An ultrasensitive electrochemical sensor based on cotton carbon fiber composites for the determination of superoxide anion release from cells.

A sensor is described for determination of superoxide anion (O2˙-). The electrode consists of nitrogen-doped cotton carbon fiber (NCFs) modified with silver nanoparticles (AgNPs) which have excellent catalytic capability. The resulting sensor, best operated at working potentials around -0.5 V (vs. SCE), can detect O2˙- over an extraordinarily wide range that covers 10 orders of magnitude, and the detection limit is 2.32 ± 0.07 fM. The electrode enables the release of O2˙- from living cells under normal or under oxidative stress conditions to be determined. The ability to scavenge the superoxide anions of antioxidants was also investigated. In the authors' perception, the method represents a viable tool for studying diseases related to oxidative stress. Graphical abstract Schematic presentation of the construction of an electrochemical sensor based on Nitrogen-doped cotton carbon fiber and silver nanoparticles. It can be used for the direct detection of superoxide anions released from Glioma cells (U87) under normal or under oxidative stress conditions.

Gold nanozyme as an excellent co-catalyst for enhancing the performance of a colorimetric and photothermal bioassay.

Advanced oxidation processes (AOPs) have recently proposed for advancing colorimetric sensing applications, owing to their excellent performance of sensitive color readout that generated from the oxidation of chromogenic substrates like 3,3',5,5'-tetramethylbenzidine (TMB) by reactive oxygen species (ROS) of AOPs such as ·OH and ·O2- radicals. However, the efficiency of ROS generation and the related H2O2 decomposition in most AOPs is quite low especially at neutral pH, which greatly hampered the practical sensing applications of the AOPs. We herein communicated that ß-cyclodextrin (ß-CD)-capped gold nanoparticles (ß-CD@AuNPs) can promote catalysis at neutral pH for AOP as an excellent co-catalyst. In this strategy, inorganic pyrophosphate (PPi) ions was first used to coordinate with Cu2+ and form Cu2+-PPi complex. In the presence of hydrogen peroxide, target inorganic pyrophosphatase (PPase) can hydrolyze PPi into inorganic phosphate (Pi) and release free Cu2+ simultaneously, resulting in a Cu2+-triggered Fenton-like AOP reaction. The introduced ß-CD@AuNPs acts as a co-catalyst, analogous to mediators in the most co-catalyzed system, to enhance the rate-limiting step of Cu2+/Cu+ conversion in Cu2+/H2O2 Fenton-like AOP and resulting in an efficient generation of ·OH and ·O2- radicals, which further producing an intense blue color by oxidizing TMB into its oxidation product (TMBox) within a short time. Finally, this reaction system was used to simply detecting target PPase with the colorimetric and photothermal readout based on the in-situ generated TMBox indicator. More significantly, we successfully demonstrated nanozyme can serve as a co-catalyst to promote the AOP catalysis at neutral pH, and inspire other strategies to overcome the pH limitation in the AOP catalysis and expand its colorimetric and photothermometric application.

A simple and an efficient strategy to synthesize multi-component nanocomposites for biosensor applications.

We demonstrate that core-shell multi-component nanocomposites can be grown in situ at room temperature by a novel one-step approach without adding any reductant and stabilizer. We have presented a one-step method for the synthesis of multi-component nanocomposites in water solution, the multi-component nanocomposites could be produced directly and quickly in an in situ wet-chemical reaction. Here, Au-polypyrrole (PPy)/Prussian blue (PB) nanocomposites have been synthesized successfully under the same circumstance. With the addition of pyrrole monomers into mixture solutions, the autopolymerization of pyrrole into PPy and AuCl(4)(-) was reduced to elemental Au instantaneously as well as simultaneously. At the same time, PB produced along with elemental Au serving as a catalyst. Furthermore, we investigated the performance of Au-PPy/PB nanocomposites as amperometric sensor toward the reduction of H(2)O(2), which displayed high sensitivity, fast response and good stability. The peak current of H(2)O(2) increased linearly with the concentration of H(2)O(2) in the range from 2.5×10(-9) to 1.2×10(-6)M, and the low detection limit of 8.3×10(-10)M (S/N=3) was obtained. Therefore, this work provides a new pathway to design and fabricate novel multi-component nanocomposites, which have unique characteristics and hold great applications in the fields of sensors, electrocatalysis and others.

Detection of DNA damage induced by styrene oxide in dsDNA layer-by-layer films using adriamycin as electroactive probe.

The detection of DNA damage is one of the most important topics in the DNA research fields. In this paper, an electrochemical method for the detection of DNA damage by combining the layer-by-layer assembly film with adriamycin (ADM) as an electrochemical probe was developed. Firstly, the layer-by-layer {dsDNA/PEI}(n) film was prepared by the alternate adsorption of polycationic polyethyleneimine (PEI) and negatively charged natural DNA onto glassy carbon electrode (GCE) surface. Its electrochemical behaviors were characterized by electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV), and the optimal value of n was determined to be 2. Secondly, the {dsDNA/PEI}(2) film was immersed into the solution of ADM and the {dsDNA/PEI}(2)-ADM was obtained. While transferred into the blank solution, the {dsDNA/PEI}(2)-ADM would gradually release ADM, exhibiting the good reversibility of ADM incorporation. Finally, the DNA damage induced by styrene oxide (SO) was investigated and the promising results showed that the present method can be a useful tool for the detection of DNA damage.

Electrochemical characterization of self-assembled thiol-porphyrin monolayers on gold electrodes by SECM.

Herein, the scanning electrochemical microscopy (SECM) approach is applied to study the formation of thiol-porphyrin self-assembled monolayer (SAMs). Using cyclic voltammetry (CV), the formation process is characterized adopting different probe molecules. The observed phenomena indicate that the formation process is affected by solution properties and the molecular structure of the probe molecules. In K(3)Fe(CN)(6) , the SAMs show a strong electron-transfer (ET) blocking effect on a pure porphyrin-modified electrode. However, addition of metal ions to the porphyrin molecules leads to ET. A consistent tendency is observed throughout the modification process using CV and SECM methods. Furthermore, k(eff) values, the apparent heterogeneous rate constants, obtained for different modification periods affirm the validity of these results. SECM images are used to collect surface information in the course of the modification process when the substrate potential is 0.5 V versus Ag/AgCl. The effect of the substrate potential indicates that the oxidation of the porphyrin molecules is supported by more positive potentials because of the similar bimolecular reaction of the porphyrin ring with positive charge and the probe molecules with negative charge.