Molybdenum-containing polypyrrole self-supporting hollow flexible electrode for hydrogen peroxide detection in living cells.

A flexible electrode based on polypyrrole-supported free-standing molybdenum oxide-molybdenum disulfide/polypyrrole nanostructure (MoO3-MoS2/PPy) was synthesized. The petal-like MoO3-MoS2 sheets grown on PPy were prepared step by step through simple electrodeposition and hydrothermal methods. The corresponding surface morphological and structural characterizations were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results showed that the prepared petal MoO3-MoS2 hybrid nanomaterials were uniformly distributed on the PPy skeleton and exhibited a three-dimensional porous network structure. The flexible electrode was used for non-enzymatic detection of hydrogen peroxide (H2O2), and the developed MoO3-MoS2/PPy nanomaterials exhibited high electrochemical sensing performance in the range of 0.3-150 µM, with the detection limit of 0.18 µM (S/N = 3). The excellent detection properties enabled the MoO3-MoS2/PPy flexible electrode to detect H2O2 released by living cells. The resulting MoO3-MoS2/PPy flexible electrode also has the advantages of customizable shape and adjustability, which provides a potential platform for constructing clinically diagnosed in vivo portable instruments and real-time environmental monitoring.

Electrochemical endotoxin aptasensor based on a metal-organic framework labeled analytical platform.

An electrochemical aptasensor for the lipopolysaccharide (LPS) detection was constructed by using copper-based metal-organic framework (Cu-MOF) as a label and the LPS aptamer of specific single-stranded DNA as a probe. The carboxyl-functionalized polypyrrole nanowires (PPy NWs) were synthesized by electrochemical polymerization method, and the amino-terminated aptamer covalently coupling with the carboxyl group of the PPy NWs was immobilized onto the modified electrode. The aptamer can specifically combine with the target LPS molecules, and Cu-MOF was labeled by adsorption based on specific interactions of LPS carbohydrate portions with anionic groups. The fabrication processes of the aptasensor were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). Differential pulse voltammetry (DPV) was used to measure electrochemical performance of the aptasensor, and the electrochemical signal can be directly measured by the electrochemical redox reaction of Cu(II)/Cu(I) existed in the Cu-MOF. The electrochemical aptasensor exhibited a high sensitivity toward LPS ranging from 1.0 pg/mL to 1.0 ng/mL with a detection limit of 0.29 pg/mL. Moreover, the developed sensor was found to have good selectivity, stability and regeneration properties, and the sensor also successfully detected LPS in real tap water samples.

Spectroscopic evidence for electrochemical effect of mercury ions on gold nanoparticles.

We demonstrated an interesting phenomenon that the electrochemical reduction of mercury ions (Hg2+) caused distinctly different morphology of gold nanorods (Au NRs) depending on the concentration of Hg2+. Specifically, in the case of low concentration, mercury formed through electrochemical reduction only deposited onto the gold surface, and then could be reversibly removed from the gold surface by electrochemical stripping process without causing obvious changes of Au NRs in shape and size. But in the case of high concentration, the reduced Hg not only deposited onto the gold surface but also entered into the interior of Au NRs making them change into gold nanospheres (Au NSs) in an irreversible manner due to the alloying effect of gold with Hg. In this situation, even though the most of Hg was removed, the Au NSs can no long return to the previous rod shape. The changing trend of Au NRs was characterized well by measuring the corresponding UV-Visible spectra. The formation of the Au/Hg nanoalloy was confirmed by high-resolution transmit electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS) results. The present study is helpful for having better understanding of the mechanism of electrochemical mercury-analysis by Au nanoparticles, and necessary to optimize the Au nanoparticles-based Hg sensing strategies.

Copper ion-assisted gold nanoparticle aggregates for electrochemical signal amplification of lipopolysaccharide sensing.

A signal amplification electrochemical aptasensor for ultrasensitive detection of lipopolysaccharide (LPS) was fabricated. The sensor was constructed with a probe of LPS aptamer and a copper ions-mediated gold nanoparticles aggregate (Cu/Au NA) as a signal amplification material. The Cu/Au NAs comprising copper ions (Cu2+) and L-cysteine modified AuNPs were fabricated by a self-assembly process. For functionalization of the electrode, the carboxylic group of a mercaptoacetic acid self-assembly layer was covalently coupled with the amine group of the aptamer. The aptamer with high specificity and affinity can effectively gather the dissociative LPS firstly, and the Cu/Au NAs were captured by anionic groups of the carbohydrate portions from LPS molecules based on the specific interactions. With the employment of the sandwich-type biosensor, the strategy can significantly amplify the electrochemical signal for determination of trace amount of LPS. The sensing performance of the electrochemical sensor was investigated by differential pulse voltammetry (DPV) and the stripping peak currents of Cu re-oxidized to Cu2+ was used to monitor the level of LPS. The electrochemical aptasensor exhibited excellent sensitivity toward LPS with a detection limit of 0.033 pg/mL (S/N = 3). The biosensor also exhibited a high specificity toward LPS in the presence of other common interfering substances and was easily regenerated. Furthermore, the fabricated biosensor showed a good practical application for LPS determination in human serum samples.

Voltammetric sensing of dopamine based on a nanoneedle array consisting of NiCo2S4 hollow core-shells on a nickel foam.

An array consisting of homogeneous NiCo2S4 hollow core-shell nanoneedles was fabricated and is shown to enable sensitive electrochemical determination of dopamine (DA). The array was grown directly on a nickel foam (NF) substrate by a two-step hydrothermal process. The hierarchical nanoarray consists of a homogeneous NiCo2S4 nanoneedle core and a NiCo2S4 nanosheet shell. A 3-dimensional micro/nano structure is formed due to the presence of the micropores of the NF. The electrode was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Compared to a plain NF electrode, the NiCo2S4-modified NF electrode displays higher electrocatalytic activity for the oxidation of DA by differential pulse voltammetry (DPV). The sensor, best operated at a typical working voltage of 134 mV (vs. saturated calomel electrode), has a linear response in the 0.5-100 µM DA concentration range and a 0.2 µM detection limit (at S/N = 3). The electrode is selective over ascorbic acid and uric acid. Graphical abstract Schematic presentation of an electrochemical sensor for selective determination of dopamine based on the use of a homogeneous NiCo2S4 hollow core-shell nanoneedle array on nickel foam.

Determination of copper ions using a phytic acid/polypyrrole nanowires modified glassy carbon electrode.

This study reports a sensitive electro-analytical method for the determination of trace amounts of Cu2+ using a phytate functionalized polypyrrole nanowires (PPy NWs) modified glass carbon electrode. The phytic acid/polypyrrole (PA/PPy) NWs were prepared by an electrostatic adsorption and ultrasonic mixing. The results showed that both PPy NWs and PA/PPy NWs modified glassy carbon electrodes have electrochemical responses toward Cu2+. However, owing to the synergistic contribution between the PPy NWs and PA, the PA/PPy NWs modified electrode exhibited higher sensitivity than that of PPy NWs modified electrode. The PA/PPy NWs composites functionalized electrodes showed a good linear relationship with Cu2+ at concentration ranges of 10-60µg·L-1, and the limit of detection (S/N=3) was 3.33µg·L-1. In addition, the electrochemical sensor was applied to assay Cu2+ in real water samples.

Functionalized gold nanoparticles/reduced graphene oxide nanocomposites for ultrasensitive electrochemical sensing of mercury ions based on thymine-mercury-thymine structure.

A sensitive, selective and reusable electrochemical biosensor for the determination of mercury ions (Hg(2+)) has been developed based on thymine (T) modified gold nanoparticles/reduced graphene oxide (AuNPs/rGO) nanocomposites. Graphene oxide (GO) was electrochemically reduced on a glassy carbon substrate. Subsequently, AuNPs were deposited onto the surface of rGO by cyclic voltammetry. For functionalization of the electrode, the carboxylic group of the thymine-1-acetic acid was covalently coupled with the amine group of the cysteamine which self-assembled onto AuNPs. The structural features of the T bases functionalized AuNPs/rGO electrode were confirmed by attenuated total reflection infrared (ATR-IR) spectroscopy and scanning electron microscopy (SEM) spectroscopy. Each step of the modification process was characterized by cyclic voltammetry (CV) and electrochemical impedence spectroscopy (EIS). The T bases modified AuNPs/rGO electrode was applied to detect various trace metal ions by differential pulse voltammetry (DPV). The proposed biosensor was found to be highly sensitive to Hg(2+) in the range of 10 ng/L-1.0 µg/L. The biosensor afforded excellent selectivity for Hg(2+) against other heavy metal ions such as Zn(2+), Cd(2+), Pb(2+), Cu(2+), Ni(2+), and Co(2+). Furthermore, the developed sensor exhibited a high reusability through a simple washing. In addition, the prepared biosensor was successfully applied to assay Hg(2+) in real environmental samples.

Complications of chemoembolization for hepatic neoplasms.

OBJECTIVE: To present a safe and effective approach to chemoembolization for hepatic neoplasms, and to discuss the complications of chemoembolization and ways of avoiding them. METHODS: The techniques and experience described herein are based on clinical practice at Yichang Central People's Hospital, Yichang, Hubei, China, where over 200 chemoembolization procedures are performed yearly, and on the results of an intensive review of 1054 chemoembolization procedures performed between July 1997 and December 2005. RESULTS: There were complications as follow: 5 cases with celiac artery branch embolization, gastric uptake in 4, 6 with gallbladder uptake and infarction, splenic uptake and infarction in 8, liver infarction and abscess formation in 3, and hepatorenal syndrome in 4, liver rupture in 2, lung uptake in 6, and spinal cord injury in 2 cases. CONCLUSION: There are numerous potential errors and complications associated with chemoembolization for unresectable liver tumors. A good understanding of the congenital and acquired variations of arterial anatomy that may be seen supplying the liver is required.