest complexes were formed that exhibit highly efficient FRET. The energy transfer efficiency of Zn-1⊃EY reached 82.4%. To better verify the occurrence of the FRET process and make full use of the harvested energy, Zn-1⊃EY was successfully used as a photochemical catalyst for the dehalogenation of α-bromoacetophenone. Furthermore, the emission color of the host-guest system Zn-1⊃SR101 could be adjusted to exhibit bright white-light emission with the CIE coordinates (0.32, 0.33). This work details a promising approach to enhance the efficiency of the FRET process by the creation of a host-guest system between the cage-like host and dye acceptor, thus serving as a versatile platform for mimicking natural light-harvesting systems.

The Effect of Transparent Conducting Oxide Films on WO3-Based Electrochromic Devices with Conducting Polymer Electrolytes

Over the past few decades, electrochromism has been a prominent topic in energy-saving applications, which is based on the mechanism of altering the optical transmittance of EC materials under the effect of a small applied voltage. Thus, tungsten oxide (WO₃) is a significant chemical compound typically applied in electrochromic devices (ECDs) as it is responsible for the optical transmittance variation. In this work, the WO₃ films were produced through a sol-gel spin-coating method. The effect of various transparent conducting oxides (TCOs, which are indium-doped tin oxide (ITO), fluorine-doped tin oxide (FTO) glass substrates, and aluminum-doped zinc oxide (AZO)) was investigated in the construction of ECDs. Based on a conducting polymer polypyrene carbonate electrolyte, ITO and aluminum-doped zinc oxide (AZO)-coated glasses were also examined as counter electrodes. The electrode combination employing FTO and ITO as the TCO and counter electrode, respectively, exhibited the most significant coloration efficiency of 72.53 cm²/C. It had coloring and bleaching transmittance of 14% and 56%, respectively, with a large optical modulation of 42%. In addition to that, ECDs with the AZO counter electrode have the advantage of lower intercalation charges compared to ITO and FTO. Hence, this research offers a new avenue for understanding the role of common TCO and counter electrodes in the development of WO₃-based ECDs with conducting polymer electrolytes.

Artificial Light-Harvesting System with White-Light Emission in a Bicontinuous Ionic Medium

Artificial light-harvesting systems (ALHSs), which are closely related to Förster resonance energy transfer (FRET), are among the most attractive scientific topics during the past few decades. Specifically, binary ALHSs that are composed of a fluid donor and acceptor have a simplified composition and high number density of the donor units. However, largely due to the difficulty in obtaining a fluid donor, investigation of these systems is still quite limited, especially for the ionic systems. Herein, we report a new type of binary ALHS using an ionic naphthalimide (NPI) derivative as a donor, which shows greatly improved photoluminescence for its bicontinuous liquid structure. When blending with an acceptor such as rhodamine 6G or trans-4-[4-(dimethylamino)styryl]-methylpyridinium iodide, efficient FRET was confirmed by both experimental results and molecular dynamics simulations, with an energy transfer efficiency up to ∼90%. Tunable color, including white-light emission, was achieved by tuning the acceptor/donor ratio, opening the door for a variety of applications such as light-emitting diodes and photoluminescent inks.

Noncovalent Polymerization-Activated Ultrastrong Near-Infrared Room-Temperature Phosphorescence Energy Transfer Assembly in Aqueous Solution

Noncovalent macrocycle-confined supramolecular purely organic room-temperature phosphorescence (RTP) is a current research hotspot. Herein, a high-efficiency noncovalent polymerization-activated near-infrared (NIR)-emissive RTP-harvesting system in aqueous solution based on the stepwise confinement of cucurbit[7]uril (CB[7]) and β-cyclodextrin-grafted hyaluronic acid (HACD), is reported. Compared with the dodecyl-chain-bridged 6-bromoisoquinoline derivative (G), the dumbbell-shaped assembly G⊂CB[7] presents an appeared complexation-induced RTP signal at 540 nm via the first confinement of CB[7]. Subsequently, benefitting from the stepwise confinement encapsulation of the β-cyclodextrin cavity, the subsequent noncovalent polymerization of the binary G⊂CB[7] assembly enabled by HACD can contribute to the further-enhanced RTP emission intensity approximately eight times in addition to an increased lifetime from 59.0 µs to 0.581 ms. Moreover, upon doping a small amount of two types of organic dyes, Nile blue or tetrakis(4-sulfophenyl)porphyrin as an acceptor into the supramolecular confinement assembly G⊂CB[7] @ HACD, efficient RTP energy transfer occurs accompanied by a long-lived NIR-emitting performance (680 and 710 nm) with a high donor/acceptor ratio. Intriguingly, the prepared RTP-harvesting system is successfully applied for targeted NIR imaging of living tumor cells by utilizing the targeting ability of hyaluronic acid, which provides a new strategy to create advanced water-soluble NIR phosphorescent materials.