Ligand-modified multi-walled carbon nanotubes for potentiometric detection of silver.

Three novel hybrid materials have been synthesized by ligands: N-(2-vinylsulfanyl-ethylidene)-benzene-1,2-dimine (SBD), N-pyridin-2-ylmethylene-benzene-1,2-dimine (NBD) and N-furan-2-ylmethylene-benzene-1,2-dimine (OBD), covalently linking to multi-walled carbon nanotubes (MWCNTs). These MWCNT hybrid materials were used both as ionophores and as ion-to-electron transducers to construct Ag(+) carbon paste electrodes. The resulting electrodes show higher selectivity to Ag(+) than other cations tested.

Multi-wall carbon nanotube-polyaniline biosensor based on lectin-carbohydrate affinity for ultrasensitive detection of Con A.

In this paper, a novel method for detecting concanavalin A (Con A) was developed based on lectin-carbohydrate biospecific interactions. Multi-wall carbon nanotube-polyaniline (MWNT-PANI) nanocomposites, synthesized by in situ polymerization, were chosen to immobilize d-glucose through the Schiff-base reaction. The immobilized D-glucose showed high binding sensitivity and excellent selectivity to its target lectin, Con A.

4-(dimethylamino)butyric acid@PtNPs as enhancer for solid-state electrochemiluminescence aptasensor based on target-induced strand displacement.

A solid-state electrochemiluminescence (ECL) aptasensor based on target-induced aptamer displacement for highly sensitive detection of thrombin was developed successfully using 4-(dimethylamino)butyric acid (DMBA)@PtNPs labeling as enhancer. Such a special aptasensor included three main parts: ECL substrate, ECL intensity amplification and target-induced aptamer displacement. The ECL substrate was made by modifying the complex of Pt nanoparticles (PtNPs) and tris(2,2-bipyridyl) ruthenium (II) (Ru(bpy)(3)(2+)) (Ru-PtNPs) onto nafion@multi-walled carbon nanotubes (nafion@MWCNTs) modified electrode surface.

Background current reduction and biobarcode amplification for label-free, highly sensitive electrochemical detection of pathogenic DNA.

By using exonuclease I and biobarcode nanoparticles, we describe a novel background current reduction strategy for amplified electrochemical detection of uropathogen specific sequences at ultralow concentrations.

Construction of an amperometric glucose biosensor based on the immobilization of glucose oxidase onto electrodeposited Pt nanoparticles-chitosan composite film.

One-step construction of Pt nanoparticles-chitosan composite film (PtNPs-CS) was firstly proposed as a novel immobilization matrix for the enzymes to fabricate glucose biosensor. This novel interface embedded in situ PtNPs in CS hydrogel was developed by one-step electrochemical deposition in solution containing CS and chloroplatinic acid (H(2)PtCl(6)). Several techniques, including scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry were employed to characterize the assembly process and performance of the biosensor.

Enzyme-nanoparticle conjugates at oil-water interface for amplification of electrochemical immunosensing.

In the current research, the preparation of biocatalytic capsule (Ab(2)-catalytic capsule) was based on utilizing "oil" (organic compound) to entrap the nano-Au/HRP/HAFP bioconjugates, which were produced by horseradish peroxidase (HRP) and HRP labeled anti-AFP (HAFP) co-conjugated on gold nanoparticles (nano-Au). For the first time, a signal amplification strategy was introduced by the prepared biocatalytic capsule as labels for electrochemical immunodetection of α-1-fetoprotein (AFP). The transmission electron microscopy (TEM) images indicated that the biocatalytic capsules were successfully synthesized.

Signal-enhanced electrochemiluminescence immunosensor based on synergistic catalysis of nicotinamide adenine dinucleotide hydride and silver nanoparticles.

A new metal-organic nanocomposite with synergistic catalysis function was prepared and developed to construct an electrochemiluminescence (ECL) immunosensor for ultrasensitive detection of tumor biomarker CA125. Silver nanoparticles (AgNPs) and nicotinamide adenine dinucleotide hydride (NADH) that can participate and catalyze the ECL reaction of Ru(bpy)(3)(2+) were employed as the metal component and the organic component to synthesize the metal-organic nanocomposite of NADH-AgNPs (NA). The novel ECL immunosensor was assembled via Ru(bpy)(3)(2+)-doped silica nanoparticles (Ru-SiO(2)) modified electrode with the NA as immune labels.

A biosensor for cholesterol based on gold nanoparticles-catalyzed luminol electrogenerated chemiluminescence.

A novel cholesterol biosensor was prepared based on gold nanoparticles-catalyzed luminol electrogenerated chemiluminescence (ECL). Firstly, l-cysteine-reduced graphene oxide composites were modified on the surface of a glassy carbon electrode. Then, gold nanoparticles (AuNPs) were self-assembled on it.

Label-free and amplified electrochemical detection of cytokine based on hairpin aptamer and catalytic DNAzyme.

In this work, by incorporating a specific DNAzyme sequence into a hairpin aptamer probe, we describe a label-free and sensitive method for electrochemical detection of cytokines using recombinant human IFN-γ as the model analyte. The hairpin aptamer probes are immobilized on a gold electrode through self-assembly. The presence of IFN-γ opens the hairpin structure and forms the hemin/G-quadruplex peroxidase-mimicking DNAzyme with subsequent addition of hemin.

Novel electrochemical catalysis as signal amplified strategy for label-free detection of neuron-specific enolase.

A label-free electrochemical immunoassay for neuron-specific enolase (NSE), a kind of lung cancer marker, was developed in this work via novel electrochemical catalysis for signal amplification. The new amplified strategy was based on the electrochemical catalysis of nickel hexacyanoferrates nanoparticles (NiHCFNPs) in the presence of dopamine (DA). NiHCFNPs, which were assembled on the porous gold nanocrystals (AuNCs) modified glassy carbon electrode (GCE), could exhibit a distinct pair of redox peaks corresponding to anodic and cathodic reactions of hexacyanoferrate (II/III).

In situ spontaneous reduction synthesis of spherical Pd@Cys-C60 nanoparticles and its application in nonenzymatic glucose biosensors.

Novel spherical Pd@Cys-C(60) nanoparticles were synthesized using an in situ spontaneous reduction process without any other reducing agent. A nonenzymatic electrochemical biosensor was developed for the detection of glucose based on the spherical nanoparticles film.

Ultrasensitive luminol electrochemiluminescence for protein detection based on in situ generated hydrogen peroxide as coreactant with glucose oxidase anchored AuNPs@MWCNTs labeling.

In this study, an ultrasensitive luminol electrochemiluminescence (ECL) immunosensor was constructed using carboxyl group functionalized multi-walled carbon nanotubes (MWCNTs) as platform and glucose oxidase (GOD) supported on Au nanoparticles (AuNPs) decorated MWCNTs (AuNPs@MWCNTs-GOD) as labels. Firstly, using poly(ethylenimine) (PEI) as linkage reagents, AuNPs@MWCNTs were prepared and introduced for binding of the secondary antibody (Ab(2)) and glucose oxidase (GOD) with high loading amount and good biological activity due to the improved surface area of AuNPs@MWCNTs and excellent biocompatibility of AuNPs. Then the GOD and Ab(2) labeled AuNPs@MWCNTs were linked to the electrode surface via sandwich immunoreactions.

Target recycling amplification for sensitive and label-free impedimetric genosensing based on hairpin DNA and graphene/Au nanocomposites.

The presence of exonuclease III leads to direct recycling and reuse of the target DNA, which in turn results in substantial signal amplification for highly sensitive, label-free impedimetric detection of specific DNA sequences.

Simultaneous electrochemical immunoassay of three liver cancer biomarkers using distinguishable redox probes as signal tags and gold nanoparticles coated carbon nanotubes as signal enhancers.

A novel strategy for simultaneous determination of three liver cancer biomarkers based on three redox labels with distinct voltammetric peaks was described. Gold nanoparticles coated carbon nanotubes were used as carriers to immobilize redox probes labeled antibodies and to amplify the signals.

Simultaneous electrochemical detection of multiple analytes based on dual signal amplification of single-walled carbon nanotubes and multi-labeled graphene sheets.

In this work, a sandwich-type electrochemical aptasensor for simultaneous sensitive detection of platelet-derived growth factor (PDGF) and thrombin is fabricated. Reduced graphene oxide sheets (rGS) are used as matrices to immobilize the redox probes, which are subsequently coated with platinum nanoparticles (PtNPs) to form the PtNPs-redox probes-rGS nanocomposites. With the employment of the as prepared nanocomposites, a signal amplification strategy was described based on bienzyme (glucose oxidase and horseradish peroxidase) modified PtNPs-redox probes-rGS nanocomposites as the tracer labels for secondary aptamers (Apt II) through sandwiched assay.

Au-nanoclusters incorporated 3-amino-5-mercapto-1,2,4-triazole film modified electrode for the simultaneous determination of ascorbic acid, dopamine, uric acid and nitrite.

A novel biosensor has been constructed by the electrodeposition of Au-nanoclusters (nano-Au) on poly(3-amino-5-mercapto-1,2,4-triazole) (p-TA) film modified glassy carbon electrode (GCE) and employed for the simultaneous determination of dopamine (DA), ascorbic acid (AA), uric acid (UA) and nitrite (NO(2)(-)). NH(2) and SH groups exposed to the p-TA layer are helpful for the electrodeposition of nano-Au. The combination of nano-Au and p-TA endow the biosensor with large surface area, good biological compatibility, electricity and stability, high selectivity and sensitivity and flexible and controllable electrodeposition process.

A multi-amplification aptasensor for highly sensitive detection of thrombin based on high-quality hollow CoPt nanoparticles decorated graphene.

In this work, we have successfully demonstrated a facile strategy to incorporate high-quality hollow CoPt bimetal alloy nanoparticles (HCoPt) onto reduced graphene oxide sheet (HCoPt-RGs). An advanced sandwich-type electrochemical aptasensor for thrombin was proposed by using the HCoPt-RGs conjugates as secondary label. The formed conjugates provided large surface area for loading plentiful redox probe thionine (Thi), horseradish peroxidase (HRP) and secondary aptamer (Apt II) with good stability and friendly biocompatibility, indicating their superior properties in electroactive mediator enrichment and biomolecule immobilization.

Graphene-promoted 3,4,9,10-perylenetetracarboxylic acid nanocomposite as redox probe in label-free electrochemical aptasensor.

Graphene/3,4,9,10-perylenetetracarboxylic acid (GPD) with three-dimensional porous structure has been successfully synthesized and served as redox probe to construct ultrasensitive electrochemical aptasensor. The GPD nanocomposite shows promoted electrochemical redox-activity of 3,4,9,10-perylenetetracarboxylic acid (PTCA) with an obvious well-defined cathodic peak from -0.7 to 0 V that never been seen from graphene or PTCA, which avoids miscellaneous redox peaks of PTCA in electrochemical characterization, offering a novel redox probe for electrochemical sensors with highly electrochemical active area and conductivity.

Dual signal amplification for highly sensitive electrochemical detection of uropathogens via enzyme-based catalytic target recycling.

We report an ultrasensitive electrochemical approach for the detection of uropathogen sequence-specific DNA target. The sensing strategy involves a dual signal amplification process, which combines the signal enhancement by the enzymatic target recycling technique with the sensitivity improvement by the quantum dot (QD) layer-by-layer (LBL) assembled labels. The enzyme-based catalytic target DNA recycling process results in the use of each target DNA sequence for multiple times and leads to direct amplification of the analytical signal.

DNAzyme-based highly sensitive electronic detection of lead via quantum dot-assembled amplification labels.

An electronic DNAzyme sensor for highly sensitive detection of Pb(2+) is demonstrated by coupling the significant signal enhancement of the layer-by-layer (LBL) assembled quantum dots (QDs) with Pb(2+) specific DNAzymes. The presence of Pb(2+) cleaves the DNAzymes and releases the biotin-modified fragments, which further hybridize with the complementary strands immobilized on the gold substrate. The streptavidin-coated, QD LBL assembled nanocomposites were captured on the gold substrate through biotin-streptavidin interactions.

Glucose biosensor based on titanium dioxide-multiwall carbon nanotubes-chitosan composite and functionalized gold nanoparticles.

In this paper, a new glucose biosensor was prepared. At first, Prussian blue (PB) was electrodeposited on a glassy carbon electrode (GCE) modified by titanium dioxide-multiwall carbon nanotubes-chitosan (TiO(2)-MWNTs-CS) composite, and then gold nanoparticles functionalized by poly(diallyldimethylammonium chloride) (PDDA-Au) were adsorbed on the PB film. Finally, the negatively charged glucose oxidase (GOD) was self-assembled on to the positively charged PDDA-Au.

Highly enhanced electrochemiluminescence based on synergetic catalysis effect of enzyme and Pd nanoparticles for ultrasensitive immunoassay.

An immunosensor based on the electrochemiluminescence (ECL) of luminol was proposed by coupling enzymatic reaction to in situ generate coreactant with Pd nanoparticles as catalyst for the ECL reaction, which was successfully applied for the ultrasensitive detection of α-1-fetoprotein with a low detection limit of 33 fg mL(-1).

In-situ produced ascorbic acid as coreactant for an ultrasensitive solid-state tris(2,2'-bipyridyl) ruthenium(II) electrochemiluminescence aptasensor.

Herein, an ultrasensitive solid-state tris(2,2'-bipyridyl) ruthenium(II) (Ru(bpy)(3)(2+)) electrochemiluminescence (ECL) aptasensor using in-situ produced ascorbic acid as coreactant was successfully constructed for detection of thrombin. Firstly, the composite of Ru(bpy)(3)(2+) and platinum nanoparticles (Ru-PtNPs) were immobilized onto Nafion coated glass carbon electrode, followed by successive adsorption of streptavidin-alkaine phosphatase conjugate (SA-ALP) and biotinylated anti-thrombin aptamer to successfully construct an ECL aptasensor for thrombin determination. In our design, Pt nanoparticles in Ru(bpy)(3)(2+)-Nafion film successfully inhibited the migration of Ru(bpy)(3)(2+) into the electrochemically hydrophobic region of Nafion and facilitated the electron transfer between Ru(bpy)(3)(2+) and electrode surface.

Highly conducting gold nanoparticles-graphene nanohybrid films for ultrasensitive detection of carcinoembryonic antigen.

A new label-free amperometric immunosensor was developed for detection of carcinoembryonic antigen (CEA) based on chitosan-ferrocene (CS-Fc) and nano-TiO(2) (CS-Fc+TiO(2)) complex film and gold nanoparticles-graphene (Au-Gra) nanohybrid. CS-Fc+TiO(2) composite membrane was first modified on a bare glass carbon electrode. Then Au-Gra nanohybrid was formed on the CS-Fc+TiO(2) membrane by self-assembly strategy.

In situ chemo-synthesized multi-wall carbon nanotube-conductive polyaniline nanocomposites: characterization and application for a glucose amperometric biosensor.

A new glucose amperometric biosensor, based on electrodeposition of platinum nanoparticles onto the surface of multi-wall carbon nanotube (MWNT)-polyaniline (PANI) nanocomposites, and then immobilizing glucose oxidase (GOD) with covalent interaction and adsorption effect, was constructed in this paper. Firstly, the MWNT-PANI nanocomposites had been synthesized by in situ polymerization and were characterized through transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, and ultraviolet and visible (UV-vis) absorption spectra. The assembled process of the modified electrode was probed by scanning electron microscopy (SEM) and cyclic voltammetry (CV).