Search

Abstract An electrochemiluminescence (ECL) biosensor based on Au NPs enhanced ECL signal of S 2 O 8 2−–O 2 system has been constructed for ultrasensitive detection of protein kinase activity. In the presence of ATP-s and protein kinase A (PKA), Au NPs can be captured on the thoil-phosphorylated peptides modified electrode surface, generating an enhanced ECL emission of S 2 O 8 2−–O 2 system. With increasing the PKA activity, more Au NPs can be captured on the modified electrode surface, resulting in the gradually enhanced ECL intensity of S 2 O 8 2−–O 2 system. Based on the Au NPs mediated the ECL amplification of S 2 O 8 2−–O 2 system, the activity of PKA can be detected sensitively with a limit of detection of 0.0002 U/mL, which is much lower than the most sensitive method in previous reports. The good conductivity and high catalytic ability of the Au NPs are revealed to account for the enhanced sensitivity in this ECL biosensor. The ECL biosensor has been successfully used for monitoring PKA activity in biological samples and screening of protein kinase inhibition. Graphical abstract ECL biosensor based on the Au NPs mediated ECL amplification of the S 2 O 8 2−–O 2 system has been designed for sensitive PKA activity detection and inhibitor screening. Unlabelled Image Highlights • ECL biosensor based on the Au NPs mediated ECL amplification of S 2 O 8 2−–O 2 has been designed. • Ultrasensitive detection of PKA activity and protein kinase inhibitor screening are realized. • Due to the good conductivity and catalytic activity of Au NPs, ECL signal for PKA detection is amplified. • This work presences an excellent PKA biosensor with a low detection limit down to 0.0002 U/mL. [ABSTRACT FROM AUTHOR]

We propose an electrochemical assay for As(III) based on trithiocyanuric acid deposited reduced graphene oxide (TTCA/rGO) using square wave anodic stripping voltammetry (SWASV). In this work, TTCA/rGO is prepared by a simple one-pot method using NaBH 4 as the reducing agent. Many TTCA molecules are successfully deposited on the surface of rGO through π-π conjugation, which endows the TTCA/rGO with excellent adsorption ability of As(III) via As−S bond. Combining the outstanding conductivity of rGO, the response of electrochemical current for As(III) determination is greatly amplified in the electrochemical detection process. Under optimum conditions, the TTCA/rGO modified gold electrode shows high sensitivity and good selectivity for the detection of As(III) with a low detection limit down to 0.054 ppb, which is promising to be applied for the rapid and sensitive determination of As(III) in complicated samples. [ABSTRACT FROM AUTHOR]

Herein, we report a novel approach to the ultrasensitive detection of DNA methyltransferase (MTase) in terms of a dual-signal recycling amplification strategy assisted by an autocatalytic and exonuclease III (Exo III). A duplex DNA probe was designed by G-quadruplex-forming oligomer (S1) hybridizing with ferrocene (Fc)-labeled DNA (S2) modified on Au electrode. With DNA adenine methylation (Dam) MTase, the response of the hairpin probe to methylation is methylated. Then it can be cleaved by the methylation-sensitive restriction endonuclease Dpn I, releasing S3. The released S3 sequence hybridizes with the dangling end of S2 sequence, forming a new duplex DNA. Then the Exo III can cleave the S2 sequence step by step, with the release of Fc from the sensing interface and autonomous generation of new secondary S3 for successive hybridization and cleavage. Meanwhile, S1 sequences on the electrode surface are folded into G-quadruplex-hemin complexes by adding K + and hemin to give a remarkable electrochemical response. Such conformational changes result in the decrease of differential pulse voltammetry (DPV) peak current of Fc and increase of the DPV peak current of G-quadruplex-hemin complexes. The dual-signal changes are linear with the concentration of DNA MTase. This novel, single electrode-based dual-signal assay strategy is superior to previous Dam assays using single electrochemical signal as output. [ABSTRACT FROM AUTHOR]

Mechanism diagram. Through the structural design at the molecular level, the ECL-COF with electrocatalytic performance and excellent electronic structure was obtained, which display an adjustable easily potential ECL platform. Meanwhile, the advanced COF'ECL platform was developed for accurate monitoring of Lu3+, indicating the inestimable application potential of COFs in environment field. [Display omitted] • The azine-linked COFs are prepared for precise ECL performance regulation. • COFs display decrease of reduction potential and increase of intensity in ECL. • Introducing nitrogen into COFs bring electrocatalysis for ECL enhancement. • COFs show efficiently carrier transport for improving ECL. • A novel COF-ECL platform is structured for Lu3+ detection. Covalent organic frameworks (COFs) have emerged as a novel class of electrochemiluminescence (ECL) materials on account of its highly tunable structure and versatile properties. However, decoding the ECL property and its luminophor structure to improve the luminous performance remains challenging, which hinders its deeper development and wider application. Herein, by condensing triphenylarene aldehydes with varying number of nitrogen atoms with 2,4,6-trimethylbenzene-1,3,5-tricarbonitrile, a series of COFs were prepared to regulate the ECL potential, opening up a new way to precisely improve ECL performance. The electron and spatial changes in the precursor are transferred to the generated COFs skeleton, resulting in a progressively decrease in the reduction potential and a gradual increase intensity in ECL with the precise increase of nitrogen content in the skeleton. Introduction of nitrogen into COFs brings electrocatalysis and planarization of the framework for more efficiently carrier transport. The conclusion is confirmed by optical, electrical tests, as well as density functional theory calculations. As a proof-of-methodology, an ECL method was developed for the selective determination of lutetium ion with a detection limit as low as 1.6 nM (S/N = 3). This work exhibits that the advanced potential-tunable ECL-COFs can be obtained accurately and easily through design structure at the molecular level, which is expected to promote the exploration of the relationship between ECL potential and framework structure, and further apply to environment-related sensing analysis. [ABSTRACT FROM AUTHOR]

A novel electrochemical immunosensor based on a signal amplification strategy was developed for sensitive detection of carcinoembryonic antigen (CEA). Graphene/chitosan–ferrocene (GO/CS–Fc) was employed as the matrix to immobilize the primary antibodies (Ab1). Owing to the larger surface area, a large amount of Ab1 was captured on GO/CS–Fc sensor platform, thus amplifying the detection signal. Fe 3 O 4 /Au NPs were functionalized as the label to conjugate with the secondary antibodies (Ab2). Due to the homogeneous and narrow size distribution of Fe 3 O 4 /Au NPs, several Ab2 were bound on each nanoparticle, thus enhanced sensitivity was achieved by introducing the Fe 3 O 4 /Au NPs/Ab2 onto the electrode surface through “sandwich” immunoreactions. On the basis of p -aminophenol (AP) redox cycling amplification strategy, the developed immunosensor showed a 10-fold increase in detection signal compared to the immunosensor without Fe 3 O 4 /Au NPs labeling. The proposed immunosensor offered a sensitive determination of CEA in the range of 0.001–30 ng mL − 1 with a detection limit of 0.39 pg/mL. This immunoassay method would open up a promising platform to detect various tumor markers for diagnosis of different cancers. [ABSTRACT FROM AUTHOR]

A novel approach to the synthesis of mono-dispersed platinum nanoparticles (Pt NPs) on multiwalled carbon nanotubes (MWNTs) has been proposed. With this method, we successfully assembled mono-dispersed Pt NPs on MWNTs. The method involved the in situ high-temperature decomposition of the precursor, platinum (II) acetylacetonate (Pt(acac) 2 ), in liquid polyols. We used X-ray diffraction, scanning electron microscopy, and transmission electron microscopy to characterize the resulting MWNTs covered with Pt NPs (Pt@MWNTs). We found that the size of the Pt NPs and the coverage density on MWNTs could be tuned easily by changing the reaction temperature and the initial mass ratio of Pt(acac) 2 to MWNTs. Electrocatalytic measurements showed that the Pt@MWNTs had excellent catalytic activities in the electrooxidation of methanol and in the oxygen reduction reaction. These Pt@MWNTs have potential applications in fuel cells and biosensors. [ABSTRACT FROM AUTHOR]

A new strategy for the sensitive assay of protein kinase activity has been constructed using Fe 3 O 4 @PNE-Ti4+ nanocomposite as stationary phase in microchip electrophoresis. Through the self-polymerization of norepinephrine in weak alkaline solution, a thin poly(norepinephrine) (PNE) film can be spontaneously formed on the surface of Fe 3 O 4 nanoparticles (NPs) to produce Fe 3 O 4 @PNE NPs. Due to the good magnetic property, Fe 3 O 4 @PNE NPs can be easily fixed in poly(dimethylsiloxane) (PDMS) channel under external magnetic field. On the other hand, the catechol hydroxyl groups in PNE can chelate Ti4+ to form Fe 3 O 4 @PNE-Ti4+ in PDMS channel. When peptides are phosphorylated by protein kinase A (PKA) in the presence of adenosine 5′-triphosphate (ATP), the Fe 3 O 4 @PNE-Ti4+ packed in PDMS channels can specifically coordinate with the phosphorylated sites of phosphopeptides, but the non-phosphorylated peptides cannot bind with Ti4+. Thus, the retention time of the phosphorylated peptides in the Fe 3 O 4 @PNE-Ti4+ packed PDMS channel was increased, and phosphorylated peptides and non-phosphorylated peptides can be separated successfully. Due to the high loading of Ti4+ on the Fe 3 O 4 @PNE, this strategy can be used for the enrichment of phosphorylated peptides and electrochemical assay of PKA activity. This method can also be used for quantitative analysis of PKA activity in cell lysate, indicating its potential application in clinical diagnosis. Unlabelled Image • Electrochemical assay of PKA activity was realized using Fe 3 O 4 @PNE-Ti4+ as stationary phase. • Fe 3 O 4 @PNE NPs can be easily fixed in PDMS microchannel under external magnetic field. • Phosphorylated peptide and non-phosphorylated peptide can be separated successfully. • The method can be used for quantitative analysis of PKA activity in cell lysate. [ABSTRACT FROM AUTHOR]

A new electrochemical biosensor for sensitive detection of telomerase activity based on the hybridization chain reaction and the dual interaction of the poly-adenine (polyA) DNA with Au electrode and Ce-Ti dioxide nanorods (Ce-Ti NRs) has been constructed. Deoxynucleotide triphosphates (dNTPs) can be incorporated at the 3´-OH of TS primer by telomerase to generate the extension products with telomeric repeats (TTAGGG) n (TEP), which can hybridize with hairpin (HP) DNA and open it to form a duplex DNA with a short poly-adenine DNA single-stranded tail (s1). The duplex DNA can be recognized and selectively cleaved into single-stranded DNA fragment s1 and TEP by exonuclease III (Exo III). The released TEP can then hybridize with the HP again to initiate the s1 recycling process, which will result in the massive release of s1 fragments from HP. The s1 fragments can be immobilized on the Au electrode surface through the interaction between polyA and Au electrode on one hand. On the other hand, Ce-Ti NRs can be adsorbed on the Au electrode surface by the interaction between Ce-Ti NRs and the phosphate groups of s1, resulting in the decrease of the differential pulse voltammetry (DPV) current of the redox probe. The higher activity of telomerase, more HP can be hybridized and cleaved, more poly-adenine and Ce-Ti NRs can be immobilized on electrode surface, and remarkable decrease of the DPV signal can be observed. The biosensor exhibited good sensitivity toward telomerase activity in HeLa cells. Unlabelled Image • A novel electrochemical biosensor for sensitive detection of telomerase activity has been designed. • HCR and dual interaction of polyA DNA with Au and Ce-Ti NRs were greatly amplified the DPV signal. • Sensitive detection of telomerase activity with a low detection limit was achieved. • The method can be used for qualitative screening of telomerase inhibitor. [ABSTRACT FROM AUTHOR]

A facile strategy has been constructed for the highly efficient discrimination of single nucleotide polymorphisms (SNPs) based on magnetic functionalized graphene oxide (GO@Fe 3 O 4) modified poly(dimethylsiloxane) microchip system coupled with electrochemical detection. A methylene blue-labeled single stranded DNA (P1) can complete complementary with target mircoRNA-21 (T1) to form a perfectly matched DNA/RNA heteroduplex (P1T1), while the hybridization of the P1 with single-base mismatched sequence of mircoRNA-21 (M1) can form a loose DNA/ms-RNA heteroduplex (P1M1). The π-stacking interaction between the loose DNA/ms-RNA heteroduplex and the GO is much stronger than that of the perfectly matched DNA/RNA heteroduplex. Moreover, GO can enhance the unwinding of unstable DNA/ms-RNA through strong interaction between GO and single stranded DNA (ssDNA) and consequently increase the retention time of single-base mismatch microRNA-21 in the GO@Fe 3 O 4 -based microchip system. Therefore, the GO@Fe 3 O 4 -based microchip system exhibited high performance for the separation and detection of microRNA-21 and single-base mismatch microRNA-21, which provide a powerful protocol for SNPs discrimination within a short analytical time. More importantly, this platform can be used for other small molecules and proteins assay in various systems by simply changing the sequence of the probe DNA. Magnetic functionalized graphene oxide-based microchip system coupled with electrochemical detection has been designed for the highly efficient discrimination of single nucleotide polymorphisms. Unlabelled Image • A GO@Fe 3 O 4 -based microchip system for the discrimination of SNPs was constructed. • Separation of microRNA-21 and single-base mismatched microRNA-21 in a microchip system was achieved. • This platform opened up an avenue for other small molecules and proteins assay in various systems. [ABSTRACT FROM AUTHOR]

In this work, a sensitive electrochemiluminescence (ECL) biosensor was proposed to detect protein kinase activity utilizing the signal amplification of bull serum albumin-templated gold nanoclusters (BSA-Au NCs) for graphite-like carbon nitride material (g-C 3 N 4). In this system, g-C 3 N 4 was utilized as a cathodic ECL emitter, and BSA-AuNCs were anchored to the phosphorylated peptides modified g-C 3 N 4 /GCE by Au S bond in the presence of adenosine 5′-[γ-thio] triphosphate (ATP-s) and protein kinase A (PKA). Attributed to the outstanding catalytic activity of BSA-AuNCs in the ECL process, the ECL intensity of this system shows 4.5-fold enhancement than that without BSA-AuNCs. Such enhancement in combination with the intensity of ECL signal and protein kinase activity enables us to fabricate an ultrasensitive ECL biosensor to detect PKA with low background. The proposed ECL platform can be utilized to analyse PKA activity of biological sample quantitatively and screen kinase inhibition qualitatively. Unlabelled Image • ECL biosensor based on the interaction between g-C 3 N 4 and Au NCs has been designed. • Au NCs can act as a catalyst to efficiently magnify the ECL intensity of g-C 3 N 4. • It provided a highly sensitive strategy for PKA activity detecting with a low detection limit. • The method proved excellent performance on the kinase inhibitor assay. [ABSTRACT FROM AUTHOR]

An electrochemiluminescence (ECL) sensing approach was designed for sensitive Hg2+ detection based on oligonucleotide hosted silver cluster (DNA-Ag NCs) as effective unit for switching the ECL signal of graphite-like carbon nitride nanosheets (g-C 3 N 4 NSs). In this system, g-C 3 N 4 NSs were first immobilized on the glassy carbon electrode surface followed by the chitosan coating and probe DNA assembly. The g-C 3 N 4 NSs exhibited stable ECL intensity which was regarded as first signal switch "on" state. DNA-Ag NCs can be captured onto the g-C 3 N 4 NSs coated electrode surface via DNA hybridization, leading to the ECL signal quenching of g-C 3 N 4 NSs attributed to the ECL resonance energy transfer (ECL-RET) between the luminophore donor g-C 3 N 4 NSs and the acceptor DNA-Ag NCs, turning to signal "off" state. While in the presence of Hg2+, the formation of T-Hg2+-T coordination between DNA-Ag NCs or DNA-Ag NCs themselves would hinder DNA-Ag NCs from embellishing on the electrode surface, resulting in the recovery of the g-C 3 N 4 NSs ECL intensity corresponding to the last signal switch "on" state. Based on this, the biosensor can be demonstrated to quantitatively analyze Hg2+ with a detection of limit of 5 pM. The proposed ECL platform has been utilized to sensitive and selective monitoring Hg2+ in environmental water samples. Image 1 • ECL biosensor based on the ECL-RET between g-C 3 N 4 NSs and Ag NCs has been designed. • A switchable "on-off-on" detection strategy was designed for monitoring Hg2+. • This work presences an excellent Hg2+ biosensor with a low detection limit down to 5 pM. [ABSTRACT FROM AUTHOR]