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A novel, economic, and highly sensitive electrochemical sensor for the determination of trans-resveratrol (RES) was fabricated by electropolymerization of poly(L-lysine) films onto glassy carbon electrode (GCE) surface. The electrochemical behavior of RES in Britton–Robinson buffer solution (pH 2.0) on the poly(L-lysine)/GCE was investigated by cyclic voltammetry and linear sweep voltammetry for the first time. Results showed that the detection range of the proposed sensor to RES was from 0.20 to 12.0 μM with the minimum detectable concentration of 0.06 μM. The reported electrochemical sensor also exhibited high selectivity, good reproducibility, and long-term stability for RES detection. In addition, the proposed method can be employed for the determination of RES in red wines with satisfactory results. The proposed electrochemical strategy presents valuable information related to evaluation of RES levels in real samples. [ABSTRACT FROM AUTHOR]

Abstract Nickel-based metal organic framework (Ni-MOF) and carbon nanotubes composite (Ni-MOF/CNTs) is constructed via in situ self-assembly of Ni-MOF in the presence of functional CNTs solution and can be used as an efficient electrocatalytic oxidation material for glucose detection. The obtained Ni-MOF displays porous structure which is in favor of the close contact between the glucose and the active centers. Amperometric study indicates that the glucose sensor displays excellent electrochemical performance, offering a low detection limit (0.82 μM), a high sensitivity of 13.85 mA mM−1 cm−2, and a wide linear range of 1 μM–1.6 mM. Importantly, good reproducibility and repeatability, long-time stability, and excellent selectivity are obtained within the as-fabricated glucose sensor. The detection results of the real samples demonstrate the Ni-MOF/CNTs composite can be a promising candidate in glucose sensing applications. Graphical abstract Image 1 Highlights • Ni-MOF/CNTs composite with porous structure is fabricated via self-assembly method. • Ni-MOF/CNTs composite is used as sensitive nonenzymatic glucose sensor. • Ni-MOF/CNTs composite displays a low detection limit and a wide linear range. [ABSTRACT FROM AUTHOR]

This paper reports a simple approach for the determination of phentolamine mesilate (PM) using a poly(sodium p-styrenesulfonate)-multi-wall carbon nanotube (PSS-MWCNT) modified glassy carbon electrode. PSS-MWCNTs were synthesised via a moderate one-step non-covalent reaction between MWCNTs and PSS. Compared with purified MWCNTs (p-MWCNTs), the introduction of PSS improved the dispersion of MWCNTs and increased the accumulation capability of PM. As a result, the detection sensitivity for PM was greatly enhanced at this voltammetric sensor. The electrochemical properties of PM were first investigated in detail and a reaction mechanism was proposed. Utilizing linear sweep voltammetry, a low detection limit (3.0 × 10 −8  mol L −1 ) and a wide linear range (8.0 × 10 −8  mol L −1 –6.0 × 10 −6  mol L −1 ) were achieved by the proposed sensor. Finally, the proposed method was successfully applied to the analysis of real-life samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel electrochemical sensor (Ag-Gly-Gr/GCE) for the determination of bergenin was proposed. • The fabrication process of electrochemical sensor is simple and environmentally friendly. • The electrochemical behavior of bergenin was investigated, which is significant for the research of pharmacological properties. Herein, an efficient method for in-situ assembly of silver (Ag) nanoparticles on glycine functionalized graphene (Gly-Gr) has been proposed, which only requires a simple one-step hydrothermal reaction. The microstructure of the material (Ag-Gly-Gr) was characterized by a series of methods, such as FT-IR, XRD, and TEM. For comparison, glycine functionalized graphene (Gly-Gr) was prepared by the same way without adding silver nitrate. The electrochemical sensor (Ag-Gly-Gr/GCE or Gly-Gr/GCE) was prepared by coating the glassy carbon electrode (GCE) surface with dispersive droplets of the related material. The outcomes of the electrochemical impedance test showed that the charge transfer resistance of Ag-Gly-Gr/GCE was less than that of Gly-Gr/GCE and GCE. Compared with the other two sensors, Ag-Gly-Gr/GCE showed a more sensitive response for bergenin. By studying the influence of the pH and sweep rate on the peak potential, the dynamics parameters were discussed to understand the electrochemical reaction mechanism of bergenin. The strategy for quantitative analysis of bergenin was further established at the working potential of 0.8 V (vs SCE). The peak current of bergenin displayed a linear dependence for concentration in 0.01–1 μM with a detection limit of 3.0 nM. Additionally, the analytical availability of Ag-Gly-Gr/GCE was demonstrated by determining bergenin in real-life samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • A dual-amplification strategy coupling ExoIII-assisted chain cycling with CHA reaction was used for TOB detection. • A Poly A structure was used to fix the probe and adjust the probe density on the electrode surface. • The biosensor has a regenerative characteristic. Based on ExoIII-assisted nucleic acid circulation and catalytic hairpin assembly (CHA) reaction, a dual-amplification electrochemical biosensors strategy for sensitive detection of tobramycin was presented. When the target was present, the trigger 1 (T1) was released to unfold hairpin DNA (H1), which allowed the ExoIII-assisted nucleic acid circulation to proceed smoothly and create a lot of trigger 2(T2). Following that, the CHA reaction between H2 and H3 proceeded under the catalysis of T2 and produced plenty of H2-H3 complex. Signal probe labeled with ferrocene was immobilized on the electrode ahead by adenine (PolyA). Finally, the H2-H3 complex combined with the probe and the DNA strand labeled with ferrocene (C2) fell off the electrode surface. The above process significantly reduced the electrochemical signal, so the biosensor has a low detection limit of 0.11 nM. Moreover, this biosensor has a satisfactory regenerability. [ABSTRACT FROM AUTHOR]

A new and sensitive voltammetric sensor for palmatine, based on an electrochemically reduced l-methionine functionalized graphene oxide modified glassy carbon electrode (l-Met-ERGO/GCE), is reported. The electrochemical characteristics of palmatine at the proposed sensor were studied systematically and some dynamic parameters were calculated for the first time. A reasonable reaction mechanism for palmatine on the l-Met-ERGO/GCE electrode was proposed and discussed, and this could be a reference for the pharmacological action of palmatine in clinical study. Under optimized conditions, the peak current had a linear relationship with palmatine concentration in the range of 1 × 10−7 to 5 × 10−5 mol L−1 with a detection limit of 6 × 10−8 mol L−1. Additionally, the proposed method was also used to detect palmatine in human urine samples, medicinal tablets and the Chinese herb Fibraurea recisa Pierre with satisfactory results. [ABSTRACT FROM AUTHOR]

Various nucleic acid molecular machines have emerged in recent years. However, when the nucleic acid tracks are fully depleted, these walkers are highly susceptible to premature release or stalling in regions where the tracks are locally exhausted. In this work, a molecular walking machine with a cleat domain preventing dissociation from the track was explored for ultrasensitive detection of miRNA. It has been verified that the cleat design can enhance the signal amplification efficiency of molecular walking machines for electrochemical miRNA-141 detection. Notably, the single-step electrochemical biosensing platform utilizing the cleat-equipped molecular walking machine (CMWM) is exceptionally straightforward and rapid, concluding the reaction within 90 min and achieving a remarkable low detection limit of 0.26 fM. The proposed molecular walking machine with this specific cleat structure was utilized for the identification of miRNA-141 in cellular lysates, exhibiting remarkable selectivity and consistent reproducibility, showcasing its effective utility in bioanalysis. Therefore, the cleat walker developed in this study introduces an innovative method for constructing a miRNA electrochemical biosensing platform, offering new perspectives for its application in biomolecule detection and clinical disease diagnosis. A rapid one-step electrochemical method based on cleat-equipped molecular walking machine. [Display omitted] • The cleat DNA walker was successfully designed for miRNA-141 detection. • The cleat design was first applied in nuclease-powered DNA walker. • The cleat strategy can enhance the signal amplification efficiency of DNA walkers. • The proposed one-step method takes only 90 min. [ABSTRACT FROM AUTHOR]

In this study, a highly ordered three dimensional (3D) DNA nanostructure was self-assembled by label-free DNA nanotweezers, which was used as recognized probe to interact with target. Once the target was recognized by the 3D DNA nanoprobe (3D DNT), DNA nanotweezers opened to release target analog (T1). This recognition process was proceeded in homogeneous solution, which can avoid complex electrode modification and improve reaction efficiency. Then these target analogs were captured by the signal DNA probes (E1) modified on the electrode. In the assistance of Exo III, E1 was digested and the T1 was released to participate in the next cycle to realize signal amplification. Finally, an ultrasensitive carcinoembryonic antigen (CEA) electrochemical biosensing with a detection limit of 4.88 fg mL−1 was developed. • Label-free 3D DNA nanoprobe based on DNA tweezers was firstly developed in electrochemical biosensing. • Homogeneous biorecognition strategy simplified experiment procedure and improved reaction efficiency. • Exo III assisted recycling amplification technology improved the sensitivity of biosensor. [ABSTRACT FROM AUTHOR]

We have prepared a new voltammetric sensor for guanine and adenine. It is based on a glassy carbon electrode modified with a Langmuir-Blodgett film made from tetraoxocalix[2]arene[2]triazine. The direct electro-oxidation of adenine and guanine was investigated and the results indicat that in contrast to a bare glassy carbon electrode both guanine and adenine cause an increase in the oxidation peak currents along with a negative shift of the oxidation potentials. The electrode enables the simultaneous determination of guanine and adenine using square wave voltammetry. Analysis of acid denatured calf thymus DNA was carried out and the value of (G + C)/(A + T) was correctly found to be 0.75. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: The interaction between anticancer herbal drug emodin and DNA was studied with differential pulse voltammetry (DPV) and cyclic voltammetry (CV) at the bare or DNA modified GCE and ultraviolet–visible (UV) spectra. The DPV of emodin showed that peak potentials shifted to more positive value and peak currents decreased with the addition of DNA. UV spectra exhibited that the absorption of emodin at about 440nm decreased with red shift. The results showed that the herbal drug emodin interacted with DNA by intercalating into the double helix of DNA. Under our experiment conditions, the decrease of peak current was proportional to DNA concentration, which can be applied to determining DNA concentration. The combining constant (β) and combing number (m) of DNA–mEM were determined too. [Copyright &y& Elsevier]

Abstract: The electrochemical behaviour of the anticancer herbal drug emodin was investigated by cyclic voltammetry (CV) at glassy carbon electrode. In 0.05M NH3-NH4Cl (50% ethanol, pH 7.2) buffer solution, a pair of quasi-reversible redox peaks at potentials of =−0.688V and =−0.628V and one irreversible anodic peak, which was a typical anodic peak of emodin, at =−0.235V appeared at a scan rate of 100mV/s. The irreversible anodic peak currents are linearly related to the emodin concentrations in a range from 8.9×10−8 M to 7.8×10−6 M with a pre-concentration time of 80s under −0.620V. Using the established method without pretreatment and pre-separation, emodin in herbal drug was determined with satisfactory results. Moreover, the electrode process dynamics parameters were also investigated by electrochemical techniques. [Copyright &y& Elsevier]

Complexing with adenosine-5′-monophosphate (AMP) was proven to be a facile way to enhance the oxidase-mimicking activity of Ce4+, and enabled nanoenzyme recovery and reuse. Additionally, the oxidase-mimicking activity of AMP-Ce4+ infinite coordination polymers (ICPs) could be specifically inhibited by Fe2+. Based on this finding, we developed a simple and highly selective colorimetric assay to detect Fe2+. [ABSTRACT FROM AUTHOR]

This paper reports a simple and sensitive approach for the determination of troxerutin using a zirconia oxide/graphene doped carbon paste electrode (ZrO2/Gr-CPE). Highly uniform and stable ZrO2 nanoparticles were deposited on Gr sheet via a rapid route. By introducing this nanocomposite into carbon paste electrode, the obtained electrochemical sensor showed sensitive response for troxerutin. Based on this sensor, an accurate sensitive analytical method for troxerutin was established with a linear range from 2 × 10−9 to 3 × 10−7 mol L−1 and a detection limit 6 × 10−10 mol L−1. Meanwhile, the electrochemical properties of troxerutin were investigated in detail. Finally, the proposed method was applied to the analysis of real-life samples with satisfactory results. [ABSTRACT FROM AUTHOR]

In this work, a facile ratiometric fluorescence sensor for GSH measurement was designed based on MnO 2 nanosheet (NS), carbon dots (CDs), as well as a simple substrate o-phenylenediamine (OPD). Herein, MnO 2 NS played triple essential roles in the sensing system. First, it could be reduced by GSH through a special reaction, and therefore served as GSH recognizer. Second, it played as a fluorescence nanoquencher to strongly quench the fluorescence of CDs. Third, it could directly oxidize OPD to yield a luminescent product 2, 3-diaminophenazine (DAP) via the intrinsic oxidase-like activity. It revealed that MnO 2 NS could be reduced to Mn2+ in the presence of GSH. Thus its oxidase-like activity and fluorescence quenching abilities were inhibited, which then restricted the generation of DAP and recovered the fluorescence of CDs. Based on this phenomenon, a novel ratiometric fluorescence sensor for GSH determination was fabricated by measuring the ratio of fluorescent intensity of DAP to that of CDs. Besides, the constructed ratiometric fluorescent sensor, which could be facilely operated with single-wavelength excitation, exhibited high sensitivity and selectivity with a wider linear range and a lower detection limit. Image 1 • A facile single-wavelength excitation ratiometric fluorescence sensor was constructed for GSH. • MnO 2 nanosheets can not only effectively quench the fluorescence of CDs but also oxidize OPD into luminescent DAP due to its intrinsic oxidase-like activity. • DAP could also quench the fluorescence of CDs through the inner filter effect. [ABSTRACT FROM AUTHOR]

The rapid and sensitive determination of antioxidant N-(1,3-dimethylbutyl)-N′-phenyl- p -henylenediamine (6-PPD) in the environment is crucial for early intervention to prevent its adverse effects. Here, a reliable electrochemical sensor based on a N–C mediated γ-Mo 2 N nanocomposite (γ-Mo 2 N@N–C) modified carbon paste electrode (CPE) was developed and applied for selective and sensitive determination of 6-PPD. Benefiting from the superior stability and faster electron diffusion coefficient, the peak current responded to 6-PPD on the sensor linearly over a concentration range from 5 × 10−8 mol L−1 to 1.0 × 10−5 mol L−1 with a detection limit of 1.67 × 10−8 mol L−1 (4.48 ng mL−1). Moreover, the sensor maintained good anti-interference ability in the determination of 6-PPD in soil samples from different regions in Zhengzhou City. Furthermore, the density functional theory (DFT) calculations combined with kinetics analysis proved that the enhanced basicity of the γ-Mo 2 N@N–C facilitated the deprotonation of 6-PPD, with the preferred orientation facet of (200) in γ-Mo 2 N playing a vital role in inducing the dissociation of 6-PPD, thereby improving the sensor's response. Such an electrochemical sensor, with its good stability and superior sensitivity, has the potential to be applied for real-time evaluation and monitoring of environmental pollutants. [Display omitted] • γ-Mo 2 N@N–C modified electrode was firstly developed for quantitative analysis of 6-PPD. • This electrochemical sensor revealed a wide linear range with an ultralow detection limit. • The functions of γ-Mo 2 N@N–C were proved by experiment and DFT calculation. • The sensor maintained good anti-interference ability for the determination of 6-PPD in environment soil. [ABSTRACT FROM AUTHOR]

Emerging contaminant N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine has caused severe threats to ecosystems, necessitating the development of highly sensitive detection methods. Herein, a reliable and ultra-sensitive electrochemical sensor based on a carbon paste electrode modified by hexagonal wurtzite zinc oxide was developed for selective determination and degradation of N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine. Experimental results demonstrated the successful application of the sensor for detecting N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine in soil samples. The contaminant contents were found to be 1.46–24.68 nmol L−1 in Zhengzhou City and 1.99–11.3 nmol L−1 in Pingdingshan City, respectively, along with a satisfactory recovery rate. Density functional theory calculations revealed that the hexagonal wurtzite zinc oxide crystal significantly decreased the activation energy of catalytic conversion compared to cubic sphalerite, resulting in a notable improvement in sensor response. Cryogenic electron microscopy technique further confirmed that the electrocatalytic degradation product of N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine was not toxic N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine quinone. Under optimal analysis conditions, the sensor achieved widely low as well as high linear ranges (0.1–800 nmol L−1 and 0.9–20 μmol L−1) with a low detection limitation (33 pmol L−1), indicating that such a highly sensitive and cost-effective electrochemical sensor has the potential for environmental pollutants monitoring. • HW-ZnO modified electrode was developed for specific recognition of 6-PPD. • Electrocatalytic ability of HW-ZnO and CS-ZnO for 6-PPD was compared. • Cryo-EM result confirmed electrocatalytic degradation of 6-PPD on HW-ZnO/CPE. • The obtained sensor showed wide linear ranges with a low detection limit. [ABSTRACT FROM AUTHOR]

This paper reports on the first electrochemical investigation of glabridin. Under hydrothermal conditions, poly(diallyldimethylammonium chloride) (PDDA) was attached to a graphene (GR) surface via a noncovalent reaction. Moreover, the morphology and structure of PDDA-GR were characterized by transmission electron microscopy (TEM), Fourier transform-infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) analysis. Based on the nanocomposite, a (PDDA-GR/GCE) sensor was prepared, which showed a significant voltammetric response to glabridin. A simple voltammetric method for the investigation of glabridin with a wide concentration range (6.0 × 10−8 mol L−1–6.0 × 10−6 mol L−1) and a low detection limit (2.0 × 10−8 mol L−1) was proposed. The kinetic parameters were calculated, and the reaction mechanism of glabridin was obtained. Additionally, when employed for the analysis of real-life samples, the proposed method showed high accuracy and selectivity. [ABSTRACT FROM AUTHOR]

A new and sensitive electrochemical sensor for rutin determination was developed based on cetyltrimethylammonium chloride (CTAC) functionalized graphene (Gr) and palladium nanoparticles (Pd) (CTAC-Gr-PdNPs) composite. Rutin displayed remarkably increased electrochemical activity on the CTAC-Gr-PdNPs composite modified electrode due to the synergistic effect of the large surface area and electrocatalytic activity of both Gr and Pd nanoparticles, which offers the feasibility for highly sensitive determination of rutin via electrochemistry. Under the optimal experimental conditions, the oxidation peak current of rutin was proportional to its concentration in the range of 2.0 × 10−8–1.0 × 10−6 mol L−1, and the limit of detection (LOD) was 5 nM (S/N = 3). The developed method was successfully applied to determine rutin in pharmaceuticals with satisfactory recoveries, which shows that the fabricated sensor has potential in pharmaceutical analysis. [ABSTRACT FROM AUTHOR]

This work reports the first example of a colorimetric H2S sensor constructed through G-quadruplex-Cu2+ (G4-Cu2+) peroxidase mimetics employing Cu2+ ions and G-rich DNA with signal amplification. In the hydrogen peroxide (H2O2)-mediated oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB), the catalytic capacity of Cu2+ can be greatly improved in the presence of 22AG DNA, where 22AG DNA acts as a signal amplifier. However, G4-Cu2+ peroxidase mimetics lose their catalytic abilities after reacting with H2S. This is employed to develop a colorimetric assay of H2S without complex synthesis and instrumentation, with a linear range from 0.01 μM to 150 μM and a detection limit of 7.5 nM. The sensitivity of the sensor can also be adjusted by changing the concentration of Cu2+. Moreover, the developed sensor is successfully applied for the quantitative determination of H2S in human serum samples. [ABSTRACT FROM AUTHOR]

In this work, a dual amplified signal enhancement approach based on coupling deoxyribozyme (DNAzyme)-driven bipedal DNA walkers (BDW) and terminal deoxynucleotidyl transferase (TdT)-mediated DNA elongation signal amplifications has been developed for highly sensitive and label-free electrochemical detection of thrombin in human serums. In presence of thrombin, the BDW complex, which is comprised from the target thrombin and two DNAzyme-containing probes, can exhibit autonomous cleavage behavior on the surface of the substrate DNA (SD) modified electrode, and remove the cleaved DNA fragment from the electrode surface. Subsequently, the TdT can catalyze the elongation of the SD with free 3′-OH termini and formation of many G-quadruplex sequence replicates with the presence of 2′-deoxyaguanosine-5′-triphosphate (dGTP) and adenosine 5′-triphosphate (dATP) at a molar ratio of 6:4. These G-quadruplex sequences bind hemin and generate drastically amplified current response for sensitive detection of thrombin in a "signal-on" and completely label-free fashion. Under optimized conditions, the response peak current was linear with the concentration of thrombin in the range from 0.5 pM to 100000 pM with detection limit of 0.31 pM. This research provides us a sustainable idea for the hyphenated multiple amplification strategies and a stable and effective method for the detection of protein biomarkers. Image 1 • A new electrochemical biosensor was developed based on dual cascade amplification strategy of DNAzyme-driven bipedal DNA walkers. • The developed electrochemical biosensor was completely label-free in a "signal-on" fashion. • The work proves the possibility of the strategy based on DNA machine hyphenating diversified amplification methods. [ABSTRACT FROM AUTHOR]

MoS 2 and nitrogen doped active carbon composite (MoS 2 /ANC) is fabricated to detect taxifolin and exhibits superior redox current response and decreased redox potential difference. Further investigation reveals that the kinetic process of the redox reaction of taxifolin on MoS 2 /ANC electrode is controlled by both adsorption and diffusion process. Under the optimum conditions, the redox peak currents linearly relate with the concentration of taxifolin in the range of 1 × 10−9–1 × 10−6 mol L−1, accompanied by the low detection limit (3 × 10−10 mol L−1). Meanwhile, outstanding selectivity, stability and repeatability are also obtained at MoS 2 /ANC electrode. At last, the proposed method is applied to quantitatively detect taxifolin in fructus polygoni orientalis and satisfactory results have been achieved. Image 1 • The kinetic process of the redox reaction of taxifolin on MoS 2 /ANC is controlled by both adsorption and diffusion. • MoS 2 /ANC sensor displays wide linear range and low detection limit. • MoS 2 /ANC reveals outstanding selectivity in fructus polygoni orientalis detection. [ABSTRACT FROM AUTHOR]

A label-free electrochemical aptasensor was developed for the sensitive detection of interferon-gamma (IFN-γ). To do this, a diblock dual-aptamer allosteric hairpin (DDAH) was designed, followed by conjugation with gold nanoparticles (DDAH&AuNP). The presence of target destroyed the stable hairpin structure, and then the catalytic cleavage of DNAzymes removed the IFN-γ-binding molecules, triggering the allosteric switching from inactive hairpin to active streptavidin aptamer (A-DDAH&AuNP) in homogeneous system. Moreover, streptavidin-inorganic hybrid nanoflowers decorated with graphene composites (SFG) were synthesized and used as substrates to modify glassy carbon electrodes (SFG/GCE). SFG specifically bind to the A-DDAH&AuNP to realize high-efficient readout of signals. Under the optimal conditions and by using differential pulse stripping voltammetry (DPSV), the response peak currents increases linearly with the logarithm of the IFN-γ concentration in the range between 0.1 pg mL−1 and 500 ng/mL. The detection limit is as low as 19 fg mL−1. The aptasensor also has excellent electrochemical performances, which exhibits broad application prospects in biometric analysis. Image 1 • A new diblock dual-aptamer allosteric hairpin switch is designed and used to improve the sensitivity and selectivity of aptasensor. • SFG was used as substrate material to amplify the signal of sensor. • The electrochemical aptasensor showed a low detection limit of 19 fg mL−1 for IFN-γ. [ABSTRACT FROM AUTHOR]

A simple, highly sensitive voltammetric method for the determination of urapidil at poly(sodium4-styrenesulfonate) functionalized graphene-modified electrode (PSS-Gr/GCE) was described. Based on the PSS-Gr composites-modified glassy carbon electrode as a simple voltammetric sensor, it exhibited good conductivity and high sensitivity to urapidil. Under the optimize condition, a good linear relationship was obtained between peak currents and urapidil concentrations in the wider range of 2.0 × 10−9–8.0 × 10−8 mol L−1 and 2.0 × 10−7–2.0 × 10−5 mol L−1 with detection limit of 8 × 10−10 mol L−1 (S/N = 3). Based on the high sensitivity and good selectivity of the proposed electrode, the proposed method could apply to the detect of urapidil in urapidil sustained release tablets with satisfactory results. [ABSTRACT FROM AUTHOR]

Herein, a signal-on electrochemical aptasensor for highly sensitive detection of thrombin (TB) was constructed based on the DNAzyme-driven DNA walker strategy. We developed a new dual functional hairpin DNA (HP) containing a substrate sequence of the Mg2+-dependent DNAzyme (in the loop region) and the G-quadruplex forming segment (in the stem region). The DNA walker (TBA 2 -DWs), containing a TB aptamer and an enzymatic sequence, was introduced onto gold electrode (GE) by aptamers-target specific recognition, and thus initiated the enzymatic sequences to hybridize with the substrate sequence. Then, the DNA walker could repeatedly bind and cleave HP in the assistance of Mg2+, unlocking many active G-quadruplex forming sequences. Finally, hemin can further bind the G-quadruplex to form G-quadruplex/hemin complexes and generate enhanced current output. The aptasensor for TB assay showed a linear detection range from 1 pM to 60000 pM with a lower detection limit of 0.58 pM. And more, the proposed detection strategy was enzyme-free and label-free. Image 1 • A signal-on electrochemical aptasensor based on DNAzyme-driven DNA Walker strategy has been developed. • DNA walker is driven by DNAzyme and induced by dual recognition of target molecules. • A new dual functional hairpin DNA (HP) was developed and used in this electrochemical anpptsensor. • A signal-on electrochemical aptasensor is designed from enzyme-free and label-free. [ABSTRACT FROM AUTHOR]

Split aptamer strategy was often used to improve the sensitivity of aptasensor. However, traditional split aptamer strategy can not be directly used to improve the label-free aptamer based Thioflavin T (ThT) displacement assay for ATP because the split ATP aptamer display much lower enhancement effects on the fluorescence of ThT than intact aptamer. In order to address this issue, this is the first report using G-rich DNA sequence to enhance the affinity of the two split ATP aptamer halves to ThT and offer lower limit of detection (LOD), wider linear range and higher selectivity through the enhanced molecular recognition. Compared to the intact aptamer/ThT complex, the ensemble of two G-rich split ATP aptamer fragments/ThT are higher fluorescent. Consequently, G-rich sequences would improve the fluorescent signal and thus the sensing performance of the proposed assay. In the optimized conditions, the LOD of the proposed fluorescent ATP aptasensor is 2 nM, which is lower than the reported ThT/ATP aptamer based methods. Additionally, our aptasensor has a wider dynamic linear range (0.1 μM - 120 μM) and higher selectivity. The proposed aptasensor has been successfully applied to detect ATP in 15% human serum. More importantly, the current study not only provides a novel method for ATP assay but also presents a way to construct a label-free split aptamer based fluorescent sensor for other species where aptamer can be generated. • G-rich sequence enhances the molecular recognition between split ATP aptamer and ThT. • G-rich sequence improves the performances of the split aptamer based ThT displacement ATP assay. • The split aptamer based ThT displacement ATP assay was successfully constructed and applied to detect ATP in human serum. [ABSTRACT FROM AUTHOR]

Abstract This work proposes a quenched photoelectrochemical sensing method for highly selective and sensitive detection of protein via Energy Transfer (ET) effect between the AuNPs and CdS:Mn quantum dots. This detection was performed on a sandwich-type aptamer sensing interface. Chitosan modified CdS:Mn/TiO 2 /ITO electrode was used to immobilize capture DNA (S1) via -CONH- bond. In the presence of target protein, AuNPs labeled DNA (AuNPs-S2) was further bonded to the protein to fabricate sandwich sensing platform, which forced the AuNPs away from the electrode surface. In this state, the photocurrent was greatly depressed, mainly due to two factors: (a) the ET effect produced by interparticle distance between CdS:Mn and AuNPs; (b) the steric hindrance of AuNPs-S2 partly obstructs the diffusion of the electron donor. The photocurrent decreased with the increasing concentration of the target protein. Using thrombin as a target, this sensitized method showed a detectable range of 0.1 pM to 8 nM and a detection limit of 30 fM. It possessed high selectivity and good stability for detection of thrombin. This method is extremely flexible and can be extended to varieties of protein targets. Graphical abstract This work proposes a quenched photoelectrochemical sensing method for highly selective and sensitive detection of protein via Energy Transfer (ET) effect between the AuNPs and CdS:Mn quantum dots. The photocurrent decreased with the increasing concentration of the target protein. Using thrombin as a target, It possessed high selectivity and good stability for detection of thrombin. fx1 Highlights • Energy transfer (ET) between CdS:Mn and AuNPs was used to construct Thrombin PEC aptasensor for the first time. • A common and simple Sandwich-type recognition mode was applied to realize the ET effect. • This strategy can be easily extended to develop PEC aptasensors for the sensitive detection of different targets. [ABSTRACT FROM AUTHOR]

Abstract Herein, a label-free and double recognition–amplification (LDRA) strategy for carcinoembryonic antigen (CEA) detection was developed, based on a new designed dual-function messenger probe (DMP) coalescing with DNA tetrahedron probes (DTPs) and hybridization chain reaction (HCR). The DMP possess dual-function to replace CEA for specific interface hybridization and initiate hybridization chain reaction. The interfacial hybridization event was quantitatively converted to an electrochemical signal by using hemin/G-quadruplex (h-Gx) formed after the hybridization chain reaction. Self-assembled DNA tetrahedron probes, which were readily decorated on an electrode surface as a scaffold with rigid support and ordered orientation, enabled the highly efficient strands hybridization and greatly increased target accessibility as well as significantly decreased noise. The proposed assay integrated dual recognition processes and HCR signal amplification processes, achieving the identification of low concentration of CEA as detection limit of 18.2 fg mL−1 (S/N = 3) and wider linearity range of 0.0001 ng mL−1–50 ng mL−1. A new electrochemical sensing method was proposed for CEA detection and used in real clinical samples. The obtained results were good consistency with those of clinical diagnosis. Highlights • A new dual-function messenger probe (DMP) was designed for specific interface hybridization and initiate HCR. • The employment of DNA tetrahedron probes increased the probability of hybridization and reduced the background signal. • The synergetic combination of DMP and hybridization chain reaction (HCR) improved the sensitivity of the detection. • The proposed strategy was used to analysis CEA in real sample and achieved a detection limit as low as 18.2 fg/mL. [ABSTRACT FROM AUTHOR]

Highlights • The Au-Co/GO was synthesized by one-step on site chemical reduction strategy. • Au-Co nanoparticles highly dispersed on GO nanosheets are bimetallic nano-alloys. • The as-prepared Au-Co/GO nanohybrid can act as an improved ECL sensing platform. Abstract Herein, we present the synthesis and electrochemiluminescence (ECL) sensing applications of the Au-Co/GO nanocomposite. Au-Co/GO nanocomposite was prepared for the first time by decorating graphene oxide (GO) with alloy-structured Au-Co bimetallic nanoparticles (BNPs) via one-step on site chemical reduction. The obtained nanocomposite was comprehensively characterized and the results showed that alloy-structured Au-Co nanoparticles (NPs) have an average size of 4 nm and are highly dispersed on GO layers. ECL measurement revealed that the as-synthesized Au-Co/GO nanocomposite displays a synergistic effect of the GO and the Au-Co BNPs on luminol-H 2 O 2 ECL signal. Further immobilization of glucose oxidase (GOD) onto the Au-Co/GO modified electrode afforded a effective ECL glucose sensor which displayed a dynamic range of 1–100 µM with a satisfactory detection limit of 0.18 μM. Furthermore, the developed enzymatic sensors were successfully applied for monitoring glucose in real human samples. [ABSTRACT FROM AUTHOR]

Abstract In this work, we proposed a ratiomatric fluorescent strategy for sensing Fe2+ by using the carbon dots (CDs) doped lanthanide coordination polymers (Ln-CPs). Herein, the Ln-CPs were prepared by self-assemble of adenosine monophosphate (AMP) with Tb3+ (AMP-Tb) through coordination reaction, and CDs were encapsulated during the assembly process as guest materials. A cofactor, phenanthroline (Phen), could incorporate into the CDs@AMP-Tb, and strongly sensitized the luminescence of Tb3+ through energy transfer. Therefore, the obtained CDs@AMP/Phen-Tb could emit dual fluorescence signals. One is the characteristic emission of Tb3+, which could be specifically quenched by Fe2+ due to the high affinity between Phen and Fe2+. Another is originated from CDs encapsulated in Ln-CPs, which did not change in the presence of Fe2+. Subsequently, CDs@AMP/Phen-Tb was chosen as the ratiomatric fluorescent probe for sensing Fe2+, where the fluorescence of Tb3+ was quenched serving as the reporter, while that of CDs remained constant serving as the internal control for self-calibration. In addition, with the help of a reducing agent, which can reduce Fe3+ to Fe2+ efficiently, the proposed method can also be applied in selective detection Fe3+. By taking advantage of the unique property of Ln-CPs, the proposed strategy promises flexibility for designing of a series of ratiometric fluorescent sensors and expanded in practical applications. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

Abstract A new nanocomposite, zirconium dioxide nanoparticles decorated poly(diallyldimethylammonium chloride)-functionalized graphene (ZrO 2 -PDDA-Gr), was successfully synthesized through a simple and green method. The simultaneous reduction of grapheme oxide (GO) and formation of ZrO 2 to produce the ZrO 2 -PDDA-Gr had been achieved under hydrothermal conditions. The ZrO 2 -PDDA-Gr showed excellent conductivity and strong adsorption ability toward Diosmin and thus was used to be an excellent probe for electrochemical sensing. The electrochemical characteristics of Diosmin were studied in detail and some dynamics parameters of electrode process were also calculated to discuss the reaction mechanism. Under the optimized conditions, a lower detection limit of 2 × 10−9 mol L−1 (S / N = 3) and a wide linear detection range from 5 × 10−9 to 2 × 10−6 mol L−1 were achieved by differential pulse voltammetry (DPV). Additionally, the proposed electroanalytical methodology was applied in fresh lemon leaves and tablets with satisfactory results, showing that fabricated sensor has potential in application. Highlights • ZrO 2 -PDDA-Gr composite was synthesized using a facile, green and effective one-pot hydrothermal route. • ZrO 2 -PDDA-Gr/GCE sensor has high highly sensitive and excellent selectivity for the determination of Diosmin. • This method can be applied in real sample detection with satisfactory result. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A new MOF-5@PDDA-rGO-Ni nanostructure is successfully synthetized for the first time. • MOF-5@PDDA-rGO-Ni/GCE sensor exercises an extraordinary response towards echinacoside as the first detection. • The ratiometric electrochemical sensor devotes a higher accuracy and repeatability than MOF-5@PDDA-rGO-Ni/GCE that affords. • The reliability and stability of the recommendable assay are fairly validated in real sample sliced Cistanche analysis. Abstract In this work, a brand new nanocomplex (denoted as MOF-5@PDDA-rGO-Ni) is elaborately designed and successfully synthesized meaning the in-situ assembly of porous-morphology Zn-based MOFs (MOF-5) onto the as-prepared PDDA-rGO-Ni (PGN for short) nanocomposites. When this nanocomplex contributes to construct the electrochemical sensor (MOF-5@PGN/GCE), it presents a highly-sensitive response towards echinacoside, and the first measurement for echinacoside by electrochemistry accordingly evolves forward. The crystallization processes are investigated by FT-IR instrument and XRD analysis, as well as micro-morphology of modified materials is visible upon SEM and TEM. Adorably, a novel ratiometric sensor was progressively fabricated by encapsulating methylene blue (MB) molecules into cubic MOF-5 framewoks (MB encased MOF-5@PGN/GCE), and apart from assisting in establishing the analysis method with extreme accuracy and favorable practicality, it dose devote a wider linear scale and a lower detection limit than that MOF-5@PGN/GCE has given out. Drawn from the developed calibration curve using differential pulse voltammetry (DPV) technique, the peak intensity ratio (I Ech /I MB) varies linearly with increased echinacoside concentration in the range of 3.0 × 10−8– 1.0 × 10−6 mol L−1 with limit of detection (LOD) reaching 1.0 × 10−8 mol L−1 (S/N = 3). Additionally, the proposed assay method has been employed to detect echinacoside in real sample sliced cistanche with satisfactory results. [ABSTRACT FROM AUTHOR]

A novel electrochemically activated nanocomposite, CoS 2 Nanoparticles and MoS 2 Nanosheets decorated poly(diallyldimethylammonium chloride)-functionalized graphene (CoS 2 -MoS 2 -PDDA-GR), was successfully synthesized through a simple and low-cost method. X-ray diffraction (XRD), Transmission electron microscopy (TEM), Electrochemical impedance spectroscopy (EIS) and Cyclic voltammetry (CV) techniques were used to characterize the nanocomposites. Based on the CoS 2 -MoS 2 -PDDA-GR nanocomposite modified glassy carbon electrode, the electrochemical properties of eriocitrin were investigated in detail and a sensitive determinative method was established synchronously. Compared with others, this sensor exhibited larger effective surface area, more reactive site and excellent voltammetric response for eriocitrin. Under optimum conditions by DPV, the oxidation peak currents responded to eriocitrin linearly over a concentration range from 2.0 × 10 −9 to 1.0 × 10 −6 mol L −1 with a detection limit of 6.7 × 10 −10 mol L −1 (S/N = 3). In addition, this fabricated sensor was successfully applied to detect eriocitrin in real samples with satisfactory results. [ABSTRACT FROM AUTHOR]

Abstract A new nanocomposite, molybdenum copper selenide (MoCuSe) nanoparticles decorated with reduced graphene oxide (rGO), was successfully prepared by a facile hydrothermal method. The MoCuSe-rGO modified glassy carbon electrode (MoCuSe-rGO/GCE) was fabricated for the first time, which provided a large surface area and exhibited a rapid electron transport rate for the bisphenol A (BPA). The electrochemical behavior of BPA was investigated with various techniques and a new electroanalytical method was established with differential pulse voltammetry. Under optimum conditions, the proposed sensor showed an excellent electrochemical response to BPA with detection limit of 9.0 × 10−10 mol L−1 and wider linear range of 3.0 × 10−9 mol L−1–1.0 × 10−4 mol L−1. Finally, the proposed method was applied to determine BPA in real samples with satisfactory results. This work might provide a new thought for the development of electrochemical sensors with hybrid materials. Graphical abstract Unlabelled Image Highlights • A new nanocomposite, MoCuSe-rGO, was successfully prepared by a facile hydrothermal method. • The MoCuSe-rGO was applied to construct voltammetric sensor for the first time. • A new voltammetric method displayed a wider detection linear range and lower detection limit for BPA detection. [ABSTRACT FROM AUTHOR]

The nanocomposite of ruthenium oxide (RuO 2 ) loaded on Poly-(dimethyldiallylammonium chloride) (PDDA) functionalized reduced graphene oxide (RuO 2 -PDDA-rGO) was synthesized based on a one-step method. Based on the RuO 2 -PDDA-rGO modified glassy carbon electrode (GCE), a new electrochemical sensor (RuO 2 -PDDA-rGO/GCE) was fabricated and used in detection of baicalein for the first time. Compared with other reported electrochemical sensors for the detection of baicalein, the prepared RuO 2 -PDDA-rGO/GCE had a wider linear range (2–400 nM) and lower detection limit (0.6 nM, S/N = 3). The other advantages were the excellent repeatability of proposed method and good stability of prepared sensor. [ABSTRACT FROM AUTHOR]

High-density and cross-linked copper-based metal-organic framework (Cu-MOF) sheets were successfully prepared via a simple oriented growth method on a carboxylated graphene-modified electrode surface. Hydrogen peroxide (H 2 O 2 ) was selected as a model molecule to examine the performance of the thin film of Cu-MOF/graphene. The proposed sensor showed an extended linear detection range from 2.00 × 10 −7 to 1.85 × 10 −4 mol L −1 ( R = 0.998), a high sensitivity of 0.792 A (mol L −1 ) −1 , and a low detection limit of 6.7 × 10 −8 mol L −1 , due to the synergistic catalysis from the porous structure and favorable electron transfer mediating function of the electroactive Cu-MOFs and the high conductive property of the graphene. The reduction peak current of H 2 O 2 changed less than 3.7% in the presence of 57-fold high concentrations (2.0 × 10 −4 mol L −1 ) of the potential interfering species. The good selectivity of the prepared modified electrode was acquired by the size exclusion (molecular sieving) for H 2 O 2 because of the proper pore shape and pore size of Cu-MOFs. The feasibility of the assay was verified by test of H 2 O 2 in disinfectant samples. The proposed strategy presents valuable information related to the construction of non-enzymatic electrochemical sensors. [ABSTRACT FROM AUTHOR]

A novel high-sensitive electrochemical sensor with glassy carbon electrode (GCE) as support for hyperin determination is successfully designed and constructed, and the well-shaped nano-meter modified material is synthesized via a one-step and facile route. Functionalized with surfactant sodium dodecyl sulfate (SDS), Single-Walled Carbon Nanotubes (SWCNTs) are synchronously grafted with ZrO 2 nanoparticles to develop into the as-prepared nano-composite (ZrO 2 -SDS-SWCNTs). Compared to the previous reports related with hyperin detection, the linear range gets wider and detection limit (LOD) becomes lower with the aid of this novel nano-composite modified glassy carbon electrode (ZrO 2 -SDS-SWCNTs/GCE). The crystalline phases and functionalization of the preparation process has been investigated by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) instrument analysis, respectively, and the micro-morphology of related modified materials is also visibly characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). In addition, electrochemical properties of the modified materials are comparably explored by means of impedance spectroscopy (EIS) and cyclic voltammograms (CV). According to the established calibration curve under optimized condition, the peak current (Differential pulse voltammetry (DPV) signal) keeps a linear relationship with hyperin concentration in the ranges of 1.0 × 10 −9 − 3.0 × 10 −7 mol L −1 , meanwhile detection limit reaches as low as 5 × 10 −10 mol L −1 (S/N = 3). As for practical applications, the proposed sensor has also worked well on sensitive hyperin determination in real species Abelmoschus manihot. [ABSTRACT FROM AUTHOR]

This work focused on the development of a novel ratiometric fluorescence sensor for detection of Hg 2+ by using dye-doped lanthanide infinite coordination polymer (Ln-ICP) particles. The dye-doped Ln-ICP used herein was prepared by self-assemble of adenosine monophosphate (AMP) with Ce 3+ and Tb 3+ (Ce/Tb-AMP) through self-adaptive chemistry, in which the fluorescent dye coumarin was encapsulated during the assembly process as a guest molecule. Under 310 nm irradiation, the obtained coumarin@Ce/Tb-AMP itself emitted characteristic green luminescence of Tb 3+ , accompanied with a weak fluorescence at 445 nm originated from coumarin encapsulated in the Ce/Tb-AMP networks. The fluorescence emission of coumarin became strong when it was released to the solution. In the presence of Hg 2+ , the coumarin@Ce/Tb-AMP was destroyed due to the specific coordination interaction between AMP and Hg 2+ , which leaded to the release of coumarin to the solution meanwhile. Consequently, the fluorescence of Ce/Tb-AMP was quenched, while that of coumarin enhanced. On the basis of this strategy, we developed a novel ratiometric fluorescent sensor for the detection of Hg 2+ by measuring the ratio of fluorescent intensity of the coumarin@Ce/Tb-AMP suspension, which showed a wide linear range from 0.08 to 1000 nM and detection limit of 0.03 nM with high selectivity and sensitivity. Furthermore, the constructed ratiometric fluorescent sensor was successfully applied in detecting Hg 2+ in drinking water and human blood serum (HBS) with satisfactory results. [ABSTRACT FROM AUTHOR]

This paper described a novel, facile and nonenzymatic electrochemical biosensor to detect hydrogen peroxide (H 2 O 2 ). The sensor was fabricated based on Pd-Pt nanocages and SnO 2 /graphene nanosheets modified electrode (PdPt NCs@SGN/GCE). The electrochemical behavior of PdPt NCs@SGN/GCE exhibited excellent catalytic activity toward H 2 O 2 with fast response, high selectivity, superior sensitivity, low detection limit of 0.3 μM and large linear range from 1 μM to 300 μM. Under these obvious advantages, the constructed biosensor provided to be reliable for determination of H 2 O 2 secreted from human cervical cancer cells (Hela cells). Hence, the proposed biosensor is a promising candidate for detection of H 2 O 2 in situ released from living cells in clinical diagnostics. [ABSTRACT FROM AUTHOR]

In this work, reduced graphene oxide loaded flower-like bismuth subcarbonate composite (Bi 2 O 2 CO 3 -rGO) has been successfully synthesized by a facile hydrothermal method. The prepared Bi 2 O 2 CO 3 -rGO as modification composite was applied to construct voltammetric sensor for the first time. The Bi 2 O 2 CO 3 -rGO modified glassy carbon electrode (Bi 2 O 2 CO 3 -rGO/GCE) exhibited highly sensitive response to urapidil. The electrochemical behavior of urapidil was studied in detail. Under optimum conditions, a lower detection limit (1.5 × 10 −9  mol L −1 ) and wider linear range (5.0 × 10 −9  mol L −1 –4.0 × 10 −6  mol L −1 ) were achieved by the proposed sensor. Finally, the proposed method was applied to the analysis of real sample, and the results showed applicable and reliable. [ABSTRACT FROM AUTHOR]

This work designed an artificial substrate peptide to synthesize peptide-hemin/G-quadruplex (peptide-DNAzyme) conjugates. In addition to enhancing catalytic activity of hemin/G-quadruplex, the peptide could also be induced and cleaved by prostate specific antigen (PSA). It was the first report on peptide-DNAzyme conjugates in application of the peptide biosensor. The polyethyleneimine-reduced graphene oxide@hollow platinum nanotubes (PEI-rGO@PtNTs) nanocomposites were cast on the glassy carbon electrode in order to form the interface of biocompatibility and huge surface area for bioprobes immobilization. In absence of PSA, the peptide-DNAzyme conjugates retained intact on the surface of the electrode to produce a strong response signal. But in presence of PSA, the peptide-DNAzyme conjugates were destroyed to release electron mediators, resulting in dramatical decrease of the electrochemicl signal. Therefore, the method had high sensitivity and super selectivity with the limit of detection calculated as 2.0 fg/mL. Furthermore, the strategy would be promising to apply for other proteases by transforming the synthetic peptide module of target. [ABSTRACT FROM AUTHOR]

Herein, we developed a high-performance electrochemical aptasensor for the detection of carcinoembryonic antigen (CEA) using highly active peptide-conjugated hemin/G-quadruplex (hGQ-peptide) and porous Pd nanoparticles (PdNPs). Of note, the hGQ-peptide showed an enhanced catalytic activity as compared to the unmodified hGQ, and thus served as efficient electrocatalyst in this biosensor. Porous PdNPs acted as supported matrixes for high immobilization of hGQ-peptide hybrids, aptamer, redox-active toluidine blue (Tb) and alcohol dehydrogenase (ADH), resulting in the formation of ADH/Tb/hGQ-peptide/aptamer/PdNPs as the proposed bioprobes. Upon the sandwich-type specific reaction between aptamer and CEA, the bioprobe was presented on the sensing interface. Highly effective signal amplification could be then achieved by the bioprobe catalyzed cascade enzymatic reaction. Compared with the original hGQ, the hGQ-peptide yielded more than 2-fold improvement in signal amplification because of the peptide-enhanced catalysis. Therefore, the designed aptasensor displayed a wide linear range from 0.0001 to 100 ng mL −1 with a lower detection limit of 20 fg mL −1 for CEA determination, presenting the better analytical performance as compared to the relevant prior biosensors. This work further expanded the application of hGQ DNAzyme in biosensor. With the good anti-interference ability and selectivity, the proposed electrochemical aptasensor held great promise for ultrasensitive detection of other proteins in clinical diagnosis. [ABSTRACT FROM AUTHOR]

In this work, we first conjugated a short peptide to thrombin binding aptamer (TBA) and bond hemin to the hybrid, effectively rendering hemin/G4-peptide more active over the original hemin/G4, so that a highly sensitive electrochemical thrombin (TB) aptasensor was developed based on it and PtNTs@rGO nanocomposite. It was the first report on the application of hemin/G4-peptide in electrochemical aptasensor. PtNTs@rGO with large surface area served as excellent nanocarrier for high loading of hemin/G4-peptide hybrids, resulting in the formation of hemin/G4-peptide–PtNTs@rGO bioconjugate as the secondary aptamer and further signal enhancement. The specific affinity of aptamer for target TB made the secondary aptamer go into the sensing interface, and then a noticeable current signal was obtained from hemin without additional redox mediators. Due to the collaborative electrocatalysis of hemin/G4-peptide and PtNTs toward H 2 O 2 , which was formed in situ during the process of hemin/G4-peptide-catalyzed oxidation of NADH with dissolved O 2 , the current intensity increased dramatically. Such an electrochemical aptasensing system could be used to detect TB with a linear range of 0.05 pM–60 nM and very lower detection limit of 15 fM. Notably, this method exhibited a higher sensitivity than that of many hemin/G4-based electrochemical strategies for TB detection due to the improvement of the catalytic activity of hemin/G4-peptide. The present works opened a new way for expanding the application of hemin/G4 in biological detection. With the mediator-free, proteinous enzyme-free yet high-sensitivity advantages, this electrochemical aptasensor held great promise for other biomarker detections in clinical diagnostics. [ABSTRACT FROM AUTHOR]

A novel electrochemical daphnetin sensor was developed by employing a nanocomposite of calcium germanate-graphene (Ca 2 GeO 4 -GR) as an effective electrode material. In this strategy, Ca 2 GeO 4 nanowires could be uniformly distributed on the GR surface with average diameter of about 30–60 nm as exhibited by transmission electron microscopy (TEM). The fabricated sensor (Ca 2 GeO 4 -GR/GCE) exhibited excellent current response towards daphnetin with linear range of 2.0 × 10 − 8 mol L − 1 to 9.0 × 10 − 7 mol L − 1 and detection limit of 6 × 10 − 9 mol L − 1 (S/N = 3). In addition, the sensor also demonstrated strong anti-interference properties in the presence of some metal ions and organic compounds. The proposed method was successfully applied for determination of daphnetin in traditional Chinese medicine (Zushima) and Zushima tablets with satisfactory results. [ABSTRACT FROM AUTHOR]

This paper demonstrated using polyethylenimine (PEI)-functionalized graphene (Gr) incorporating tin oxide (SnO2) hybrid nanocomposite as a platform for nonenzymatic H2O2 electrochemical sensor. The results of UV-vis spectroscopy and X-ray diffraction (XRD) confirmed the simultaneous formation of tin oxide (SnO2) nanocomposite and reduction of graphene oxide (GO). Transmission electron microscopy (TEM) images showed a uniform distribution of nanometer-sized tin oxide nanoparticles on the grapheme sheets, which could be achieved using stannous chloride (SnCl2) complex instead of tin oxide as precursor. The electrochemical measurements, including cyclic voltammetry (CV) and amperometric performance (I-t), showed that the PEI-functionalized Gr supported SnO2 (SnO2-PEI-Gr) exhibited an excellent electrocatalytic activity toward the H2O2. The corresponding calibration curve of the current response showed a linear detection range of 9×10−6∼1.64×10−3 mol L−1, while the limit of detection was estimated to be 1×10−6 mol L−1. Electrochemical studies indicated that SnO2 and functionalized Gr worked synergistically for the detection of H2O2. [ABSTRACT FROM AUTHOR]

Baicalein and baicalin are the major flavonoids found in Scutellariae Radix, an essential herb which has had a presence in traditional Chinese medicine (TCMs) for more than two thousands of years. Owing to their similar characteristics and physiochemical properties, sensitive, it is a great challenge to detect both of them simultaneously. In this work, a novel, facile and sensitive electrochemical method was proposed based on tantalum oxide (Ta 2 O 5 ), niobium oxide (Nb 2 O 5 ) particles and antiseptic chitosan modified carbon paste electrode (Ta 2 O 5 -Nb 2 O 5 @CTS-CPE). Scanning electron microscope (SEM), X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV) and electrochemical impedance spectrum (EIS) were used to characterize the properties and investigate the electrochemical response of the sensor. The electrochemical behaviors and redox mechanisms of two analytes were investigated at the target electrode. Under the optimum conditions, the highly sensitive and simultaneous determination of baicalein and baicalin was successfully achieved with a linear response range of 0.08–8.0 μM for both of them. The obtained detection limits for baicalein and baicalin were of 0.05 and 0.03 μM (S/N=3), respectively. Furthermore, the proposed sensor displayed high sensitivity, excellent stability and satisfactory results in Scutellariae Radix samples analysis and hydrolysis process analysis of baicalin in vivo . [ABSTRACT FROM AUTHOR]

trans-Resveratrol is often considered as one of the quality standards of red wine, and the development of a sensitive and reliable method for monitoring the trans-resveratrol levels in red wine is an urgent requirement for the quality control. Here, a novel voltammetric approach was described for probing trans-resveratrol using a graphene-modified glassy carbon (GC) electrode. The proposed electrode was prepared by one-step electrodeposition of reduced graphene oxide (ERGO) at a GC electrode. Compared with the bare GC electrode, the introduced graphene film on the electrode surface dramatically improved the sensitivity of the sensor response due to the π-π interaction between the graphene and trans-resveratrol. The developed sensor exhibited low detection limit of 0.2 μM with wide linear range of 0.8–32 μM and high stability. For the analysis of trans-resveratrol in red wine, the high anti-interference ability and the good recoveries indicated the great potential for practical applications. [ABSTRACT FROM AUTHOR]

In this work, poly(sodium p-styrenesulfonate) (PSS)-functionalized graphene supported palladium nanoparticles (Pd) composites were fabricated with simple ultrasonic bath method. The morphology and structure of PSS-GR-Pd composites were characterized using UV–vis absorption spectra, X-ray diffraction and Transmission Electron Microscopy. By combining the merits of the PSS-GR and Pd NPs, a new electrochemical sensor was erected to detect amaranth based on the PSS-GR-Pd nanocomposites. The electrochemical behavior of amaranth was investigated systematically in 0.1 mol L −1 phosphate buffer solution (PBS 2.0). At the optimum parameter, I pa was found to be linearly dependent on the concentrations of amaranth (1×10 −7 –9×10 −6 mol L −1 ). The detection limit was 7 nM (S/N=3) and sensitivity was 5.85 μA μM −1 . Finally, this system was utilized for determining amaranth in soft drink using the standard addition method. [ABSTRACT FROM AUTHOR]

A one-step and facile method using SnCl 2 ·H 2 O as reducing agent to reduce graphene oxide (GO) was performed in the aid of poly(diallyldimethylammonium chloride) solution (PDDA). SnCl 2 ·H 2 O is not only a reducing agent for graphene oxide (GO), but also a precursor of SnO 2 . SnO 2 -PDDA-GR composite was characterized by various surface, structural and electrochemical analysis techniques, such as transmission electron microscopy (TEM), UV spectrum (UV–vis), Infrared Spectrum (IR), X-ray diffraction (XRD), Cyclic voltammograms (CV) and electrochemical impedance (EIS). The SnO 2 -PDDA-GR composite was used to constructed electrochemical sensor (SnO 2 -PDDA-GR/GCE) for the determination of daidzein. Under the optimized experimental condition, it was found that the response of peak current is linear to the concentration of daidzein in the ranges of 2.0×10 −8 −1.0×10 −6 mol L −1 , and the detection limit was estimated to be 6.7×10 −9 mol L −1 (S/N=3). Furthermore, this sensor was successfully applied for the determination of daidzein in traditional Chinese medicine (pueraria lobata) and Daidzein tablets. [ABSTRACT FROM AUTHOR]

In this work, we propose a strategy for the fluorescence assay of histidine (His) and cysteine (Cys) by using lanthanide coordination polymer nanoparticles (Ln-CPN) as a fluorescent probe. The Ln-CPN were prepared by self-assembly of adenosine monophosphate (AMP) with Tb3+, i.e. AMP-Tb. The nonluminescent AMP-Tb could be efficiently sensitized by 5-sulfosalicylic acid (SSA). The fluorescence of AMP-Tb-SSA can be remarkably quenched by Cu2+, and that of the resulting Cu/SSA/AMP-Tb can be significantly enhanced by His and Cys. Thus, a specific fluorescence “turn-on” assay for His and Cys was developed by using Cu/SSA/AMP-Tb as a sensing platform. The enhanced fluorescence intensity was proportional to the His and Cys concentration in the range from 0.2 to 150 μM and 0.5 to 200 μM, respectively, with the detection limits of 70 nM and 100 nM. Additionally, taking advantage of a masking agent for His, the differentiation of His from Cys was achieved in our system. Furthermore, the protocol can also work well for analyzing His and Cys in practical plasma samples with recovery in the range of 100.3–104.1%. [ABSTRACT FROM AUTHOR]

Chrysin and baicalein are the major flavonoids found in oroxylum indicum, an essential herb in traditional Chinese medicine (TCM). Owing to their similar characteristics and physiochemical property, it is a great challenge to detect both of them simultaneously. In this work, tantalum oxide (Ta 2 O 5 ) particles and chitosan modified carbon paste electrode (Ta 2 O 5 -CTS-CPE) was prepared and characterized by scanning electron microscope (SEM), X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV) and electrochemical impedance spectrum(EIS). Under the optimum conditions, the prepared Ta 2 O 5 -CTS-CPE exhibited excellent electrocatalytic activity toward the oxidation of chrysin and baicalein, and it could serve as the sensor for highly sensitive and simultaneous determination both of them. The linear range is 0.08–4.0 μM for both of them, and the detection limits were determined to be 0.03 and 0.05 μM (S/N=3) for chrysin and baicalein, respectively. Furthermore, the proposed electrochemical sensor displayed high sensitivity, excellent stability and got satisfactory results in oroxylum indicum samples analysis. [ABSTRACT FROM AUTHOR]