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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 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, 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]

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]

Gold nanoparticles (GNPs) were allowed to self-assemble onto a glassy carbon electrode (GCE) that was prior modified by l-cysteine. The modified electrode was then used as a voltammetric sensor in detecting the neurotransmitter serotonin. The electrode exhibited a linear voltammetric response for serotonin within a concentration range of 6.0 × 10−8M to 6 × 10−6M, with a detection limit of 2 × 10−8M. The detection of serotonin was found to be unaffected by the presence of epinephrine, dopamine, ascorbic acid and folic acid. The electrode was applied to detect serotonin added to human blood serum, with an average recovery value of 104.67%. [ABSTRACT FROM AUTHOR]

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]

A twice-walk strategy based on a three-dimensional (3D) cleat-equipped DNA walking machine with a high signal amplification efficiency was investigated for ultrasensitive detection of miRNA. Impressively, addition of duplex-specific nuclease (DSN) just once drove the twice-walk strategy, making the strategy simpler. With the advantages of being simple, rapid and ultrasensitive, the biosensor offers potential for use in early clinical diagnosis.

Complexing with adenosine-5'-monophosphate (AMP) was proven to be a facile way to enhance the oxidase-mimicking activity of Ce 4+ , and enabled nanoenzyme recovery and reuse. Additionally, the oxidase-mimicking activity of AMP-Ce 4+ infinite coordination polymers (ICPs) could be specifically inhibited by Fe 2+ . Based on this finding, we developed a simple and highly selective colorimetric assay to detect Fe 2+ .

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.

A novel voltammetric sensor, based on DNA immobilized on the surface of an ethylenediamine/polyglutamic (En/PGA) modified glassy carbon electrode (GCE), was constructed and used for determination of dihydromyricetin (DMY). The electrochemical behaviour of DMY at this sensor was investigated in pH 3.6 NaAc-HAc buffer solutions by cyclic voltammetry (CV) and differential pulse anodic voltammetry (DPV). The oxidation of DMY is an adsorption-controlled irreversible process. The oxidation mechanism was proposed and discussed. It was found that the modified electrode exhibited a linear voltammetric response for DMY in the range of 4.0 × 10(-8) mol L(-1) to 2 × 10(-6) mol L(-1), with a detection limit of 2 × 10(-8) mol L(-1). The method was also applied successfully to detect DMY in an ampelopsis sample with satisfactory results.

An electrochemical sensor, based on a graphene oxide (GO)-Nafion composite film modified glassy carbon electrode (GCE), was developed and used for detection of trace amounts of colchicine. Owing to the large surface area, good conductivity of GO and good affinity of Nafion, the sensor exhibited excellent electrocatalytic activity for the oxidation of colchicine, displaying a wide linear response from 5.0 × 10(-8) to 2.0 × 10(-5) mol L(-1) and a low detection limit of 1.5 × 10(-8) mol L(-1) in 0.1 mol L(-1) H(2)SO(4) solution. And this modified electrode exhibited a superior immunity from epinephrine, dopamine and ascorbic acid interference. The method was also applied successfully to detect colchicine in medicinal tablets.