Fluorescent Polymeric Micelles with Aggregation-Induced Emission Properties for Monitoring the Encapsulation of Doxorubicin

Anti-hepatoma effect of homologous delivery of doxorubicin by HepG2 cells

Compared to conventional polymer-based and biomaterial carriers, cells as vehicles for delivering bioactive molecules in the treatment of tumor diseases offer characteristics such as non-toxicity, biocompatibility, low immunogenicity, and prolonged in vivo circulation. However, the focus of current cell drug delivery systems predominantly lies on live cells, such as red blood cells, white blood cells and others. Here, a drug delivery strategy targeting liver cancer utilizing cryo-shocked liver cancer cells (HepG2) as carriers was presented, and non-proliferative HepG2 cells particles loaded with DOX (HepG2-DOX) was effectively prepared, which has good homologous targeting. Subsequent in vitro and in vivo experiments demonstrated the non-proliferative and non-pathogenic nature of this drug delivery system. The outcomes of in vitro experiments revealed that the inhibitory effect of HepG2-DOX on HepG2 was approximately five times higher than that of free DOX, with the IC50 value of HepG2-DOX being 0.0739 µg/mL and free DOX being 0.3606 µg/mL. Furthermore, in comparison to the positive DOX group, the HepG2-DOX group has a very significant advantage in tumor inhibition rate (91.34 % vs. 64.20 %). Cell uptake experiments indicated significant HepG2-DOX uptake by HepG2 cells compared to 4T1, LO2, and Raw cell groups, highlighting the excellent cell specificity of HepG2-DOX. Fluorescence imaging conducted in mice following the administration of HepG2-DOX demonstrated prompt drug localization within the tumor region, highlighting exceptional in vivo targeting precision. To sum up, this study introduced a novel strategy utilizing cryo-shocked liver cancer cells as a drug delivery system, effectively treating liver tumor by enhancing tumor targeting specificity.

Fluorescent sensing copolymers: Synthesis, nanofiber fabrication and application in picric acid sensors

Increasing attention has been paid to the detection of explosives due to the occurrence of terrorist attacks around the world. Here, we used free radical polymerization to develop two different types of fluorescent copolymers for use in detecting picric acid. One exhibits aggregation-caused quenching (ACQ) and is called PNNS [poly (N-isopropyl acrylamide-co-N-hydroxymethyl acrylamide -co-styrene-pyrene), poly (NIPAAm-co-NMA-co-St-Py)]. The other possesses aggregation-induced emission (AIE) properties and is called PNNP [poly (N-isopropyl acrylamide-co-N-hydroxymethyl acrylamide-co-2-(1,2,3,4,5-pentaphenyl-1H-silol-1-yloxy) ethyl methacrylate), poly (NIPAAm-co-NMA-co-PPS-HEMA)]. Nanofibrous thin films of these copolymers were obtained by electrospinning. Upon interaction with picric acid, the fluorescence intensity of each copolymer was quenched due to photo-induced electron transfer (PET). The average diameters of PNNS and PNNP nanofibers were 179 ± 28 nm and 235 ± 143 nm, respectively. Sensing performance was evaluated by Stern-Volmer analysis. The Stern-Volmer constant (Ksv) values for PNNS and PNNP nanofibers were 0.012 μΜ-1 and 0.119 μΜ-1, respectively. Since the aggregated state of PNNP nanofibrous thin films can increase dramatically, the AIE property of this material provides a large dynamic range. Finally, the reusability of water- and methanol-washed nanofiber thin films was tested, revealing that the nanofiber sensors were reusable for detecting picric acid.

The in vivo fate of polymeric micelles

This review aims to provide a systemic analysis of the in vivo, as well as subcellular, fate of polymeric micelles (PMs), starting from the entry of PMs into the body. Few PMs are able to cross the biological barriers intact and reach the circulation. In the blood, PMs demonstrate fairly good stability mainly owing to formation of protein corona despite controversial results reported by different groups. Although the exterior hydrophilic shells render PMs "long-circulating", the biodistribution of PMs into the mononuclear phagocyte systems (MPS) is dominant as compared with non-MPS organs and tissues. Evidence emerges to support that the copolymer poly(ethylene glycol)-poly(lactic acid) (PEG-PLA) is first broken down into pieces of PEG and PLA and then remnants to be eliminated from the body finally. At the cellular level, PMs tend to be internalized via endocytosis due to their particulate nature and disassembled and degraded within the cell. Recent findings on the effect of particle size, surface characteristics and shape are also reviewed. It is envisaged that unraveling the in vivo and subcellular fate sheds light on the performing mechanisms and gears up the clinical translation of PMs.

Brush-like Polymer Prodrug with Aggregation-Induced Emission Features for Precise Intracellular Drug Tracking

In this study, a brush-like polymer with aggregation-induced emission (AIE) features was synthesized for drug delivery and intracellular drug tracking. The polymer consisting of tetraphenylethene (TPE) chain-end as well as oligo-poly (ethylene glycol) (PEG) and hydrazine functionalities was successfully synthesized through copper (0)-mediated reversible-deactivation radical polymerization (Cu0-mediated RDRP). Anticancer drug doxorubicin (DOX) was conjugated to the polymer and formed a prodrug named TPE-PEGA-Hyd-DOX, which contains 11% DOX. The hydrazone between DOX and polymer backbone is a pH-sensitive linkage that can control the release of DOX in slightly acidic conditions, which can precisely control the DOX release rate. The drug release of 10% after 96 h in normal cell environments compared with about 40% after 24 h in cancer cell environments confirmed the influence of the hydrazone bond. The ratiometric design of fluorescent intensities with peaks at 410 nm (emission due to AIE feature of TPE) and 600 nm (emission due to ACQ feature of DOX) provides an excellent opportunity for this product as a precise intracellular drug tracker. Cancer cells confocal microscopy showed negligible DOX solution uptake, but an intense green emission originated from prodrug uptake. Moreover, a severe red emission in the DOX channel confirmed a promising level of drug release from the prodrug in the cytoplasm. The merged images of cancer cells confirmed the high performance of the TPE-PEGA-Hyd-DOX compound in the viewpoints of cellular uptake and drug release. This polymer prodrug successfully demonstrates low cytotoxicity in healthy cells and high performance in killing cancer cells.

Recent Progress in Polymeric AIE-Active Drug Delivery Systems: Design and Application

Aggregation-induced emission (AIE) provides a new opportunity to overcome the drawbacks of traditional aggregation-induced quenching of chromophores. The applications of AIE-active fluorophores have spread across various fields. In particular, the employment of AIEgens in drug delivery systems (DDSs) can achieve imaging-guided therapy and pharmacodynamic monitoring. As a result, polymeric AIE-active DDSs are attracting increasing attention due to their obvious advantages, including easy fabrication and tunable optical properties by molecular design. Additionally, the design of polymeric AIE-active DDSs is a promising method for cancer therapy, antibacterial treatment, and pharmacodynamic monitoring, which indeed helps improve the effectiveness of related disease treatments and confirms its potential social importance. Here, we summarize the current available polymeric AIE-active DDSs from design to applications. In the design section, we introduce synthetic strategies and structures of AIE-active polymers, as well as responsive strategies for specific drug delivery. In the application section, typical polymeric AIE-active DDSs used for cancer therapy, bacterial treatment, and drug delivery monitoring are summarized with selected examples to elaborate on their wide applications.

Modulation of Aggregation-Induced Emission by Excitation Energy Transfer: Design and Application

Excitation energy transfer (EET) as a fundamental photophysical process is well-explored for developing functional materials with tunable photophysical properties. Compared to traditional fluorophores, aggregation-induced emission luminogens (AIEgens) exhibit unique advantages for building EET systems, especially serving as energy donors, due to their outstanding photophysical properties such as bright fluorescence in aggregation state, broad absorption and emission spectra, large Stokes shift, and high photobleaching resistance. In addition, the photophysical properties of AIEgens can be modulated by energy transfer for improved luminescence performance. Therefore, a variety of EET systems based on AIEgens have been constructed and their applications in different areas have been explored. In this review, we summarize recent progress in the design strategy of AIE-based energy transfer systems for light-harvesting, fluorescent probes and theranostic systems, with an emphasis on design strategies to achieve desirable properties. The limitations, challenges and future opportunities of AIE-EET systems are briefly outlined. Design strategies and applications (light-harvesting, fluorescent probe and theranostics) of AIEgen-based excitation energy systems are discussed in this review.

Preserving High-Efficiency Luminescence Characteristics of an Aggregation-Induced Emission-Active Fluorophore in Thermostable Amorphous Polymers

Luminophores usually suffer from luminescent quenching when introduced into a polymer backbone or side chain, which leads to the inefficient luminescence or even no luminescence of the polymer. In this work, alicyclic imide rings were found to be capable of balancing the donor-acceptor properties between the rigid spacer and the aggregation-induced emission-active fluorophore in light-emitting polymers. Along with the nonplanar and rigid emitter, the suppressed intramolecular charge-transfer effect and interchain disturbance can efficiently preserve the luminescence characteristics of the active center, resulting in high solid-state photoluminescence quantum yields of up to 89%. The amorphous polyimides exhibit excellent thermal properties, such as high glass transition temperature (T_g) values (398 °C) and high thermal decomposition temperature (T_d) values (538 °C). As far as we know, these luminescent polymer materials are of excellent heat resistance with the highest luminescence efficiency reported. The results have significant impact for the precise prediction of the optical properties of light-emitting polymers by appropriate monomer design, providing controllable ways for synthesizing high thermal stability polymeric materials with efficient fluorescence properties.

Self-reporting of payload release in polymer coatings based on the inner filter effect

New polymeric nanoparticle sensors are developed for monitoring the release of non-fluorescent payloads in coatings by the naked eye.

Rational Design for Multicolor Flavone-Based Fluorophores with Aggregation-Induced Emission Enhancement Characteristics and Applications in Mitochondria-Imaging

Fluorophores with aggregation-induced emission enhancement (AIEE) properties have attracted more attention in recent years. In order to realise more valuable applications, the different kinds of AIEE molecules are in serious need of further development. Therefore, a novel flavone-based AIEE system derived from restriction of intramolecular rotation (RIR) was designed and synthesized in this work. The results revealed that six of the compounds showed typical AIEE characteristics, with fluorescence emissions from purple, blue, cyan to green, tunable by changing substituent groups. This flavone-based AIEE system has never been reported before. The AIEE characteristics were investigated by optical spectroscopy, fluorescence photographs, scanning electron microscopy (SEM), fluorescence quantum yields (Ф_F) and fluorescence lifetime in the CH₃OH/H₂O mixed solution. Moreover, benefiting from the simple structures and small molecular weight, they could permeate cells faster than current high-molecular-weight AIEE molecules. Furthermore, to examine possible biomedical applications, fluorescence imaging in living A549 lung cells and cell viabilities were examined, and the results displayed that these fluorophores showed good cellular uptake and low cytotoxicity within the experimental concentration range. In addition, these AIEE compounds possessed excellent specificity for mitochondrial targeting and mitochondrial morphological change tracking, besides, they displayed superior photostability, which indicated they are potential candidates for mitochondrial imaging.

Gemini-Type Tetraphenylethylene Amphiphiles Containing [12]aneN3 and Long Hydrocarbon Chains as Nonviral Gene Vectors and Gene Delivery Monitors

Four gemini amphiphiles decorated with triazole-[12]aneN₃ as the hydrophilic moiety and various long hydrocarbons as hydrophobic moieties, 1-4, were designed to form micelles possessing the aggregation-induced emission (AIE) property for gene delivery and tracing. All four amphiphiles give ultralow critical micelle concentrations, are pH-/photostable and biocompatible, and completely retard the migration of plasmid DNAs at low concentrations. The DNA-binding abilities of the micelles were fully assessed. The coaggregated nanoparticles of 1-4 with DNAs could convert back into AIE micelles. In vitro transfections indicated that lipids 1 and 2 and their originated liposomes bearing decent delivering abilities have great potentials as nonviral vectors. Finally, on the basis of the transfection and the transitions between condensates and micelles, lipid 2 was singled out as the first example for real-time tracing of the intracellular deliveries of nonlabeled DNA, which provides spatiotemporal messages about the processes of condensate uptake and DNA release.

Zwitterionic Phosphorylcholine-TPE Conjugate for pH-Responsive Drug Delivery and AIE Active Imaging

Polymeric micelles have emerged as a promising nanoplatform for cancer theranostics. Herein, we developed doxorubicin (DOX) encapsulated pH-responsive polymeric micelles for combined aggregation induced emission (AIE) imaging and chemotherapy. The novel zwitterionic copolymer poly(2-methacryloyloxyethylphosphorylcholine-co-2-(4-formylphenoxy)ethyl methacrylate) (poly(MPC-co-FPEMA)) was synthesized via RAFT polymerization and further converted to PMPC-hyd-TPE after conjugation of tetraphenylethene (TPE, a typical AIE chromophore) via acid-cleavable hydrazone bonds. The AIE activatable copolymer PMPC-hyd-TPE could self-assemble into spherical PC-hyd-TPE micelles, and DOX could be loaded through hydrophobic interactions. The zwitterionic micelles exhibited excellent physiological stability and low protein adsorption due to the stealthy phosphorylcholine (PC) shell. In addition, the cleavage of hydrophobic TPE molecules under acidic conditions could induce swelling of micelles, which was verified by size changes with time at pH 5.0. The in vitro DOX release profile also exhibited accelerated release rate with pH value decreasing from 7.4 to 5.0. Fluorescent microscopy and flow cytometry studies further demonstrated fast internalization and accumulation of drug loaded PC-hyd-TPE-DOX micelles in HepG2 cells, resulting in considerable time/dose-dependent cytotoxicity. Meanwhile, high-quality AIE imaging of PC-hyd-TPE micelles was confirmed in HepG2 cells. Notably, ex vivo imaging study exhibited efficient accumulation and drug release of PC-hyd-TPE-DOX micelles in the tumor tissue. Consequently, the multifunctional micelles with combined nonfouling surface, AIE active imaging, and pH-responsive drug delivery showed great potential as novel nanoplatforms for a new generation of cancer theranostics.

Subcellular Behaviour Evaluation of Nanopharmaceuticals with Aggregation-Induced Emission Molecules

Nanopharmaceuticals possess a myriad of advantages for disease treatment, not only in delivering therapeutic agents, but also in deciphering their innate intracellular or subcellular behaviours, providing detailed diagnostic and prognostic information, quantifying treatment efficacy and designing better therapeutics. To evaluate the subcellular behaviour of nanopharmaceuticals, colourful fluorescence is the most potential technique, because it is capable of painting the subcellular detail in three dimensions with high resolution. Furthermore, the fluorescence is switchable, and thus the subcellular details can be lightened specifically without the undesirable background. However, most nanopharmaceuticals lack a fluorescent report group, and its introduction requires extra steps. Moreover, the introduced fluorescent groups can suffer from concentration quenching or aggregation-caused quenching (ACQ) when they are embedded in nanopharmaceuticals at a high concentration. The unique aggregation-induced emission (AIE) effect provides a straightforward solution. The aromatic cores of AIE molecules are always hydrophobic and do not undergo the ACQ effect even at high concentrations. Hence, AIE molecules can be directly introduced as building blocks to provide the driving force for the self-assembly of nanopharmaceuticals and can allow us to develop label-free, ACQ-free and luminescent nanopharmaceuticals that can simultaneously implement drug delivery and subcellular behaviour evaluation. This review presents different types of AIE molecules-based nanopharmaceuticals and their biological properties and applications for imaging subcellular behaviours, including the drug releasing process, metabolism of nanopharmaceuticals, subcellular distributions of drug and carriers, and therapeutic effect. With detailed acquaintance of these subcellular behaviours, we anticipate that the research we discuss in this review can inspire other scientists to develop next generation nanopharmaceuticals that can be guided by fluorescence imaging and thus can realize concisely controllable drug delivery.

Fluorescent Polymer Nanoparticles Based on Dyes: Seeking Brighter Tools for Bioimaging

Speed, resolution and sensitivity of today's fluorescence bioimaging can be drastically improved by fluorescent nanoparticles (NPs) that are many-fold brighter than organic dyes and fluorescent proteins. While the field is currently dominated by inorganic NPs, notably quantum dots (QDs), fluorescent polymer NPs encapsulating large quantities of dyes (dye-loaded NPs) have emerged recently as an attractive alternative. These new nanomaterials, inspired from the fields of polymeric drug delivery vehicles and advanced fluorophores, can combine superior brightness with biodegradability and low toxicity. Here, we describe the strategies for synthesis of dye-loaded polymer NPs by emulsion polymerization and assembly of pre-formed polymers. Superior brightness requires strong dye loading without aggregation-caused quenching (ACQ). Only recently several strategies of dye design were proposed to overcome ACQ in polymer NPs: aggregation induced emission (AIE), dye modification with bulky side groups and use of bulky hydrophobic counterions. The resulting NPs now surpass the brightness of QDs by ≈10-fold for a comparable size, and have started reaching the level of the brightest conjugated polymer NPs. Other properties, notably photostability, color, blinking, as well as particle size and surface chemistry are also systematically analyzed. Finally, major and emerging applications of dye-loaded NPs for in vitro and in vivo imaging are reviewed.

Soft fluorescent nanomaterials for biological and biomedical imaging

Soft fluorescent nanomaterials have attracted recent attention as imaging agents for biological applications, because they provide the advantages of good biocompatibility, high brightness, and easy biofunctionalization. Here, we provide a survey of recent developments in fluorescent soft nano-sized biological imaging agents. Various soft fluorescent nanoparticles (NPs) (including dye-doped polymer NPs, semiconducting polymer NPs, small-molecule organic NPs, nanogels, micelles, vesicles, and biomaterial-based NPs) are summarized from the perspectives of preparation methods, structure, optical properties, and surface functionalization. Based on both optical and functional properties of the nano-sized imaging agents, their applications are then reviewed in terms of in vitro imaging, in vivo imaging, and cellular-process imaging, by means of specific or nonspecific targeting.

Self-assembled liquid-crystalline folate nanoparticles for in vitro controlled release of doxorubicin

Liquid-crystalline folate nanoparticles are ordered in structure which offers several advantages like high encapsulation of drugs, controlled release rates, biocompatible in nature. Moreover, it facilitates the cellular uptake of nanodrugs without any extra step of folate ligand based targeting. The size of these nanocarriers as well as the release profiles of drugs from these nano-carriers can be controlled precisely. Folate molecules self-assemble in ordered stacks and columns even at low concentration of 0.1wt%. Doxorubicin molecules get intercalated within the folate stacks and are developed into nanoparticles. These nanoparticles are composed of highly ordered folate self-assembly which encapsulate doxorubicin molecules. These drug molecules can be released in a controlled manner by disrupting this assembly in the environment of monovalent cations. The ordered structure of folate nanoparticles offers low drug losses of about 4-5%, which is significant in itself. This study reports the size-control method of forming doxorubicin encapsulated folate nanoparticles as well as the parameters to control the release rates of doxorubicin through liquid-crystalline folate nanoparticles. It has been demonstrated that doxorubicin release rates can be controlled by controlling the size of the nanoparticles, cross-linking cation and cross-linking concentration. The effect of different factors like drug loading, release medium, and pH of the medium on doxorubicin release rates was also studied. Moreover, this study also addresses the comparative in vitro cytotoxic performance of Doxorubicin loaded folate nanoparticles and cellular uptake of nano-carriers on cancer and normal cell line.

Supramolecular assembly-induced yellow emission of 9,10-distyrylanthracene bridged bis(pillar[5]arene)s

Newly synthesized DSA-bridged bis(pillar[5]arene)s with AIE properties form linear supramolecular polymers upon binding to a neutral guest linker, exhibiting supramolecular assembly-induced yellow fluorescence emission.

Spectroscopic analysis and in vitro imaging applications of a pH responsive AIE sensor with a two-input inhibit function

A novel terpyridine derivative formed stable aggregates in aqueous media (DMSO/H₂O = 1/99) with dramatically enhanced fluorescence compared to its organic solution.

A facile strategy to generate polymeric nanoparticles for synergistic chemo-photodynamic therapy

Polymeric nanoparticles generated by mPEG-tetrakis(4-carboxyphenyl)porphyrin amphiphiles were used to trap doxorubicin for synergistic chemo-photodynamic therapy.

Imaging intracellular anticancer drug delivery by self-assembly micelles with aggregation-induced emission (AIE micelles)

Nanoformulations show many therapeutic advantages over conventional formulations. We seek to develop traceable nanoformulations in order to closely monitor delivery. Herein, we developed a new drug delivery system (DDS) using tetraphenylethene (TPE) to fabricate a self-assembly micelle with aggregation-induced emission (AIE micelle). AIE makes the nanocarriers visible for high-quality imaging, and the switching on and off of the AIE is intrinsically controlled by the assembly and disassembly of the micelles. This DDS was tested for doxorubicin (DOX) delivery and intracellular imaging. For the DOX-loaded micelles (TPED), the DOX content reached as much as 15.3% by weight, and the anticancer efficiency was higher than for free DOX. Meanwhile, high-quality imaging was obtained to trace the intracellular delivery of the TPED.

Aggregation-induced emission block copolymers based on ring-opening metathesis polymerization

AIE amphiphilic block copolymers were developed from ROMP for the first time. By self-assembly in selective solvents, water soluble fluorescent nano-objects were prepared with varied structures including micelles and vesicles.

AIE macromolecules: syntheses, structures and functionalities

A comprehensive review of macromolecules with aggregation-induced emission attributes is presented, covering the frontiers of syntheses, structures, functionalities and applications.