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Abstract: A one-compartment glucose/O2 biofuel cell based on an electrostatic layer-by-layer (LbL) technique on three-dimensional ordered macroporous (3DOM) gold electrode was described. A 3DOM gold electrode was synthesized electrochemically by an inverted colloidal crystal template technique. Then the macroporous gold electrodes were functionalized with Au nanoparticles (AuNPs) and enzyme, glucose dehydrogenase (GDH) or laccase. The (AuNPs/GDH) n multilayer modified macroporous gold electrode showed excellent bioelectrocatalytic activity towards glucose. The direct electroreduction towards oxygen was realized at (AuNPs/laccase) n films on 3DOM gold electrodes. The maximum power density of the cell with the macroporous film as matrix was 178μWcm−2 at 226mV, which was 16 times larger than that of the biofuel cell with the flat electrode under the same condition. The proposed method is simple and would be applicable to enhance the power output of miniaturized biofuel cell. [Copyright &y& Elsevier]

Abstract: Single-walled carbon nanohorns (SWNHs), distinguished by their high purity and distinct structure, were noncovalently functionalized with poly(sodium 4-styrenesulfonate). The functionalized SWNHs were characterized by scanning electron microscopy, atomic force microscopy, ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and thermogravimetry. Heme protein myoglobin was adsorbed onto surface of functionalized SWNHs to prepare electrochemical biosensor. Surface assembly process and direct electrochemistry of immobilized myoglobin were investigated by electrochemical impedance spectroscopy and cyclic voltammetry, respectively. The proposed biosensor exhibited good electrocatalysis to the reduction of hydrogen peroxide. The response was linear over the range 3–350μM with a detection limit of 0.5μM. Good reproducibility and stability of the biosensor were obtained toward hydrogen peroxide detection. [Copyright &y& Elsevier]

Abstract: We report a sensitively amplified electrochemical aptasensor using adenosine triphosphate (ATP) as a model. ATP is a multifunctional nucleotide that is most important as a “molecular currency” of intracellular energy transfer. In the sensing process, duplexes consisting of partly complementary strand (PCS1), ATP aptamer (ABA) and another partly complementary strand (PCS2) were immobilized onto Au electrode through the 5′-HS on the PCS1. Meanwhile, PCS2 was grafted with the Au nanoparticles (AuNPs) to amplify the detection signals. In the absence of ATP, probe methylene blue (MB) bound to the DNA duplexes and also bound to guanine bases specifically to produce a strong differential pulse voltammetry (DPV) signal. But when ATP exists, the ABA-PCS2 or ABA-PCS1 part duplexes might be destroyed, which decreased the amount of MB on the electrode and led to obviously decreased DPV signal. This phenomenon can be used to detect ATP and get a very sensitive detection limit low to 0.1nM, and the detection range could extend up to 10−7 M. Compared to the sensing platform without PCS2 grafted AuNPs, amplified function of this sensing system was also evidently proved. Therefore, such PCS1-ABA-PCS2/AuNPs sensing system could provide a promising signal-amplified model for aptamer-based small-molecules detection. [Copyright &y& Elsevier]

DNAzyme-based chemiluminescence assay exhibits excellent performance in bioanalysis but their operation in acid conditions remains challengeable. Herein, we constructed an acid-improved DNAzyme-based isothermal enzyme-free concatenated DNA circuit with significantly reduced background and simultaneously improved signal-to-noise ratio for miRNA detection. The chemiluminescence miRNA assay is composed of catalyzed hairpin assembly (CHA), hybridization chain reaction (HCR), and hemin/G-quadruplex DNAzyme units. The analyte initiates the self-assembly of CHA hairpins into numerous dsDNA, which triggers the subsequent autonomous cross-opening of HCR hairpins to generate long nanowires consisting of the hemin/G-quadruplex DNAzyme. The DNAzyme catalyzes the oxidation of luminol by hydrogen peroxide for the cascaded amplified chemiluminescence signal. The acid-improved property was demonstrated to be closely associated with the low catalytic activity of aggregated hemin under acidic conditions and the remained multiple amplified signal through concatenated DNA circuit. The general DNA circuit exhibited high sensitivity for miRNA-21 detection and chemiluminescence imaging under acidic conditions with a recognition hairpin. The acid-improved DNAzyme-based concatenated DNA circuit is promising to expand the application of chemiluminescence assay and provide a valuable strategy for early diagnosis and prognosis of cancer. An acid-improved concatenated chemiluminescence DNA circuit was successfully constructed for sensitive and selective detection and imaging of miRNA with significantly reduced background and simultaneously improved signal-to-noise ratio. [Display omitted] • The acid-improved hemin/G-quadruplex DNAzyme-based concatenated DNA circuit was constructed with high signal-to-noise ratio. • The acid-improved property is demonstrated to be closely associated with the low catalytic activity of aggregated hemin. • The concatenated chemiluminescence DNA biosensor exhibits high sensitivity and selectivity for miRNA detection and imaging. [ABSTRACT FROM AUTHOR]

Abstract: We developed a stable, sensitive electrochemiluminescence (ECL) biosensor based on the synthesis of a new sol–gel material with the ion-exchange capacity sol–gel to coimmobilize the Ru(bpy)3 2+ and enzyme. The partial sulfonated (3-mercaptopropyl)-trimethoxysilane sol–gel (PSSG) film acted as both an ion exchanger for the immobilization of Ru(bpy)3 2+ and a matrix to immobilize gold nanoparticles (AuNPs). The AuNPs/PSSG/Ru(bpy)3 2+ film modified electrode allowed sensitive the ECL detection of NADH as low as 1nM. Such an ability of AuNPs/PSSG/Ru(bpy)3 2+ film to promote the electron transfer between Ru(bpy)3 2+ and the electrode suggested a new, promising biocompatible platform for the development of dehydrogenase-based ECL biosensors. With alcohol dehydrogenase (ADH) as a model, we then constructed an ethanol biosensor, which had a linear range of 5μM to 5.2mM with a detection limit of 12nM. [Copyright &y& Elsevier]

Abstract: A NADH and glucose biosensor based on thionine cross-linked multiwalled carbon nanotubes (MWNTs) and Au nanoparticles (Au NPs) multilayer functionalized indium-doped tin oxide (ITO) electrode were presented in this paper. The effect of light irradiation on the enhancement of bioelectrocatalytic processes of the biocatalytic systems by the photovoltaic effect was investigated. This bioelectrode exhibited excellent catalytic activity of the oxidation towards dihydronicotinamide adenine dinucleotide (NADH). Most interesting, the performance of this NADH sensor could be tuned by the visible light. When the biosensor was performed in the dark, the anodic current increased linearly with NADH concentration over the range from 0.5 to 237μM with detection limit 0.1μM and sensitivity 17nAμM−1. The sensitivity became 115nAμM−1 with detection limit 0.05μM with the light irradiation. Compared with the reaction in dark, the sensitivity increased around 7 folds while the detection limit decreased 2 folds. The glucose biosensor also exhibited the same behavior. The linear range was from 10μM to 2.56mM with the sensitivity of 7.8μAmM−1 and detection limit 5.0μM in the dark. After the light irradiation, the linear range was from 1μM to 3.25mM with the sensitivity of 18.5μAmM−1 and detection limit 0.7μM. It indicated a potential to provide an operational access to develop new kinds of photocontrolled dehydrogenase enzyme-based bioelectronics. [Copyright &y& Elsevier]

Polynucleotide kinase (PNK) plays a crucial role in phosphorylation-related DNA repair, while its real time tracking and monitoring is unexplored for limited sensitivity and robustness of current PNK sensing strategies in complex biological environment. Herein, we proposed a concatenated hybridization chain reaction (Con-HCR)-based PNK sensing platform for ultra-sensitive PNK assay and intracellular imaging. In the presence of PNK, the 5′-hydroxyl termini of hairpin H p was phosphorylated for λ exonuclease (λ Exo)-mediated DNA cleavage reaction. This leads to the generation of initiator I for stimulating the subsequent Con-HCR-motivated assembly of branched dsDNA nanostructures with tremendously amplified Förster resonance energy transfer (FRET) signal. Owing to the multiple-responsive recognitions of PNK/exonuclease and the dual amplification of Con-HCR, the proposed method realized the sensitive and selective PNK assay as well as the screening of PNK inhibitors. This FRET-based signal transduction provides a straightforward and accurate procedure for analyzing PNK from complex cell lysate. Furthermore, the robust feature of the present system enabled their extensive application in monitoring the varied expression levels of intracellular PNK in living cells. In view of these remarkable characters, our Con-HCR-mediated PNK sensing strategy shows more potential applications in clinical diagnosis and new drug discovery researches. A concatenated hybridization chain reaction (Con-HCR)-mediated polynucleotide kinase (PNK) sensing platform was successfully constructed for sensitively and selectively detecting PNK, for screening PNK inhibitors and for realizing intracellular PNK imaging. Image 1 • An isothermal autonomous cascaded hybridization chain reaction (Con-HCR) circuit is constructed with ultralow background. • The Con-HCR-mediated polynucleotide kinase (PNK) sensing platform exhibits high sensitivity and selectivity in cell lysates. • Our Con-HCR imaging system can track the varied expressions of intracellular PNK with high robustness and accuracy. [ABSTRACT FROM AUTHOR]