Molecular Engineering Towards Efficient Aggregation-Induced Delayed Fluorescence Luminogens as Emitters and Sensitizers for High-Performance Organic Light-Emitting Diodes.

Exploring efficient thermally-activated delayed fluorescence materials having maximum external quantum efficiencies (ηext,maxs) exceeding 30% for organic light-emitting diodes (OLEDs) still remains challenging because it generally requires efficient reverse intersystem crossing (RISC), high photoluminescence quantum yield (ΦPL), and large optical out-coupling efficiency (Φout) simultaneously. Herein, two green aggregation-induced delayed fluorescence (AIDF) luminogens, named XTCz-2 and XTCz-3, are designed and constructed by using xanthone (XT) as electron acceptor and phenylcarbazole-substituted carbazole as donors. XTCz-2 and XTCz-3 exhibit distinguished advantages of high thermal stability (439‒560 oC), excellent ΦPLs (84‒88%) and fast RISC rates (1.9 × 105‒4.2 × 105 s-1), and prefer horizontal dipole orientation and thus have high Φouts. Consequently, they can achieve the state-of-the-art electroluminescence (EL) performances with ηext,maxs of up to 35.0%. Moreover, XTCz-3 is selected as a sensitizer for sky-blue multi-resonance delayed fluorescence emitter in hyperfluorescence OLEDs, providing narrow EL spectra and excellent ηext,maxs of up to 33.8% with low efficiency roll-offs. The splendid comprehensive performances demonstrate the significant application potential of these AIDF luminogens as both light-emitting materials and sensitizers for OLEDs.

A high-performance organic fluorescent probe with aggregation-induced emission properties for long-term tumor monitoring.

Near-infrared organic fluorescent probes have great need in biological sciences and medicine but most of them are still largely unable to meet demand. In this work, a delicate multipurpose organic fluorescent probe (DPPM-TPA) with aggregation-induced emission performances is designed and prepared by facile method to reflect fluorescence labeling, two-photon imaging, and long-term fluorescent tracking. Specifically, DPPM-TPA NPs was constructed from 4-(diphenylamino)phenylboronic acid and DPPM-Br by classical Suzuki coupling reaction and then coated with F127. Such nanoprobe possessed high stability in diverse medium under ambient temperatures, low cytotoxicity, and brilliant fluorescence performance. More importantly, DPPM-TPA NPs showed excellent two-photon imaging and extraordinary long-term fluorescence tracing capacity to malignant tumor, and it can last up to 9 days. These results indicated that DPPM-TPA NPs is expected to serve as a fluorescent probe for photodiagnostic and providing a new idea for the development of long-term fluorescent tracker.

Creating Efficient Red Thermally Activated Delayed Fluorescence Materials with Cyano-Substituted 11,12-Diphenyldipyrido[3,2-a:2',3'-c]phenazine Acceptors.

Red luminescent materials are essential components for full color display and white lightening based on organic light-emitting diode (OLED) technology, but the extension of emission color towards red or deep red region generally leads to decreased photoluminescence and electroluminescence efficiencies. Herein, we wish to report two new luminescent molecules (2CNDPBPPr-TPA and 4CNDPBPPr-TPA) consisting of cyano-substituted 11,12-diphenyldipyrido[3,2-a:2',3'-c]phenazine acceptors and triphenylamine donors. As the increase of cyano substituents, the emission wavelength is greatly red-shifted and the reverse intersystem crossing process is promoted, resulting in strong red delayed fluorescence. Meanwhile, due to the formation of intramolecular hydrogen bonds, the molecular structures become rigidified and planarized, which brings about large horizontal dipole ratios. As a result, 2CNDPBPPr-TPA and 4CNDPBPPr-TPA can perform as emitters efficiently in OLEDs, furnishing excellent external quantum efficiencies of 28.8 % at 616 nm and 20.2 % at 648 nm, which are significantly improved in comparison with that of the control molecule without cyano substituents. The findings in this work demonstrate that the introduction of cyano substituents to the acceptors of delayed fluorescence molecules could be a facile and effective approach to explore high-efficiency red or deep red delayed fluorescence materials.

High-Performance Orange-Red Organic Light-Emitting Diodes with External Quantum Efficiencies Reaching 33.5% based on Carbonyl-Containing Delayed Fluorescence Molecules.

Developing orange to red purely organic luminescent materials having external quantum efficiencies (ηext s) exceeding 30% is challenging because it generally requires strong intramolecular charge transfer, efficient reverse intersystem crossing (RISC), high photoluminescence quantum yield (ΦPL ), and large optical outcoupling efficiency (Φout ) simultaneously. Herein, by introducing benzoyl to dibenzo[a,c]phenazine acceptor, a stronger electron acceptor, dibenzo[a,c]phenazin-11-yl(phenyl)methanone, is created and employed for constructing orange-red delayed fluorescence molecules with various acridine-based electron donors. The incorporation of benzoyl leads to red-shifted photoluminescence with accelerated RISC, reduced delayed lifetimes, and increased ΦPL s, and the adoption of spiro-structured acridine donors promotes horizontal dipole orientation and thus renders high Φout s. Consequently, the state-of-the-art orange-red organic light-emitting diodes are achieved, providing record-high electroluminescence (EL) efficiencies of 33.5%, 95.3 cd A-1 , and 93.5 lm W-1 . By referring the control molecule without benzoyl, it is demonstrated that the presence of benzoyl can exert significant positive effect over improving delayed fluorescence and enhancing EL efficiencies, which can be a feasible design for robust organic luminescent materials.

Improving Image-Guided Surgical and Immunological Tumor Treatment Efficacy by Photothermal and Photodynamic Therapies Based on a Multifunctional NIR AIEgen.

Multimodal therapy is attracting increasing attention to improve tumor treatment efficacy, but generally requires various complicated ingredients combined within one theranostic system to achieve multiple functions. Herein, a multifunctional theranostic nanoplatform based on a single aggregation-induced-emission luminogen (AIEgen), DDTB, is designed to integrate near-infrared (NIR) fluorescence, photothermal, photodynamic, and immunological effects. Intravenously injected AIEgen-based nanoparticles can efficiently accumulate in tumors with NIR fluorescence to provide preoperative diagnosis. Most of the tumors are excised under intraoperative fluorescence navigation, whereafter, some microscopic residual tumors are completely ablated by photodynamic and photothermal therapies for maximally killing the tumor cells and tissues. Up to 90% of the survival rate can be achieved by this synergistic image-guided surgery and photodynamic and photothermal therapies. Importantly, the nanoparticles-mediated photothermal/photodynamic therapy plus programmed death-ligand 1 antibody significantly induce tumor elimination by enhancing the effect of immunotherapy. This theranostic strategy on the basis of a single AIEgen significantly improves the survival of cancer mice with maximized therapeutic outcomes, and holds great promise for clinical cancer treatment.

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.

The combination of Diels-Alder reaction and redox polymerization for preparation of functionalized CNTs for intracellular controlled drug delivery.

Carbon nanotubes (CNTs) are a novel type of one-dimensional carbon nanomaterials that have been widely utilized for biomedical applications such as drug delivery, cancer photothermal treatment owing to their high surface area and unique interaction with cell membranes. However, their biomedical applications are still impeded by some drawbacks, including poor water dispersibility, lack of functional groups and toxicity. Therefore, surface modification of CNTs to overcome these issues should be importance and of great interest. In this work, we reported for the first time that CNTs could be surface modification through the combination of Diels-Alder (D-A) reaction and redox polymerization, this strategy shows the advantages of mild reaction conditions, water tolerance, low temperature and hydroxyl-surfaced initiator. In this modification procedure, the hydroxyl groups were introduced on the surface of CNTs through the D-A reaction that was adopted for grafting the copolymers, which were initiated by the Ce(IV)/HNO3 redox system using the hydrophilic and biocompatible poly(ethylene glycol) methyl ether methacrylate (PEGMA) and carboxyl-rich acrylic acid (AA) as monomers. The final CNTs-OH-PAA@PEGMA composites were characterized by a series of characterization techniques. The drug loading and release results suggested that anticancer agent cis­platinum (CDDP) could be loaded on CNTs-OH-PAA@PEGMA composites through coordination with carboxyl groups and drug release behavior could be controlled by pH. More importantly, the cell viability results clearly demonstrated that CNTs-OH-PAA@PEGMA composites displayed low toxicity and the drug could be transported in cells and still maintain their therapeutic effects.

Red aggregation-induced emission luminogen and Gd3+ codoped mesoporous silica nanoparticles as dual-mode probes for fluorescent and magnetic resonance imaging.

Fluorescence imaging and magnetic resonance imaging have been research hotspots for adjuvant therapy and diagnosis. However, traditional fluorescent probes or contrast agents possess insurmountable weaknesses. In this work, we reported the preparation of dual-mode probes based on mesoporous silica nanomaterials (MSNs), which were doped with an aggregation-induced emission (AIE) dye and Gd3+ through a direct sol-gel method. In this system, the obtained materials emitted strong red fluorescence, in which the maximum emission wavelength was located at 669 nm, and could be applied as effective fluorescence probes for fluorescence microscopy imaging. Furthermore, the introduction of Gd3+ made the nanoparticles effective contrast agents when applied in contrast-enhanced magnetic resonance (MR) imaging because they could improve the contrast of MR imaging. The excellent biocompatibility of these nanoparticles, as demonstrated via a typical CCK-8 assay, and their performance in fluorescence cell imaging and MR imaging shows their potential for applications in biomedical imaging.

Preparation and biological imaging of fluorescent hydroxyapatite nanoparticles with poly(2-ethyl-2-oxazoline) through surface-initiated cationic ring-opening polymerization.

Fluorescent hydroxyapatite (HAp) nanoparticles have received significant attention in biomedical fields due to their outstanding advantages, such as low immunogenicity, excellent biocompatibility and biodegradability. However, fluorescent HAp nanoparticles with well controlled size and morphology are coated with hydrophobic molecules and their biomedical applications are largely restricted by their poor dispersibility in physiological solutions. Therefore, surface modification of these hydrophobic fluorescent HAp nanoparticles to render them water dispersibility is of utmost importance for biomedical applications. In this work, we reported for the first time for preparation of water-dispersible hydrophilic fluorescent Eu3+-doped HAp nanoparticles (named as HAp-PEOTx) through the cationic ring-opening polymerization using hydrophilic and biocompatible 2-ethyl-2-oxazoline (EOTx) as the monomer. The characterization techniques, such as nuclear magnetic resonance (NMR) spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) have been used to characterize these samples. Results confirmed that we could successfully obtain the hydrophilic fluorescent HAp-PEOTx composites through the strategy described above. These fluorescent HAp-PEOTx composites display great water dispersibility, unique fluorescent properties and excellent biocompatibility, making them promising for in vitro bioimaging applications.

Click multiwalled carbon nanotubes: A novel method for preparation of carboxyl groups functionalized carbon quantum dots.

As potential alternatives to conventional semiconductor quantum dots, fluorescent carbon quantum dots (CQDs) have received increasing research attention in biomedical fields owing to their splendid advantages of low cytotoxicity, strong fluorescence and excellent water dispersion. However, the preparation procedures of CQDs with designable chemical properties and functions are complicated and low efficient. In this work, we developed a facile, economical and straightforward strategy to prepare CQDs by a one-step thiol-ene click reaction between multiwalled carbon nanotubes (CNTs) and thiomalic acid (TA). The successful synthesis of CQDs was confirmed by a series of characterization data. The results manifested that CQDs were well combined with TA through surface thiol-ene click chemistry. In addition, the optical property is also desirable, the maximum emission wavelength was located in 500 nm and CQDs still could emit strong blue fluorescent light after irradiation with UV irradiation for 3 h. Besides, the pH value makes no significant changes for fluorescence emission wavelength of CQDs and CQDs can emit strongest fluorescence in weak acid solution. Furthermore, CQDs could be internalized by cells and show great cell dyeing performance and low cytotoxicity. All these features imply that TA functionalized CQDs possess great potential for biological imaging. The one-step thiol-ene click strategy provided a novel tool to prepare functionalized CQDs with great potential for biomedical applications.

Facile preparation of fluorescent nanodiamond based polymer nanoparticles via ring-opening polymerization and their biological imaging.

Fluorescent nanodiamond (ND) has been regarded as one of the most promising fluorescent nanoprobes owing to their chemical inert, biocompatibility, optical properties, and rich surface chemistry. The fluorescent ND has been mainly fabricated through high-energy ion beam irradiation of type Ib diamonds and subsequent thermal annealing. The generation of nitrogen-vacancy centers is the reason for the fluorescence. However, the physical method is relatively complicated and it need to expensive equipment as well as high cost. On the other hand, the resultant fluorescent ND particles are lack of functional groups and difficult to be dispersed in aqueous solution. Therefore, the development of facile methods to direct preparation of fluorescent ND and surface modification with functional polymers is of great research interest for expanding the biomedical applications of fluorescent ND. In this report, a facile strategy was reported for the first time to prepare hydrophilic polymers functionalized fluorescent ND (named as ND-PhE-PETOx) composites through the ring-opening polymerization and simultaneous simple nucleophilic substitution reaction using the non-fluorescent detonation ND as the raw material. The obtained fluorescent ND composites were characterized by various characterization techniques in details. The as-obtained ND-PhE-PETOx composites exhibit high water dispersibility, low toxicity and strong fluorescence intensity. Cell uptake results indicating that the fluorescent ND based composites can be effectively internalized by cells. Taken together, we have developed a novel and simple method for the preparation of fluorescent ND based composites, which show excellent physicochemical properties and great potential for biomedical applications.

Recent development and prospects of surface modification and biomedical applications of MXenes.

MXenes, as a novel kind of two-dimensional (2D) materials, were first discovered by Gogotsi et al. in 2011. Owing to their multifarious chemical compositions and outstanding physicochemical properties, the novel types of 2D materials have attracted intensive research interest for potential applications in various fields such as energy storage and conversion, environmental remediation, catalysis, and biomedicine. Although many achievements have been made in recent years, there still remains a lack of reviews to summarize these recent advances of MXenes, especially in biomedical fields. Understanding the current status of surface modification, biomedical applications and toxicity of MXenes and related materials will give some inspiration to the development of novel methods for the preparation of multifunctional MXene-based materials and promote the practical biomedical applications of MXenes and related materials. In this review, we present the recent developments in the surface modification of MXenes and the biomedical applications of MXene-based materials. In the first section, some typical surface modification strategies were introduced and the related issues were also discussed. Then, the potential biomedical applications (such as biosensor, biological imaging, photothermal therapy, drug delivery, theranostic nanoplatforms, and antibacterial agents) of MXenes and related materials were summarized and highlighted in the following sections. In the last section, the toxicity and biocompatibility of MXenes in vitro were mentioned. Finally, the development, future directions and challenges about the surface modification of MXene-based materials for biomedical applications were discussed. We believe that this review article will attract great interest from the scientists in materials, chemistry, biomedicine and related fields and promote the development of MXenes and related materials for biomedical applications.

Efficient Near-Infrared Photosensitizer with Aggregation-Induced Emission for Imaging-Guided Photodynamic Therapy in Multiple Xenograft Tumor Models.

Photodynamic therapy (PDT) strategy has been widely used in tumor treatment, and the reagents for reactive oxygen species (ROS) play a crucial role. Herein, we develop a fluorogen (TTB) containing an electron-accepting benzo[1,2-b:4,5-b']dithiophene 1,1,5,5-tetraoxide core and electron-donating 4,4'-(2,2-diphenylethene-1,1-diyl)bis(N,N-diphenylaniline) groups for image-guided targeting PDT application. TTB exhibits a prominent aggregation-induced emission (AIE) property with strong near-infrared (NIR) fluorescence in aggregates and is capable of efficiently generating ROS of O2•- and 1O2 under white light irradiation. The nanoparticles (RGD-4R-MPD/TTB NPs) with NIR emission (∼730 nm), high photostability, and low dark cytotoxicity are fabricated by encapsulating TTB within polymeric matrix and then modified with RGD-4R peptide. They show excellent performance in targeting PDT treatment of PC3, HeLa, and SKOV-3 cancer cells in vitro. The investigations on pharmacokinetics, biodistribution, and long-term tracing in vivo reveal that RGD-4R-MPD/TTB NPs can selectively accumulate in tumors for real-time, long-term image-guided PDT treatment. The RGD-4R-MPD/TTB NPs-mediated PDT in multiple xenograft tumor models disclose that the growth of cervical, prostate, and ovarian cancers in mice can be effectively inhibited. These results demonstrate that the reagents employing NIR fluorogen TTB as a photosensitizer could be promising candidates for in vivo image-guided PDT treatments of tumors.

A novel strategy for fabrication of fluorescent hydroxyapatite based polymer composites through the combination of surface ligand exchange and self-catalyzed ATRP.

A novel and facile strategy that combination of surface ligand exchange and photo-initiated atom transfer radical polymerization (ATRP) has been developed for the preparation of fluorescent hydroxyapatite (HAp) based polymer composites, which were utilized for biological imaging applications. In particular, the photo-initiated ATRP not only inherited advantages of traditional ATRP but also overcome its deficiencies such as high energy consumption, transition metal contamination and long reaction time. In this method, a hydrophilic and biocompatible PEGMA was introduced to enhance the hydrophilic and biocompatibility of HAp nanocomposites. Simultaneously, the HAp-poly(PEGMA-co-AcFl) composites are endowed with bright green fluorescence by grafting with AcFl on the surface via copolymerization. The physicochemical properties of HAp-poly(PEGMA-co-AcFl) composites were characterized by a series of methods in detail. Results confirmed that HAp-poly(PEGMA-co-AcFl) composites possess controlled size and morphology, high water dispersibility and strong fluorescence. The cell viability and cell uptake behavior demonstrated that HAp-poly(PEGMA-co-AcFl) composites present low toxicity and can be potentially used for biological imaging. Taken together, we have developed a facile and efficient method for the fabrication of fluorescent HAp composites with desirable physicochemical and biological properties.

AIE-active self-assemblies from a catalyst-free thiol-yne click reaction and their utilization for biological imaging.

Aggregation-induced emission (AIE) should be the most interest fluorescent phenomenon over the past few decades. The luminescence polymeric nanoparticles (LPNs) with AIE characteristic have attracted great research attention for biological imaging and many other biomedical applications owing to their good biocompatibility and negative toxicity. However, the preparation of LPNs with desirable optical properties using traditional organic dyes still remains a great challenge for the aggregation-caused quenching (ACQ) effect and aggregation of hydrophobic dyes in the core of LPNs. In this work, we reported a novel and simple method for fabrication of biodegradable AIE-active LPNs via the combination of condensation and click reactions. For preparation of these AIE-active LPNs, the thiol groups-containing hydrophilic copolymers (PEG-MA) were first synthesized through the condensation reaction between polyethylene glycol and mercaptosuccinic acid. The PEG-MA copolymers were further reacted with AIE dye PhE-OE through a catalyst-free thiol-yne click reaction. These obtained PEG-MA-PhE LPNs were fully characterized by a number of characterization techniques. All the results confirmed that PEG-MA-PhE LPNs possess excellent compatibility, intense red luminescence, great photostability and high water dispersibility. These features make PEG-MA-PhE LPNs promising candidates for various biomedical applications.

Facile fabrication of luminescent hyaluronic acid with aggregation-induced emission through formation of dynamic bonds and their theranostic applications.

Aggregation-induced emission (AIE) is an abnormal phenomenon, which has been extensively explored for various applications. Taken advantage of the unique AIE feature, a number of luminescent nanoprobes with strong fluorescence intensity could thus be fabricated through different strategies; however, the fabrication of AIE-active carbohydrate polymers is still challenge owing to the poor solubility of carbohydrate polymers in most of organic solvents. In this work, a rather facile strategy has been developed for fabricating AIE-active sodium hyaluronate (Sh) through the formation of dynamic phenyl borate between the phenylboronic acid groups of AIE dye (An-B(OH)2)) and Sh in a "one-pot" route. This reaction could occur under low temperature, air atmosphere and in the present water. The physicochemical properties, biocompatibility, biological imaging and drug delivery performance of the final An-Sh fluorescent organic nanoparticles (FNPs) were confirmed by different characterization techniques. Results suggested that An-Sh FNPs possess high water dispersibility, strong fluorescence, and good biocompatibility. These excellent properties make An-Sh FNPs great potential for biological imaging and controlled drug delivery applications. In conclusion, we have developed a facile one-pot strategy for the preparation of AIE-active FNPs through the formation of dynamic bonds in rather mild experimental conditions. The outstanding properties and performance of An-Sh FNPs make them promising candidates for biological imaging and controlled drug delivery applications.

Fabrication and characterization of hyperbranched polyglycerol modified carbon nanotubes through the host-guest interactions.

Carbon nanotubes (CNTs) are novel carbon composites that have received extensive research attention for biomedical applications thanks to their excellent cell membrane penetration capability and large specific surface areas. Nevertheless, the poor dispersibility in aqueous solution still perplexes the biomedical applications of CNTs. Although, there are many researched about that modify hydrophilic polymers to the surface of CNTs, facile and efficient strategies are still highly desirable to be developed. In this produce, an efficient and facile strategy for surface modification of CNTs with excellent water dispersibility was developed via supramolecular chemistry. On the one hand, we synthesize the ß-CD-HPG via anionic polymerization. On the other hand, adamantane chloride was first reacted with the hydroxyl group of radiant CNTs through esterification to obtain CNT-Ad. Finally, it only need mild reaction conditions and fast reaction time (30 min) that ß-CD-HPG form an exact 1:1 inclusion complex with CNT-Ad via host-guest interaction. The successful preparation of CNT-ß-CD-HPG composites could be confirmed via a series of characterization techniques. Then, we further verify that CNT-ß-CD-HPG composites possess the remarkable water dispersibility and enormous potential for controlled drug delivery systems. Therefore the facile strategy for the preparation of CNT-ß-CD-HPG composites with excellent water dispersibility via supramolecular chemistry would possess rosy prospects in biomedical applications.

Preparation of water dispersible and biocompatible nanodiamond-poly(amino acid) composites through the ring-opening polymerization.

Nanodiamond (ND) is one of the most fascinating carbon materials that have been extensively investigated for biomedical applications owing to its small size, high specific surface areas, chemical inert and desirable biocompatibility. It has been reported that surface modification of ND with polymers could not only improve the dispersibility of final ND based composites but also endow them novel functions to fulfill the requirement for biomedical applications. Although some strategies have been developed previously, surface modification of ND with poly(amino acid)s has not been reported previously. In this work, poly(amino acid)s functionalized ND composites were fabricated through a ring-opening polymerization of α-amino acid N-carboxyanhydrides (NCAs), which was synthesized by conjugation of hydrophilic ethylene glycol with glutamic acid. The successful preparation of ND-GluEG composites was confirmed by a series of characterization techniques. The results suggest that the water dispersibility of final ND-GluEG composites is obviously improved. Moreover, ND-GluEG composites show low toxicity and are of great potential for biomedical applications.

Synthesis and biological imaging of cross-linked fluorescent polymeric nanoparticles with aggregation-induced emission characteristics based on the combination of RAFT polymerization and the Biginelli reaction.

Fluorescent probes have long been regarded as tools for imaging living organisms with advantages such as high sensitivity, good designability and multifunctional potential. Many fluorescent probes, especially the probes based on aggregation-induced emission (AIE) dyes, have received increasing attention since the AIE phenomenon was discovered. These AIE dye-based fluorescent probes could elegantly overcome the notorious quenching effect caused by aggregation of conventional organic dyes. However, it is still difficult to directly apply these AIE-active dyes for biomedical applications owing to their hydrophobic nature. Therefore, the development of novel and facile strategies to endow them with water dispersibility is of critical importance. In this work, we exploit an efficient and simple strategy to fabricate an AIE dye-based fluorescent copolymer through the combination of reversible addition-fragmentation chain transfer and the Biginelli reaction. Moreover, the copolymer can self-assemble to fluorescent polymeric nanoparticles (FPNs) in water solution. Hydrophilic poly(PEGMA-co-AEMA) was reacted with the AIE-active dye 4',4‴-(1,2-diphenylethene-1,2-diyl)bis([1,1'-biphenyl]-4-carbaldehyde (CHO-TPE-CHO) to form amphiphilic luminescent polymers using urea as the connection bridge. The successful synthesis of the final products (poly(PEGMA-co-AEMA-TPE) FPNs) was confirmed by various instruments. Furthermore, Transmission electron microscopy (TEM) images manifest that poly(PEGMA-co-AEMA-TPE) copolymers will self-assemble into spherical nanoparticles in aqueous environments with sizes between 100 nm and 200 nm. The cell uptake and bioimaging experiment confirm that poly(PEGMA-co-AEMA-TPE) FPNs have excellent biocompatibility and emit strong green fluorescence in a cellular environment. Thus, poly(PEGMA-co-AEMA-TPE) FPNs are excellent candidates for biomedical applications.

Facile fabrication of organic dyed polymer nanoparticles with aggregation-induced emission using an ultrasound-assisted multicomponent reaction and their biological imaging.

Ultrasound as a powerful technique has increasingly been used in both industry and academia in recent years. Herein, an efficient approach to the ultrafast preparation of cross-linked fluorescent copolymers (PEGMA-AEMA-TPE) with aggregation-induced emission (AIE) via an ultrasound-assisted multicomponent reaction (MCR) is described. A number of characterization techniques were carried out to certify the successful preparation of these AIE-active copolymers. Due to the introduction of a hydrophilic PEG fragment and a hydrophobic AIE-active dye, the obtained fluorescent copolymers showed amphiphilic properties and could assemble into organic dyed polymer nanoparticles (ODPNs) with great water dispersibility. The final PEGMA-AEMA-TPE ODPNs demonstrated intense fluorescence, strong photostability, a low critical micelle concentration (CMC) of 0.007 mg mL-1 and high biocompatibility. More importantly, the PEGMA-AEMA-TPE ODPNs show obvious AIE characteristics, which could elegantly overcome the quenching effect caused by the aggregation of ODPNs based on conventional organic dyes. Considered the above results, we believe that these AIE-active ODPNs should be promising candidates for biological imaging and other biomedical applications.