Cytophilic fluorescent bioprobes for long-term cell tracking

Mechanistic analysis of viscosity-sensitive fluorescent probes for applications in diabetes detection

Diabetes is one of the most detrimental diseases affecting the human life because it can initiate several other afflictions such as liver damage, kidney malfunctioning, and cardiac inflammation. The primary method for diabetes diagnosis involves the analysis of blood samples to quantify the level of glucose, while secondary diagnostic methods involve the qualitative analysis of obesity, fatigue, etc. However, all these symptoms start showing up only when the patient has been suffering from diabetes for a certain period of time. In order to avoid such delay in diagnosis, the development of specific fluorescent probes has attracted considerable attention. Prominent biomarkers for diabetes include abundance of certain analytes in blood serum, e.g., glucose, methylglyoxal, albumin, and reactive oxygen species; high intracellular viscosity; alteration of enzyme functionality, etc. Among these, high viscosity can greatly affect the fluorescence properties of various chromophores owing to the environment sensitivity of fluorescence spectra. In this review article, we have illustrated the application of some prominent fluorophores such as coumarin, BODIPY, xanthene, and rhodamine in the development of viscosity-dependent fluorescent probes. Detailed mechanistic aspects determining the influence of viscosity on the fluorescent properties of the probes have also been elaborated. Fluorescence mechanisms that are directly affected by the high-viscosity heterogeneous microenvironment are based on intramolecular rotations like twisted intramolecular charge transfer (TICT), aggregation-induced emission (AIE), and through-bond energy transfer (TBET). In this regard, this review article will be highly useful for researchers working in the field of diabetes treatment and fluorescent probes. It also provides a platform for the planning of futuristic clinical translation of fluorescent probes for the early-stage diagnosis and therapy of diabetes.

The innovative design of a delivery and real-time tracer system for anti-encephalitis drugs that can penetrate the blood-brain barrier

As a "wall" between blood flow and brain cells, the blood-brain barrier (BBB) makes it really difficult for drugs to cross this barrier and work. This is particularly the case for pharmaceuticals of acute encephalitis therapies, largely excluded from the brain following systemic administration. Herein we report an advanced drug delivery system that can cross the BBB and target acute inflammation based on the controlled release of macrophage-camouflaged glow nanoparticles via a Trojan horse strategy. Benefiting from afterglow imaging that eliminates background interference and RAW 264.7 cells (RAW) with special immune homing and long-term tracking capabilities, polydopamine (PDA)-modified afterglow nanoparticles (ANPs) as near-infrared photo-responsive drug carriers in a controlled delivery system camouflaged by macrophages can penetrate the BBB by crossing the intercellular space and trigger the anti-inflammatory drug by photothermal conversion in the brain parenchyma dexamethasone (Dex) release, exhibiting good acute inflammation recognition and healing ability. APD@RAW was monitored to cross the BBB and image deep brain inflamed areas in a model of acute brain inflammation. Meanwhile, the delivered Dex mitigated the brain damage caused by inflammatory cytokines secretion (IL-6, TNF-α, and IL-1β). Overall, this drug delivery system holds excellent potential for BBB penetrating and acute encephalitis therapies.

AIEgen-Based Nanomaterials for Bacterial Imaging and Antimicrobial Applications: Recent Advances and Perspectives

Microbial infections have always been a thorny problem. Multi-drug resistant (MDR) bacterial infections rendered the antibiotics commonly used in clinical treatment helpless. Nanomaterials based on aggregation-induced emission luminogens (AIEgens) recently made great progress in the fight against microbial infections. As a family of photosensitive antimicrobial materials, AIEgens enable the fluorescent tracing of microorganisms and the production of reactive oxygen (ROS) and/or heat upon light irradiation for photodynamic and photothermal treatments targeting microorganisms. The novel nanomaterials constructed by combining polymers, antibiotics, metal complexes, peptides, and other materials retain the excellent antimicrobial properties of AIEgens while giving other materials excellent properties, further enhancing the antimicrobial effect of the material. This paper reviews the research progress of AIEgen-based nanomaterials in the field of antimicrobial activity, focusing on the materials' preparation and their related antimicrobial strategies. Finally, it concludes with an outlook on some of the problems and challenges still facing the field.

Facile synthesis of nitrogen-doped carbon dots as sensitive fluorescence probes for selective recognition of cinnamaldehyde and l-Arginine/l-Lysine in living cells

The disorder of amino acid metabolism and the abuse of small molecule drugs pose serious threats to public health. However, due to the limitations of existing detection technologies in sensing cinnamaldehyde (CAL) and l-Arginine/l-Lysine (l-Arg/l-Lys), there is an urgent need to develop new sensing strategies to meet the severe challenges currently facing. Herein, nitrogen-doped carbon dots (N-CDs) were developed using a simple one-pot hydrothermal carbonization method. These N-CDs exhibited numerous distinctive characteristics such as excellent photoluminescence, high water dispersibility, favorable biocompatibility, and superior chemical inertness. Strikingly, the as-prepared CDs as a highly efficient fluorescent probe possessed significant sensitivity and selectivity toward CAL and l-Arg/l-Lys over other analytes with a low detection limit of 58 nM and 16 nM/18 nM, respectively. The fluorescence of N-CDs could be quenched by CAL through an electron transfer process. Then, the strong electrostatic interaction between l-Arg/l-Lys and N-CDs induced the efficient fluorescence recovery. More importantly, the outstanding biosafety and excellent analyte-responsive fluorescence characteristics of N-CDs have also been verified in living cells as well as in serum and urine. Overall, the N-CDs had a wide application prospect in the diagnosis of amino acid metabolic diseases and small molecule drug sensing.

Precise and long-term tracking of mitochondria in neurons using a bioconjugatable and photostable AIE luminogen

Tracking mitochondrial movement in neurons is an attractive but challenging research field as dysregulation of mitochondrial motion is associated with multiple neurological diseases. To realize accurate and long-term tracking of mitochondria in neurons, we elaborately designed a novel aggregation-induced emission (AIE)-active luminogen, TPAP-C5-yne, where we selected a cationic pyridinium moiety to target mitochondria and employed an activated alkyne terminus to achieve long-term tracking through bioconjugation with amines on mitochondria. For the first time, we successfully achieved the accurate analysis of the motion of a single mitochondrion in live primary hippocampal neurons and the long-term tracking of mitochondria for up to a week in live neurons. Therefore, this new AIEgen can be used as a potential tool to study the transport of mitochondria in live neurons.

Visualization of Acute Inflammation through a Macrophage-Camouflaged Afterglow Nanocomplex

Acute inflammation is a basic innate, immediate, and stereotyped immune response to injury, which is characterized by rapid recruitment of immune cells to the vasculature and extravasation into the damaged parenchyma. Visualization of acute inflammation plays an important role in monitoring the disease course and understanding pathogenesis, which lacks specific targeted and observing tools in vivo. Here, we report a Trojan horse strategy of a macrophage-camouflaged afterglow nanocomplex (UCANPs@RAW) to specifically visualize acute inflammation. Due to the advantages of optical antibackground interference elimination, as well as particular immune homing and long-term tracking capacity, UCANPs@RAW demonstrates an excellent acute inflammatory recognition ability. In an arthritis model, previously intravenously injected UCANPs@RAW could directionally migrate from the liver to the inflammation site as soon as 3 h after the model was induced, which could be continuously lighted for at least 36 h with the highest imaging signal-to-background ratio (SBR) as 382 at the time point of 9 h. Additionally, UCANPs@RAW is observed to penetrate the blood-brain barrier and image the deep brain inflamed region covered by the thick skull in an acute brain inflammation model with an SBR_max of 258, which is based on the strong recruiting ability of macrophages to immune response. In view of this smart nanocomplex, our strategy holds great potential for inflammatory detection and treatments.

Synthesis and optical properties of conjugated maleimide molecules containing amino with aggregation-induced emission enhancement (AIEE)

Maleimide-based luminophores bearing conjugated units and various amino substituents are attracting intensive scientific interest as organic luminophores, owing to their excellent light emission properties and wide applications.

AIEgens for Bacterial Imaging and Ablation

Accurate and sensitive diagnosis of pathogenic bacterial infection is a fundamental first step for correct bacteria management, helping to avoid the development of drug-resistant bacteria caused by the inappropriate use and overuse of antibiotics. Fluorescence probes as a promising visual tool can help identify pathogens rapidly and reliably. However, rigidly structured traditional fluorescence probes generally suffer from the drawback of aggregation-caused quenching (ACQ) effect, which greatly undermines their advantages with respect to sensitivity. Luminogens with aggregation-induced emission properties, namely AIEgens, can overcome the ACQ effect and certain AIEgen-based materials are capable of generating reactive oxygen species (ROS) in the aggregate states. Hence, they have become powerful tools for imaging and killing bacteria. This review summarizes the recent advances in AIEgens for the diagnosis and treatment of pathogen infections. Special attention has been paid to the molecular design, the application in bacterial imaging and ablation in vitro and in vivo, and the biocompatibility of AIEgens. Finally, the challenges and prospects are discussed in terms of using AIEgens to advance precision therapies for pathogen infections.

Aggregation-induced emission from silole-based lumophores embedded in organic-inorganic hybrid hosts

Aggregation-induced emitters - or AIEgens - are often symbolised by their photoluminescence enhancement as a result of aggregation in a poor solvent. However, for some applications, it is preferable for the AIE response to be induced in the solid-state. Here, the ability of an organic-inorganic hybrid polymer host to induce the AIE response from embedded silole-based lumophores has been explored. We have focussed on understanding how the incorporation method controls the extent of lumophore aggregation and thus the associated photophysical properties. To achieve this, two sample concentration series have been prepared, based on either the parent AIEgen 1,1-dimethyl-2,3,4,5-tetraphenylsilole (DMTPS) or the silylated analogue (DMTPS-Sil), which were physically doped or covalently grafted, respectively, to dU(600) - a member of the ureasil family of poly(oxyalkylene)/siloxane hybrids. Steady-state and time-resolved photoluminescence measurements, coupled with confocal microscopy studies, revealed that covalent grafting leads to improved dispersibility of the AIEgen, reduced scattering losses, increased photoluminescence quantum yields (up to ca. 40%) and improved chemical stability. Moreover, the ureasil also functions as a photoactive host that undergoes excitation energy transfer to the embedded DMTPS-Sil with an efficiency of almost 70%. This study highlights the potential for designing complex photoluminescent hybrid polymers exhibiting an ehanced AIE response for solid-state optical applications.

Patented AIE materials for biomedical applications

In recent years aggregation induced emission (AIE) concept has attracted researcher's interest worldwide. Several organic building blocks are developed as AIE materials. This chapter discusses the patented AIE material and their utilization related in biological, medicinal and biotechnology fields. It is demonstrated that AIE chromophores such as tetraphenylethylene (TPE) as well as other AIE building blocks became important fluorescent emissive bioactive materials. Such emissive materials are widely employed as bioprobes for the detection of mitochondria, cellular imaging and tracking, protein carrier detection of S-phase DNA, detection of d-glucose, visualization of cancer treatment, drug screening, image-guided therapy, bacterial imaging, photodynamic therapy and drug screening. Such AIE materials upon imaging in cellular environment displays significant enhancement of fluorescence emission. Such patented AIE chromophores has a great potential for bioimaging and biomedical applications. In this chapter we compile some patented representative examples to explore their bioimaging/medicinal imaging applications since lot of new inventions are reported every day.

One-Step Synthesis of Carbon Nanoparticles Capable of Long-Term Tracking Lipid Droplet for Real-Time Monitoring of Lipid Catabolism and Pharmacodynamic Evaluation of Lipid-Lowering Drugs

Lipid droplets (LDs) are intracellular lipid-rich organelles, which not only serve as neutral lipid reservoirs but also involve in many physiological processes and are associated with a variety of metabolic diseases and cancers. Long-term tracking of the state and behavior of LDs is of great significance but challenging. The difficulty is largely due to the lack of low cytotoxicity, high photobleaching resistance, and long intracellular retention probes that are capable of long-term tracking LDs. Herein, we report the discovery of two amphiphilic LD-targeting carbon nanoparticles (CNPs, i.e., CPDs and CDs) prepared by one-step room-temperature and hydrothermal methods. Their high lipid-water partition coefficient (log P > 2.13) and strong positive solvatochromism property ensure the quality of LD imaging. Especially, CDs exhibit favorable biocompatibility (2 mg mL^-1, cell viability >90%), excellent photostability (after continuous laser irradiation on a confocal microscope for 2 h, relative FL intensity >85%), and superior intracellular retention ability, thereby enabling long-term tracking of LDs in hepatocytes for up to six passages. Based on the excellent long-term tracking ability, CDs are successfully applied to observe autophagy in a typical catabolic process and to evaluate the effect of a commonly used lipid-lowering drug atorvastatin on hepatocyte lipid uptake.

Recent Advances on Fabrication of Polymeric Composites Based on Multicomponent Reactions for Bioimaging and Environmental Pollutant Removal

As the core of polymer chemistry, manufacture of functional polymers is one of research hotspots over the past several decades. Various polymers are developed for diverse applications due to their tunable structures and unique properties. However, traditional step-by-step preparation strategies inevitably involve some problems, such as separation, purification, and time-consuming. The multicomponent reactions (MCRs) are emerging as environmentally benign synthetic strategies to construct multifunctional polymers or composites with pendant groups and designed structures because of their features, such as efficient, fast, green, and atom economy. This mini review summarizes the latest advances about fabrication of multifunctional fluorescent polymers or adsorptive polymeric composites through different MCRs, including Kabachnik-Fields reaction, Biginelli reaction, mercaptoacetic acid locking imine reaction, Debus-Radziszewski reaction, and Mannich reaction. The potential applications of these polymeric composites in biomedical and environmental remediation are also highlighted. It is expected that this mini-review will promote the development preparation and applications of functional polymers through MCRs.

Fabrication of claviform fluorescent polymeric nanomaterials containing disulfide bond through an efficient and facile four-component Ugi reaction

Multicomponent reactions (MCRs) have attracted broad interest for preparation of functional nanomaterials especially for the synthesis of functional polymers. Herein, we utilized an "old" MCR, the four-component Ugi reaction, to synthesize disulfide bond containing poly(PEG-TPE-DTDPA) amphiphilic copolymers with aggregation-induced emission (AIE) feature. This four-component Ugi reaction was carried out under rather mild reaction conditions, such as room temperature, no gas protection and absent of catalysts. The amphiphilic poly(PEG-TPE-DTDPA) copolymers with high number-average molecular weight (up to 86,440 Da) can self-assemble into claviform fluorescent polymeric nanoparticles (FPNs) in aqueous solution, and these water-dispersed nanoparticles exhibited strong emission, large Stokes shift (142 nm), low toxicity and remarkable ability in cellular imaging. Moreover, owing to the introduction of 3,3'-dithiodipropionic acid with disulfide bond, the resultant AIE-active poly(PEG-TPE-DTDPA) could display reduction-responsiveness and be utilized for synthesis of photothermal agents in-situ. Therefore, the AIE-active poly(PEG-TPE-DTDPA) could be promising for controlled intracellular delivery of biological activity molecules and fabrication of multifunctional AIE-active materials. Therefore, these novel AIE-active polymeric nanoparticles could be of great potential for various biomedical applications, such as biological imaging, stimuli-responsive drug delivery and theranostic applications.

A conformational tweak for enhanced cellular internalization, photobleaching resistance and prolonged imaging efficacy

A strategy of conformational tweaking regulates the condensed state behavior of naphthalimide skeletal isomers (NSIs) and enhances their photophysical properties, cellular uptake and prolonged imaging capability. This salient approach results in a large Stokes shift (>120 nm), rapid cellular internalization, photobleaching resistance, and efficient bioimaging of the ribbon-like nano-assembly superior to that of its electronically similar micro-flower isomer.

Enzyme-responsive polymeric micelles with fluorescence fabricated through aggregation-induced copolymer self-assembly for anticancer drug delivery

The TPE moiety with AIE is employed as functional hydrophobic chain to induce copolymer self-assembly and form polymeric micelle that can show enzyme-responsive drug delivery.

Retrosynthesis of Tunable Fluorescent Carbon Dots for Precise Long-Term Mitochondrial Tracking

Mitochondria play a significant role in many cellular processes. Precise long-term tracking of mitochondrial status and behavior is very important for regulating cell fate and treating mitochondrial diseases. However, developing probes with photostability, long-term tracking capability, and tunable long-wavelength fluorescence has been a challenge in mitochondrial targeting. Carbon dots (CDs) as new fluorescent nanomaterials with low toxicity and high stability show increasing advantages in bioimaging. Herein, the mitochondria tracking CDs (MitoTCD) with intrinsic mitochondrial imaging capability and tunable long-wavelength fluorescence from green to red are synthesized where the lipophilic cation of rhodamine is served as the luminescent center of CDs. Due to the excellent photostability, superior fluorescence properties and favorable biocompatibility, these MitoTCD are successfully used for mitochondrial targeting imaging of HeLa cells in vitro and can be tracked as long as six passages, which is suitable for long-term cell imaging. Moreover, these MitoTCD can also be used for zebrafish imaging in vivo.

Tetraphenylethylene@Graphene Oxide with Switchable Fluorescence Triggered by Mixed Solvents for the Application of Repeated Information Encryption and Decryption

Aggregation-induced emission (AIE) materials present unique solid-state fluorescence. However, there remains a challenge in the switching of fluorescence quenching/emitting of AIE materials, limiting the application in information encryption. Herein, we report a composite of tetraphenylethylene@graphene oxide (TPE@GO) with switchable microstructure and fluorescence. We choose GO as a fluorescence quencher to control the fluorescence of TPE by controlling the aggregation structure. First, TPE coating with an average thickness of about 31 nm was deposited at the GO layer surface, which is the critical thickness at which the fluorescence can be largely quenched because of the fluorescence resonance energy transfer. After spraying a mixed solvent (good and poor solvents of TPE) on TPE@GO, a blue fluorescence of TPE was emitted during the drying process. During the treatment of mixed solvents, the planar TPE coating was dissolved in THF first and then the TPE molecules aggregated into nanoparticles (an average diameter of 65 nm) in H₂O during the volatilization of THF. We found that the fluorescence switching of the composite is closely related to the microstructural change of TPE between planar and granular structures, which can make the upper TPE molecules in and out of the effective quenching region of GO. This composite, along with the treatment method, was used as an invisible ink in repeated information encryption and decryption. Our work not only provides a simple strategy to switch the fluorescence of solid-state fluorescent materials but also demonstrates the potential for obtaining diverse material structures through compound solvent treatment.

Real-Time Mapping of Ultratrace Singlet Oxygen in Rat during Acute and Chronic Inflammations via a Chemiluminescent Nanosensor

Sensing nonradiation-induced singlet oxygen (¹ O₂ ) in whole-animal is deemed as one of the most challenging tasks in noninvasive techniques due to the µs level lifetime of ¹ O₂ and quenching by numerous reductants in tissues. Here a distinct chemiluminescent (CL) nanosensor (NTPE-PH) that boasts ultrahigh concentrated CL units in one nanoparticle is reported. Taking advantage of the intramolecular energy transfer mechanism that promises high energy transfer efficiency and the aggregation-induced emission behavior that guarantees high CL amplification, the NTPE-PH sensor is sensitive to a nm level ¹ O₂ . Experiments demonstrate that the NTPE-PH yields a highly selective CL response toward ¹ O₂ among common reactive oxygen species. With proved low cytotoxicity and good animal compatibility, real-time mapping of ultratrace ¹ O₂ in whole-animal during acute and chronic inflammations is first achieved. It is anticipated that the NTPE-PH sensor can be a useful tool for monitoring ¹ O₂ variation during immune response and pathological processes corresponding to different stimuli, even with drug treatment included.

Amphiphilic Tetraphenylethene-Based Pyridinium Salt for Selective Cell-Membrane Imaging and Room-Light-Induced Special Reactive Oxygen Species Generation

The cell membrane is the protecting frontier of cells, which is crucial for maintaining cell integrity, and has a close relationship with cell growth and death. There is a growing need for cell membrane imaging and monitoring in both living and dying cells. Herein, we report a new amphiphilic tetraphenylethene-based pyridinium salt (TPE-MEM) with aggregation-induced emission features for discriminatory cell membrane imaging. The fluorogenic probe with high yield was synthesized following asymmetric McMurry reaction, Williamson ether synthesis reaction, Suzuki coupling, and aldol condensation between a double-charged pyridinium salt and hexyloxytetraphenylethene benzaldehyde. TPE-MEM shows good water solubility, biocompatibility, and cell membrane specificity. Interestingly, a reactive oxygen species (ROS) is produced by the molecule (TPE-MEM) under room-light irradiation, which could destroy the integrity of the plasma membrane and cause cell necrosis. This enables a visible observation of cell necrosis and the phototherapeutic effect under a mild condition. Preliminary animal investigations also demonstrated the photodynamic therapy (PDT) effectiveness of TPE-MEM in tumor growth inhibition. We conclude that TPE-MEM is potentially a cell membrane-selective photosensitizer for PDT and it is worthy of further exploration of the phototherapeutic effect on animals systematically.

Carbon dots and AIE molecules for highly efficient tandem luminescent solar concentrators

High-performance tandem LSCs fabricated using N-doped carbon dots and AIE fluorescent materials can be obtained.

Photostable and highly emissive glassy organic dots exhibiting thermally activated delayed fluorescence

TADF nanoparticles have been demonstrated as a bright probe for bio-imaging. These nanoparticles show a high PLQY, long lifetime emission and high photostability.

Organic nanoparticles based on Lewis-pair formation: observation of prototropically controlled dual fluorescence

We successfully synthesize fluorescent organic nanoparticles of a Lewis-pair consisting of an amino-type hydrogen-bonding molecule (Lewis base) and a borinate derivative (Lewis acid). 2-(2'-Aminophenyl)benzothiazole (o-ABT) is chosen as the fluorophore. This molecule has a transferable proton in the amino group, but it does not exhibit ESIPT (excited-state intramolecular proton transfer) reaction in solution and thus shows a single normal emission solely from the enamine form. Organic nanoparticles are prepared by the reprecipitation method in which the fluorophore (o-ABT) in conjunction with a Lewis acid (diphenylborinic anhydride; DPBA) dissolved in a good solvent is rapidly injected into water under sonication. Interestingly, the nanoparticles produced exhibit a characteristic dual fluorescence that can be ascribed to the enamine and imine tautomers of o-ABT generated in the ground-state prototropy, which can be revealed by UV-vis absorption and excitation spectroscopy, IR spectroscopy and computational approaches. In the o-ABT/DPBA Lewis-pair nanoparticles, highly Stokes-shifted emission from the imine tautomer is enhanced in comparison with that from the molecularly dissolved state, suggesting that the present nanofabrication methodology based on Lewis acid-base chemistry (or N-B bonding interaction) plays a key role in tuning the fluorescence colour for the new type of organic nanoparticle.

Self-Assembled Fluorescent Organic Nanomaterials for Biomedical Imaging

Fluorescent nanomaterials, self-assembled from building blocks through multiple intermolecular interactions show diversified structures and functionalities, and are potential fluorescence contrast agents/probes for high-performance biomedical imaging. Self-assembled nanomaterials exhibit high stability, long circulation time, and targeted biological distribution. This review summarizes recent advances of self-assembled nanomaterials as fluorescence contrast agents/probes for biomedical imaging. The self-assembled nanomaterials are classified into two groups, i.e., ex situ and in situ construction of self-assembled nanomaterials. The advantages of ex situ as well as in situ constructed nanomaterials for biomedical applications are discussed thoroughly. The directions of future developments for self-assembled nanomaterials are provided.

Application of amphiphilic fluorophore-derived nanoparticles to provide contrast to human embryonic stem cells without affecting their pluripotency and to monitor their differentiation into neuron-like cells

Fluorogenic labeling is a potential technique in biology that allows for direct detection and tracking of cells undergoing various biological processes. Compared to traditional genetic modification approaches, labeling cells with nanoparticles has advantages, especially for the additional safety they provide by avoiding genomic integration. However, it remains a challenge to determine whether nanoparticles interfere with cell traits and provide long-lasting signals in living cells. We employed an amphiphilic fluorophore-derived nanoparticle (denoted by TPE-11) bearing a tetraphenylethene (TPE) moiety and two ionic heads; this nanoparticle has an aggregation-induced emission (AIE) effect and the ability to self-assemble. TPE-11 exhibited the property of higher or longer fluorescence intensities in cell imaging than the other two nanomaterials under the same conditions. We used this nanomaterial to label human embryonic stem (hES) cells and monitor their differentiation. Treatment with low concentrations of TPE-11 (8.0 μg/mL) resulted in high-intensity labeling of hES cells, and immunostaining analysis and teratoma formation assays showed that at this concentration, their pluripotency remained unaltered. TPE-11 nanoparticles allowed for long-term monitoring of hES cell differentiation into neuron-like cells; remarkably, strong nanoparticle signals were detected throughout the nearly 40-day differentiation process. Thus, these results demonstrate that the TPE-11 nanoparticle has excellent biocompatibility for hES cells and is a potential fluorogen for labeling and tracking the differentiation of human pluripotent stem cells.

STATEMENT OF SIGNIFICANCE

This study uses a nanoparticle-based approach to label human embryonic stem (hES) cells and monitor their differentiation. hES cells are distinguished by two distinctive properties: the state of their pluripotency and the potential to differentiate into various cell types. Thus, these cells will be useful as a source of cells for transplantation or tissue engineering applications. We noticed the effect of aggregation-induced emission, and the ability to self-assemble could enhance the persistence of signals. Treatment with low concentrations of TPE-11 nanoparticles showed high-intensity labeling of hES cells, and immunostaining analysis and teratoma formation assays showed that at this concentration, their pluripotency remained unaltered. Additionally, these nanoparticles allowed for long-term monitoring of hES cell differentiation into neuron-like cells lasting for 40 days.

Trojan Horse nanotheranostics with dual transformability and multifunctionality for highly effective cancer treatment

Nanotheranostics with integrated diagnostic and therapeutic functions show exciting potentials towards precision nanomedicine. However, targeted delivery of nanotheranostics is hindered by several biological barriers. Here, we report the development of a dual size/charge- transformable, Trojan-Horse nanoparticle (pPhD NP) for delivery of ultra-small, full active pharmaceutical ingredients (API) nanotheranostics with integrated dual-modal imaging and trimodal therapeutic functions. pPhD NPs exhibit ideal size and charge for drug transportation. In tumour microenvironment, pPhD NPs responsively transform to full API nanotheranostics with ultra-small size and higher surface charge, which dramatically facilitate the tumour penetration and cell internalisation. pPhD NPs enable visualisation of biodistribution by near-infrared fluorescence imaging, tumour accumulation and therapeutic effect by magnetic resonance imaging. Moreover, the synergistic photothermal-, photodynamic- and chemo-therapies achieve a 100% complete cure rate on both subcutaneous and orthotopic oral cancer models. This nanoplatform with powerful delivery efficiency and versatile theranostic functions shows enormous potentials to improve cancer treatment.

Size and charge can significantly affect delivery of therapeutic agents to tumours. Here, the authors report on nanoparticles optimised for delivery to the tumour which release smaller particles and change charge in the tumour microenvironment to optimise tumour penetration and cellular uptake.

An AIE-based metallo-supramolecular assembly enabling an indicator displacement assay inside living cells

We report a novel metallo-supramolecular assembly (Z/E-TPE2CyZn-PV), which consists of a tetraphenylethene (TPE)-based dinuclear Zn2+-cyclen complex and pyrocatechol violet (PV). The assembly is developed for indicator-displacement assays (IDAs) inside living cells.

Self-indicating, fully active pharmaceutical ingredients nanoparticles (FAPIN) for multimodal imaging guided trimodality cancer therapy

Conventional drug delivery systems contain substantial amounts of excipients such as polymers and lipids, typically with low drug loading capacity and lack of intrinsic traceability and multifunctionality. Here, we report fully active pharmaceutical ingredient nanoparticles (FAPIN) which were self-assembled by minimal materials, but seamlessly orchestrated versatile theranostic functionalities including: i) self-delivery: no additional carriers were required, all components in the formulation are active pharmaceutical ingredients; ii) self-indicating: no additional imaging tags were needed. The nanoparticle itself was composed of 100% imaging agents, so that the stability, drug release, subcellular dispositions, biodistribution and therapeutic efficacy of FAPINs can be readily visualized by ample imaging capacities, including energy transfer relay dominated, dual-color fluorogenic property, near-infrared fluorescence imaging and magnetic resonance imaging; and iii) highly effective trimodality cancer therapy, encompassing photodynamic-, photothermal- and chemo-therapies. FAPINs were fabricated with very simple material (a photosensitizer-drug conjugate), unusually achieved ∼10 times better in vitro antitumor activity than their free counterparts, and were remarkably efficacious in patient-derived xenograft (PDX) glioblastoma multiforme animal models. Only two doses of FAPINs enabled complete ablation of highly-malignant PDX tumors in 50% of the mice.

Synthesis and studies of axial chiral bisbenzocoumarins: Aggregation-induced emission enhancement properties and aggregation-annihilation circular dichroism effects

Axial chiral bisbenzocoumarins were synthesized for the first time by converting naphthanol units in 1,1'-binaphthol (BINOL) molecule to the benzocoumarin rings. The substitute groups on 3,3'-positions of bisbenzocoumarins showed significant influence on their aggregation-induced emission enhancement (AEE) properties. It was also found that BBzC1 with ester groups on 3,3'-positions exhibit an abnormal aggregation-annihilation circular dichroism (AACD) phenomenon, which could be caused by the decrease of the dihedral angle between adjacent benzocoumarin rings in the aggregation state. The single crystal structure of BBzC1 showed that the large dihedral angle in molecule prohibited the strong π-π stacking interactions, which could be main factors for its AEE properties.

AIEgen-Based Fluorescent Nanomaterials: Fabrication and Biological Applications

In recent years, luminogens with the feature of aggregation-induced emission (AIEgen) have emerged as advanced luminescent materials for fluorescent nanomaterial preparation. AIEgen-based nanomaterials show enhanced fluorescence efficiency and superior photostability, which thusly offer unique advantages in biological applications. In this review, we will summarize the fabrication methods of AIEgen-based nanomaterials and their applications in in vitro/in vivo imaging, cell tracing, photodynamic therapy and drug delivery, focusing on the recent progress.

Tailoring the morphology of AIEgen fluorescent nanoparticles for optimal cellular uptake and imaging efficacy

The rational design of robust fluorescent organic materials for long-term cell tracing is still challenging, and aggregation-caused quenching of emission is a big limitation of this strategy. Organic dyes with aggregation-induced emission (AIE) can effectively address this problem. Herein, AIEgen-containing nanoparticles, with different morphologies and emission, were prepared by assembling amphiphilic copolymers with an AIEgen. We compared the physical and chemical properties of rod-like and spherical nanoparticles, particularly investigating the effects of the shape on internalization and the imaging effect. The formulated nanoparticles exhibit advantageous features, such as a large Stokes shift, robust stability in physiological conditions, strong fluorescent emission, and photobleaching resistance. Interestingly, the rod-like nanoparticles were internalized more efficiently than their spherical counterparts, and their strong green fluorescence can still be clearly observed even after 15 days in vitro and in vivo. This work demonstrates the great potential of regulating the morphology of nanoparticles to obtain an ideal biological function.

Gated photochromic molecules with AIEgen: turn-on the photochromism with an oxidation reagent

Gated photochromic molecule: switchable photochromic materials with AIEgen were achieved. Oxidation reagents act as gates to switch the photochromic properties.