Construction of cellulose-based hybrid hydrogel beads containing carbon dots and their high performance in the adsorption and detection of mercury ions in water.

Cellulose-based adsorbents have been extensively developed in heavy metal capture and wastewater treatment. However, most of the reported powder adsorbents suffer from the difficulties in recycling due to their small sizes and limitations in detecting the targets for the lack of sensitive sensor moieties in the structure. Accordingly, carbon dots (CDs) were proposed to be encapsulated in cellulosic hydrogel beads to realize the simultaneous detection and adsorption of Hg (II) in water due to their excellent fluorescence sensing performance. Besides, the molding of cellulose was beneficial to its recycling and further reduced the potential environmental risk generated by secondary pollution caused by adsorbent decomposition. In addition, the detection limit of the hydrogel beads towards Hg (II) reached as low as 8.8 × 10-8 M, which was below the mercury effluent standard declared by WHO, exhibiting excellent practicability in Hg (II) detection and water treatment. The maximum adsorption capacity of CB-50 % for Hg (II) was 290.70 mg/g. Moreover, the adsorbent materials also had preeminent stability that the hydrogel beads could maintain sensitive and selective sensing performance towards Hg (II) after 2 months of storage. Additionally, only 3.3% of the CDs leaked out after 2 weeks of immersion in water, ensuring the accuracy of Hg (II) evaluation. Notably, the adsorbent retained over 80% of its original adsorption capacity after five consecutive regeneration cycles, underscoring its robustness and potential for sustainable environmental applications.

PEGylated AIEgens for dual sensing of ATP and H2S and cancer cells photodynamic therapy.

Fluorescent sensors have been widely applied for biosensing, but probes for both multiple analytes sensing and photodynamic therapy (PDT) effect are less reported. In this article, we reported three AIE-based probes anchored with different mass-weight polyethylene glycol (PEG) tails, i.e., TPE-PEG160, TPE-PEG350, and TPE-PEG750, for both adenosine-5'-triphosphate (ATP) and hydrogen sulfide (H2S) detection and also cancer cells photodynamic therapy. TPE-PEGns (n = 160, 350 and 750) contain the tetraphenylethylene-based fluorophore core, the pyridinium and amide anion binding sites, the H2S cleavable disulfide bond, and the hydrophilic PEG chain. They exhibit a good amphiphilic property and can self-assemble nona-aggregation with a moderated red emission in an aqueous solution. Importantly, the size of aggregation, photophysical property, sensing ability and photosensitivity of these amphiphilic probes can be controlled by tuning the PEG chain length. Moreover, the selected probe TPE-PEG160 has been successfully used to detect environmental H2S and image ATP levels in living cells, and TPE-PEG750 has been used for photodynamic therapy of tumor cells under light irradiation.

Bis-Schiff base cellulosic nanocrystals for Hg (II) removal from aqueous solution with high adsorptive capacity and sensitive fluorescent response.

Mercury pollution in aqueous solutions is a severe problem in environmental protection and the contaminated water may cause serious risks to human health. Based on the constant development of adsorptive materials, adsorption technique is widely applied as an efficient and convenient approach to eliminate mercury species from waters. In this work, we report a one-pot procedure to prepare a bis-Schiff base cellulosic adsorbent to integrate the advantages of large adsorptive capacity and excellent fluorescent recognition towards mercury ions. The adsorption experiments demonstrate that sulfydryl-contained cellulosic nanocrystals exhibit specific affinity with mercury species and the adsorption capacity reaches as high as 624.8 mg/g at room temperature. Besides, the introduction of rhodamine moiety endows the material a 19 times enhancement of selective "off-on" fluorescent sensing while exposed to mercury. Additionally, the bifunctional adsorbent material shows high sensitivity towards mercury ions in aqueous solution with detection limits of as low as 8.29 × 10-8 M for fluorescence and 5.9 × 10-9 M for UV-vis spectrum, respectively. The fitting results of the adsorption models indicate a monolayer adsorption during the uptake of mercury ions and the removal process follows the pseudo-second order kinetics. Moreover, density functional theory studies are employed to further understand the adsorptive and responsive mechanisms.

A GSH-activated AIE-based polymer photosensitizer for killing cancer cells.

Developing efficient photosensitizers which are sensitive to therapeutic tumor signals, but non-toxic to normal cells has always been a tremendous challenge in photodynamic therapy (PDT) process. Herein, a novel copolymer P1 was developed by ring-opening metathesis polymerization (ROMP) with disulfide bond linked ferrocene-norbornene dyad NB-SS-PyFc and the aggregation-induced emission (AIE) fluorephore anchored norbornene NB-TPE, and its nanoparticles (NPs) were obtained by using the amphiphilic Pluronic F-127 as the surfactant via a nanoprecipitation method. The P1 NPs show a weak emission and a low 1O2 generation for the quenching effect from the ferrocene moiety to the AIE group. However, the addition of GSH can recover the AIE fluorephore emission and 1O2 generation for cleavage the disulfide bond. Importantly, P1 NPs have been used for image-guided cancer cells apoptosis for the GSH activated 1O2 generation.

Dansyl-labelled cellulose as dual-functional adsorbents for elimination and detection of mercury in aqueous solution via aggregation-induced emission.

Dansyl chloride fluorophore exhibits typical aggregation induced fluorescence emission behavior in acetone/water solution. To realize the integration of detective and adsorptive functions, dansyl chloride is covalently immobilized on cellulose substrate to fabricate an efficient adsorbent for mercury ions in water. The as-prepared material exhibits excellent fluorescence sensing performance exclusively for Hg (II) with the presence of other metal ions. A sensitive and selective fluorescence quenching across the concentration range of 0.1-8.0 mg/L is observed with a detection limit of 8.33 × 10-9 M as a result of the inhibition of aggregation induced emission caused by the coordination between adsorbent and Hg (II). Besides, the adsorption properties for Hg (II) including the influence of initial concentration and contact time are investigated. Langmuir model and pseudo-second-order kinetics are demonstrated to fit well with the adsorption experiment for the uptake of Hg (II) by the functionalized adsorbent, also, intraparticle diffusion kinetic model is proved to aptly describe the Hg (II) removal in aqueous solution. In addition, the recognition mechanism is considered to originate from the Hg (II) triggered structural reversals of naphthalene ring units which are verified by the X-ray photoelectron spectroscopy and density functional theory calculation. Moreover, the synthesis method used in this work also provides a strategy for the sensing application of organic sensor molecules with AIE properties in which the aggregated behavior could be appropriately realized.

Direct grafting of cellulose nanocrystals with poly(ionic liquids) via Gamma-ray irradiation and their utilization for adsorptive removal of CR.

In this work, a simple but effective method based on Gamma-ray initiated polymerization was reported for the first time through direct irradiation of CNCs and ionic liquid monomer to obtain poly (ionic liquids) functionalized CNCs (IL@CNCs). The adsorptive removal of Congo red (CR) from aqueous solution by IL@CNCs was also examined and the influence of contact time, pH values, initial concentrations and temperature on adsorption behavior was investigated in detail. Under the same adsorption conditions, the adsorption capacity was increased from 59.72 mg/g (CNCs) to 195.83 mg/g (IL@CNCs). The results of the adsorption isotherm and adsorption kinetics showed that the experimental data were more suitable to be described by the Freundlich isotherm adsorption model and the pseudo-second-order model. The adsorption process of CR on the surface of the adsorbent was endothermic and spontaneous. When the aqueous solution was acidic, it was more conducive to the adsorption of CR. At 100% breakthrough, the value of adsorption capacity is 199.95 mg/g and the value of partition coefficient is 9.64. Moreover, the adsorption capacity is expected to be further improved through adjustment of polymerization parameters and this method can also be used for preparation other poly (ionic liquids) modified composites.

Aminoquinoline-anchored polynorbornene for sequential fluorescent sensing of Zn2+ and ATP.

A novel aminoquinoline functionalized norbornene (1) and its ring-opening metathesis polymerization (ROMP) copolymer P1 have been designed and synthesized. The polymer probe P1 can self-assemble nano aggregation in aqueous solution. The fluorescent experiments revealed that both 1 and P1 show a ratiometric fluorescence response toward Zn2+ over other mental ions in Tris-HCl buffer solution, with the polymer probe P1 shows a better photostability and higher binding affinity than that of the small molecular probe 1. Furthermore, the in situ formed P1-Zn2+ ensemble was successfully used as the secondary sensor for ATP. P1 is also successfully used for monitoring intracellular Zn2+ and ATP in living cells.

Pyridinium-conjugated polynorbornenes for nanomolar ATP sensing using an indicator displacement assay and a PET strategy.

An indicator displacement assay, namely polymeric PNPY-n/UD consisting of a cationic polynorbornene backbone with pyridinium functional groups (PNPY-1,2,3) and an anionic uranine dye (UD) as an indicator, has been developed for highly sensitive "turn-on" fluorescence sensing of ATP. While PNPY-1/UD itself is non-emissive, a bright green fluorescence signal was observed in the presence of ATP [Ka = 2.17 × 105 M-1, LOD = 5.7 nM]. The potential of a highly photostable system PNPY-1/UD was also validated in detecting ATP levels in live-cell imaging applications.

AIE based GSH activatable photosensitizer for imaging-guided photodynamic therapy.

A novel ferrocene decorated vinyl pyridinium-substituted tetraphenylethylene (TPEPY-S-Fc) linked by a disulfide bond was designed as a GSH activatable photosensitizer by aggregation-induced emission for imaging-guided photodynamic therapy of cancer cells.

Nanomolar detection of adenosine triphosphate (ATP) using a nanostructured fluorescent chemosensing ensemble.

We report a novel nanostructured chemosensing ensemble PyNp-C13/UD, obtained by self-assembling uranine dye (UD) and an amphiphilic pyridinium salt PyNp-C13. The ensemble was developed for the fluorescence turn-on sensing of ATP in aqueous solutions and inside living cells. The assembly operates via an indicator displacement assay (IDA) method with an ultra-low detection limit of 6.8 nM.

Fluorescence-sensitive adsorbent based on cellulose using for mercury detection and removal from aqueous solution with selective "on-off" response.

A new fluorogenic bio-adsorbent was successfully synthesized for detection and adsorption of mercury ions in aqueous solution. It showed high sensitivity in removing Hg (II) at low concentration with a detection limit of 84 ppb which was below the maximum discharge standard in enterprise drain off water in China, besides, the adsorbent had good selectivity towards Hg (II) among numerous kinds of cations in water that it showed fluorescent quenching properties for Hg (II) ions due to photo-induced electron transfer. In addition, batch adsorption experiments were investigated to study the influence of initial concentration of metal ions, contact time, pH of the solution on the adsorption capacity. Equilibrium adsorption isotherms demonstrated the Hg (II) removing process fitted well with Langmuir isotherm model, and the maximum adsorption capacity for mercury was measured to be 143.88 mg/g. Furthermore, the adsorption kinetics was found to follow pseudo-second-order model. FTIR spectra and SEM-elemental mapping clearly confirmed the adsorbed heavy metal ions.

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 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.

Synthesis of fluorescent dendrimers with aggregation-induced emission features through a one-pot multi-component reaction and their utilization for biological imaging.

Hyperbranched polymers have attracted wide research attention owing to their unique topological structure, physicochemical properties and great potential for applications such asadditives, drug delivery, catalysts and nanotechnology. Among these, the polyamidoamine(PAMAM) dendrimers are some of the most important dendrimers. However, the synthesis and biomedical applications of fluorescent PAMAM dendrimers have received only limited attention. In this work, we present a rather effective and convenient approach for synthesis of fluorescent PAMAM dendrimers with aggregation-induced emission (AIE) properties through a one-pot catalyst-free Mannich reaction under rather mild experimental conditions (e.g., low reaction temperature, air atmosphere in the presence of water). The obtained AIE-active amphiphiles (PhE-PAD) could self-assemble into fluorescent organic nanoparticles (FONs). The obtained AIE-active FONs (PhE-PAD FONs) were fully characterized, and their successful construction was confirmed by 1H NMR spectroscopy, FT-IR spectroscopy and transmission electron microscopy. Fluorescence and UV-Visible absorption spectroscopy results demonstrated that the final PhE-PAD FONs showed strong yellow fluorescence, desirable photostability and good water dispersity. The cell viability evaluation and confocal laser scanning microscope imaging results suggested that PhE-PAD FONs possessed low cytotoxicity and excellent biocompatibility. Taken together, these results demonstrate that we have developed a facile and efficient strategy for the fabrication of AIE-active FONs, which possess many desirable features for biomedical applications.

Multifunctional Fluorescent Nanoprobe for Sequential Detections of Hg2+ Ions and Biothiols in Live Cells.

Herein, we report an amphiphilic fluorescent probe consisting of a dansyl fluorophore as a reporter and a hydrophobic cetyl chain bridged by a triazole unit. The cetyl-based probe can self-assemble to form nanoaggregates in aqueous solution, as confirmed by Tyndall effect, dynamic light scattering (DLS), and transmission electron microscopy (TEM) measurements. This probe exhibited an "on-off" fluorescence quenching response toward Hg2+ ions in aqueous solution over other tested metal ions. In contrast, the analogous methyl-based probe barely exhibits Hg2+ ion sensing behavior under the same conditions. Moreover, the resulting complex of the cetyl-based probe and Hg2+ (1-Hg2+, 1:1 stoichiometry) exhibited an efficient fluorescence "off-on" sensing for thiol-containing amino acids, including cysteine (Cys), homocysteine (Hcy), and glutathione (GSH). This nanoprobe exhibited minimal cytotoxicity with excellent cell permeability and was efficiently tested for the imaging of intracellular Hg2+ and cysteine in live cells.

Ultrafast microwave-assisted multicomponent tandem polymerization for rapid fabrication of AIE-active fluorescent polymeric nanoparticles and their potential utilization for biological imaging.

The fabrication and biomedical applications of fluorescent polymeric nanoparticles (FPNs) with aggregation-induced emission (AIE) feature has attracted the most intensive research interest since the first discovery of AIE phenomenon by Tang' group. Although great attention has been devoted to preparation of AIE-active FPNs, an efficient, facile and versatile strategy is still highly desirable to advance their biomedical applications. In this work, a one-pot microwave-assisted multicomponent tandem polymerization was proposed to fabricate AIE-active FPNs based on a microwave-assisted Kabachnik-Fields (KF) reaction, which involves the conjugation of aldehyde group containing polyethylene glycol (CHO-PEG-CHO) and amino-group terminating AIE dye (H2N-PhE-NH2) using diethyl phosphate as the lock. The KF reaction can occur under rather facile and mild experimental conditions (e.g. absent of catalyst and solvents, air atmosphere) with the assistance of microwave irradiation in 5min. The resultant (PEG-DP-PhE) copolymers would self-assemble into FPNs that showed high water dispersibility and enhanced fluorescence intensity. The desirable cytocompatibility and cell uptake efficiency of PEG-DP-PhE FPNs endow their great potential for biomedical applications. Considering the convenience and effectiveness, the method should be promising for fabrication of many AIE-active functional materials with great application potential.

Preparation of AIE-active fluorescent polymeric nanoparticles through a catalyst-free thiol-yne click reaction for bioimaging applications.

Fluorescent polymeric nanoparticles (FPNs) with aggregation-induced emission (AIE) characteristics have attracted much attention for biomedical applications due to their remarkable AIE feature, high water dispersity and desirable biocompatibility. The development of facile and effective strategies for fabrication of these AIE-active FPNs therefore should be of great importance for their biomedical applications. In this work, we reported that a catalyst-free thiol-yne click reaction can be utilized for fabrication of AIE-active FPNs in short reaction time and even without protection of inert gas. The results indicated that the obtained AIE-active amphiphilic copolymers (PEGMA-PhE) can readily self-assemble into luminescent nanoparticles (PEGMA-PhE FPNs) with high water dispersity, uniform size and morphology, red fluorescence. Cell viability examination and cell uptake behavior of PEGMA-PhE FPNs confirmed that these AIE-active FPNs possess low toxicity towards cells and can be easily internalized by cells through non-specific route. Therefore the remarkable properties of PEGMA-PhE FPNs such as high water dispersity, AIE-active fluorescence and nanoscale size as well as excellent biocompatibility make them promising for biomedical applications.

Microwave-assisted multicomponent reactions for rapid synthesis of AIE-active fluorescent polymeric nanoparticles by post-polymerization method.

The development of simple and effective methods for synthesis of fluorescent polymeric nanoparticles (FPNs) with aggregation-induced emission (AIE) plays an important role for the biomedical applications of AIE-active FPNs. In present work, we developed a facile strategy for the fabrication of AIE-active FPNs by a post-polymerization method based on the microwave-assisted Kabachnik-Fields (KF) reaction, which can conjugate with poly(PEGMA-NH2), AIE-active dye (TPE-CHO) and diethyl phosphate (DP) under microwave irradiation within 5min. The characterization results confirm that PEGMA-TPE FPNs are successfully prepared through the microwave-assisted KF reaction. The resultant AIE-active FPNs show high water dispersity, intensive fluorescence and low cytotoxicity. These features make these AIE-active FPNs great potential for biomedical applications. Moreover, the microwave-assisted KF reaction is simple, fast, atom economy that should be a general strategy for the fabrication of various multifunctional AIE-active FPNs. We believe this work will open up a new avenue for the preparation of AIE-active functional materials with great potential for different applications.

Facile fabrication of luminescent polymeric nanoparticles containing dynamic linkages via a one-pot multicomponent reaction: Synthesis, aggregation-induced emission and biological imaging.

Luminescent polymeric nanoparticles (LPNs) with aggregation-induced emission (AIE) feature have emerged as the most promising candidates for biological imaging owing to their unique AIE feature, great water dispersity, strong fluorescence, low cytotoxicity and biocompatibility. Although numerous successful strategies for construction of AIE-active LPNs have been developed, the preparation of dynamic linkages containing AIE-active LPNs based on multicomponent reactions has been rarely reported. In this work, we report a facile method for the formation of AIE-active LPNs via a one-pot conjugation of PEG-B(OH)2, 1-thioglycerol and AIE-active dye PhE-alc in short time under rather mild reaction conditions (e.g. ambient temperature, air atmosphere, absent of metal catalysts and in the present of water). The successful formation of AIE-active mPEG-PhE LPNs was confirmed by different characterization techniques in details. The great optical and biological properties certified their applicable for biological imaging application. More importantly, the novel method for the formation of AIE-active LPNs is rather simple, high efficiency and atom economy, which greatly enriched their practical biomedical applications.

A facile one-pot Mannich reaction for the construction of fluorescent polymeric nanoparticles with aggregation-induced emission feature and their biological imaging.

Multicomponent reactions (MCRs) have recently attracted great attention as one of the most important tools for the construction of various organic compounds in modern organic chemistry. In this work, we introduced an efficient one-pot strategy to successfully fabricate the fluorescent polymeric nanoparticles (FPNs) with aggregation-induced emission (AIE) characteristic via the conjugation of hyperbranched polyamino compound polyethyleneimine (PEI), AIE dye (named as PhE-OH) and paraformaldehyde (PF) through a Mannich reaction. The final amphiphilies (PEI-PF-PhE) can self-assemble into micelles in aqueous solution. We demonstrated PEI-PF-PhE FPNs showed high water dispersity, intense orange-yellow fluorescence, excellent photostability, low toxicity and high cell imaging performance. As compared with other construction strategies, the one-pot Mannich reaction possesses a number of advantages, such as simplicity, atom economy, high-efficiency and multifunctional potential. Combined with the remarkable properties of the AIE-active FPNs and the one-pot Mannich reaction, we could expect that the strategy developed in this work should be a useful tool for construction of various AIE-active functional materials for biomedical applications.