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Objective:To establish an aggregation-induced emission vesicle material based on supramolecular host-guest chemical assembly (AIE-HG-Vesicle) for siRNA delivery and fluorescence imaging, and to explore its uptake effect by tumor cells and siRNA-based cell killing effect.Methods:By synthesizing β-cyclodextrin modified with polyethyleneimine dendrimer (H-β-CD-dendrimer) as a host compound and a Bola type adamantane containing tetrastyrene AIE group (G-Ada-AIE) as a guest compound, the nanovesicle material was prepared by a supramolecular host-guest self-assembly process for loading siRNA. The morphology and size of the materials were tested by transmission electron microscopy and the dynamic light scattering method. The aggregation-induced luminescence properties of the materials were investigated by fluorescence spectrophotometry. The loading effect of the material on siRNA was investigated by gel retardation experiments. The delivery effect of siRNA-loaded AIE-HG-Vesicle vesicles in tumor cells was observed by a confocal laser scanning microscope. The killing effect of siRNA-loaded AIE-HG-Vesicle vesicles on tumor cells was tested by an MTT assay.Results:The prepared host-guest compounds can be assembled into vesicles with a size of about 100 nm and wall thickness of 9 nm in solution, and the positively charged vesicles on the surface can efficiently load siRNA. The siRNA-loaded AIE-HG-Vesicle vesicles can deliver siRNA into HeLa tumor cells and can be observed through aggregation-induced luminescence. The siRNA-loaded vesicles have an obvious killing effect on HeLa tumor cells.Conclusions:A vesicle material with aggregation-induced luminescence properties was prepared by a method based on supramolecular host-guest chemical assembly, which can be used to deliver siRNA. The material has fluorescence imaging and siRNA-based tumor cytotoxic effects and is expected to be applied to tumor treatment in vivo.
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Objective:To prepare a peptide fluorescent probe based on aggregation-induced emission and to investigate its application in the detection of early caries.Methods:Eight aspartate-serine-serine (DSS) were combined with aggregation-induced emission material to prepare peptide fluorescent probes, and an artificial demineralization model was established in vitro. The samples were immersed in the peptide fluorescent probe solution for 1 min, and a fluorescence imaging system was applied to examine the tooth samples and collect images and fluorescence data. Scanning electron microscopy was also applied to observe the phenotype of the teeth, and electron microscopy was applied to detect the calcium-phosphorus ratio on the enamel surface of the teeth. Polarized light microscopy was also applied to observe the enamel area of the teeth. Results:The fluorescence intensity of demineralized teeth was clearly observed to be lower than that of normal teeth in the peptide fluorescent probe-treated area, and the difference was statistically significant ( P < 0.05). The results of scanning electron microscopy showed that the enamel surface of the demineralized group had more irregular pores, while the enamel surface of the undemineralized group was flatter with only some irregular accumulation of flakes. The results of polarized light microscopy showed that a clear birefringence could be observed in the enamel region of normal teeth, while a black area or the disappearance of the birefringence effect accompanied by a partial black dark shadow could be observed in the enamel region of demineralized teeth. Conclusions:An aggregation-induced luminescence-based peptide fluorescent probe was successfully prepared, which can precisely localize the enamel and show some application value in early caries detection.
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Objective:To construct an aggregation induced emission (AIE) self-assembled probe based on glutathione (GSH) response covalent cyclization and evaluate it in vitro.Methods:The peptide sequence containing the 2-cyano-6-aminobenzothiazole-cysteine (CBT-Cys) condensation sequence was synthesized by the solid-phase peptide synthesis method. After coupling with an AIE molecule by click chemical reaction, an AIE self-assembled probe 1 based on GSH response covalent cyclization was constructed, and probe 2 lacking Cys structure was used as the control. The absorption and emission spectra of probes were tested and the specificity of probes to GSH was analyzed. The hydrodynamic diameter and structure of the probes after response were compared. The effects of different pH values, temperatures, probe concentrations, and GSH concentrations on fluorescence intensity were investigated. The toxicity of probes to tumor cells such as HeLa, HepG2 and MDA-MB-231 was evaluated.Results:After GSH response, the fluorescence of probe 1 was enhanced by about 6 times and that of probe 2 was enhanced by about 2 times; probe 1 was converted into a dimer with a hydrodynamic diameter of about 896.1 nm. Probe 2 lacked a cyclization motif and was converted into a monomer with a hydrodynamic diameter of about 427.4 nm. The fluorescence intensity of probe 1 was significantly higher than that of probe 2 at pH=7.0 and 37 ℃, and the toxicity of probes to tumor cells (HeLa, HepG2 and MDA-MB-231) was low.Conclusions:After the disulfide bond of probe 1 was reduced by GSH, the probe molecule lost the hydrophilic sequence, resulting in fluorescence turn-on (the first aggregation), and probe 1 immediately generates an AIE dimer (the second aggregation) because it contains a CBT-Cys cyclization sequence, which realizes the dual AIE effect compared with the single aggregation of probe 2, and significantly enhances the fluorescence emission. Probe 1 has better applicability in physiological environments, which provides an idea for in-situ generation of covalent cycling probes in vivo and is expected to be used in tumor imaging and treatment in the later stages.
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Inflammatory bowel disease (IBD) is a chronic intestinal disease with painful clinical manifestations and high risks of cancerization. With no curative therapy for IBD at present, the development of effective therapeutics is highly advocated. Drug delivery systems have been extensively studied to transmit therapeutics to inflamed colon sites through the enhanced permeability and retention (EPR) effect caused by the inflammation. However, the drug still could not achieve effective concentration value that merely utilized on EPR effect and display better therapeutic efficacy in the inflamed region because of nontargeted drug release. Substantial researches have shown that some specific receptors and cell adhesion molecules highly expresses on the surface of colonic endothelial and/or immune cells when IBD occurs, ligand-modified drug delivery systems targeting such receptors and cell adhesion molecules can specifically deliver drug into inflamed sites and obtain great curative effects. This review introduces the overexpressed receptors and cell adhesion molecules in inflamed colon sites and retrospects the drug delivery systems functionalized by related ligands. Finally, challenges and future directions in this field are presented to advance the development of the receptor-mediated targeted drug delivery systems for the therapy of IBD.
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Nanocrystal formulations have been explored to deliver poorly water-soluble drug molecules. Despite various studies of nanocrystal formulation and delivery, much more understanding needs to be gained into absorption mechanisms and kinetics of drug nanocrystals at various levels, ranging from cells to tissues and to the whole body. In this study, nanocrystals of tetrakis (4-hydroxyphenyl) ethylene (THPE) with an aggregation-induced emission (AIE) property was used as a model to explore intracellular absorption mechanism and dissolution kinetics of nanocrystals. Cellular uptake studies were conducted with KB cells and characterized by confocal microscopy, flow cytometry, and quantitative analyses. The results suggested that THPE nanocrystals could be taken up by KB cells directly, as well as in the form of dissolved molecules. The cellular uptake was found to be concentration- and time-dependent. In addition, the intracellular THPE also could be exocytosed from cells in forms of dissolved molecules and nanocrystals. Kinetic modeling was conducted to further understand the cellular mechanism of THPE nanocrystals based on first-order ordinary differential equations (ODEs). By fitting the kinetic model against experimental measurements, it was found that the initial nanocrystal concentration had a great influence on the dynamic process of dissolution, cellular uptake, and exocytosis of THPE nanocrystals. As the nanocrystal concentration increased in the culture media, dissolution of endocytosed nanocrystals became enhanced, subsequently driving the efflux of THPE molecules from cells.
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The role of point-of-care (POC) diagnostics is important in public health. With the support of smartphones, POC diagnostic technologies can be greatly improved. This opportunity has arisen from not only the large number and fast spread of cell-phones across the world but also their improved imaging/diagnostic functions. As a tool, the smartphone is regarded as part of a compact, portable, and low-cost system for real-time POC, even in areas with few resources. By combining near-infrared (NIR) imaging, measurement, and spectroscopy techniques, pathogens can be detected with high sensitivity. The whole process is rapid, accurate, and low-cost, and will set the future trend for POC diagnostics. In this review, the development of smartphone-based NIR fluorescent imaging technology was described, and the quality and potential of POC applications were discussed.
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@#Lipid rafts composed of saturated phospholipids,sphingomyelin,and cholesterol are usually defined as liquid ordered microdomains located in the cell membrane. Lipid rafts are involved in many physiological and pathological processes of cells. Based on the difference in composition and distribution between lipid raft and non-raft domains,a lipid raft probe with aggregation-induced emission (AIE),cholesterol-triethylene glycol-tetraphenylethylene (TCHS-TPE),was designed and synthesized for convenient and specific imaging of lipid raft domains on cell membranes in this study. In this paper,TCHS-TPE was successfully synthesized,and the photophysical properties of TCHS-TPE were measured to evaluate its AIE characteristics. And finally the specific imaging of TCHS-TPE on the lipid raft region of B16F10 melanoma cell membrane was studied using confocal laser scanning microscopy. Compared with the existing lipid raft probe cholera toxin B (CTxB),the TCHS-TPE lipid raft probe has the advantages of simple operation and high specificity. The successful synthesis of the fluorescent probe will provide a useful tool for studying the physiological and pathological processes related to lipid raft domains,and offer a theoretical basis for the design of imaging probes for other lipid raft domains.
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The in vivo fate is a crucial factor that governs the successful translation of nanoformulations. However, one of the current biggest challenges is with the real-time monitoring of the body of the nanoparticles themselves. Conventional radioactive or fluorescent probes give signals even after they are disassociated from the particle matrix, generating interference to bioimaging and leading to misjudgment of results. Environment-responsive fluorescent dyes are regarded as promising tools due to signal switching in response to the changes in the environment. Currently, there are three categories of dyes in bioimaging of nanoparticles based on Förster resonance energy transfer (FRET), aggregation-induced emission (AIE) and aggregation-caused quenching (ACQ). They have similar characteristics that strong fluorescence is emitted when they are embedded in the matrix of nanocarriers, whereas the fluorescence quenches upon release from the matrix due to dissociation of nanocarriers. The fluorescence switching reflects the existing status of the nanocarriers and therefore helps to interpret the in vivo behaviors. FRET and AIE probes have been widely used in elucidating the interactions between nanoparticles and cell models. However, they show intrinsic defects in studying in vivo fate of nanoparticles. ACQ-based dyes are sensitive to water, a universal factor in the biological environment. Therefore, with the help of bioimaging equipment, the in vivo trafficking process of nanoparticles can be unraveled. This review article tends to provide an overview on the rationale, pros and cons and applications of the three categories of environment-responsive fluorescent dyes in the investigation of the in vivo fate of nanocarriers.
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Mitochondrial targeting is a promising approach for solving current issues in clinical application of chemotherapy and diagnosis of several disorders. Here, we discuss direct conjugation of mitochondrial-targeting moieties to anticancer drugs, antioxidants and sensor molecules. Among them, the most widely applied mitochondrial targeting moiety is triphenylphosphonium (TPP), which is a delocalized cationic lipid that readily accumulates and penetrates through the mitochondrial membrane due to the highly negative mitochondrial membrane potential. Other moieties, including short peptides, dequalinium, guanidine, rhodamine, and F16, are also known to be promising mitochondrial targeting agents. Direct conjugation of mitochondrial targeting moieties to anticancer drugs, antioxidants and sensors results in increased cytotoxicity, anti-oxidizing activity and sensing activity, respectively, compared with their non-targeting counterparts, especially in drug-resistant cells. Although many mitochondria-targeted anticancer drug conjugates have been investigated and , further clinical studies are still needed. On the other hand, several mitochondria-targeting antioxidants have been analyzed in clinical phases I, II and III trials, and one conjugate has been approved for treating eye disease in Russia. There are numerous ongoing studies of mitochondria-targeted sensors.
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Fluorescent bio-probes have attracted increasing attentions in studies for screening bioactive compounds from traditional Chinese medicines. In this study, a new-type fluorescent probe with the function of aggregation-induced emission (AIE) was used to screen dipeptidyl peptidase-4 (DPP-4) inhibitor from Xiaokean formula, which has been clinically used for the treatment of type 2 diabetes mellitus. Potential DPP-4 inhibitors were screened by the fluorescent probe, with diprotin A as the positive control; totally 43 components were isolated from Xiaokean formula by systematic separation. The results showed that 13 components can exert inhibitory effects on DPP-4 activity; 16 compounds were further identified by liquid chromatography-mass spectrometry (LC-MS) from those active components. The inhibitory effects of 14 compounds were further verified, while five of them showed significant inhibition against DPP-4. Salvianolicacid C, ginsenoside Rg₅ and timosaponin AI inhibited DPP-4 activity at the concentration of 5-50 μmol•L⁻¹ in a dose-dependent manner. Thus, our study provided a successful example for screening bioactive compounds from traditional Chinese medicines by using a novelfluorescent probe.