Novel Strategy toward AIE-Active Fluorescent Polymeric Nanoparticles

Research Article Cite This: ACS Sustainable Chem. Eng. 2017, 5, 9955-9964

pubs.acs.org/journal/ascecg

Novel Strategy toward AIE-Active Fluorescent Polymeric Nanoparticles from Polysaccharides: Preparation and Cell Imaging Qing Wan,†,∥ Ruming Jiang,†,∥ Lili Guo,‡ Shengxian Yu,† Meiying Liu,† Jianwen Tian,† Guoqiang Liu,§ Fengjie Deng,† Xiaoyong Zhang,*,† and Yen Wei*,§ †

Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031, China Department of Physiology, Medical School of Nanchang University, Nanchang 330006, P. R. China § Department of Chemistry and the Tsinghua Center for Frontier Polymer Research, Tsinghua University, Beijing, 100084, P. R. China ‡

S Supporting Information *

ABSTRACT: Fluorescent polymeric nanoparticles (FPNs) as novel theranostic agents for cancer diagnosis and treatment have been widely investigated in recent years. However, most FPNs were constructed with typical inorganic quantum dots, fluorescent proteins, and conventional organic dyes, which have still suffered from many obstacles such as serious cytotoxicity, easy enzymolysis, and vicious aggregation-caused fluorescence quenching (ACQ). Herein, to overcome these problems, we design and synthesize novel FPNs with a unique aggregation-induced emission (AIE) feature using resourceful and cost-effective oxidized sodium alginate (OSA) as natural polymer protected shells of FPNs. Moreover, differing from commercial or synthetic polymers such as PEG, BSA, and lecithin, sodium alginate from marine seaweeds is a cheaper, abundant source and excellent has biocompatibility. Thus-prepared AIE-active OSA-Phe-OSA FPNs by the facile Schiff base condensation have many advantages, such as strong fluorescence, great water dispersity, excellent photostability and desirable biocompatibility, and stained performance. These features endow them great potential for various biomedical applications. KEYWORDS: Aggregation-induced emission, Carbohydrate polymers, Fluorescent polymeric nanoparticles, Biomedical applications

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INTRODUCTION The biological imaging techniques have been extensively explored for cancer diagnosis and therapy applications over the past several decades.1−4 Biological imaging techniques, such as X-ray imaging,5 magnetic resonance imaging,6,7 radionuclide imaging,8,9 computed tomography,10 and fluorescent imaging,11−13 have been used for these purposes. Among these techniques, fluorescent imaging has received increasing attention and been widely developed because of its obvious advantages of easy operation, high sensitivity and selectivity, and satisfying visualization. Up to now, the appeared fluorescent materials for various biomedical applications were majorly divided into inorganic fluorescent nanomterials (semiconductor quantum dots,14−17 carbon dots,18−20 Ln ion doped nanomaterials, 21−23 silicon quantum dots, and metallic clusters),24−29 fluorescent proteins,30−32 and conventional organic dyes (perylene, fluorescein, and rhodamine).33−36 However, it is regrettable that the inherent drawbacks of inorganic quantum dots such as relatively difficult preparation, potential toxicity, poor biodegradability, and difficult surface modification limit their promising potential in biomedical applications. As another powerful tool of bioprobes, fluorescent proteins were often limited in their employment due to their © 2017 American Chemical Society

high cost, low molar absorptivity, easy enzymolysis, and low photobleaching thresholds. On the other hand, conventional organic dyes have been deemed as a class of ideal luminescent agents, which have been extensively used in biological imaging, target tracing, and cancer diagnosis. Unfortunately, because most conventional organic dyes were constructed by abundant hydrophobic aromatic rings, which are usually in the same plane, this results in the intramolecular accumulation by the π−π interaction when in the states of aggregated or high concentrations. This intramolecular accumulation behavior of fluorescent organic dyes leads to the luminescence quenching effect due to the fact that the energy from the excited state to the ground state emits by a way of nonradiative channel. This common phenomenon of conventional dyes was named as the aggregation-caused quenching (ACQ) effect. In other words, conventional fluorescent dyes usually have a luminescent effect in the single molecular state, while the fluorescence quenched at aggregated state. Because of the natural hydrophobicity of conventional fluorescent dyes, they often aggregated into Received: June 13, 2017 Revised: August 31, 2017 Published: September 25, 2017 9955

DOI: 10.1021/acssuschemeng.7b01908 ACS Sustainable Chem. Eng. 2017, 5, 9955−9964

Research Article

ACS Sustainable Chemistry & Engineering nanoparticles and caused fluorescence quenching in aqueous and physiological environment. Although adopting hydrophilic polymers to encapsulate hydrophobic organic dyes to enhance their hydrophilicity, the fluorescent dyes are still aggregated in the polymeric micelles, causing luminescence quenching. Reducing concentrations of organic dyes in polymeric micelles could reduce the ACQ effect; however, the fluorescence intensity was also decreased. This would influence their sensitivity and visualization in vivo. Therefore, discovering a novel fluorescent agent to overcome the aforementioned disadvantages from conventional fluorophores is extremely urgent. Aggregation-induced emission phenomenon (AIE) is exactly opposite to the ACQ effect. The AIE-active organic molecules will emit strong fluorescence in the aggregated or solid state but weak or nonfluorescence in the single molecular state.37−41 Since the first report by Tang et al. in 2001,42 more and more endeavors have been devoted to designing and synthesizing novel fluorescent small molecules with unique AIE performance. For this reason, according to the statement by Thomson Reuters in 2015, the synthesis of AIE fluorophores and AIEbased materials in biomedical applications have become one of the research hotspots in top two chemistry frontier fields. AIEactive functional polymeric materials have shown great potential in the research fields of chem/biosensors,43−45 biomedical applications,37,46−57 and optoelectronic devices.58−64 Thanks to the unique AIE features, many research works focus on the design and synthesis of various AIEgens with specific performances such as near-infrared emission wavelength,65,66 target label,67,68 and photodynamic therapy.69−71 However, these synthetic functional AIEgens have bad solubility or dispersity in aqueous and physiological solution, which hinder their biological applications. Aiming at the water-soluble problem of AIEgens, many efforts have been made to resolve it. For example, modifying the ionic groups in AIEgens to enhance their water solubility is effective, but these synthetic AIEgens containing positive charges are toxic to normal cells.72,73 Another method is adopting amphiphilic polymers to encapsulate AIEgens to form AIE dye doped fluorescent polymeric nanoparticles (FPNs), which can effectively avoid injuries for normal cells because of the great biocompatibility and low cytotoxicity of FPNs. However, these FPNs were easily decomposed by existed degrading enzymes in vivo, which would bring about fast leakage of AIEgens from FPNs before arriving to the targeted position in the human body. Considering these problems, fabrication of AIE-active FPNs with great stability is extremely important. Many covalent fabricated strategies of AIE-active FPNs, such as chemical postmodification,54,74 emulsion polymerization,75 RAFT polymerization,76−78 and ring-opening polymerization,79,80 have been reported in recent years. Thus-prepared AIE-active FPNs possess many merits containing great stability and hydrophilicity, excellent biocompatibility, and stained performance for living cells. Nevertheless, the amphiphilic polymers used in previous works are of high cost and difficult synthesis, and the experimental conditions are rigorous (oxygen-free, water-free, and high temperature). Therefore, the preparation of AIEactive FPNs with a simple operation procedure using low cost and abundant natural polymers is still desirable in the future. In this contribution, we prepare AIE-active FPNs (OSA-PheOSA) with red emission, excellent photostability, and biocompatibility for living cells using oxidized sodium alginate (OSA) as polymer protected shells and synthetic AIEgen (Phe-

NH2) as a luminescent core by a facile Schiff base condensation method (Scheme 1). Sodium alginate (SA) is a resourceful, low Scheme 1. Synthesis of OSA and OSA-Phe-OSA Polymers

cost, nontoxic, and natural polysaccharide with a number of negative carboxyl groups.81−84 It can be extracted from brown seaweed and has been regarded as safe by the Food and Drug Administration. The SA has been extensively used for fabrication of different functional materials with great interest for various applications, including emulsifiers for food additives, formation of hydrogel, and indigestion tablets for biological active components.85−87 However, original SA is not well soluble in aqueous solution, to improve its water solubility, the SA can be oxidized by sodium periodate to introduce aldehyde and carboxyl groups, in which the aldehyde group could react with the amino group and form a Schiff base, while the carboxyl group could enhance its water solubility and be used for carrying anticancer agents (such as cisplatin (CDDP)). Moreover, the Schiff base condensation is a facile conjugation reaction under low temperature, catalyst-free, air atmosphere and in the present of water. Combining superior of original materials and facile method, thus-prepared FPNs have extensive biomedical application value. Through investigating the biological toxicity and imaging capability of OSA-Phe-OSA FPNs for living cells, results demonstrate that OSA-Phe-OSA FPNs have great biocompatibility and strong stained performance for living cells. Based on these outstanding performances of OSAPhe-OSA FPNs, these prepared FPNs have huge potential in biomedical applications.

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EXPERIMENTAL PROCEDURES

Materials and Characterization. All agents and solvents were provided from commercial sources and used directly without further purification. The aqueous solution used in the experimental process was deionized water. Sodium periodate and sodium alginate were purchased from Aladdin company. The AIEgen (PheNH2) was synthesized from our previous work.80 1H nuclear magnetic resonance (NMR) spectra were recorded on Bruker Avance-400 spectrometer with D2O as the solvents. The synthetic materials were characterized by Fourier transform infrared spectroscopy (FT-IR) using KBr pellets. The FT-IR spectra were supplied from Nicolet5700 (Thermo Nicolet corporation). Transmission electron microscopy (TEM) images were recorded on a Hitachi 7650B microscope operated at 80 kV; the TEM specimens were obtained by putting a drop of the nanoparticle ethanol suspension on a carbon-coated copper grid. The fluorescence data were obtained from the fluorescence spectrophotometer (FSP, model C11367-11), which was purchased from Hamamatsu (Japan). The UV−visible absorption spectrum was recorded on a spectrometer (TU-1810, Persee). The size distribution of OSA-Phe-OSA FPNs in 9956


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ACS Sustainable Chemistry & Engineering

removed, and the cells were washed with phosphate buffer saline (PBS) five times. A total of 10 μL of CCK-8 dye and 100 μL of Dulbecco’s modified eagle medium (DMEM) cell culture medium were added to each well and incubated for another 3 h. Afterward, plates were analyzed using a microplate reader (VictorIII, PerkinElmer). Measurements of formazan dye absorbance were carried out at 450 nm, with the reference wavelength at 620 nm. The values were proportional to the number of live cells. The percent reduction of CCK-8 dye was compared to controls, which represented 100% CCK-8 reduction. Three replicate wells were used per microplate, and the experiment was operated for three times. Cell survival was expressed as the absorbance relative to that of untreated controls. Results are presented as mean ± standard deviation (SD). Cell Imaging Based OSA-Phe-OSA FPNs. Biological imaging of L929 cells using OSA-Phe-OSA FPNs was conducted with a confocal laser scanning microscope (CLSM) Zeiss 710 3-channel (Zeiss, Germany), as the excitation wavelength of the laser was set as 488 nm. L929 cells were cultured in a supplement with 10% heat-inactivated FBS, 2 mM glutamine, 100 U mL−1 penicillin, and 100 μg mL−1 of streptomycin. The environment of the cell culture was controlled in a humidified condition of 95% air and 5% CO2 in RPMI1640 culture medium at 37 °C. The culture medium should be updated every day to maintain the exponential growth of the cells. On the day before treatment, cells were set in a glass bottom dish with a density of 1 × 105 cells per dish. On the day of treatment, the OSA-Phe-OSA FPNs (80 μg mL−1) were incubated with cells for 3 h at 37 °C. Afterward, the cells were washed three times with PBS to remove the OSA-PheOSA FPNs and then fixed with 4% paraformaldehyde for 10 min at room temperature.

water was determined using a zeta Plus particle size analyzer (ZetaPlus, Brookhaven Instruments, Holtsville, NY). Preparation of Oxidized Sodium Alginate (OSA). The synthetic procedure of OSA with great water solubility derives from a previous method with a slight modification.88 In brief, SA (2.0 g) was dissolved in 200 mL of distilled water, and then sodium periodate (2.5 g) was added into SA solution and stirred in the dark at room temperature for 6 h. The reaction was terminated by adding ethylene glycol (3 mL) and magnetically stirred for another 1 h. Afterward, the oxidized solution was dialyzed with a dialysis bag (MWCO: 3500 Da) for 3 days with frequent distilled water. Finally, a large amount of ethanol was added to the dialyzed OSA solution to obtain a white precipitate. The white powder could be achieved after filtrating and freeze-drying. Thus-obtained pure OSA powder was stored in a low temperature environment for further application and characterizations. Preparation of AIE-Active OSA Biopolymers (OSA-Phe-OSA). The specific synthetic route of OSA-Phe-OSA is shown in Figure 1.

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RESULT AND DISCUSSION Characterization of OSA-Phe-OSA FPNs. Fluorescent nanoparticles with a unique AIE feature have promising application potentials for optical imaging and cancer diagnosis and treatment. Compared to a conventional fluorescent diagnose system, such as inorganic quantum dots, organic dyes, and fluorescent proteins, AIE-active FPNs possess a series of merits including great dispersibility in physiological solution, strong fluorescence, favorable photostability, excellent biocompatibility, and stained ability for living cells. Since the first discovery of AIE phenomenon, bioimaging applications and cancer therapeutic system based on AIEgens have acquired many achievements. This work introduces that preparation of AIE-active polysaccharide nanoparticles by a facile method. Compared with commercial biocompatible polymers such as PEG and BSA, polysaccharide SA is resourceful and low cost. More importantly, excellent cytocompatibility and abundant hydroxyl groups of OSA make synthetic OSA-Phe-OSA FPNs easy endocytosis by cells and convenient introduction of functional components such as targeted agents, proteins, anticancer drug, DNA, and RNA by the reaction with abundant hydroxyl groups. To evidence the successful preparation of AIE-active polysaccharide nanoparticles, many characterizations such as TEM, 1H NMR, DLS, FT-IR, UV−vis, and FL spectra have been conducted. Furthermore, to evaluate the biomedical application potential of OSA-Phe-OSA FPNs, cells viability evaluation and long-term imaging effects have also been carried out. As shown in Figure 2, the 1H NMR spectra of OSA and OSA-Phe-OSA samples were compared to evidence successful preparation of AIE-active biopolymers. Focusing on the OSA spectrum, the peak at 8.3 ppm was ascribed to the −CHO groups. The hydrogen atoms of the sugar moiety were located between 3.4 and 4.5 ppm. The 1H NMR signals about abundant hydroxyl group of sugar moiety were found from 4.8 to 5.6 ppm. After conjugating with PheNH2, as shown in the

Figure 1. Synthetic route of OSA and AIE-active OSA-Phe-OSA polymers. The synthetic procedure of AIE dye doped biopolymers (OSA-PheOSA) by simple and facile Schiff based condensation method was described. The OSA (300 mg) was dissolved in distilled water (5 mL), and then synthetic AIEgen PheNH2 (100 mg) in THF (5 mL) was mixed with OSA solution. The mixture was magnetically stirred at room temperature for 12 h. After that, the THF solvent was removed from mixture solution by the rotary evaporate. The fluorescent OSA biopolymers were freeze-dried to obtain red powders. Finally, the thusobtained red OSA-Phe-OSA polysaccharides were washed with THF to remove residual Phe-NH2 dyes for 5 times until the eluant become clear. The dried OSA-Phe-OSA biopolymers can be obtained after freeze-drying. On the other hand, in the procedure of removing THF from the mixture solution, these fluorescent OSA biopolymers can selfassemble into nanoparticles due to their amphiphilic property. Therefore, the morphology of the resulting OSA-Phe-OSA is spherical in size with Phe as the core and OSA as protected shells of polysaccharide nanoparticles. Cytotoxicity Evaluation of Fluorescent OSA-Phe-OSA Nanoparticles. Fluorescent nanoparticles possessed promising biomedical applications potential due to their remarkable advantages containing intense emission for convenient recognition, easy endocytosis by cells, and prolong the cycling time in blood systems. However, the ideal biomedical nanoprobes should have great biocompatibility. To evaluate the biomedical application potential of synthetic OSA-PheOSA FPNs, the cell viability of OSA-Phe-OSA FPNs with desirable red fluorescence (fluorescence quantum yield is 7%) on L929 cells was calculated by cell counting kit-8 (CCK-8) assay.89−92 Cells were put into 96-well microplates at a density of 5 × 104 cells mL−1 in 160 μL of respective media containing 10% fetal bovine serum (FBS). After cell attachment for 24 h, the OSA-Phe-OSA FPNs with different concentrations (20−100 μg mL−1) were incubated with cells for 24 h. After that, the residual FPNs existing on the outside of cells were 9957


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because of the existence of abundant −OH in most polysaccharides. After reacting with PheNH2, some new peaks first appeared in the spectrum of OSA-Phe-OSA. For instance, the peak at 2185 cm−1 was the stretching vibration of −CN, which is consistent with the −CN group of PheNH2 dye according to its IR spectrum (Figure S1). According to previous work in our group, the structure of PheNH2 contained a −CN group, while SA and OSA samples do not contain this group. In addition, some new peaks appear in the position ranging from 650 to 780 cm−1, which were ascribed to the out-of-plane blending vibration of aromatic rings. Therefore, we can confirm the successful preparation of OSA-Phe-OSA. Furthermore, a new peak at 1548 cm−1 was contributed to the stretching vibration of the CN bond. Combining analysis of 1H NMR and FT-IR spectra, we can demonstrate successful preparation of AIE-active OSA-Phe-OSA biopolymers via a facile Schiff base condensation reaction at room temperature. Beside 1H NMR and FT-IR measurements, X-ray photoelectron spectroscopy (XPS) was also used to evidence the successful preparation of OSA-Phe-OSA fluorescent natural polymers with a novel AIE feature. As is well-known, the polysaccharide OSA is majorly constructed by four elements of H, C, O, and Na, and ionic OSA possess great water solubility and biocompatibility. After conjugating with PheNH2 AIEgen, this biocompatible OSA was endowed with desirable luminescence, and other new elements were thereby introduced into OSA polysaccharide. As shown in Figure 4, except four elements (H, C, O, and Na), another two new elements of S and N could be discovered in the OSA-Phe-OSA samples (Figure 4A). Respectively, Figure 4B−F shows clear peaks of S 2p, C 1s, N 1s, O 1s, and Na 1s signals, which respectively locate at 169.13, 287.41, 400.02, 533.01, and 1062.53 eV. The appearance of new elements (S and N) could demonstrate that the PheNH2 fluorophore was linked with OSA polysaccharide. On the other hand, Table 1 shows the element content of C, N, O, S, and Na in fluorescent OSA-Phe-OSA samples. The element contents of S and N are 0.39% and 0.94%, while Na content is 1.48%. According to the content data of S and Na elements, we can calculate the content of PheNH2 dye in OSAPhe-OSA polysaccharide to be about 26.4%, while polysaccharide chain content in FPNs is about 73.6%. Fluorophore PheNH2 with a unique AIE feature has strong stained ability. When the PheNH2 connects with biocompatible OSA by the formation of Schiff base bonds, resulting in OSA possesses strong emission property under UV irradiation. On the other hand, OSA conjugated with PheNH2 could endow the final polymers with great water dispersity. As shown in Figure 5A, the inset image shows clear red water solution of OSA-Phe-OSA fluorescent polymers and the background of word “Phe” can be directly observed. It demonstrated the excellent water dispersibility of OSA-Phe-OSA FPNs. The UV−vis spectrum of the OSA-Phe-OSA water solution is used to analyze the structure of OSA-Phe-OSA FPNs. The absorption spectrum of pure OSA in water demonstrates no obvious peak ranging from 300 to 800 nm. After conjugating with PheNH2, two obvious characteristic peaks respectively locate at 325 and 431 nm, suggesting that abundant π−π* conjugated systems existed in the OSA-Phe-OSA samples. According to the chemical structure of PheNH2 from Scheme 1, this AIEgen is constructed by many π−π* conjugated systems. Herein, we can conclude successful preparation of AIE-active polysaccharides. On the other hand, a fluorophore with an AIE feature exists in OSA polymers, resulting in strong

Figure 2. 1H NMR spectra of PheNH2 (A), OSA (B), and OSA-PheOSA (C). Compared to the 1H NMR spectrum of the OSA sample, the spectrum of OSA-Phe-OSA shows new peaks at the positions of 7.8 and 1.7 ppm, which was respectively ascribed to aromatic rings and alkyl chain existing in PheNH2 AIEgen, suggesting successful connection between OSA and PheNH2 with Schiff base bonds.

OSA-Phe-OSA 1H NMR spectrum, the peak at 8.3 ppm disappeared, while a new peak at 7.8 ppm appears, which can be contributed to the aromatic ring. Because of the formation of amphiphilic nanoparticles, the OSA-Phe-OSA samples just greatly dispersed in D2O, leading to the difficult detection of aromatic rings. Previous work has demonstrated that aromatic peaks were difficult to detect in the samples of AIE-active polysaccharides.93 On the other hand, there are other new peaks at 1.7, 2.2, and 2.5 ppm. These peaks can be assigned to the alkyl chain of PheNH2. Therefore, successful conjugation of PheNH2 with OSA polysaccharides by the Schiff base reaction is shown according to the 1H NMR results. Of course, other characterizations would synergistically evidence this conclusion. The FT-IR characterization technique was also used to confirm successful reaction between OSA and PheNH2 by the formation of Schiff base bonds (Figure 3). According to FT-IR spectra of three samples (SA, OSA, and OSA-Phe-OSA), we also can confirm prosperous syntheses of AIE-active polysaccharides. The broad peak at 3340 cm−1 was −OH groups

Figure 3. FT-IR spectra of SA, OSA, and OSA-Phe-OSA samples. Some characteristic peaks at 2185 and 1548 cm−1 were respectively ascribed to −CN and CN groups, and peaks ranging from 650 to 780 cm−1 were contributed to the out-of-plane blending vibration of aromatic rings, demonstrating successful preparation of AIE-active fluorescent OSA biopolymers. 9958


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Figure 4. XPS spectra of OSA-Phe-OSA fluorescent natural polymers: (A) survey signal, (B) S 2p signal, (C) C 1s signal, (D) N 1s signal, (E) O 1s signal, and (F) Na 1s signal.

Fluorescent nanoparticles should have excellent stability in the human body. To evaluate the stability of fluorescent OSAPhe-OSA polymers, the relationship of fluorescent strength vs irradiating time and physiological condition should be measured. First, the change of fluorescence intensity of OSAPhe-OSA polymers in aqueous solution after irradiating by UV lamp for 24 h should be determined. As shown in Figure 6A, the fluorescence intensity of the OSA-Phe-OSA aqueous solution is 2280 au, while the fluorescence intensity of the polymer solution reduced to 1670 au after irradiating with a UV lamp for 24 h. The reduced fluorescence intensity is calculated to be about 26.8%, demonstrating better photostability of the OSA-Phe-OSA polymers. On the other hand, the pH environment of extracellular compartments and intracellular organelles is different. Usually, the pH value in normal cells environment is about 7.35−7.45, while the physiological environment of cancer cells and lysosome is acidic. To evaluate the influence of different pH physiological environments for OSA-Phe-OSA FPNs, the FL spectra of OSA-Phe-OSA polymers in different physiological conditions with pH 7.4, 5.5, and 4.5 were investigated. As shown in Figure 6B, the similar excitation and emission wavelengths of the OSA-PheOSA solution could be observed. However, the fluorescence intensity is enhanced when fluorescent polysaccharides solution is dispersed in acidic environment. This phenomenon suggests that OSA-Phe-OSA can still keep excellent fluorescence in

Table 1. Elemental Signal Peak and Quantification name

start BE

peak BE

end BE

at. %

S 2p C 1s N 1s O 1s Na 1s

175.33 298.33 410.33 545.33 1079.33

169.13 287.41 400.02 533.01 1071.87

157.53 279.53 392.53 525.53 1062.53

0.39 57.38 0.94 39.80 1.48

emission of OSA-Phe-OSA polymers. According to Figure 5B, strong red fluorescence of the OSA-Phe-OSA aqueous solution can be noticed after exposure under UV lamp shown in the inset of Figure 5B. FL spectrum of the OSA-Phe-OSA solution shows the maximum emission wavelength is 607 nm, while optimal excitation wavelength locates at 495 nm. On the basis of optical pictures and spectra, these OSA-Phe-OSA polymers have great dispersibility in aqueous solution and strong red fluorescence, which primarily shows their promising potential in biomedical applications. Meanwhile, the unique AIE property of OSA-Phe-OSA polymers shows in Figure S2, which is opposite to pure synthetic AIEgen (PheNH2). This reason is that the original PheNH2 dye has great solubility in the THF solvent, while it aggregates in water. However, OSAPhe-OSA polymers possess bad solubility in any organic solvents and great dispersity in aqueous solution.

Figure 5. UV−vis and fluorescent optical spectra of the OSA-Phe-OSA polymer in aqueous solution. (A) UV−vis spectrum of OSA-Phe-OSA in distilled water, the inset using word “Phe” as background shows fluorescent polymers dispersed in water; (B) FL spectrum of OSA-Phe-OSA polymer in distilled water, the inset show strong fluorescence of OSA-Phe-OSA in water by irradiating under UV lamp. 9959


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Figure 6. FL spectra of OSA-Phe-OSA dispersed in aqueous solution. (A) Fluorescence intensity value vs time under irradiating by UV lamp for 24 h; (B) different pH environment (4.5, 5.5, and 7.4).

Figure 7. (A) TEM image of OSA-Phe-OSA dispersed in aqueous solution; (B) histogram shows particle size distribution of OSA-Phe-OSA. Combing these two characterization techniques, we think the particles size of OSA-Phe-OSA is about 250 nm.

solution, through detecting the fluorescence intensity of OSAPhe-OSA polymers with different concentrations, the CMC value is calculated to be 0.067 mg/mL. The low CMC value demonstrates that FPNs with a unique AIE feature can stably exist in aqueous solution. On the other hand, the inset of Figure S2 reveals a clear “Tyndall effect” of OSA-Phe-OSA FPNs, which can also prove successful formation of fluorescent nanoparticles via self-assembly. Cytotoxicity Evaluation of OSA-Phe-OSA FPNs. The great water dispersibility, strong fluorescence, great photostability, stable structure with low CMC value, and smaller size make the OSA-Phe-OSA FPNs promising biomedical applications. To research their biomedical application potential, the biocompatibility of OSA-Phe-OSA FPNs should be first investigated. As shown in Figure 8, different concentrations of OSA-Phe-OSA FPNs are used to culture L929 cells. When the concentration of FPNs is 20 μg mL−1, the cell viability is

acidic conditions. On the other hand, to evaluate their stability in acid and alkaline conditions, the change of fluorescence intensity in different pH environments is shown in Figure S4, the fluorescence strength is stable in alkaline condition, while reduced fluorescence intensity in strong acid environment. Even so, the fluorescence strength remained desirable in pH 4− 6 condition, which make them promising potential in various biomedical applications such as cancer trace, anticancer drug delivery, and cancer therapy. As is well-known, OSA has great hydrophilic properties, while PheNH2 is a hydrophobic fluorescent dye. When they are connected by a facile Schiff base reaction, thus-prepared OSAPhe-OSA polymers have significant amphiphilic property. When they dispersed in aqueous solution, hydrophobic PheNH2 was first aggregated into the core, while hydrophilic OSA was coated on the surface of the hydrophobic core and directly extended in water. As shown in Figure 7A, TEM images are used to prove that self-assembly of OSA-Phe-OSA into nanoparticles in aqueous solution. Many spherical nanoparticles can be directly observed from Figure 7A, the diameter of these nanoparticle is about 200−300 nm. Dynamic light scattering (DLS) technique is also used to estimate the hydrodynamic size of OSA-Phe-OSA FPNs. As we can see from Figure 7B, the major distribution of particle size of OSA-Phe-OSA ranges from 100 to 400 nm, and the compact district is 160 to 300 nm, which is close to the TEM result. Therefore, combining TEM and DLS results, we think the particle size of these OSA-PheOSA FPNs is about 250 nm. The smaller particles size of OSAPhe-OSA FPNs makes them easy candidates for endocytosis by living cells for various biomedical applications. Furthermore, in order to determine the stability of OSA-Phe-OSA in aqueous solution, their critical micelles concentration (CMC) value is detected (Figure S2). Adopting light scattering method to detect the CMC value of OSA-Phe-OSA FPNs in aqueous

Figure 8. Cytotoxicity evaluation of OSA-Phe-OSA FPNs for L929 cells. The cells were incubated with 20−100 μg mL−1 of OSA-PheOSA FPNs for 24 h. 9960


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Figure 9. CLSM images of OSA-Phe-OSA FPNs in L929 cells for 3 h. (A) Excited with 488 laser, (B) bright field, and (C) merged image of A and B. Scale bar = 20 μm.

them have promising potential in various biomedical applications. Compared with other fluorescent nanoparticles with short emission wavelength, these biocompatible FPNs with red fluorescence are more suitable for the applications of biological optical imaging, targeted tracer, cancer diagnosis, and treatment due to reduced damage for normal cells. Moreover, compared to previous commercial biocompatible polymers, modified SA polysaccharides (OSA) are resourceful, convenient preparation, and compatible for human tissue and cells, which can reduce cost for the preparation of FPNs. More importantly, abundant hydroxyl groups still remain on the surface of AIEactive FPNs, which are convenient for further conjugation of multifunctional components. We therefore expect these OSAPhe-OSA FPNs to show huge potential for various biomedical applications.

97%. When the culture concentration of FPNs was increased to 60 μg mL−1, the cell viability value remained above 93%. When the concentration of FPNs was 100 μg mL−1, the survival cells are still close to 90%. According to the results of cells viability, we can confirm that synthetic OSA-Phe-OSA FPNs possess excellent biocompatibility, which makes them have promising biomedical applications. Bioimaging of OSA-Phe-OSA FPNs. On the basis of the cytotoxicity evaluation result of OSA-Phe-OSA FPNs, the ability of OSA-Phe-OSA FPNs for biological imaging was investigated by using CLSM. According to the result of cell viability, we know ultralow cytotoxicity of synthetic FPNs when the concentration of FPNs reaches 80 μg mL−1. Therefore, we choose this concentration to evaluate their bioimaging ability. As shown in Figure 9, we can observe almost all of the L929 cells ingest effectively OSA-Phe-OSA FPNs, and the cellular morphology remained normal after culture with OSA-Phe-OSA FPNs during the cell imaging procedure, further indicating the good biocompatibility of OSA-Phe-OSA FPNs. On the other hand, the weak fluorescence can be observed in cell nuclei, demonstrating these FPNs are majorly taken up into the cytoplasm instead of cell nuclei. This phenomenon is decided by the direct endocytosis process of living cells. Most importantly, strong fluorescence can be observed after cells uptake these FPNs for 3 h, evidencing strong stained performance of OSA-Phe-OSA FPNs for living cells. Many carboxyl groups have been introduced in the OSA-Phe-OSA FPNs. These AIE-active FPNs should be also promising for drug delivery applications owing to the coordination interaction between carboxyl groups and cisplatin. It has been demonstrated that the carboxyl groups could effectively carry cisplatin and controlled release the anticancer agent through a pHdependent behavior.94 Therefore, these AIE-active FPNs could also be utilized for controlled delivery of cisplatin with selfreporting capability.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acssuschemeng.7b01908. FT-IR spectrum of PheNH2, AIE feature, CMC, and effect of pH on the fluorescence properties of OSA-PheOSA. (PDF)

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. ORCID

Xiaoyong Zhang: 0000-0003-4116-3773 Author Contributions ∥

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Q.W. and R.J. contributed equally to this work.

Notes

The authors declare no competing financial interest.

CONCLUSION In conclusion, AIE-active FPNs based on PheNH2 with far-red emission as the core and OSA as the shells have been prepared by a facile Schiff base condensation reaction in this work. Thanks to encapsulating the AIEgen into nanoparticles, the final OSA-Phe-OSA FPNs possess strong fluorescence and great photostability. On the other hand, the introduction of OSA to serve as protected coating of FPNs endows them with desirable water dispersibility and biocompatibility. In addition, low CMC value and suitable size allow these AIE-active FPNs to stably exist in physiological environment and easily endocytosed by living cells. From the evaluation of cytotoxicity and biological imaging of OSA-Phe-OSA FPNs for living cells, the excellent biocompatibility and stained performance make

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ACKNOWLEDGMENTS This research was supported by the National Natural Science Foundation of China (Nos. 51363016, 21474057, 21564006, 21561022, and 21644014) and Natural Science Foundation of Jiangxi Province in China (Nos. 20161BAB203072 and 20161BAB213066).

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REFERENCES

(1) Delgado, J. L.; de la Cruz, P.; Langa, F.; Urbina, A.; Casado, J.; López Navarrete, J. T. Microwave-assisted sidewall functionalization of single-wall carbon nanotubes by Diels−Alder cycloaddition. Chem. Commun. 2004, 1734−1735.

9961


Research Article

ACS Sustainable Chemistry & Engineering (2) Hahn, M. A.; Singh, A. K.; Sharma, P.; Brown, S. C.; Moudgil, B. M. Nanoparticles as contrast agents for in-vivo bioimaging: current status and future perspectives. Anal. Bioanal. Chem. 2011, 399, 3−27. (3) Kim, J. H.; Park, K.; Nam, H. Y.; Lee, S.; Kim, K.; Kwon, I. C. Polymers for bioimaging. Prog. Polym. Sci. 2007, 32, 1031−1053. (4) Peng, F.; Su, Y.; Zhong, Y.; Fan, C.; Lee, S. T.; He, Y. Silicon nanomaterials platform for bioimaging, biosensing, and cancer therapy. Acc. Chem. Res. 2014, 47, 612−623. (5) Kim, D.; Park, S.; Lee, J. H.; Jeong, Y. Y.; Jon, S. Antibiofouling polymer-coated gold nanoparticles as a contrast agent for in vivo X-ray computed tomography imaging. J. Am. Chem. Soc. 2007, 129, 7661− 7665. (6) Jun, Y. w.; Huh, Y. M.; Choi, J. s.; Lee, J. H.; Song, H. T.; Kim, S.; Kim, S.; Yoon, S.; Kim, K. S.; Shin, J. S. Nanoscale size effect of magnetic nanocrystals and their utilization for cancer diagnosis via magnetic resonance imaging. J. Am. Chem. Soc. 2005, 127, 5732−5733. (7) Kuhl, C. K.; Schrading, S.; Leutner, C. C.; Morakkabati Spitz, N.; Wardelmann, E.; Fimmers, R.; Kuhn, W.; Schild, H. H. Mammography, breast ultrasound, and magnetic resonance imaging for surveillance of women at high familial risk for breast cancer. J. Clin. Oncol. 2005, 23, 8469−8476. (8) McCarthy, J. R.; Weissleder, R. Multifunctional magnetic nanoparticles for targeted imaging and therapy. Adv. Drug Delivery Rev. 2008, 60, 1241−1251. (9) de Barros, A. L. B.; de Oliveira Ferraz, K. S.; Dantas, T. C. S.; Andrade, G. F.; Cardoso, V. N.; de Sousa, E. M. B. Synthesis, characterization, and biodistribution studies of 99m Tc-labeled SBA-16 mesoporous silica nanoparticles. Mater. Sci. Eng., C 2015, 56, 181−188. (10) Hillner, B. E.; Siegel, B. A.; Liu, D.; Shields, A. F.; Gareen, I. F.; Hanna, L.; Stine, S. H.; Coleman, R. E. Impact of positron emission tomography/computed tomography and positron emission tomography (PET) alone on expected management of patients with cancer: initial results from the National Oncologic PET Registry. J. Clin. Oncol. 2008, 26, 2155−2161. (11) Robinson, K. M.; Janes, M. S.; Pehar, M.; Monette, J. S.; Ross, M. F.; Hagen, T. M.; Murphy, M. P.; Beckman, J. S. Selective fluorescent imaging of superoxide in vivo using ethidium-based probes. Proc. Natl. Acad. Sci. U. S. A. 2006, 103, 15038−15043. (12) Sawa, M.; Hsu, T. L.; Itoh, T.; Sugiyama, M.; Hanson, S. R.; Vogt, P. K.; Wong, C. H. Glycoproteomic probes for fluorescent imaging of fucosylated glycans in vivo. Proc. Natl. Acad. Sci. U. S. A. 2006, 103, 12371−12376. (13) Zhu, H.; Mavandadi, S.; Coskun, A. F.; Yaglidere, O.; Ozcan, A. Optofluidic fluorescent imaging cytometry on a cell phone. Anal. Chem. 2011, 83, 6641−6647. (14) Ding, L.; Li, T.; Zhong, Y.; Fan, C.; Huang, J. Synthesis and characterization of a novel nitric oxide fluorescent probe CdS-PMMA nanocomposite via in-situ bulk polymerization. Mater. Sci. Eng., C 2014, 35, 29−35. (15) Ding, Z.; Bligh, S. A.; Tao, L.; Quan, J.; Nie, H.; Zhu, L.; Gong, X. Molecularly imprinted polymer based on MWCNT-QDs as fluorescent biomimetic sensor for specific recognition of target protein. Mater. Sci. Eng., C 2015, 48, 469−479. (16) Gallina, M. E.; Zhou, Y.; Johnson, C. J.; Harris-Birtill, D.; Singh, M.; Zhao, H.; Ma, D.; Cass, T.; Elson, D. S. Aptamer-conjugated, fluorescent gold nanorods as potential cancer theradiagnostic agents. Mater. Sci. Eng., C 2016, 59, 324−332. (17) Liu, J.; Hu, R.; Liu, J.; Zhang, B.; Wang, Y.; Liu, X.; Law, W.-C.; Liu, L.; Ye, L.; Yong, K.-T. Cytotoxicity assessment of functionalized CdSe, CdTe and InP quantum dots in two human cancer cell models. Mater. Sci. Eng., C 2015, 57, 222−231. (18) Ma, C.; Zhang, X.; Yang, L.; Wu, Y.; Liu, H.; Zhang, X.; Wei, Y. Preparation of fluorescent organic nanoparticles from polyethylenimine and sucrose for cell imaging. Mater. Sci. Eng., C 2016, 68, 37−42. (19) Zhang, X.; Wang, S.; Zhu, C.; Liu, M.; Ji, Y.; Feng, L.; Tao, L.; Wei, Y. Carbon-dots Derived from Nanodiamond: Photoluminescence Tunable Nanoparticles for Cell Imaging. J. Colloid Interface Sci. 2013, 397, 39−44.

(20) Zhang, X.; Wang, S.; Liu, M.; Yang, B.; Feng, L.; Ji, Y.; Tao, L.; Wei, Y. Size Tunable Fluorescent Nano-graphite Oxides: Preparation and Cell Imaging Applications. Phys. Chem. Chem. Phys. 2013, 15, 19013−19018. (21) Peng, H.; Cui, B.; Li, G.; Wang, Y.; Li, N.; Chang, Z.; Wang, Y. A multifunctional β-CD-modified Fe 3 O 4@ ZnO: Er 3+, Yb 3+ nanocarrier for antitumor drug delivery and microwave-triggered drug release. Mater. Sci. Eng., C 2015, 46, 253−263. (22) Zheng, X.; Liu, M.; Hui, J.; Fan, D.; Ma, H.; Zhang, X.; Wang, Y.; Wei, Y. Ln 3+-doped hydroxyapatite nanocrystals: controllable synthesis and cell imaging. Phys. Chem. Chem. Phys. 2015, 17, 20301− 20307. (23) Zhang, X.; Hui, J.; Yang, B.; Yang, Y.; Fan, D.; Liu, M.; Tao, L.; Wei, Y. PEGylation of Fluoridated HAp: Ln3+ Nanorods for Cell Imaging. Polym. Chem. 2013, 4, 4120−4125. (24) Sahu, S.; Behera, B.; Maiti, T. K.; Mohapatra, S. Simple one-step synthesis of highly luminescent carbon dots from orange juice: application as excellent bio-imaging agents. Chem. Commun. 2012, 48, 8835−8837. (25) Wang, F.; Liu, X. Upconversion multicolor fine-tuning: visible to near-infrared emission from lanthanide-doped NaYF4 nanoparticles. J. Am. Chem. Soc. 2008, 130, 5642−5643. (26) Yang, S. T.; Cao, L.; Luo, P. G.; Lu, F.; Wang, X.; Wang, H.; Meziani, M. J.; Liu, Y.; Qi, G.; Sun, Y. P. Carbon dots for optical imaging in vivo. J. Am. Chem. Soc. 2009, 131, 11308−11309. (27) Yurtsever, A.; Weyland, M.; Muller, D. A. Three-dimensional imaging of nonspherical silicon nanoparticles embedded in silicon oxide by plasmon tomography. Appl. Phys. Lett. 2006, 89, 151920. (28) Zhou, L.; Gu, Z.; Liu, X.; Yin, W.; Tian, G.; Yan, L.; Jin, S.; Ren, W.; Xing, G.; Li, W. Size-tunable synthesis of lanthanide-doped Gd 2 O 3 nanoparticles and their applications for optical and magnetic resonance imaging. J. Mater. Chem. 2012, 22, 966−974. (29) Shang, L.; Azadfar, N.; Stockmar, F.; Send, W.; Trouillet, V.; Bruns, M.; Gerthsen, D.; Nienhaus, G. U. One-Pot Synthesis of NearInfrared Fluorescent Gold Clusters for Cellular Fluorescence Lifetime Imaging. Small 2011, 7, 2614−2620. (30) Betzig, E.; Patterson, G. H.; Sougrat, R.; Lindwasser, O. W.; Olenych, S.; Bonifacino, J. S.; Davidson, M. W.; Lippincott Schwartz, J.; Hess, H. F. Imaging intracellular fluorescent proteins at nanometer resolution. Science 2006, 313, 1642−1645. (31) Chen, T. W.; Wardill, T. J.; Sun, Y.; Pulver, S. R.; Renninger, S. L.; Baohan, A.; Schreiter, E. R.; Kerr, R. A.; Orger, M. B.; Jayaraman, V. Ultrasensitive fluorescent proteins for imaging neuronal activity. Nature 2013, 499, 295−300. (32) Shaner, N. C.; Lin, M. Z.; McKeown, M. R.; Steinbach, P. A.; Hazelwood, K. L.; Davidson, M. W.; Tsien, R. Y. Improving the photostability of bright monomeric orange and red fluorescent proteins. Nat. Methods 2008, 5, 545−551. (33) Becker, V.; von Delius, S.; Bajbouj, M.; Karagianni, A.; Schmid, R. M.; Meining, A. Intravenous application of fluorescein for confocal laser scanning microscopy: evaluation of contrast dynamics and image quality with increasing injection-to-imaging time. Gastrointest. Endosc. 2008, 68, 319−323. (34) Gao, B.; Li, H.; Liu, H.; Zhang, L.; Bai, Q.; Ba, X. Water-soluble and fluorescent dendritic perylene bisimides for live-cell imaging. Chem. Commun. 2011, 47, 3894−3896. (35) Sivaraman, G.; Anand, T.; Chellappa, D. Turn-on fluorescent chemosensor for Zn (II) via ring opening of rhodamine spirolactam and their live cell imaging. Analyst 2012, 137, 5881−5884. (36) Sivaraman, G.; Chellappa, D. Rhodamine based sensor for naked-eye detection and live cell imaging of fluoride ions. J. Mater. Chem. B 2013, 1, 5768−5772. (37) Hong, Y.; Lam, J. W.; Tang, B. Z. Aggregation-induced emission: phenomenon, mechanism and applications. Chem. Commun. 2009, 4332−4353. (38) Hong, Y.; Lam, J. W.; Tang, B. Z. Aggregation-induced emission. Chem. Soc. Rev. 2011, 40, 5361−5388. 9962


Research Article

ACS Sustainable Chemistry & Engineering (39) Mei, J.; Leung, N. L.; Kwok, R. T.; Lam, J. W.; Tang, B. Z. Aggregation-induced emission: together we shine, united we soar! Chem. Rev. 2015, 115, 11718−11940. (40) Zhang, X.; Zhang, X.; Tao, L.; Chi, Z.; Xu, J.; Wei, Y. Aggregation induced emission-based fluorescent nanoparticles: fabrication methodologies and biomedical applications. J. Mater. Chem. B 2014, 2, 4398−4414. (41) Zhang, X.; Wang, K.; Liu, M.; Zhang, X.; Tao, L.; Chen, Y.; Wei, Y. Polymeric AIE-based nanoprobes for biomedical applications: recent advances and perspectives. Nanoscale 2015, 7, 11486−11508. (42) Luo, J.; Xie, Z.; Lam, J. W.; Cheng, L.; Chen, H.; Qiu, C.; Kwok, H. S.; Zhan, X.; Liu, Y.; Zhu, D. Aggregation-induced emission of 1methyl-1, 2, 3, 4, 5-pentaphenylsilole. Chem. Commun. 2001, 1740− 1741. (43) Kwok, R. T.; Leung, C. W.; Lam, J. W.; Tang, B. Z. Biosensing by luminogens with aggregation-induced emission characteristics. Chem. Soc. Rev. 2015, 44, 4228−4238. (44) Wang, M.; Zhang, G.; Zhang, D.; Zhu, D.; Tang, B. Z. Fluorescent bio/chemosensors based on silole and tetraphenylethene luminogens with aggregation-induced emission feature. J. Mater. Chem. 2010, 20, 1858−1867. (45) Feng, X.; Liu, L.; Wang, S.; Zhu, D. Water-soluble fluorescent conjugated polymers and their interactions with biomacromolecules for sensitive biosensors. Chem. Soc. Rev. 2010, 39, 2411−2419. (46) Mei, J.; Hong, Y.; Lam, J. W.; Qin, A.; Tang, Y.; Tang, B. Z. Aggregation-Induced Emission: The Whole Is More Brilliant than the Parts. Adv. Mater. 2014, 26, 5429−5479. (47) Wu, W. C.; Chen, C. Y.; Tian, Y.; Jang, S. H.; Hong, Y.; Liu, Y.; Hu, R.; Tang, B. Z.; Lee, Y. T.; Chen, C. T. Enhancement of Aggregation-Induced Emission in Dye-Encapsulating Polymeric Micelles for Bioimaging. Adv. Funct. Mater. 2010, 20, 1413−1423. (48) Zhang, X.; Liu, M.; Yang, B.; Zhang, X.; Chi, Z.; Liu, S.; Xu, J.; Wei, Y. Cross-linkable Aggregation Induced Emission Dye Based Red Fluorescent Organic Nanoparticles and Their Cell Imaging Applications. Polym. Chem. 2013, 4, 5060−5064. (49) Zhang, X.; Liu, M.; Yang, B.; Zhang, X.; Wei, Y. Tetraphenylethene-based aggregation-induced emission fluorescent organic nanoparticles: facile preparation and cell imaging application. Colloids Surf., B 2013, 112, 81−86. (50) Zhang, X.; Zhang, X.; Yang, B.; Liu, M.; Liu, W.; Chen, Y.; Wei, Y. Facile fabrication and cell imaging applications of aggregationinduced emission dye-based fluorescent organic nanoparticles. Polym. Chem. 2013, 4, 4317−4321. (51) Zhang, X.; Zhang, X.; Yang, B.; Liu, M.; Liu, W.; Chen, Y.; Wei, Y. Polymerizable aggregation-induced emission dye-based fluorescent nanoparticles for cell imaging applications. Polym. Chem. 2014, 5, 356−360. (52) Wang, M.; Zhang, D.; Zhang, G.; Tang, Y.; Wang, S.; Zhu, D. Fluorescence turn-on detection of DNA and label-free fluorescence nuclease assay based on the aggregation-induced emission of silole. Anal. Chem. 2008, 80, 6443−6448. (53) Wan, Q.; Liu, M.; Xu, D.; Mao, L.; Huang, H.; Gao, P.; Deng, F.; Zhang, X.; Wei, Y. Fabrication of amphiphilic fluorescent nanoparticles with an AIE feature via a one-pot clickable mercaptoacetic acid locking imine reaction: synthesis, self-assembly and bioimaging. Polym. Chem. 2016, 7, 4559−4566. (54) Wan, Q.; Wang, K.; Du, H.; Huang, H.; Liu, M.; Deng, F.; Dai, Y.; Zhang, X.; Wei, Y. A rather facile strategy for the fabrication of PEGylated AIE nanoprobes. Polym. Chem. 2015, 6, 5288−5294. (55) Wan, Q.; Wang, K.; He, C.; Liu, M.; Zeng, G.; Huang, H.; Deng, F.; Zhang, X.; Wei, Y. Stimulus Responsive Cross-linked AIE-active polymeric Nanoprobes: Fabrication and Biological Imaging Application. Polym. Chem. 2015, 6, 8214−8221. (56) Wang, K.; Zhang, X.; Zhang, X.; Fan, X.; Huang, Z.; Chen, Y.; Wei, Y. Preparation of biocompatible and photostable PEGylated red fluorescent nanoparticles for cellular imaging. Polym. Chem. 2015, 6, 5891−5898. (57) Wang, K.; Zhang, X.; Zhang, X.; Yang, B.; Li, Z.; Zhang, Q.; Huang, Z.; Wei, Y. Red fluorescent cross-linked glycopolymer

nanoparticles based on aggregation induced emission dyes for cell imaging. Polym. Chem. 2015, 6, 1360−1366. (58) Li, W.; Bing, W.; Huang, S.; Ren, J.; Qu, X. Mussel Byssus-Like Reversible Metal-Chelated Supramolecular Complex Used for Dynamic Cellular Surface Engineering and Imaging. Adv. Funct. Mater. 2015, 25, 3775−3784. (59) Ning, Z.; Chen, Z.; Zhang, Q.; Yan, Y.; Qian, S.; Cao, Y.; Tian, H. Aggregation-induced Emission (AIE)-active Starburst Triarylamine Fluorophores as Potential Non-doped Red Emitters for Organic Lightemitting Diodes and Cl2 Gas Chemodosimeter. Adv. Funct. Mater. 2007, 17, 3799−3807. (60) Qiu, Z.; Han, T.; Kwok, R. T.; Lam, J. W.; Tang, B. Z. Polyarylcyanation of Diyne: A one-pot three-component convenient route for in situ generation of polymers with AIE characteristics. Macromolecules 2016, 49, 8888. (61) Yuan, W. Z.; Gong, Y.; Chen, S.; Shen, X. Y.; Lam, J. W.; Lu, P.; Lu, Y.; Wang, Z.; Hu, R.; Xie, N. Efficient solid emitters with aggregation-induced emission and intramolecular charge transfer characteristics: molecular design, synthesis, photophysical behaviors, and OLED application. Chem. Mater. 2012, 24, 1518−1528. (62) Zheng, C.; Deng, H.; Zhao, Z.; Qin, A.; Hu, R.; Tang, B. Z. Multicomponent Tandem Reactions and Polymerizations of Alkynes, Carbonyl Chlorides, and Thiols. Macromolecules 2015, 48, 1941−1951. (63) He, B.; Su, H.; Bai, T.; Wu, Y.; Li, S.; Gao, M.; Hu, R.; Zhao, Z.; Qin, A.; Ling, J. Spontaneous Amino-yne Click Polymerization: A Powerful Tool toward Regio-and Stereospecific Poly (β-aminoacrylate) s. J. Am. Chem. Soc. 2017, 139, 5437−5443. (64) Long, Z.; Liu, M.; Wang, K.; Deng, F.; Xu, D.; Liu, L.; Wan, Y.; Zhang, X.; Wei, Y. Facile synthesis of AIE-active amphiphilic polymers: Self-assembly and biological imaging applications. Mater. Sci. Eng., C 2016, 66, 215−220. (65) Liu, J.; Chen, C.; Ji, S.; Liu, Q.; Ding, D.; Zhao, D.; Liu, B. Long wavelength excitable near-infrared fluorescent nanoparticles with aggregation-induced emission characteristics for image-guided tumor resection. Chem. Sci. 2017, 8, 2782−2789. (66) Gao, M.; Su, H.; Li, S.; Lin, Y.; Ling, X.; Qin, A.; Tang, B. Z. An easily accessible aggregation-induced emission probe for lipid dropletspecific imaging and movement tracking. Chem. Commun. 2017, 53, 921−924. (67) Chen, C.; Song, Z.; Zheng, X.; He, Z.; Liu, B.; Huang, X.; Kong, D.; Ding, D.; Tang, B. Z. AIEgen-based theranostic system: targeted imaging of cancer cells and adjuvant amplification of antitumor efficacy of paclitaxel. Chem. Sci. 2017, 8, 2191. (68) Wang, K.; Fan, X.; Zhao, L.; Zhang, X.; Zhang, X.; Li, Z.; Yuan, Q.; Zhang, Q.; Huang, Z.; Xie, W. Aggregation Induced Emission Fluorogens Based Nanotheranostics for Targeted and Imaging-Guided Chemo-Photothermal Combination Therapy. Small 2016, 12, 6568− 6575. (69) Jin, G.; Feng, G.; Qin, W.; Tang, B. Z.; Liu, B.; Li, K. Multifunctional organic nanoparticles with aggregation-induced emission (AIE) characteristics for targeted photodynamic therapy and RNA interference therapy. Chem. Commun. 2016, 52, 2752−2755. (70) Li, M.; Gao, Y.; Yuan, Y.; Wu, Y.; Song, Z.; Tang, B. Z.; Liu, B.; Zheng, Q. C. One-Step Formulation of Targeted Aggregation-Induced Emission Dots for Image-Guided Photodynamic Therapy of Cholangiocarcinoma. ACS Nano 2017, 11, 3922. (71) Yuan, Y.; Xu, S.; Zhang, C. J.; Zhang, R.; Liu, B. Dual-targeted activatable photosensitizers with aggregation-induced emission (AIE) characteristics for image-guided photodynamic cancer cell ablation. J. Mater. Chem. B 2016, 4, 169−176. (72) Ooyama, Y.; Sugino, M.; Enoki, T.; Yamamoto, K.; Tsunoji, N.; Ohshita, J. Aggregation-induced emission (AIE) characteristic of water-soluble tetraphenylethene (TPE) bearing four sulfonate salts. New J. Chem. 2017, 41, 4747. (73) Chen, Q.; Bian, N.; Cao, C.; Qiu, X. L.; Qi, A. D.; Han, B. H. Glucosamine hydrochloride functionalized tetraphenylethylene: A novel fluorescent probe for alkaline phosphatase based on the aggregation-induced emission. Chem. Commun. 2010, 46, 4067−4069. 9963


Research Article

ACS Sustainable Chemistry & Engineering (74) Zhang, X.; Zhang, X.; Yang, B.; Hui, J.; Liu, M.; Liu, W.; Chen, Y.; Wei, Y. PEGylation and Cell Imaging Applications of AIE Based Fluorescent Organic Nanoparticles via Ring-opening Reaction. Polym. Chem. 2014, 5, 689−693. (75) Zhang, X.; Zhang, X.; Yang, B.; Liu, M.; Liu, W.; Chen, Y.; Wei, Y. Fabrication of Aggregation Induced Emission Dye-based Fluorescent Organic Nanoparticles via Emulsion Polymerization and Their Cell Imaging Applications. Polym. Chem. 2014, 5, 399−404. (76) Zhang, X.; Zhang, X.; Yang, B.; Hui, J.; Liu, M.; Chi, Z.; Liu, S.; Xu, J.; Wei, Y. A Novel Method for Preparing AIE Dye based Crosslinked Fluorescent Polymeric Nanoparticles for Cell Imaging. Polym. Chem. 2014, 5, 683−688. (77) Huang, Z.; Zhang, X.; Zhang, X.; Fu, C.; Wang, K.; Yuan, J.; Tao, L.; Wei, Y. Amphiphilic fluorescent copolymers via one-pot combination of chemoenzymatic transesterification and RAFT polymerization: synthesis, self-assembly and cell imaging. Polym. Chem. 2015, 6, 607−612. (78) Wan, Q.; Jiang, R.; Mao, L.; Xu, D.; Zeng, G.; Shi, Y.; Deng, F.; Liu, M.; Zhang, X.; Wei, Y. A powerful “one-pot” tool for fabrication of AIE-active luminescent organic nanoparticles through the combination of RAFT polymerization and multicomponent reactions. Mater. Chem. Front 2017, 1, 1051−1058. (79) Zhang, X.; Zhang, X.; Yang, B.; Hui, J.; Liu, M.; Chi, Z.; Liu, S.; Xu, J.; Wei, Y. Facile Preparation and Cell Imaging Applications of Fluorescent Organic Nanoparticles that Combine AIE Dye and Ringopening Polymerization. Polym. Chem. 2014, 5, 318−322. (80) Wan, Q.; Zeng, G.; He, Z.; Mao, L.; Liu, M.; Huang, H.; Deng, F.; Zhang, X.; Wei, Y. Fabrication and biomedical applications of AIE active nanotheranostics through the combination of a ring-opening reaction and formation of dynamic hydrazones. J. Mater. Chem. B 2016, 4, 5692−5699. (81) Eiselt, P.; Yeh, J.; Latvala, R. K.; Shea, L. D.; Mooney, D. J. Porous carriers for biomedical applications based on alginate hydrogels. Biomaterials 2000, 21, 1921−1927. (82) Seeli, D. S.; Dhivya, S.; Selvamurugan, N.; Prabaharan, M. Guar gum succinate-sodium alginate beads as a pH-sensitive carrier for colon-specific drug delivery. Int. J. Biol. Macromol. 2016, 91, 45−50. (83) Tønnesen, H. H.; Karlsen, J. Alginate in drug delivery systems. Drug Dev. Ind. Pharm. 2002, 28, 621−630. (84) Sood, A.; Arora, V.; Shah, J.; Kotnala, R.; Jain, T. K. Multifunctional gold coated iron oxide core-shell nanoparticles stabilized using thiolated sodium alginate for biomedical applications. Mater. Sci. Eng., C 2017, 80, 274. (85) Lv, L.; Wu, X.; Li, M.; Zong, L.; Chen, Y.; You, J.; Li, C. Modulating Zn (OH) 2 Rods by Marine Alginate for Templates of Hybrid Tubes with Catalytic and Antimicrobial Properties. ACS Sustainable Chem. Eng. 2017, 5, 862−868. (86) Schneider Teixeira, A.; Deladino, L.; Zaritzky, N. Yerba mate (Ilex paraguariensis) waste and alginate as a matrix for the encapsulation of N fertilizer. ACS Sustainable Chem. Eng. 2016, 4, 2449−2458. (87) Kumar, A.; Paul, P.; Nataraj, S. K. Bionanomaterial Scaffolds for Effective Removal of Fluoride, Chromium, and Dye. ACS Sustainable Chem. Eng. 2017, 5, 895−903. (88) Wei, Z.; Yang, J. H.; Liu, Z. Q.; Xu, F.; Zhou, J. X.; Zrínyi, M.; Osada, Y.; Chen, Y. M. Novel Biocompatible Polysaccharide-Based Self-Healing Hydrogel. Adv. Funct. Mater. 2015, 25, 1352−1359. (89) Zhang, X.; Hu, W.; Li, J.; Tao, L.; Wei, Y. A Comparative Study of Cellular Uptake and Cytotoxicity of Multi-walled Carbon Nanotube, Graphene Oxide, and Nanodiamond. Toxicol. Res. 2012, 1, 62−68. (90) Zhang, X.; Liu, M.; Zhang, X.; Deng, F.; Zhou, C.; Hui, J.; Liu, W.; Wei, Y. Interaction of Tannic Acid with Carbon Nanotubes: Enhancement of Dispersibility and Biocompatibility. Toxicol. Res. 2015, 4, 160−168. (91) Zhang, X.; Qi, H.; Wang, S.; Feng, L.; Ji, Y.; Tao, L.; Li, S.; Wei, Y. Cellular responses of aniline oligomers: a preliminary study. Toxicol. Res. 2012, 1, 201−205.

(92) Zhang, X.; Wang, S.; Liu, M.; Hui, J.; Yang, B.; Tao, L.; Wei, Y. Surfactant-dispersed Nanodiamond: Biocompatibility Evaluation and Drug Delivery Applications. Toxicol. Res. 2013, 2, 335−346. (93) Wang, Z.; Chen, S.; Lam, J. W.; Qin, W.; Kwok, R. T.; Xie, N.; Hu, Q.; Tang, B. Z. Long-Term Fluorescent Cellular Tracing by the Aggregates of AIE Bioconjugates. J. Am. Chem. Soc. 2013, 135, 8238− 8245. (94) Heng, C.; Liu, M.; Wang, P.; Wang, K.; Zheng, X.; Fan, D.; Hui, J.; Zhang, X.; Wei, Y. Preparation of silica nanoparticles based multifunctional therapeutic systems via one-step mussel inspired modification. Chem. Eng. J. 2016, 296, 268−276.

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