A Biosensor for Simultaneous Detection of Epinephrine and Ascorbic Acid Based on Fe(III)-Polyhistidine-Functionalized Multi-Wall Carbon Nanotube Composites.

Epinephrine (EP) is a very important chemical transmitter in the transmission of nerve impulses in the central nervous system of mammals. Ascorbic acid (AA) is considered to be the most important extracellular fluid antioxidant and has important antioxidant properties in the cell. In this study, a series of transition metal-polyhistidine-carboxylated multi-wall carbon nanotube nanocomposites were synthesized, and their simultaneous catalytic effects on epinephrine and ascorbic acid were investigated. The results showed that nanocomposites based on iron ions had the highest catalytic activity. The prepared biosensor expressed high selectivity toward EP and AA with LOD values of 0.1 µΜ (AA) and 0.01 µΜ (EP), and sensitivity values of 4.18 µA mM-1 with a range of 0.001-5 mM (AA), 50.98 µA mM-1 with a range of 0.2-100 µM (EP), and 265.75 µA mM-1 with a range of 0.1-1.0 mM (EP). Moreover, it showed good stability, good repeatability and high selectivity in real sample detection. This work is a reference for the design of new electrochemical enzyme-free biosensors and the detection of biomarkers.

Circ_0021573 acts as a competing endogenous RNA to promote the malignant phenotypes of human ovarian cancer cells.

Circular RNAs (circRNAs) have been reported to be implicated in the tumorigenesis and progression of ovarian cancer. Here, the study was designed to explore the activity of human circ_0021573 in ovarian cancer pathogenesis and its regulation through the competing endogenous RNA (ceRNA) crosstalk. Circ_0021573, microRNA (miR)- 936, and cullin 4B (CUL4B) were quantified by qRT-PCR and western blot. Cell proliferation ability was detected by XTT, 5-Ethynyl-2'-Deoxyuridine (EdU), and colony formation assays. Cell apoptosis, migration, and invasion were assessed by flow cytometry, wound-healing, and transwell assays, respectively. Dual-luciferase reporter and RNA immunoprecipitation (RIP) assays were used to evaluate the direct relationship between miR-936 and circ_0021573 or CUL4B 3'UTR. Xenograft studies were applied to assess the role of circ_0021573 in tumor growth. Our data showed that circ_0021573 expression is enhanced in human ovarian cancer. Inhibition of circ_0021573 impedes cell proliferation, migration, and invasion and promotes apoptosis in vitro, as well as diminishes tumor growth in vivo. Mechanistically, circ_0021573 contains a miR-936 binding site, and miR-936 is a relevant mediator of circ_0021573 regulation. MiR-936 direct targets and inhibits CUL4B. MiR-936-mediated suppression of CUL4B hinders cell proliferation, migration, and invasion and accelerates apoptosis in vitro.. These data suggested that circ_0021573 might promote the malignant phenotypes of ovarian cancer cells by functioning as a ceRNA for miR-936 to induce CUL4B, which provided a promising target for the prevention and inhibition of ovarian cancer.

A Novel Nanocomposite of Zn(II)-Protoporphyrin-Chitosan-Multi Walled Carbon Nanotubes and the Application to Caffeic Acid Sensing.

Caffeic acid is an antioxidant that has been widely been related to the health benefits of people in recent years. In this paper, the amino side chains of chitosan (CS) were modified with protoporphyrin IX by amide cross-linking, and then Zn ions were chelated. The properties of metalloporphyrin-preparing functionalized multi-walled carbon nanotubes (MWCNTs) and Zn ions chelated by protoporphyrin IX composites were used as sensitive-selective electrochemical biosensors for the determination of caffeic acid. The morphology and structure of nanocomposite Zn-PPIX-CS-MWCNTs were observed by X-ray spectroscopy mapping (EDX mapping), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR). The electrochemical behaviors of Zn-PPIX-CS-MWCNT-modified glassy carbon (GC) electrodes were evaluated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results show that the modified electrode had good electrocatalytic activity towards caffeic acid with a wide linear range of 0.0008-1.6 mM, an excellent sensitivity of 886.90 µAmM-1cm-1, and a detection limit of 0.022 µM. In addition, the caffeic acid sensor had excellent reproducibility, stability, and selectivity to various interfering substances. Therefore, the modified electrode prepared by this experiment can also be applied to electrochemical sensors of other substances.

Jaridon 6, a new diterpene from Rabdosia rubescens (Hemsl.) Hara, can display anti-gastric cancer resistance by inhibiting SIRT1 and inducing autophagy.

Tumor resistance is the main cause of treatment failure and is associated with many tumor factors. Jaridon 6, a new diterpene extracted from Rabdosia rubescens (Hemsl.) Hara, which has been previously extracted by our research team, has been tested having more obvious advantages in resistant tumor cells. However, its mechanism is unclear. In this study, we studied the effect and the specific mechanism of Jaridon 6 in resistant gastric cancer cells. Cytotoxicity test, colony test, western blotting, and nude test verified the anti-drug resistance ability of Jaridon 6 in the MGC803/PTX and MGC803/5-Fu cells. Jaridon 6 has shown obvious inhibitory effects in the sirtuin 1 (SIRT1) enzyme test. Transmission electron microscopy and immunofluorescence tests further proved the autophagic action of Jaridon 6. Jaridon 6 could inhibit the proliferation of the resistant gastric cancer cell in vivo and in vitro. Jaridon 6 inhibited SIRT1 enzyme and induced autophagy by inhibiting the phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) pathway. Thus, it may be considered for treating gastric cancer resistance by individual or combined administration, as an SIRT1 inhibitor and autophagy inducer.

A novel oriented immunosensor based on AuNPs-thionine-CMWCNTs and staphylococcal protein A for interleukin-6 analysis in complicated biological samples.

Interleukin-6 (IL-6) is of high importance for disease diagnosis and prognosis in human health since it's a crucial component in immune homeostasis, hematopoiesis, and metabolism. Herein, an immunosensor has been developed for monitoring IL-6, which is fabricated by Au nanoparticles (Au NPs)-thionine (THI)-carboxylated multi walled carbon nanotubes (CMWCNTs) as the substrate with high conductivity. Staphylococcal protein A (SPA) could directionally capture antibody to reduce steric hindrance caused by random immobilization. Built upon the high efficiency of IL-6 antibody immobilization by the SPA on the sensing surface, the immunosensor exhibited a favorable activity for IL-6 detection. Under optimal conditions, the biosensor presented a LOD of 2.87 pg mL-1 and a wide linear range from 0.01 ng mL-1 to 800 ng mL-1 in serum samples. Furthermore, the assembled sensor successfully quantified the IL-6 concentration in serum and different tissue lapping liquids (lung, heart, liver) from rats with myocardial infarction. The satisfactory performance of the proposed sensor not only broadens its application in clinical monitoring of IL-6 but also provides a novel approach to study inflammation in rats.

Electrochemical Detection for Uric Acid Based on ß-Lactoglobulin-Functionalized Multiwall Carbon Nanotubes Synthesis with PtNPs Nanocomposite.

In this work, a simple and highly selective electrochemical biosensor for determination of uric acid (UA) is synthesized by using ß-lactoglobulin (BLG)-functionalized multiwall carbon nanotubes (MWCNTs) and a platinum nanoparticles (PtNPs) nanocomposite. Urate oxidase (UOx) can oxidize uric acid to hydrogen peroxide and allantoin, which provides a good opportunity for electrochemical detection for UA. Under the optimized conditions, the current changes by the UOx/Bull Serum Albumin (BSA)/BLG-MWCNTs-PtNPs/Glassy Carbon (GC) electrode with the electrochemical method was proportional to the concentration of UA. According to experiments, we obtained a linear response with a concentration range from 0.02 to 0.5 mM and achieved a high sensitivity of 31.131 µA mM-1 and a low detection limit (0.8 µΜ). Meanwhile, nanoparticles improved the performance of the biosensor and combined with BLG not only prevented the accumulation of composite nanomaterials, but also provided immobilization of uricase through electrostatic adsorption. This improves the stability and gives the constructed electrode sensing interface superior performance in UA detection.

A novel catalase mimicking nanocomposite of Mn(II)-poly-L-histidine-carboxylated multi walled carbon nanotubes and the application to hydrogen peroxide sensing.

In this work, a novel enzyme-mimicking nanocomposite of Mn(II)-poly-L-histidine (PLH) functionalized carboxylated multi walled carbon nanotubes (CMWCNTs) was designed and synthesized. Based on the catalase-like activity of the nanocomposite, a non-enzymatic hydrogen peroxide (H2O2) biosensor was then established and explored for H2O2 electrochemical detection. The nanocomposite was characterized by Fourier transform infrared spectra, Raman spectroscopy, and transmission electron microscopy. Due to the enlarged effective surface area and the efficient electrocatalytic activity of the Mn(II)-PLH redox-active units, the obtained Mn(II)-PLH-CMWCNT electrode showed excellent electrocatalytic performance toward H2O2 disproportionation. Under the selected optimum conditions, the prepared biosensor exhibited highly sensitive response toward H2O2, and the response current had a good linear relationship between the response currents and H2O2 concentrations in the range of 0.002-1.0 mM, a low detection limit of 0.5 µM and a sensitivity of 464.18 µA mM-1 cm-2. With the good stability, reproducibility and selectivity, the proposed biosensor was successfully applied to the determination of H2O2 in real-life samples, and showed satisfactory results. In summary, the Mn(II)-PLH-CMWCNT nanocomposite could be a promising enzyme-mimicking nanomaterial for the researches of electrocatalysis, biosensing and relevant fields.

Facile Synthesis of ß-Lactoglobulin-Functionalized Reduced Graphene Oxide and Trimetallic PtAuPd Nanocomposite for Electrochemical Sensing.

The use of graphene has leapt forward the materials field and the functional modification of graphene has not stopped. In this work, ß-lactoglobulin (BLG) was used to functionalize reduced graphene oxide (RGO) based on its amphiphilic properties. Also, trimetallic PtAuPd nanoparticles were reduced to the surface of BLG-functionalized RGO and formed BLG-PtAuPd-RGO nanocomposite using facile synthesis. Transmission electron microscopy, energy-dispersive X-ray spectroscopy and Fourier transform infrared spectra were used to characterize the nanocomposite. Electrocatalytic analysis was evaluated through cyclic voltammetry and chronoamperometry methods. We developed a glucose sensor by fabricating GOD-BLG-PtAuPd-RGO/glassy carbon (GC) electrode. It presented a remarkable sensitivity of 63.29 µA mM-1 cm-2 (4.43 µA mM-1), a wider linear range from 0.005 to 9 mM and a lower detection limit of 0.13 µM (S/N = 3). Additionally, the glucose sensor exhibited excellent testing capability in human serum samples.

Copper (II)-ploy-L-histidine functionalized multi walled carbon nanotubes as efficient mimetic enzyme for sensitive electrochemical detection of salvianic acid A.

In this work, carboxylated multi walled carbon nanotubes (CMWCNTs) were firstly prepared and functionalized with poly-L-histidine (PLH), which were then chelated with copper (II) ions to from the nanocomposites of Cu(II)-PLH-CMWCNTs. The nanocomposites could be exploited as an efficient mimic enzyme for sensitive electrochemical detection of salvianic acid A (SAA). Cu(II)-PLH-CMWCNTs owned good charge transfer property and excellent synergetic catalytic effect between the overoxidized imidazole groups and the copper redox-active units. Therefore, highly sensitive electrochemical response to SAA was achieved under optimum experimental conditions. A good linear relationship between differential pulse voltammetry (DPV) peak current and the SAA concentration was established in the range of 0.4-1000 µM. A low detection limit of 0.037 µM and a sensitivity of 0.27 µA µM-1 cm-2 were achieved. The developed biosensor also had advantages of good repeatability, stability and high selectivity, thus, it was successfully applied to the determination of SAA in real samples with satisfactory results, which may have great potential for further exploitation of electroanalysis applications.

Facile fabrication of a 3,4,9,10-perylene tetracarboxylic acid functionalized graphene-multiwalled carbon nanotube-gold nanoparticle nanocomposite for highly sensitive and selective electrochemical detection of dopamine.

A novel non-enzymatic electrochemical sensor for highly sensitive and selective detection of dopamine was developed based on a 3,4,9,10-perylene tetracarboxylic acid functionalized graphene-multiwalled carbon nanotube-gold nanoparticle nanocomposite modified glassy carbon electrode (PTCA-RGO-MWCNTs-Au NPs/GCE). The nanocomposite film was prepared by a facile, eco-friendly and controllable route and its morphology was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopic (EDX) analysis, and X-ray diffraction (XRD) spectroscopy, respectively. Cyclic voltammetry and chronoamperometry were used for evaluating the electrochemical behaviors of the prepared sensor. The DA sensor exhibited excellent electrochemical performance toward DA with a sensitivity as high as 0.124 µA mM-1, a wide linear range of 1-100 µM and a low detection limit of 0.07 µM (S/N = 3). Moreover, it showed good selectivity toward DA without any obvious interference by AA and UA. Furthermore, the prepared DA sensor was applied to detect DA in real samples with satisfactory results.

Generation and characterization of a paclitaxel-resistant human gastric carcinoma cell line.

The main aim of this study was to establish a novel paclitaxel (PTX)-resistant human gastric carcinoma cell line and to investigate its biological significance. A cell line, MGC803/PTX, was established by gradually increasing PTX density on the basis of MGC803 over a period of 10 months. In addition, a pair of resistant cell lines (SW620 and SW620/PTX) were added to further explain the resistant mechanism of PTX. The drug resistance index and stability of MGC803/PTX cells were detected using the Cell Counting Kit-8 method. The morphological features were observed using inverted microscopy. Apoptosis was measured by flow cytometry (FCM) and Hoechst 33258 fluorescence staining. The distribution of the cell cycle was determined by FCM, and protein expressions of P-gp, Bcl-2, Bax, and PARP were detected by western blot analysis. When characterizing the resistance in vitro, we found that MGC803/PTX cells were 10.3-fold more resistant to PTX compared with MGC803 cells. In addition, MGC803/PTX cells showed cross-resistance to 5-fluorouracil and adriamycin. FCM and Hoechst 33258 fluorescence staining indicated that MGC803/PTX cells had a significantly lower percentage of apoptotic cells after treatment with PTX compared with MGC803 cells. Other differences between parental cells and resistant cells included morphology, proliferation rate, doubling time, cell cycle distribution, and colony-formation rate. Western blot analysis indicated that P-gp, Bcl-2, and PARP protein were more abundant in MGC803/PTX and SW620/PTX cells compared with MGC803 and SW620 cells, whereas Bax protein levels were lower in resistant cells. Furthermore, MGC803/PTX cells showed obvious resistance to PTX in vivo. To our knowledge, this is the first report on the establishment of a PTX-resistant MGC803 cell line, which is an important tool to explore the resistance of anticancer drugs and to overcome tumor drug resistance.

Synthesis of tetrahexahedral Au-Pd core-shell nanocrystals and reduction of graphene oxide for the electrochemical detection of epinephrine.

An innovative epinephrine sensor was fabricated by integrating tetrahexahedral (THH) Au-Pd core-shell nanocrystals on reduced graphene oxide (rGO) nanosheets. Furthermore, the nanocomposites combined the large specific areas of rGO with the high-index facets and excellent electrocatalytic activity of the THH Au-Pd nanocrystals, and the nanocomposites were an essential adapter for detecting epinephrine. In the present work, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were used to identify and characterize these unique nanocomposites, and the results revealed that a unique THH Au-Pd/rGO core-shell nanostructure was synthesized successfully. To further explore the electrochemical behaviors of these nanomaterials at a GC electrode, we applied cyclic voltammetry (CV), differential pulse voltammetry (DPV) and amperometry to study the conductivity and electrocatalytic activity of the proposed sensor, and the results suggested that the sensor based on Au-Pd/rGO presented a lower limit of detection (0.0012 µM at a signal to noise ratio of 3), wide linear detection range (0.001 µM to 1000 µM), and extraordinary selectivity and reproducibility. Moreover, the data showed that the sensor possessed good stability and acceptable accuracy to detect epinephrine in human serum samples. In summary, this work is not only a potential way to manufacture various nonenzymatic sensors but also a significant contribution to further studies in catalysis, cell fuel cells and other relevant applications.

Structure-Activity Relationship Studies of ß-Lactam-azide Analogues as Orally Active Antitumor Agents Targeting the Tubulin Colchicine Site.

We have synthesized a series of new ß-lactam-azide derivatives as orally active anti-tumor agents by targeting tubulin colchicine binding site and examined their structure activity relationship (SAR). Among them, compound 28 exhibited the most potent antiproliferative activity against MGC-803 cells with an IC50 value of 0.106 µM by induction of G2/M arrest and apoptosis and inhibition of the epithelial to mesenchymal transition. 28 acted as a novel inhibitor of tubulin polymerization by its binding to the colchicine site. SAR analysis revealed that a hydrogen atom at the C-3 position of the ß-lactam was required for the potent antiproliferative activity of ß-lactam-azide derivatives. Oral administration of compound 28 also effectively inhibited MGC-803 xenograft tumor growth in vivo in nude mice without causing significant loss of body weight. These results suggested that compound 28 is a promising orally active anticancer agent with potential for development of further clinical applications.

Gene expression profiling and pathway network analysis of anti-tumor activity by Jaridon 6 in esophageal cancer.

Jaridon 6, a novel ent-kaurene diterpenoid derived from Rabdosia rubescens (Hemsl.) Hara, possesses strong anti-tumor activity in esophageal cancer cells. In this study, we explored the underlying molecular events of the anti-tumor activity of Jaridon 6. Cell viability and apoptosis results obtained by flow cytometry confirmed the tumor inhibitory effect of Jaridon 6 in esophageal cancer cells. A cDNA microarray was performed and the observations were validated using quantitative reverse transcription polymerase chain reaction. The microarray data showed that 151 genes were differentially expressed between the untreated group and the Jaridon 6-treated group, among these were 57 upregulated genes, and 94 downregulated genes (P < 0.01, fold change threshold: 2). These included genes such as Wnt, peroxisome, and genes involved in chemokine signaling pathways. In addition, Western blot analysis demonstrated that Jaridon 6 regulated the expression of Wnt pathway proteins, including reduced levels of Dvl 2, survivin and cyclin D1, and increased levels of p-ß-catenin, and AXIN2 in EC109 and EC9706 esophageal cancer cells. In addition, recombinant murine Wnt3a could change the regulation of Jaridon 6 on Wnt pathway proteins. Immunohistochemical analysis indicated that the anti-tumor activity of Jaridon 6 was closely related to the Wnt signaling pathway in esophageal cancer cells.

A nanocomposite-based electrochemical sensor for non-enzymatic detection of hydrogen peroxide.

Hydrogen peroxide (H2O2) plays important signaling roles in normal physiology and disease. However, analyzing the actions of H2O2 is often impeded by the difficulty in detecting this molecule. Herein, we report a novel nanocomposite-based electrochemical sensor for non-enzymatic detection of H2O2. Graphene oxide (GO) was selected as the dopant for the synthesis of polyaniline (PANI), leading to the successful fabrication of a water-soluble and stable GO-PANI composite. GO-PANI was subsequently subject to cyclic voltammetry to generate reduced GO-PANI (rGO-PANI), enhancing the conductivity of the material. Platinum nanoparticles (PtNPs) were then electrodeposited on the surface of the rGO-PANI-modified glassy carbon electrode (GCE) to form an electrochemical H2O2 sensor. Compared to previously reported sensors, the rGO-PANI-PtNP/GCE exhibited an expanded linear range, higher sensitivity, and lower detection limit in the quantification of H2O2. In addition, the sensor displayed outstanding reproducibility and selectivity in real-sample examination. Our study suggests that the rGO-PANI-PtNP/GCE may have broad utility in H2O2 detection under physiological and pathological conditions.

Facile fabrication of Pt-Ag bimetallic nanoparticles decorated reduced graphene oxide for highly sensitive non-enzymatic hydrogen peroxide sensing.

A new electrocatalyst, Pt-Ag bimetallic nanoparticles decorated reduced graphene oxide nanocomposite, was successfully synthesized by a facile, eco-friendly and controllable route. The morphological characterization of RGO/Pt-Ag NPs nanocomposite was examined by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) analyzer, X-ray diffraction (XRD) spectrum, and Fourier transform infrared spectrum (FT-IR), respectively. And then, the RGO/Pt-Ag NPs nanocomposite was immobilized on the surface of glassy carbon (GC) electrode to fabricate a novel and highly sensitive non-enzymatic hydrogen peroxide sensor. The electrochemical behaviors of the prepared sensor were investigated by cyclic voltammetry and chronoamperometry. The sensor showed excellent performance toward H2O2 with sensitivity as high as 699.6 µA mM(-1)cm(-2) and 402.7 µA mM(-1)cm(-2), wide linear range of 0.005-1.5mM and 1.5-7mM, and low detection limit of 0.04µM (S/N=3). Moreover, the prepared hydrogen peroxide sensor was applied to in real samples with satisfactory results. These excellent results indicate that the prepared RGO/Pt-Ag NPs nanocomposite has broad application prospect in the field of sensors.

One step electrodeposition of dendritic gold nanostructures on ß-lactoglobulin-functionalized reduced graphene oxide for glucose sensing.

Dendritic gold nanostructures (AuNDs) were successfully synthesized by one step electrodeposition on reduced graphene oxide (rGO) functionalized by a globular protein, ß-lactoglobulin (BLG), for the first time. Owing to its sulfhydryl groups, water-soluble BLG-rGO provided a superb platform for the growth of AuNDs. Scanning electron microscopy, Raman spectroscopy and X-ray spectroscopy analysis were used to investigate the as prepared BLG-rGO-AuNDs nanocomposite. Electrocatalytic ability of the nanocomposite was evaluated by cyclic voltammetry and chronoamperometric method. In order to prove the superiority of BLG-rGO-AuNDs, we developed a novel glucose biosensor on the nanocomposite modified glassy carbon electrode (GCE) through a cross-linking method. The biosensor exhibited a remarkable sensitivity of 46.2 µA mM(-1) cm(-2), a wide linear range of 0.05-6 mM glucose, a low detection limit of 22.9 µM (S/N=3), and a rapid response time (within 6 s). The prepared biosensor also used to detect glucose in human serum and statistical analysis in the respect of reproducibility was done.