Copper nanocluster‐based fluorescence enhanced determination of d‐penicillamine

Taking advantage of the compelling properties of d ‐penicillamine (d ‐PA) combined with copper, a method for the sensitive and selective determination of d ‐PA was established using copper nanocluster (Cu NC)‐based fluorescence enhancement. d ‐PA molecules containing a thiol compound showed a strong tendency to combine with the surface of Cu NCs, causing the re‐dispersion of nanoclusters and therefore fluorescence intensity was enhanced. Fluorescence enhancement efficiency of Cu NCs induced by d ‐PA was linear, with the d ‐PA concentration varying from 0.6–30 μg ml^?1 (R² = 0.9952) and with a detection limit of 0.54 μg ml^?1. d ‐PA content in human urine samples was detected with recoveries of 104.8–112.99%. Fluorescence‐enhanced determination of d ‐PA using Cu NCs was established for the first time and this rapid, easy and sensitive method should attract much attention for this application.     

Biosynthesis of flower-shaped Au nanoclusters with EGCG and their application for drug delivery

Background

In the last decade, the biosynthesis of metal nanoparticles using organisms have received more and more considerations. However, the complex composition of organisms adds up to a great barrier for the characterization of biomolecules involved in the synthesis process and their biological mechanisms.

Results

In this research, we biosynthesized a kind of flower-shaped Au nanoclusters (Au NCs) using one definite component—epigallocatechin gallate (EGCG), which was the main biomolecules of green tea polyphenols. Possessing good stability for 6 weeks and a size of 50 nm, the Au NCs might be a successful candidate for drug delivery. Hence, both methotrexate (MTX) and doxorubicin (DOX) were conjugated to the Au NCs through a bridge of cysteine (Cys). The introduction of MTX provided good targeting property for the Au NCs, and the conjugation of DOX provided good synergistic effect. Then, a novel kind of dual-drug loaded, tumor-targeted and highly efficient drug delivery system (Au-Cys-MTX/DOX NCs) for combination therapy was successfully prepared. The TEM of HeLa cells incubated with Au-Cys-MTX/DOX NCs indicated that the Au-Cys-MTX/DOX NCs could indeed enter and kill cancer cells. The Au-Cys-MTX/DOX NCs also possessed good targeting effect to the FA-receptors-overpressed cancer cells both in vitro and in vivo. Importantly, the Au-Cys-MTX/DOX NCs resulted in an excellent anticancer activity in vivo with negligible side effects.

Conclusions

These results suggest that the biosynthesized Au-Cys-MTX/DOX NCs could be a potential carrier with highly efficient anticancer properties for tumor-targeted drug delivery.

     

DNA-Ag nanoclusters as fluorescence probe for turn-on aptamer sensor of small molecules

As promising substitutes for organic dyes and quantum dots, few-atom fluorescent silver nanoclusters (Ag NCs) have recently gained much attention in a wide range from cellular imaging to chemical/biological detection applications owing to their ultrasmall size (<2 nm), excellent photostability, good biocompatibility and water solubility. Herein, we design an aptamer, guanine-rich (G-rich) DNA and Ag NCs nanocomplex to investigate its ability for the detection of small molecules. The design contains two DNA strands which are both chimeric conjugates of the DNA aptamer sequence fragment and G-rich sequence fragment. Using cocaine as a model molecule, the two DNA strands are in free state if there is no cocaine present, and the formed Ag NCs through the reduction of Ag(+) by NaBH(4) show weak fluorescence emission. In the presence of cocaine, however, the two aptamer fragments bind cocaine, which in turn puts the two G-rich sequence fragments in proximity and the fluorescent intensity of DNA-Ag NCs enhances greatly. As a result, DNA-Ag NCs are demonstrated as a novel, cost-effective and turn-on fluorescent probe for the analysis of cocaine, with a detection limit of 0.1 μM. Besides, successful detection of adenosine triphosphate (ATP) with detection limit of 0.2 μM demonstrates its potential to be a general method.     

Cytotoxicity Study on Luminescent Nanocrystals Containing Phospholipid Micelles in Primary Cultures of Rat Astrocytes

Luminescent colloidal nanocrystals (NCs) are emerging as a new tool in neuroscience field, representing superior optical probes for cellular imaging and medical diagnosis of neurological disorders with respect to organic fluorophores. However, only a limited number of studies have, so far, explored NC applications in primary neurons, glia and related cells. Indeed astrocytes, as resident cells in the central nervous system (CNS), play an important pathogenic role in several neurodegenerative and neuroinflammatory diseases, therefore enhanced imaging tools for their thorough investigation are strongly amenable. Here, a comprehensive and systematic study on the in vitro toxicological effect of core-shell type luminescent CdSe@ZnS NCs incorporated in polyethylene glycol (PEG) terminated phospholipid micelles on primary cultures of rat astrocytes was carried out. Cytotoxicity response of empty micelles based on PEG modified phospholipids was compared to that of their NC containing counterpart, in order to investigate the effect on cell viability of both inorganic NCs and micelles protecting NC surface. Furthermore, since the surface charge and chemistry influence cell interaction and toxicity, effect of two different functional groups terminating PEG-modified phospholipid micelles, namely amine and carboxyl group, respectively, was evaluated against bare micelles, showing that carboxyl group was less toxic. The ability of PEG-lipid micelles to be internalized into the cells was qualitatively and quantitatively assessed by fluorescence microscopy and photoluminescence (PL) assay. The results of the experiments clearly demonstrate that, once incorporated into the micelles, a low, not toxic, concentration of NCs is sufficient to be distinctly detected within cells. The overall study provides essential indications to define the optimal experimental conditions to effectively and profitably use the proposed luminescent colloidal NCs as optical probe for future in vivo experiments.     

Highly fluorescent au nanoclusters: Electrostatically induced phase transfer synthesis for Cu2+ sensing

This paper reports a convenient method for the synthesis of highly fluorescent Au nanoclusters (NCs) via electrostatically induced phase transfer. Furthermore, on the basis of an aggregation‐induced fluorescence quenching mechanism, the potential application for Cu²⁺ sensing on the fluorescence emission of the Au NCs is discussed. These prepared fluorescent Au NCs offer acceptable sensitivity, high selectivity, and a limit of quantitation of 0.02 μM for the measurement of Cu²⁺, which is lower than the maximum level (1 ppm, equals to 15.6 μM) of Cu²⁺ permitted in drinking water in China. This study contributes to the further development of practical applications with fluorescent NCs.     

The role of glutathione in copper metabolism and toxicity

Cellular copper metabolism and the mechanism of resistance to copper toxicity were investigated using a wild type hepatoma cell line (HAC) and a copper-resistant cell line (HAC600) that accumulates copper and has a highly elevated level of metallothionein (MT). Of the enzymes involved in reactive oxygen metabolism, only glutathionine peroxidase was elevated (3-4-fold) in resistant cells, suggestive of an increase in the cellular flux of hydrogen peroxide. A majority of the cytoplasmic copper (greater than 60%) was isolated from both cell lines as a GSH complex. Kinetic studies of 67Cu uptake showed that GSH bound 67Cu before the metal was complexed by MT. Depletion of cellular GSH with buthionine sulfoximine inhibited the incorporation of 67Cu into MT by greater than 50%. These results support a model of copper metabolism in which the metal is complexed by GSH soon after entering the cell. The complexed metal is then transferred to MT where it is stored. This study also indicates that resistance to metal toxicity in copper-resistant hepatoma cells is due to increases in both cellular GSH and MT. Furthermore, it is suggested that elevated levels of GSH peroxidase allows cells to more efficiently accommodate an increased cellular hydrogen peroxide flux that may occur as a consequence of elevated levels of cytoplasmic copper.     

Effect of polymer grafting density on silica nanoparticle toxicity

Nanoparticles are commonly engineered with a layer of polymers on the surface used to increase their stability and biocompatibility, as well as providing multifunctional properties. Formulating the nanoparticle size and surface properties with polymers directly affects the way these nanoparticles interact with a biological system. Many previous studies have emphasized the importance of nanoparticle size and surface charge in affecting their toxicity in cells. However, the potential weakness in many of these studies is that the polymer grafting densities on nanoparticles have been disregarded during toxicity evaluation. In the current study, we hypothesized that the density of polymers on nanoparticles will affect their toxicity to cells, especially for nanoparticle cores that are toxic themselves. To address this issue, we synthesized a range of RAFT (reversible addition fragmentation chain transfer) polymers bearing different surface charges and coated them onto silica nanoparticles (SiNPs) with different grafting densities. The in vitro cytotoxicity of these SiNPs was evaluated using the MTT (thiazolyl blue tetrazolium bromide) assay with Caco-2 cells. We found that neutral (biocompatible) polymers with a high grafting density on SiNPs were effective at protecting the cells from the toxicity of the silica core. High cellular toxicity was only observed for cationic polymer-SiNPs, while all other neutral and anionic polymer-SiNPs induced limited cellular toxicity. In contrast, the toxic effects induced by low density polymer-coated SiNPs were mostly attributed to the silica core, while the polymer coatings had a limited contribution. These findings are important indicators for the future evaluation of the toxicological profile of polymer-coated nanoparticles.     

Ultrasensitive chemiluminescence assay for cimetidine detection based on the synergistic improving effect of Au nanoclusters and graphene quantum dots

A novel and sensitive chemiluminescence (CL) procedure based on the synergetic catalytic effects of gold nanoclusters (Au NCs) and graphene quantum dots (GQDs) was developed for the reliable measurement of cimetidine (CM). The initial experiments showed that the KMnO₄‐based oxidation of alkaline rhodamine B (RhoB) generated a very weak CL emission, which was intensively enhanced in the simultaneous presence of Au NCs and GQDs. CL intermediates can be adsorbed and gathered on the surface of Au NCs, becoming more stable. GQDs participate in the energy transferring processes and facilitate them. These improving effects were simultaneously obtained by adding both Au NCs and GQDs into the RhoB‐KMnO₄ reaction. Consequently, the increasing effect of the Au NCs/GQDs mixture was more than that of pure Au NCs or GQDs, and a new nano‐assisted powerful CL system was achieved. Furthermore, a marked quenching in the emission of the introduced CL system was observed in the presence of CM, so the system was examined to design a sensitive sensor for CM. After optimization of influencing parameters, the linear lessening in CL emission intensity of KMnO₄‐RhoB‐Au NCs/GQDs was verified for CM concentrations in the range 0.8–200 ng ml^?1. The limit of detection (3S_b/m) was 0.3 ng ml^?1. Despite being a simple CL method, good sensitivity was obtained for CM detection with reliable results for CM determination in human urine samples.     

Selective Divalent Cobalt Ions Detection Using Ag2O3-ZnO Nanocones by ICP-OES Method for Environmental Remediation

Here, we have synthesized Ag₂O₃-ZnO nanocones (NCs) by a wet-chemical route using reducing agents at low temperature. The structural, optical and morphological properties of Ag₂O₃-ZnO NCs were investigated by several conventional techniques such as powder XRD, XPS, FESEM, XEDS, FTIR and UV/vis. spectroscopy. The analytical parameters of prepared NCs were also calculated for a selective detection of divalent cobalt [Co(II)] prior to its determination by inductively coupled plasma-optical emission spectrometry (ICP-OES). The selectivity of NCs toward various metal ions, including Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Ni(II), and Zn(II) was studied. Results of the selectivity study demonstrated that Ag₂O₃-ZnO NC phase was the most selective towards Co(II) ion. The uptake capacity for Co(II) ion was experimentally calculated to be ∼76.69 mgg⁻¹. Moreover, adsorption isotherm data provided that the adsorption process was mainly monolayer on homogeneous adsorbent surfaces of Ag₂O₃-ZnO NCs. Kinetic study revealed that the adsorption of Co(II) on Ag₂O₃-ZnO NCs phase followed the pseudo-second-order kinetic model. In addition, thermodynamic results provided that the adsorption mechanism of Co(II) ions on Ag₂O₃-ZnO NCs was a spontaneous process and thermodynamically favorable. Finally, the proposed method was validated by applying it to real environmental water samples with reasonable results.     

Bioconjugation of InGaP quantum dots for molecular sensing

Fluorescence-based molecular sensing and cellular imaging are commonly carried out with the application of organic dyes. Quantum dots (QDs) are now recognized as better tools because they are brighter, size tunable, and more photostable than dyes. Most of the proposed QD-based biosensing systems involve elements of known toxicity. The present work reports the functionalization of biocompatible InGaP/ZnS core-shell QDs with anti-bovine serum albumin (anti-BSA) to exploit them as fluorescent probes for antigen detection. Successful bioconjugation was characterized with the absorption and emission spectra showing blue shifts of around 40 and 30 nm, respectively. Gel electrophoresis and particle size distribution studies further confirmed the mass increment of QDs after their functionalization with anti-BSA. Surface plasmon resonance spectrometry has been used to study the affinity of QD-(anti-BSA) probes for bovine serum albumin (BSA). Photoluminescence quenching of the developed probe is observed in the presence of BSA.     

Asymmetric intercellular communication between bone cells: Propagation of the calcium signaling

Bone functional adaptation by remodeling is achieved by harmonized activities of bone cells in which osteocytes in the bone matrix are believed to play critical roles in sensing mechanical stimuli and transmitting signals to osteoclasts/osteoblasts on the bone surface in order to regulate their bone remodeling activities through the lacuno-canalicular network with many slender osteocytic processes. In this study, we investigated the intercellular communication between bone cells, particularly focusing on its directionality, through in vitro observations of the calcium signaling response to mechanical stimulus and its propagation to neighboring cells (NCs). Direct mechanical stimulus was applied to isolated bone cells from chick calvariae, osteocytes (Ocys) and bone surface cells (BSCs) mainly containing osteoblasts, and the percentage of calcium signaling propagation from the stimulated cell to NCs was analyzed. The results revealed that, regardless of the type of stimulated cell, the signaling propagated to BSCs with a significantly higher percentage, implying that calcium signaling propagation between bone cells strongly depends on the type of receiver cell and not the transmitter cell. In addition, in terms of mutual communication between Ocys and BSCs, the percentage of propagation from Ocys to BSCs is significantly higher than that in the opposite direction, suggesting that the calcium signaling mainly propagates asymmetrically with a bias from Ocys in bone matrix to BSCs on bone surfaces. This asymmetric communication between Ocys and BSCs suggests that osteocytic mechanosensing and cellular communications, which significantly affect bone surface remodeling activities to achieve functional adaptation, seem to be well coordinated and active at the location of biologically suitable and mechanically sensitive regions close to the bone surfaces.     

Quantum dots-based multifunctional dendritic superstructure for amplified electrochemiluminescence detection of ATP

A novel multifunctional dendrimeric CdSe-CdS-Quantum dots (QDs) hybrid superstructure with highly intense electrochemiluminescence (ECL), fluorescence and excellent magnetic property is prepared for the first time, and successfully applied to amplified ECL assays of ATP using DNA cycle amplification technique. The magnetic nanoparticles (MNPs) were firstly assembled with unique dendrimer nanoclusters (NCs), then large numbers of QDs were labeled onto the dendrimer NCs, the superstructure exhibits highly enhanced ECL and fluorescence than the pure QDs. Remarkable ECL quenching of the nanocomposites by gold nanoparticles (GNPs) was observed, based on which a novel strategy for highly sensitive ATP detection was developed by cycle amplification technique. Furthermore, the nanocomposites with excellent magnetic properties can be easily labeled, separated and immobilized onto a magnetic electrode. In particular, all the procedures such as linking GNPs, sensing target and DNA cycle amplification were directly accomplished on the nanocomposites, which is more rapid, convenient, complete and has better reproducibility than the conventional methods on electrode. To the best of our knowledge, this is the first report on the multifunctional QDs superstructure with highly intense ECL, fluorescence, excellent magnetism and its ECL biosensing, which opens a new pathway for developing QD-based nanocomposites for broad applications in ECL bioassays and optical imaging.     

Preparation and application of solvent‐modulated self‐doped N–S multicolour fluorescence carbon quantum dots

In this paper, two types of carbon quantum dot (CQDs) were prepared using biocompatible l ‐methionine as the carbon source and urea as the nitrogen source and a one‐step hydrothermal treatment. By changing the reaction solvents (deionized (DI) water and dimethylformamide (DMF)), the maximum emission of the resulting CQDs shifted from blue to red light. Specifically, the emission wavelength of the CQDs moved from 433 nm to 625 nm following embedding of a new functional group (–CONH–) on the surface of the CQDs. Photoluminescence quantum yields of the CQDs with blue and red emission reached 64% and 61%, respectively. The R‐CQDs were used to detect metal ions and a linear relationship was demonstrated between ln(F/F₀) and Fe³⁺ concentration in the range 0–0.5 mmol/L with a detection limit of 0.067 μM. Therefore these R‐CQDs have great potential as fluorescent probes for Fe³⁺ detection. We expect that the excellent water‐soluble, biocompatible and optical properties of the CQDs developed in this work mean that they will be widely used to detect biological cells.     

Solar Selective Absorbers for High-efficiency Photothermal Conversion via Core–Shell Nanocone Structured Surface

Nanostructured surface, a promising photon management strategy, enables to enhance photon-to-heat conversion efficiency by manipulating spectral radiative properties ranging from solar spectrum (0.3–2.5 μm) to mid-infrared spectrum (2.5–20 μm). Here, a core–shell nanocone structured surface made of silica core and tungsten shell as a solar selective absorber is introduced. The photothermal conversion efficiency (PTCE) is calculated in consideration of solar spectrum absorption and mid-infrared emission. It is obvious that high solar spectrum absorption and low mid-infrared emission are beneficial for high PTCE. The influence of structural parameters on the PTCE is studied, and then the absorption enhancement mechanism is elucidated in detail. Meanwhile, the influences of incident angle, polarized state, and lattice arrangement are also presented. The calculated results exhibit that our optimized solar absorber possesses the total solar absorption of 97.3% and total thermal emission of 7.6%, resulting in a maximum PTCE of 91.4% under one sun illumination conditions at normal incidence. Moreover, our solar selective absorber is independent to the incident angle and polarization state. The excellent photothermal conversion performance with wide-angle and polarization-insensitive properties for the solar selective absorber can serve as a good candidate for various solar thermal applications including seawater desalination, steam generation, thermophotovoltaic, and photocatalysis.

     

Stability of luminescence in LaPO4, LaPO4:RE3+ (RE = Dy,Eu) nanophosphors

The property of high refractive index, low solubility in water as well as stability to high temperature variation of lanthanum phosphate (LaPO₄) proved it was the most effective candidate for the production of display lamps, and plasma display panel devices and sensors. The morphological and nanostructural characteristics play a key role in the working efficiency of the luminescent material. These properties can be controlled by the synthesis method, which we have adopted in this paper. We have prepared LaPO₄ nanoparticles at a relatively low temperature (110 ºC) in polyethylene glycol medium by using a wet chemical one‐step synthesis. The phase composition and structural properties of the sample have been characterized by X‐ray diffraction, Fourier transform infrared, transmission electron microscopy and the luminescent property by photoluminescence and thermoluminescence. The samples were well crystallized and the average crystallite size of 15 nm has been calculated for pure LaPO₄ using the Debye–Scherrer equation. The result from heat‐treated samples shows the phase combination and morphological structure of the powder depend on the annealing temperature. The heat treatment changes the structure of LaPO₄ from cuboid rods to fine grains at about 600 °C. The emission spectrum of LaPO₄ shows the broad emission band at 368 nm and shoulder at 465 nm with emission of blue color when monitored at an excitation wavelength at 256 nm. The stability of phosphor has been studied with respect to humidity, temperature, doping, doping concentration, γ‐ray exposures, etc. The prepared nanosized phosphors were thermally stable and may be a promising blue phosphor for lighting technology as well as radiation dosimetry. Copyright © 2014 John Wiley & Sons, Ltd.     

Europium‐activated rare earth fluoride (LnF3:Eu3+–Ln = La,Gd) nanocrystals prepared by using ionic liquid/NH4F as a fluorine source via hydrothermal synthesis

Lanthanide (Ln) fluorides are considered exceptional luminescent rigid host matrices for various optical active Ln³⁺ ions due to their high refractive index, high chemical stability and low phonon energy, leading to the low probability of non‐radiative decay, which results in higher photoluminescence quantum yield (PLQY) (usually higher than oxide hosts). In this study, Eu³⁺‐activated Ln fluorides (LnF₃:Eu³⁺–Ln = La, Gd) are synthesized by the hydrothermal method using 1‐butyl‐3‐methylimidazolium tertrafluoroborate [BMIBF₄] and NH₄F as fluorine precursors. The synthesized nanocrystals (NCs) are structurally and morphologically characterized, and their optical properties investigated using spectrofluorometry. The X‐ray diffraction (XRD) patterns of Eu³⁺‐substituted and ‐unsubstituted LnF₃ (prepared from a different fluorine source) are indexed based on the hexagonal and orthorhombic crystal structure, respectively. Average crystalline sizes are calculated using the Scherrer equation and it is found that the synthesized NCs have an average crystalline size of 12–35 nm. Transmission electron microscopy (TEM) images reveal that the NCs are well dispersed and nearly ellipsoid, with an average size of ~ 5 nm. Eu³⁺‐activated NCs show characteristic excitation and emission spectra. The emission spectra show both magnetic (⁵D₀–⁷F₁) and electric (⁵D₀–⁷F₂) dipole transition with appropriate CIE color coordinates; however, the intensity of the magnetic dipole transition is high, which is in accordance with local site symmetry. Owing to their unique size and excellent optical properties, the synthesized NCs may have potential application in the fields bio‐imaging and solar concentrators. Copyright © 2016 John Wiley & Sons, Ltd.     

Homocysteine potentiates copper- and amyloid beta peptide-mediated toxicity in primary neuronal cultures: possible risk factors in the Alzheimer's-type neurodegenerative pathways

Oxidative stress may have an important role in the progression of neurodegenerative disorders such as Alzheimer's disease (AD) and prion diseases. Oxidative damage could result from interactions between highly reactive transition metals such as copper (Cu) and endogenous reducing and/or oxidizing molecules in the brain. One such molecule, homocysteine, a thiol-containing amino acid, has previously been shown to modulate Cu toxicity in HeLa and endothelial cells in vitro. Due to a possible link between hyperhomocysteinemia and AD, we examined whether interaction between homocysteine and Cu could potentiate Cu neurotoxicity. Primary mouse neuronal cultures were treated with homocysteine and either Cu (II), Fe (II or III) or Zn (II). Homocysteine was shown to selectively potentiate toxicity from low micromolar concentrations of Cu. The toxicity of homocysteine/Cu coincubation was dependent on the ability of homocysteine to reduce Cu (II) as reflected by the inhibition of toxicity with the Cu (I)-specific chelator, bathocuproine disulphonate. This was supported by data showing that homocysteine reduced Cu (II) more effectively than cysteine or methionine but did not reduce Fe (III) to Fe (II). Homocysteine also generated high levels of hydrogen peroxide in the presence of Cu (II) and promoted Abeta/Cu-mediated hydrogen peroxide production and neurotoxicity. The potentiation of metal toxicity did not involve excitotoxicity as ionotropic glutamate receptor antagonists had no effect on neurotoxicity. Homocysteine alone also had no effect on neuronal glutathione levels. These studies suggest that increased copper and/or homocysteine levels in the elderly could promote significant oxidant damage to neurons and may represent additional risk factor pathways which conspire to produce AD or related neurodegenerative conditions.     

Cu‐doped quantum dots: a new class of near‐infrared emitting fluorophores for bioanalysis and bioimaging

Transition metal ion‐doped quantum dots (QDs) exhibit unique optical and photophysical properties that offer significant advantages over undoped QDs, such as larger Stokes shift to avoid self‐absorption/energy transfer, longer excited‐state lifetimes, wider spectral window, and improved chemical and thermal stability. Among the doped QDs emitters, Cu is widely introduced into the doped QDs as novel, efficient, stable, and tunable optical materials that span a wide spectrum from blue to near‐infrared (NIR) light. Their unique physical and chemical characteristics enable the use of Cu‐doped QDs as NIR labels for bioanalysis and bioimaging. In this review, we discuss doping mechanisms and optical properties of Cu‐doped QDs that are capable of NIR emission. Applications of Cu‐doped QDs in in vitro biosensing and in in vivo bioimaging are highlighted. Moreover, a prospect of the future of Cu‐doped QDs for bioanalysis and bioimaging are also summarized.     

Models and Methods to Evaluate Transport of Drug Delivery Systems Across Cellular Barriers

Sub-micrometer carriers (nanocarriers; NCs) enhance efficacy of drugs by improving solubility, stability, circulation time, targeting, and release. Additionally, traversing cellular barriers in the body is crucial for both oral delivery of therapeutic NCs into the circulation and transport from the blood into tissues, where intervention is needed. NC transport across cellular barriers is achieved by: (i) the paracellular route, via transient disruption of the junctions that interlock adjacent cells, or (ii) the transcellular route, where materials are internalized by endocytosis, transported across the cell body, and secreted at the opposite cell surface (transyctosis). Delivery across cellular barriers can be facilitated by coupling therapeutics or their carriers with targeting agents that bind specifically to cell-surface markers involved in transport. Here, we provide methods to measure the extent and mechanism of NC transport across a model cell barrier, which consists of a monolayer of gastrointestinal (GI) epithelial cells grown on a porous membrane located in a transwell insert. Formation of a permeability barrier is confirmed by measuring transepithelial electrical resistance (TEER), transepithelial transport of a control substance, and immunostaining of tight junctions. As an example, ~200 nm polymer NCs are used, which carry a therapeutic cargo and are coated with an antibody that targets a cell-surface determinant. The antibody or therapeutic cargo is labeled with ¹²⁵I for radioisotope tracing and labeled NCs are added to the upper chamber over the cell monolayer for varying periods of time. NCs associated to the cells and/or transported to the underlying chamber can be detected. Measurement of free ¹²⁵I allows subtraction of the degraded fraction. The paracellular route is assessed by determining potential changes caused by NC transport to the barrier parameters described above. Transcellular transport is determined by addressing the effect of modulating endocytosis and transcytosis pathways.     

β‐Cyclodextrin protected Cu nanoclusters as a novel fluorescence sensor for graphene oxide in environmental water samples

This paper proposed a simple and sensitive approach for detecting graphene oxide (GO) in a wide pH range in environmental water samples using fluorescent β‐CD protected Cu NCs based on the hydrogen‐bond interactions between GO and 6‐SH‐β‐CD. The influences of dilution ratio and pH were investigated. We found that the fluorescence quenching efficiency of Cu NCs by GO remained almost the same under pH from 4 to 10, which benefitted the monitoring of GO under different pH conditions in real samples. The fluorescence quenching mechanism was also discussed. The fluorescence of β‐CD protected Cu NCs could be quenched in the presence of GO with a lowest detection concentration of 0.1 mg·L^?1. Good linear correlations were obtained over the concentration range from 0 to 30 mg·L^?1 at different pH values (pH = 4, pH = 7 and pH = 12). In addition, this method was successfully applied to the determination of GO in real samples which presents more opportunities for application in environmental and material sciences.