Rational design of a near-infrared fluorescent probe for monitoring butyrylcholinesterase activity and its application in development of inhibitors.

Butyrylcholinesterase (BChE) is widely expressed in multiple tissues and has a vital role in several key human disorders, such as Alzheimer's disease and tumorigenesis. However, the role of BChE in human disorders has not been investigated. Thus, to quantitatively detect and visualize dynamical variations in BChE activity is essential for exploring the biological roles of BChE in the progression of a number of human disorders. Herein, based on the substrate characteristics of BChE, we customized and synthesized three near-infrared (NIR) fluorescent probe substrates with cyanine-skeleton, and finally selected a NIR fluorescence probe substrate named CYBA. The CYBA demonstrated a significant increase in fluorescence when interacting with BChE, but mainly avoided AChE. Upon the addition of BChE, CYBA could be specifically hydrolyzed to TBO, resulting in a significant NIR fluorescence signal enhancement at 710 nm. Systematic evaluation revealed that CYBA exhibited exceptional chemical stability in complex biosamples and possessed remarkable selectivity and sensitivity towards BChE. Moreover, CYBA was successfully applied for real-time imaging of endogenous BChE activity in two types of nerve-related living cells. Additionally, CYBA demonstrated exceptional stability in the detection of complex biological samples in plasma recovery studies (97.51%-104.01%). Furthermore, CYBA was used to construct a high-throughput screening (HTS) method for BChE inhibitors using human plasma as the enzyme source. We evaluated inhibitory effects of a series of natural products and four flavonoids were identified as potent inhibitors of BChE. Collectively, CYBA can serve as a practical tool to track the changes of BChE activity in complicated biological environments due to its excellent capabilities.

One-Step Exfoliation Method for Plasmonic Activation of Large-Area 2D Crystals.

Advanced exfoliation techniques are crucial for exploring the intrinsic properties and applications of 2D materials. Though the recently discovered Au-enhanced exfoliation technique provides an effective strategy for the preparation of large-scale 2D crystals, the high cost of gold hinders this method from being widely adopted in industrial applications. In addition, direct Au contact could significantly quench photoluminescence (PL) emission in 2D semiconductors. It is therefore crucial to find alternative metals that can replace gold to achieve efficient exfoliation of 2D materials. Here, the authors present a one-step Ag-assisted method that can efficiently exfoliate many large-area 2D monolayers, where the yield ratio is comparable to Au-enhanced exfoliation method. Differing from Au film, however, the surface roughness of as-prepared Ag films on SiO2 /Si substrate is much higher, which facilitates the generation of surface plasmons resulting from the nanostructures formed on the rough Ag surface. More interestingly, the strong coupling between 2D semiconductor crystals (e.g., MoS2 , MoSe2 ) and Ag film leads to a unique PL enhancement that has not been observed in other mechanical exfoliation techniques, which can be mainly attributed to enhanced light-matter interaction as a result of extended propagation of surface plasmonic polariton (SPP). This work provides a lower-cost and universal Ag-assisted exfoliation method, while at the same time offering enhanced SPP-matter interactions.

Resveratrol inhibits MUC5AC expression by regulating SPDEF in lung cancer cells.

BACKGROUND: MUC5AC was recently identified to play important roles in the proliferation and metastasis of malignant mucinous lung tumor cells. Resveratrol (Res), a natural compound with anticancer effects in lung cancer cells, has been reported to inhibit mucin production in airway epithelial cells. This study aimed to investigate the inhibitory effect of Res on MUC5AC expression in lung mucinous adenocarcinoma cells and the potential mechanisms. METHODS: Mucus-producing A549 human lung carcinoma cells were used to test the effects of Res on SPDEF and MUC5AC expression. Gene and protein expression was assessed by real-time quantitative PCR (qPCR), immunofluorescence and western blotting assays. SPDEF lentivirus was used to upregulate SPDEF expression levels in mucus-producing A549 human lung carcinoma cells. Cell proliferation was assessed by Cell Counting Kit-8 (CCK-8) assay. RESULTS: Res decreased MUC5AC expression in an SPDEF-dependent manner in mucus-producing A549 human lung carcinoma cells, and this change was accompanied by decreased ERK expression and AKT pathway activation. Moreover, SPDEF was found to be overexpressed in lung adenocarcinoma (LUAD), especially in mucinous adenocarcinoma. In-vitro functional assays showed that overexpression of SPDEF reduced the chemosensitivity of A549 cells to cisplatin (DDP). In addition, Res treatment increased A549 cell chemosensitivity to DDP by inhibiting the SPDEF-MUC5AC axis. CONCLUSION: Our results indicate that the SPDEF-MUC5AC axis is associated with DDP sensitivity, and that Res decreases SPDEF and MUC5AC expression by inhibiting ERK and AKT signaling in A549 cells, which provides a potential pharmacotherapy for the prevention and therapeutic management of mucinous adenocarcinoma.

The Zuo Jin Wan Formula increases chemosensitivity of human primary gastric cancer cells by AKT mediated mitochondrial translocation of cofilin-1.

Resistance to cisplatin (DDP)-based chemotherapy is a major cause of treatment failure in human gastric cancer (GC). It is necessary to identify the drugs to re-sensitize GC cells to DDP. In our previous research, Zuo Jin Wan Formula (ZJW) has been proved could increase the mitochondrial apoptosis via cofilin-1 in a immortalized cell line, SGC-7901/DDP. Due to the immortalized cells may still difficult highly recapitulate the important molecular events in vivo, primary GC cells model derived from clinical patient was constructed in the present study to further evaluate the effect of ZJW and the underlying molecular mechanism. Immunofluorescent staining was used to indentify primary cultured human GC cells. Western blotting was carried out to detect the protein expression. Cell Counting Kit-8 (CCK-8) was used to evaluate cell proliferation. Flow cytometry analysis was performed to assess cell apoptosis. ZJW inhibited proliferation and induced apoptosis in primary DDP-resistant GC cells. Notably, the apoptosis in GC cells was mediated by inducing cofilin-1 mitochondrial translocation, down-regulating Bcl-2 and up-regulating Bax expression. Surprisingly, the level of p-AKT protein was higher in DDP-resistant GC cells than that of the DDP-sensitive GC cells, and the activation of AKT could attenuate ZJW-induced sensitivity to DDP. These data revealed that ZJW can increase the chemosensitivity in DDP-resistant primary GC cells by inducing mitochondrial apoptosis and AKT inactivation. The combining chemotherapy with ZJW may be an effective therapeutic strategy for GC chemoresistance patients.

Expression and biological function of rhotekin in gastric cancer through regulating p53 pathway.

BACKGROUND/AIM: Gastric cancer (GC) is one of a most threatening cancer globally. Rhotekin (RTKN), a Rho effector, has been reported to be upregulated in GC tissues. This study aimed to investigate the underlying regulatory roles of RTKN in the biological behavior of GC. METHODS: Real-time PCR and Western blotting were carried out to detect the mRNA and protein expression, respectively. Cell Counting Kit-8 and xenograft nude mice model were used to evaluate cell proliferation. Flow cytometry analysis was performed to assess cell cycle distribution and cell apoptosis. RESULTS: RTKN had high expression level in GC compared with normal tissues. RTKN expression strongly associated with tumor size, TNM stage, lymphnode metastasis and the poor prognosis of patients with GC. Downregulation of RTKN significantly repressed GC cell proliferation, but increased cell population in G1/S phase and induced cell apoptosis. Moreover, the RTKN expression level was related to the p53 signaling pathway and histone deacetylase (HDAC) Class I pathway. RTKN knockdown caused a notable increment in the acetylation level of p53 (Lys382), and the expression of p53-target genes (p21, Bax, and PUMA), as well as a reduction in the expression of a potential deacetylase for p53, HDAC1. Notably, downregulation of HDAC1 had similar effects as RTKN knockdown, and RTKN overexpression could hardly abrogate the effects of HDAC1 knockdown on GC cells. CONCLUSION: RTKN could work as an oncogene via regulating HDAC1/p53 and may become a promising treatment strategy for GC.

Nonvolatile Memory Based on Molecular Ferroelectric/Graphene Field Effect Transistor.

Ferroelectric thin films are extensively attractive as next-generation nonvolatile memories. Recently, molecular ferroelectrics (MFe), as an emerging new class, have been a new research focus because of their desirable characteristics such as good solution processability, tunable chemical properties, and bio-friendly compositions. However, traditional uniaxial MFe only possess one polar axis which greatly limits their application, as it requires restricted orientational control in single crystal. To achieve macroscopic ferroelectricity and thus fully realize technological advantages of MFe, development of multiaxes is imperative to maximize effective polarization in specific crystallographic orientations. Herein, we present an early exploration on polycrystalline multiaxial MFe thin films of [Hdabco][ReO4] with a two-dimensional graphene hybrid nonvolatile memory device. The polarization switching of MFe is experimentally realized by the nonvolatile modulation of two current states in graphene. Such a hybrid device can exhibit large memory window ∼35 V implying its great potential in memory applications. Hence, by taking the advantages of multiple polarization axes of MFe, the low cost and large area MFe/graphene hybrid memory manifests new possibilities for the integration of these materials as flexible next generation memory devices.

Zuo Jin Wan Reverses DDP Resistance in Gastric Cancer through ROCK/PTEN/PI3K Signaling Pathway.

Gastric cancer (GC) is the third leading cause of cancer-related death. Chemotherapy resistance remains the major reason for GC treatment failure and poor overall survival of patients. Our previous studies have proved that Zuo Jin Wan (ZJW), a traditional Chinese medicine (TCM) formula, could significantly enhance the sensitivity of cisplatin (DDP)-resistant gastric cancer cells to DDP by inducing apoptosis via mitochondrial translocation of cofilin-1. However, the underlying mechanism remains poorly understood. This study aimed to evaluate the effects of ROCK/PTEN/PI3K on ZJW-induced apoptosis in vitro and in vivo. We found that ZJW could significantly activate the ROCK/PTEN pathway, inhibit PI3K/Akt, and promote the apoptosis of SGC-7901/DDP cells. Inhibition of ROCK obviously attenuated ZJW-induced apoptosis as well as cofilin-1 mitochondrial translocation, while inhibition of PI3K had the opposite effects. In vivo, combination treatment of DDP and ZJW (2000 mg/kg) significantly reduced tumor growth compared with DDP alone. Moreover, the combined administration of ZJW and DDP increased the expression of cleaved ROCK and p-PTEN while it decreased p-PI3K and p-cofilin-1, which was consistent with our in vitro results. These findings indicated that ZJW could effectively inhibit DDP resistance in GC by regulating ROCK/PTEN/PI3K signaling and provide a promising treatment strategy for gastric cancer.

Autoantibodies against CD80 in patients with COPD.

Chronic obstructive pulmonary disease (COPD) is an inflammation disorder and possibly an autoimmune disease. The components of the autoimmune response in the circulatory system are of considerable interest to clinicians. Because aberrations of costimulation status have been noted in COPD, the presence of autoantibodies to B7 costimulatory factor CD80 were investigated in a cohort of patients. Recombinant rs1CD80 (lacking the transmembrane domain of CD80) was used for Western blot analysis and ELISA to investigate the presence of autoantibodies in sera of patients with stable COPD and in controls without COPD. Cytokines IL-6 and IL-8 were detected using ELISA. Western blot revealed a specific band reacting to rs1CD80 by diluting sera pool of patients, which indicated the existence of autoantibodies to CD80. The serum level of anti-rs1CD80 was higher in patients with COPD than in controls(P=0.0185) and was positively correlated to the serum level of IL-6 (r=0.797, P<0.001) and IL-8 (r=0.608, P<0.001). There was a tendency that more higher level of anti-rs1CD80, more severe COPD stage. The existence of autoantibodies to costimulatory factor CD80 may suggest a pathogenic role of costimulatory factors in COPD.

Resveratrol inhibits mucus overproduction and MUC5AC expression in a murine model of asthma.

Previous in vitro studies have demonstrated that resveratrol is able to significantly inhibit the upregulation of mucin 5AC (MUC5AC), a major component of mucus; thus indicating that resveratrol may have potential in regulating mucus overproduction. However, there have been few studies regarding the resveratrol­mediated prevention of MUC5AC overproduction in vivo, and the mechanisms by which resveratrol regulates MUC5AC expression have yet to be elucidated. In the present study, an ovalbumin (OVA)­challenged murine model of asthma was used to assess the effects of resveratrol treatment on mucus production in vivo. The results demonstrated that resveratrol significantly inhibited OVA­induced airway inflammation and mucus production. In addition, the mRNA and protein expression levels of MUC5AC were increased in the OVA­challenged mice, whereas treatment with resveratrol significantly inhibited this effect. The expression levels of murine calcium­activated chloride channel (mCLCA)3, an important key mediator of MUC5AC production, were also reduced following resveratrol treatment. Furthermore, in vitro studies demonstrated that resveratrol significantly inhibited human (h)CLCA1 and MUC5AC expression in a dose­dependent manner. These results indicated that resveratrol was effective in preventing mucus overproduction and MUC5AC expression in vivo, and its underlying mechanism may be associated with regulation of the mCLCA3/hCLCA1 signaling pathway.

Bandgap-opened bilayer graphene approached by asymmetrical intercalation of trilayer graphene.

A novel graphene structure formed by asymmetrical intercalation of FeCl3 molecules into a trilayer graphene is reported. The trilayer graphene is divided into a single layer and a bilayer graphene by the inserted FeCl3 layer. Theoretical calculation shows that such graphene bilayers with broken inversion symmetry present a prominent opened bandgap of ∼0.13 eV.

Flexible transformation plasmonics using graphene.

The flexible control of surface plasmon polaritons (SPPs) is important and intriguing due to its wide application in novel plasmonic devices. Transformation optics (TO) offers the capability either to confine the SPP propagation on rigid curved/uneven surfaces, or to control the flow of SPPs on planar surfaces. However, TO has not permitted us to confine, manipulate, and control SPP waves on flexible curved surfaces. Here, we propose to confine and freely control flexible SPPs using TO and graphene. We show that SPP waves can be naturally confined and propagate on curved or uneven graphene surfaces with little bending and radiation losses, and the confined SPPs are further manipulated and controlled using TO. Flexible plasmonic devices are presented, including the bending waveguides, wave splitter, and Luneburg lens on curved surfaces. Together with the intrinsic flexibility, graphene can be served as a good platform for flexible transformation plasmonics.

Thickness identification of two-dimensional materials by optical imaging.

Two-dimensional materials, e.g. graphene and molybdenum disulfide (MoS(2)), have attracted great interest in recent years. Identification of the thickness of two-dimensional materials will improve our understanding of their thickness-dependent properties, and also help with scientific research and applications. In this paper, we propose to use optical imaging as a simple, quantitative and universal way to identify the thickness of two-dimensional materials, i.e. mechanically exfoliated graphene, nitrogen-doped chemical vapor deposition grown graphene, graphene oxide and mechanically exfoliated MoS(2). The contrast value can easily be obtained by reading the red (R), green (G) and blue (B) values at each pixel of the optical images of the sample and substrate, and this value increases linearly with sample thickness, in agreement with our calculation based on the Fresnel equation. This method is fast, easily performed and no expensive equipment is needed, which will be an important factor for large-scale sample production. The identification of the thickness of two-dimensional materials will greatly help in fundamental research and future applications.

Prohibitin induces apoptosis in BGC823 gastric cancer cells through the mitochondrial pathway.

Prohibitin (PHB), an evolutionarily-conserved protein, has been found to be over-expressed in gastric cancer and be closely related with tumor malignancy. In this study, to investigate the relationship between PHB expression and cell apoptosis in the BGC823 gastric cancer cell line, low and high expression PHB in BGC823 cells was accomplished using RNA interference technology and gene transfer techniques. Cell proliferation, cell cycling, apoptosis, Bax, Bcl-2 and Cyt.c protein expression and the activation of Caspase-3,9 were assessed after 48 h. Over-expression of PHB gene in BGC823 cells resulted in slow cell growth, cell arrest in G2 phase, and an increased apoptosis ratio while the opposite was found for PHB under-expressing cells. In PHB over-expressing cells, the expression of Bax gene was increased, the expression of Bcl-2 was decreased, the activation level of Caspase-3, 9 was increased, but the activation level of Caspase-8 demonstrated no change. These results indicate that PHB induced apoptosis through the mitochondrial pathway.

Low temperature edge dynamics of AB-stacked bilayer graphene: naturally favored closed zigzag edges.

Closed edges bilayer graphene (CEBG) is a recent discovered novel form of graphene structures, whose regulated edge states may critically change the overall electronic behaviors. If stacked properly with the AB style, the bilayer graphene with closed zigzag edges may even present amazing electronic properties of bandgap opening and charge separation. Experimentally, the CEBG has been confirmed recently with HRTEM observations after extremely high temperature annealing (2000 °C). From the application point of view, the low temperature closing of the graphene edges would be much more feasible for large-scale graphene-based electronic devices fabrication. Here, we demonstrate that the zigzag edges of AB-stacked bilayer graphene will form curved close structure naturally at low annealing temperature (< 500 °C) based on Raman observation and first principles analysis. Such findings may illuminate a simple and easy way to engineer graphene electronics.

Thermal dynamics of graphene edges investigated by polarized Raman spectroscopy.

In this report, we present Raman spectroscopy investigation of the thermal stability and dynamics of graphene edges. It is found that graphene edges (both armchair and zigzag) are not stable and undergo modifications even at temperature as low as 200 °C. On the basis of polarized Raman results, we provide possible structural models on how graphene edges change during annealing. The zigzag edges rearrange and form armchair segments that are ±30° relative to the edge direction, while armchair edges are dominated by armchair segments even at annealing temperature as high as 500 °C. The modifications of edge structures by thermal annealing (zigzag segments rearrange in form of armchair segments) provide a flexible way to control the electronic properties of graphene and graphene nanostructures.

Probing charged impurities in suspended graphene using Raman spectroscopy.

Charged impurity (CI) scattering is one of the dominant factors that affects the carrier mobility in graphene. In this paper, we use Raman spectroscopy to probe the charged impurities in suspended graphene. We find that the 2D band intensity is very sensitive to the CI concentration in graphene, while the G band intensity is not affected. The intensity ratio between the 2D and G bands, I(2D)/I(G), of suspended graphene is much stronger compared to that of nonsuspended graphene, due to the extremely low CI concentration in the former. This finding is consistent with the ultrahigh carrier mobility in suspended graphene observed in recent transport measurements. Our results also suggest that at low CI concentrations that are critical for device applications, the I(2D)/I(G) ratio is a better criterion in selecting high quality single layer graphene samples than is the G band blue shift.

Uniaxial strain on graphene: Raman spectroscopy study and band-gap opening.

Graphene was deposited on a transparent and flexible substrate, and tensile strain up to approximately 0.8% was loaded by stretching the substrate in one direction. Raman spectra of strained graphene show significant red shifts of 2D and G band (-27.8 and -14.2 cm(-1) per 1% strain, respectively) because of the elongation of the carbon-carbon bonds. This indicates that uniaxial strain has been successfully applied on graphene. We also proposed that, by applying uniaxial strain on graphene, tunable band gap at K point can be realized. First-principle calculations predicted a band-gap opening of approximately 300 meV for graphene under 1% uniaxial tensile strain. The strained graphene provides an alternative way to experimentally tune the band gap of graphene, which would be more efficient and more controllable than other methods that are used to open the band gap in graphene. Moreover, our results suggest that the flexible substrate is ready for such a strain process, and Raman spectroscopy can be used as an ultrasensitive method to determine the strain.

Tunable stress and controlled thickness modification in graphene by annealing.

Graphene has many unique properties which make it an attractive material for fundamental study as well as for potential applications. In this paper, we report the first experimental study of process-induced defects and stress in graphene using Raman spectroscopy and imaging. While defects lead to the observation of defect-related Raman bands, stress causes shift in phonon frequency. A compressive stress (as high as 2.1 GPa) was induced in graphene by depositing a 5 nm SiO(2) followed by annealing, whereas a tensile stress ( approximately 0.7 GPa) was obtained by depositing a thin silicon capping layer. In the former case, both the magnitude of the compressive stress and number of graphene layers can be controlled or modified by the annealing temperature. As both the stress and thickness affect the physical properties of graphene, this study may open up the possibility of utilizing thickness and stress engineering to improve the performance of graphene-based devices. Local heating techniques may be used to either induce the stress or reduce the thickness selectively.