Zhan Wu

Development of a highly sensitive sensing platform for T4 polynucleotide kinase phosphatase and its inhibitors based on WS2 nanosheets

Dephosphorylation of the 3′ termini of nucleic acids, catalyzed by various repair enzymes is important for cellular events, such as DNA replication and recombination. Here, using T4 polynucleotide kinase phosphatase (T4 PNKP) as a model target, a novel fluorescence nanosensor based on the FRET between dye labelled DNA and WS2 nanosheets has been developed for monitoring the activity and inhibition of T4 PNKP. In this assay, we designed a single-stranded dye labelled probe that forms a self-complementary structure at one end and a 3′-phosphoryl end that served as the substrate for T4 PNKP. Once the phosphorylated probe was hydrolyzed by T4 PNKP, the resulting probe with a 3′-hydroxyl end was immediately elongated to form a double-stranded product by Klenow fragment polymerase (KF polymerase). WS2 nanosheets were introduced to quench the fluorescence of the single-stranded dye labelled probe without polymerase elongation. The dye labelled double-stranded product preserves most of the fluorescence when mixed with WS2 nanosheets. Because of the super quenching ability and the high specific surface area of WS2 nanosheets, the as-proposed platform exhibits an excellent performance with a wide linear range and a low detection limit. Additionally, the effect of its inhibitors has also been investigated. The method not only provides a universal platform for monitoring the activity and inhibition of DNA 3′-phosphatases but also shows great potential for biological process research, drug discovery, and clinical diagnostics.

Graphene quantum dots and Nafion composite as an ultrasensitive electrochemical sensor for the detection of dopamine

A novel electrochemical sensor for highly sensitive and selective detection of dopamine (DA) was developed based on a graphene quantum dots (GQDs) and Nafion composite modified glassy carbon electrode (GCE). GQDs were synthesized by a hydrothermal approach for cutting graphene sheets into GQDs and characterized by TEM, UV-vis, photoluminescence, and FT-IR spectra. The GQDs had carboxyl groups with a negative charge, which not only provided good stability, but also enabled interaction with amine functional groups in DA through electrostatic interaction to enhance the specificity of DA. The interaction and electron communication between GQDs and DA can be further strengthened via π–π stacking force. Nafion was used as an anchoring agent to increase the robustness of GQDs on the electrode surface and sensor stability and reproducibility. The GQDs–Nafion composite exhibits a good linear range of 5 nM to 100 μM and a limit of detection as low as 0.45 nM in the detection of DA. The proposed electrochemical sensor also displays good selectivity and high stability and could be used for the determination of DA in real samples with satisfactory results. The present study provides a powerful avenue for the design of an ultrasensitive detection method for clinical application.

One-pot facile synthesis of platinum nanoparticle decorated reduced graphene oxide composites and their application in electrochemical detection of rutin

We report on the synthesis of platinum nanoparticle–reduced graphene oxide (PtNP–rGO) composites and their application as a novel architecture in electrochemical detection of rutin. PtNPs anchored over rGO are synthesized through a facile one-pot synthesis method, where the reduction of GO and in situ generation of PtNPs occurred concurrently. The characterization results of transmission electron microscopy (TEM) demonstrate that PtNPs with small particle sizes are dispersed on the rGO matrix. Electrochemical measurements reveal that a PtNP–rGO modified glass carbon electrode (GCE) directly catalyzes rutin oxidation and displays an enhanced current response compared with a bare GCE. Under the optimal experimental conditions, the peak current was linear with rutin concentration in the range of 5 × 10−8 to 1 × 10−5 M with the detection limit of 1 × 10−8 M (S/N = 3) by differential pulse voltammetry. The proposed method was successfully applied to determine rutin in tablet samples with satisfactory results.

An acetylcholinesterase inhibition biosensor based on a reduced graphene oxide/silver nanocluster/chitosan nanocomposite for detection of organophosphorus pesticides

A sensitive electrochemical acetylcholinesterase (AChE) biosensor based on a reduced graphene oxide (rGO) and silver nanocluster (AgNC) modified glassy carbon electrode (GCE) was developed. rGO and AgNC nanomaterials with excellent conductivity, catalytic activity and biocompatibility offered an extremely hydrophilic surface, which facilitated the immobilization of AChE to fabricate the organophosphorus pesticide biosensor. Carboxylic chitosan (CChit) was used as a cross-linker to immobilize AChE on a rGO and AgNC modified GCE. The AChE biosensor showed favorable affinity to acetylthiocholine chloride (ATCl) and could catalyze the hydrolysis of ATCl. Based on the inhibition effect of organophosphorus pesticides on the AChE activity, using phoxim as a model compound, the inhibition effect of phoxim was proportional to its concentration ranging from 0.2 to 250 nM with a detection limit of 81 pM estimated at a signal-to-noise ratio of 3. The developed biosensor exhibited good sensitivity, stability and reproducibility, thus providing a promising tool for analysis of enzyme inhibitors and direct analysis of practical samples.

Promising biomass-derived activated carbon and gold nanoparticle nanocomposites as a novel electrode material for electrochemical detection of rutin

In this paper, six types of typical bio-wastes are used to prepare activated carbons (ACs) by high-temperature carbonization and activation with KOH. A novel electrochemical sensor for rutin was developed based on a peanut shell-derived activated carbon and gold nanoparticle composite modified glassy carbon electrode (P-AC/AuNPs/GCE). The as-synthesized ACs and composites were characterized by a variety of physicochemical techniques. The proposed sensor exhibits ideal electrochemical behavior for rutin with a wide linear range, low detection limit, and good selectivity. The desirable electrochemical performance enables the biomass-derived ACs and their composites to act as new sources of carbonaceous materials for electrochemical sensors.

Determination of Ascorbic Acid by a Gold–Zinc Oxide Nanoparticle-Modified Glassy Carbon Electrode

ABSTRACT A novel electrochemical sensing platform was developed based on flower-like gold–zinc oxide core–shell nanoparticles and a graphene nanocomposite-modified glassy carbon electrode. The gold–zinc oxide core–shell nanoflowers were synthesized by seed growth and characterized by high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, and ultraviolet-visible absorption spectroscopy. The modified electrode provided good electrocatalytic properties, rapid response, high stability, and favorable reproducibility for determination of ascorbic acid. The performance of the sensor included a linear dynamic range from 1.0 × 10−7 to 6.0 × 10−4 M, a limit of detection of 3.9 × 10−8 M, and a sensitivity of 24.12 µA/mM. The nanocomposite also provided excellent selectivity and lower potential for the oxidation of ascorbic acid. The sensor was used for the determination of ascorbic acid in tablets with satisfactory results. This device provides rapid, simple, and selective determination of ascorbic acid.