Self-Assembly and Disassembly of Amphiphilic Zwitterionic Perylenediimide Vesicles for Cell Membrane Imaging

Self-Assembly of Nanovesicles for Enhanced Adsorption and Efficient Photodegradation of 2,4,6-Trichlorophenol

The compound 2,4,6-trichlorophenol poses significant risks to both the aquatic environment and human health. Its inherent persistence and stability present challenges in achieving complete purification, thus warranting its inclusion as a priority pollutant. The present study reports the development of an amphiphilic small-molecule compound that self-assembles into nanovesicles exhibiting remarkable adsorption and photodegradation capabilities. Through the synergistic effects of hydrogen bonding, van der Waals forces, π-π interactions, and electrostatic interactions, these vesicles efficiently adsorb 2,4,6-trichlorophenol from aqueous solutions within 1 min while demonstrating exceptional environmental stability and broad applicability. Upon self-assembly into vesicles, not only are more adsorption sites exposed, but charge separation and migration within the vesicles are also facilitated. Through the synergistic effects of adsorption and photodegradation, complete removal of 2,4,6-trichlorophenol in aqueous solution can be achieved within 8 h while exhibiting excellent recycling capability. This approach offers a viable strategy for designing and synthesizing pure organic photodegradable materials.

Dual-Modality Imaging with a Zwitterionic Fluorescent Probe for Reversible Monitoring of Mitochondrial Membrane Potential Dynamics

Traditional fluorescence intensity-based probes face challenges in accurately measuring mitochondrial membrane potential (MMP) due to intramolecular fluorescence quenching. In this work, we introduce a novel approach by incorporating quenching moieties within the zwitterionic probe to eliminate self-quenching interference, thus, enabling real-time and precise visualization of reversible MMP changes. We synthesized a zwitterionic fluorescent probe consisting of silicon-rhodamine (SiR) that was hydroxyl-substituted on the bay position of perylene diimides (PDIs) connected via a polyethylene glycol (PEG) linker. The lipophilic cationic SiR facilitates the entry of the PDI into the mitochondria, where the alkaline pH environment (pH = 8.0) ionizes the hydroxyl to a negatively charged species, affecting the quenching efficiency of SiR depending on the distance between the PDI and SiR moieties regulated by the MMP. The rigid aromatic ring of the PDI and strong hydrophobic interactions with the lipid bilayer, along with the inhibitory effect of the negatively charged hydroxyl on internalization, ensure the retention of PDI within the mitochondria. As the MMP decreases, SiR shifts outward, reducing quenching by phenolic anions and restoring fluorescence. Conversely, as the MMP increases, SiR moves inward, intensifying quenching by phenolic ions and reducing fluorescence, enabling reversible visualization monitoring of the MMP. This strategy overcomes the limitations of traditional intensity-based probes, providing a new avenue for reversible monitoring of the MMP.

Betaine-Based and Polyguanidine-Inserted Zwitterionic Micelle as a Promising Platform to Conquer the Intestinal Mucosal Barrier

Developing nanocarriers for oral drug delivery is often hampered by the dilemma of balancing mucus permeation and epithelium absorption, since huge differences in surface properties are required for sequentially overcoming these two processes. Inspired by mucus-penetrating viruses that universally possess a dense charge distribution with equal opposite charges on their surfaces, we rationally designed and constructed a poly(carboxybetaine)-based and polyguanidine-inserted cationic micelle platform (hybrid micelle) for oral drug delivery. The optimized hybrid micelle exhibited a great capacity for sequentially overcoming the mucus and villi barriers. It was demonstrated that a longer zwitterionic chain was favorable for mucus diffusion for hybrid micelles but not conducive to cellular uptake. In addition, the significantly enhanced internalization absorption of hybrid micelles was attributed to the synergistic effect of polyguanidine and proton-assisted amine acid transporter 1 (PAT1). Moreover, the retrograde pathway was mainly involved in the intracellular transport of hybrid micelles and transcytosis delivery. Furthermore, the prominent intestinal mucosa absorption in situ and in vivo liver distribution of the oral hybrid micelle were both detected. The results of this study indicated that the hybrid micelles were capable of conquering the intestinal mucosal barrier, having a great potential for oral application of drugs with poor oral bioavailability.

Regulation of the alkyl chain of fluorescent probes to selectively target the cell membrane or mitochondria in living cells

The visualization of cell membrane and mitochondrial behavior in living cells is of great life science value, but challenging due to the lack of ideal probes. In this work, two novel fluorescent probes based on different lengths of alkyl chains were reported for selective targeting of cell membranes or mitochondria of living cells. The probe CTM (1-Octadecyl-4-[9-ethyl-6-(diphenylamino)-9H-carbazol-3-yl] pyridinium) achieved cell membrane-specific staining in cells. Moreover, the probe CTM could monitor cell membrane damage through subcellular migration. Once the cell membrane was damaged, the probe CTM migrated into the mitochondria as a signal reporter. In addition, the probe MTM (1-Dodecly-4-[9-ethyl-6-(diphenylamino)-9H-carbazol-3-yl] pyridinium) with the shorter alkyl chain bearing the same skeleton structure penetrated the cell membrane and exhibited high affinity to mitochondria. This work will provide a useful tool to visualize the behavior of cell membranes and mitochondria in living cells.

Recent Advances in Applications of Fluorescent Perylenediimide and Perylenemonoimide Dyes in Bioimaging, Photothermal and Photodynamic Therapy

The emblematic perylenediimide (PDI) motif which was initially used as a simple dye has undergone incredible development in recent decades. The increasing power of synthetic organic chemistry has allowed it to decorate PDIs to achieve highly functional dyes. As these PDI derivatives combine thermal, chemical and photostability, with an additional high absorption coefficient and near-unity fluorescence quantum yield, they have been widely studied for applications in materials science, particularly in photovoltaics. Although PDIs have always been in the spotlight, their asymmetric counterparts, perylenemonoimide (PMI) analogues, are now experiencing a resurgence of interest with new efforts to create architectures with equally exciting properties. Namely, their exceptional fluorescence properties have recently been used to develop novel systems for applications in bioimaging, biosensing and photodynamic therapy. This review covers the state of the art in the synthesis, photophysical characterizations and recently reported applications demonstrating the versatility of these two sister PDI and PMI compounds. The objective is to show that after well-known applications in materials science, the emerging trends in the use of PDI- and PMI-based derivatives concern very specific biomedicinal applications including drug delivery, diagnostics and theranostics.

Controlled Aggregation of a Perylene-Derived Probe for Near-Infrared Fluorescence Imaging and Phototherapy

The design and synthesis of water-soluble phototherapeutic agents with near-infrared (NIR) fluorescence emission is highly desirable for cancer diagnosis and treatment. Here, we report the construction of an amphiphilic perylene-derived photosensitizer, AP. AP shows NIR emission with large Stokes shift (130 nm) and high 1O2 quantum yield (22%). It can self-assemble into nanoparticles in aqueous solution with quenched fluorescence emission due to aggregation-induced quenching. Upon membrane anchoring, AP is able to disassemble into free monomer molecules and specifically "light up" the cell membrane without the usually required washing procedures. Furthermore, AP is subsequently used for the efficient photodynamic therapy against cancer cells and solid tumors. The in vitro and in vivo experiments clearly indicate that AP is suitable for biological imaging and can serve as a promising photosensitizer for tumor suppression.

Nanometerization of thiamethoxam by a cationic star polymer nanocarrier efficiently enhances the contact and plant-uptake dependent stomach toxicity against green peach aphids

BACKGROUND

The utilization efficiency of conventional insecticides is comparatively low in agricultural production, which leads to their excessive application and environmental pollution. Insecticide nanometerization by polymers and polymeric materials has advantages, particularly increased utilization efficiency and reduced insecticide application.

RESULTS

To increase the utilization efficiency of insecticides, a star polycation (SPc) was selected as a drug carrier that could be complexed with thiamethoxam through electrostatic interaction. Formation of the complex decreased the particle size of thiamethoxam from 575.77 to 116.16 nm in aqueous solution. Plant uptake of SPc-delivered thiamethoxam was increased 1.69-1.84 times compared with thiamethoxam alone. Nano-sized thiamethoxam/SPc complexes showed enhanced contact and stomach toxicity against green peach aphids.

CONCLUSION

SPc is a promising insecticide adjuvant for insecticide nanometerization, and is beneficial in improving insecticidal activity and decreasing the application amounts and application rates of conventional insecticides. © 2020 Society of Chemical Industry.

A perylene monoimide probe based fluorescent micelle sensor for the selective and sensitive detection of picric acid

A hydroxyl functionalized perylene monoimide probe (PMI-OH) was prepared and self-assembled with the nonionic surfactant Triton X-100 (TX100) to fabricate a fluorescent micelle sensor for the selective and sensitive detection of picric acid (PA), a common explosive and environmental pollutant. The synthesized PMI-OH probe exhibited excimer fluorescence emission, and the intensity of the excimer fluorescence emission was significantly enhanced after the PMI-OH probe formed micelles with TX100. The obtained PMI-OH@TX100 micelles presented excellent photoluminescence properties and had a maximum fluorescence emission at 630 nm. The red fluorescence of the PMI-OH@TX100 micelles was quenched upon introduction of the nitro explosive PA due to electron transfer from the donor (PMI-OH) to the acceptor (PA). The fluorescence quenching of the fluorescent micelle sensor was proportional to the concentration of PA in the range of 2 to 10 μM. The limit of detection was 500 nM using 3σ/k. Thus, the developed PMI-OH@TX100 micelle sensor has great potential to detect PA in ordinary samples.

Dual-Mode Fluorescence and Magnetic Resonance Imaging by Perylene Diimide-Based Gd-Containing Magnetic Ionic Liquids

Bioimaging plays a key role in the diagnosis/treatment of diseases and in scientific research studies. Compared with single imaging techniques, dual-mode and multimode imaging techniques facilitate high accuracy. In this work, a perylene diimide (PDI)-based Gd-containing magnetic ionic liquid, Per-6-Diimi[Gd(NO₃)₄], is reported for dual-modal imaging, in which a Gd(III) complex was used for magnetic resonance imaging (MRI), while PDI was used for fluorescence imaging. Because of the difference in the biological microenvironment, there is a switch between dispersed and aggregated states of Per-6-Diimi[Gd(NO₃)₄] molecules in hydrophobic and hydrophilic media. When it was in the aqueous solution, the intensive π-π interaction of PDI cores made Per-6-Diimi[Gd(NO₃)₄] aggregates to form particles. The paramagnetic nanoparticles ensure prolonging the rotational correlation time, which results in a strong enhancement of MRI with a longitude relaxation coefficient of 14.94 mM^-1 s^-1. In an in vivo MRI experiment, the tumor site is imaged by MRI through the enhanced permeability and retention effect. However, when the molecule is present on the hydrophobic membrane of the cells, the dispersed Per-6-Diimi[Gd(NO₃)₄] showed good fluorescence imaging capabilities due to the high fluorescence quantum yield of PDI. Thus, the fluorescence imaging of cells can be carried out. Moreover, ex vivo fluorescence imaging of organs is performed after MRI. Per-6-Diimi[Gd(NO₃)₄] is enriched in the liver, kidneys, and tumors.

Cell Membrane-Specific Fluorescent Probe Featuring Dual and Aggregation-Induced Emissions

A cell membrane-specific fluorescent probe was prepared by conjugating a coumarin dye with a tetraphenylethene (TPE) derivative through an α,β-unsaturated ketone connection. The probe has two absorptions: one from the TPE moiety at 300 nm and a second one due to the coumarin moiety at 458.5 nm. The probe fluoresces at 470 nm in tetrahydrofuran (THF) solution. The probe exhibits a useful aggregation-induced emission (AIE) property. A gradual increase in the water content of a THF solution causes a significant decrease and 12 nm red shift in the fluorescence peak at 470 nm, giving rise to a new strong fluorescence peak at 591 nm at a 95% water content. The probe is hydrophobic with an AIE property and binds to cell membranes, resulting in 591 nm fluorescence upon implantation into cells. The probe possesses a long retention time despite the lack of a long, cell membrane-anchored hydrophobic alkyl chain, which is typical for traditional membrane-specific probes. Our probe also displays low cytotoxicity and excellent photostability.

A single component self-assembled thermally activated delayed fluorescence nanoprobe

A novel versatile thermally activated delayed fluorescence (TADF) nanoprobe, AI-Cz-NP, was constructed by self-assembly of a single-component amphiphilic monomer for potential applications in confocal imaging and time-resolved fluorescence imaging.

A benzoperylene self-assembly complex with turn-on excimer emission for wash-free cell membrane fluorescence imaging

A rational design of a benzoperylene probe BP-3 with positive charge allows for turn-on excimer emission, and wash-free cell membrane imaging. BP-3 possesses excellent chemical, thermal and photo stability. And the Stokes shift of the excimer emission is considerably large (90-100 nm), which very much avoids the background fluorescence interference.

Designer Peptide Amphiphiles: Self-Assembly to Applications

Peptide amphiphiles (PAs) are extremely attractive as molecular building blocks, especially in the bottom-up fabrication of supramolecular soft materials, and have potential in many important applications across various fields of science and technology. In recent years, we have designed and synthesized a large group of peptide amphiphiles. This library of PAs has the ability to self-assemble into a variety of aggregates such as fibers, nanosphere, vesicles, nanosheet, nanocups, nanorings, hydrogels, and so on. The mechanism behind the formation of such a wide range of structures is intriguing. Each system has its individual method of aggregation and results in assemblies with important applications in areas including chemistry, biology, and materials science. The aim of this feature article is to bring together our recent achievements with designer PAs with respect to their self-assembly processes and applications. Emphasis is placed on rational design, mechanistic aspects of the self-assembly processes, and the applications of these PAs. We hope that this article will provide a conceptual demonstration of the different approaches taken toward the construction of these task-specific PAs.

Highly photostable two-photon NIR AIEgens with tunable organelle specificity and deep tissue penetration

Photostability is a particularly important parameter for fluorescence imaging especially long-term dynamic tracking in live samples. However, many organic fluorophores show poor photostability under one-photon and two-photon continuous irradiation. In addition, these traditional fluorophores also suffer from aggregation-caused quenching (ACQ) in aggregate state in insolvable water environment. Therefore, it remains challenging to develop photostable and ACQ-free fluorophores for biological imaging. In this work, we developed two highly photostable aggregation-induced emission luminogens (AIEgens) based on the cyanostilbene core for in vitro and ex vivo bioimaging. These AIEgens named CS-Py⁺SO₃^- and CS-Py⁺ exhibit near-infrared solid-state emission, large Stokes shift (>180 nm), high fluorescence quantum yield (12.8%-13.7%) and good two-photon absorption cross section (up to 88 GM). CS-Py⁺SO₃^- and CS-Py⁺ show specific organelle staining with high biocompatibility in membrane and mitochondria in live cells, respectively. In addition, selective two-photon mitochondria visualization in live rat skeletal muscle tissues with deep-tissue penetration (about 100 μm) is successfully realized by using CS-Py⁺. Furthermore, these AIEgens especially CS-Py⁺ exhibit remarkably high resistance to photobleaching under one-photon and two-photon continuous irradiation. These highly photostable AIEgens could be potentially utilized in visualizing and tracking specific organelle-associated dynamic changes in live systems.

Diels–Alder reaction on perylenediimides: synthesis and theoretical study of core-expanded diimides

(Un)substituted perylenediimides react with (un)functionalized benzynes yielding core-expanded diimides.

A smart perylene derived photosensitizer for lysosome-targeted and self-assessed photodynamic therapy

A perylene probe PC4 is explored as a dual-function photosensitizer for photodynamic therapy and self-assessment imaging.

Polymer Vesicles: Modular Platforms for Cancer Theranostics

As an emerging field that is receiving an increasing amount of interest, theranostics is becoming increasingly important in the field of nanomedicine. Among the various smart platforms that have been proposed for use in theranostics, polymer vesicles (or polymersomes) are among the most promising candidates for integration of designated functionalities and modalities. Here, a brief summary of typical theranostic platforms is presented with a focus on modular polymer vesicles. To highlight modularity, the different methodologies for designing therapeutic and diagnostic modules are classified and current examples of theranostic vesicles that excel in both performance and design principle are provided. Finally, future prospects for theranostic polymer vesicles that can be readily prepared with functional modules are proposed. Overall, theranostic polymer vesicles with modular modalities and functions are more promising in nanomedicine than simply being "over-engineered".

pH-Triggered Peptide Self-Assembly for Targeting Imaging and Therapy toward Angiogenesis with Enhanced Signals

Mild acidic environment and angiogenesis are two typical characteristics of tumor. The specific response toward both lower pH and angiogenesis may enhance the targeting ability both for drug and diagnostic probe delivery. Herein, we present a kind of dual responding self-assembled nanotransformation material that is tumor angiogenesis targeting and pH triggered based on amphiphilic conjugation between peptides (STP) and aromatic molecules (tetraphenylethylene (TPE)). The morphology of the self-assembled peptide conjugates is responsibly changed from nanoparticles in neutral condition to nanofibers in acidic condition, which "turn on" the in vivo targeting imaging and accelerate the efficient drug delivery and in vivo therapy. On the basis of the well-controlled nanotransformation both in vitro and in vivo, we envisioned the successful demonstration of the responding materials would open a new avenue in turn on targeting imaging diagnostics and specific cancer therapeutics.

Membrane and nucleus targeting for highly sensitive cancer cell detection using pyrophosphate and alkaline phosphatase activity-mediated fluorescence switching of functionalized carbon dots

Fluorescence-switching of Cu²⁺–CD for specific membrane and nucleus targeting based on PPi and ALP activity in tumor cells.

Fluoride-mediated alkoxylation and alkylthio-functionalization of halogenated perylenediimides

The presence of fluoride ions in the reaction of chloro- or bromo-PDIs with alcohols and thiols leads to a spectacular increase in the yields of substituted compounds.