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Photocathodic methods in photoelectrochemical (PEC) analysis are based on the use of functional photocathodes. Heterojunction cathodes consisting of different kinds of semiconductors are being considered as favorite schemes when compared to the single-component ones. A semiconductor heterojunction between CuBi 2 O 4 (CBO) and other semiconductors has not been exploited in PEC assays so far. Herein, CBO nanospheres were initially electrochemically deposited on a fluorine-doped tin oxide (FTO) conductive glass and then coupled to chemically deposited AgI nanoparticles to obtain an electrode of type AgI/CBO/FTO. It was applied as a cathode in the PEC detection of L-cysteine as a model analyte. The sensor can selectively detect L-cysteine, and it is assumed that this is due to the selective interaction between the L-cysteine and both copper and silver via the formation of Cu-S and Ag-S bonds. The photocurrent of the electrode increases linearly with the logarithm of the cysteine concentration in the range from 0.1 and 50 μM, and the detection limit is 0.1 μM. Graphical abstract Schematic presentation of the preparation of an AgI/CuBi 2 O 4 (AgI/CBO) heterojunction on a fluorine-doped tin oxide (FTO) electrode and its application to the cathodic photoelectrochemical detection of L-cysteine.

This work reports the liposome-mediated in situ formation of the AgI/Ag/BiOI Z-scheme heterojunction on foamed nickel electrode for signal-on cathodic photoelectrochemical (PEC) bioanalysis. Specifically, in a proof-of-concept study, Ag nanoparticle-encapsulated liposomes were initially confined via the sandwich immunobinding and then processed to release numerous Ag + ions, which were then directed to react with the BiOI/Ni electrode, resulting in the in situ generation of a AgI/Ag/BiOI Z-scheme heterojunction on the electrode. The enhanced cathodic signal could be correlated to the target concentration, which thus underlays a novel signal-on cathodic liposomal PEC bioanalysis strategy. Different from previous anodic liposomal PEC bioanalysis, this work features the first cathodic liposomal PEC bioanalysis on the basis of the in situ formation of a Z-scheme heterojunction. More generally, integrated with various biorecognition events, this protocol could serve as a common basis for addressing numerous targets of interest.

With DNA as a rigid spacer, Ag nanoparticles (NPs) were bridged to CdS quantum dots (QDs) for the stimulation of exciton-plasmon interactions (EPI) in a photoelectrochemical (PEC) system. Due to their natural absorption overlap, the exciton of the QDs and the plasmon of Ag NPs could be induced simultaneously. The EPI resonant nature enabled manipulating photoresponse of the QDs via tuning interparticle distances. Specifically, the photocurrent of the QDs could be greatly attenuated and even be completely damped by the generated EPI. The work opens a different horizon for EPI investigation through an engineered PEC nanosystem, and provides a viable mechanism for new DNA sensing protocol.

Herein we demonstrate the protocol of a biocatalytic precipitation (BCP)-based sandwich photoelectrochemical (PEC) horseradish peroxidase (HRP)-linked immunoassay on the basis of their synergy effect for the ultrasensitive detection of mouse IgG (antigen, Ag) as a model protein. The hybrid film consisting of oppositely charged polyelectrolytes and CdS quantum dots (QDs) is developed by the classic layer by layer (LbL) method and then employed as the photoactive antibody (Ab) immobilization matrix for the subsequent sandwich-type Ab-Ag affinity interactions. Improved sensitivity is achieved through using the bioconjugates of HRP-secondary antibodies (Ab(2)). In addition to the much enhanced steric hindrance compared with the original one, the presence of HRP would further stimulate the BCP onto the electrode surface for signal amplification, concomitant to a competitive nonproductive absorption that lowers the photocurrent intensity. As a result of the multisignal amplification in this HRP catalyzed BCP-based PEC immunoassay, it possesses excellent analytical performance. The antigen could be detected from 0.5 pg/mL to 5.0 ng/mL with a detection limit of 0.5 pg/mL.

Single‐cell epigenetics is envisioned to decipher manifold epigenetic phenomena and to contribute to our accurate knowledge about basic epigenetic mechanisms. Engineered nanopipette technology has gained momentum in single‐cell studies; however, solutions to epigenetic questions remain unachieved. This study addresses the challenge by exploring N6‐methyladenine (m6A)‐bearing deoxyribozyme (DNAzyme) confined within a nanopipette for profiling a representative m6A‐modifying enzyme, fat mass and obesity‐associated protein (FTO). Electroosmotic intracellular extraction of FTO could remove the m6A and cause DNAzyme cleavage, leading to the altered ionic current signal. Because the cleavage can release a DNA sequence, we simultaneously program it as an antisense strand against FTO‐mRNA, intracellular injection of which has been shown to induce early stage apoptosis. This nanotool thus features the dual functions of studying single‐cell epigenetics and programmable gene regulation. [ABSTRACT FROM AUTHOR]

Single‐cell protein therapeutics is expected to promote our in‐depth understanding of how a specific protein with a therapeutic dosage treats the cell without population averaging. However, it has not yet been tackled by current single‐cell nanotools. We address this challenge by the use of a double‐barrel nanopipette, in which one lumen was used for electroosmotic cytosolic protein delivery and the other was customized for ionic evaluation of the consequence. Upon injection of protein DJ‐1 through the delivery lumen, upregulation of the antioxidant protein could protect neural PC‐12 cells against oxidative stress from phorbol myristate acetate exposure, as deduced by targeting of the cytosolic hydrogen peroxide by the detecting lumen. The nanotool developed in this study for single‐cell protein therapeutics provides a perspective for future single‐cell therapeutics involving different therapeutic modalities, such as peptides, enzymes and nucleic acids. [ABSTRACT FROM AUTHOR]

New tools for single‐cell interrogation enable deeper understanding of cellular heterogeneity and associated cellular behaviors and functions. Information of RNA expression in single cell could contribute to our knowledge of the genetic regulatory circuits and molecular mechanism of disease development. Although significant progresses have been made for intracellular RNA analysis, existing methods have a trade‐off between operational complexity and practical feasibility. We address this challenge by combining the ionic current rectification property of nanopipette reactor with duplex‐specific nuclease‐assisted hybridization chain reaction for signal amplification to realize a simple and practical intracellular nanosensor with minimal invasiveness, which enables single‐cell collection and electrochemical detection of intracellular RNA with cell‐context preservation. Systematic studies on differentiation of oncogenic miR‐10b expression levels in non‐malignant breast cells, metastatic breast cancer cells as well as non‐metastatic breast cancer cells were then realized by this nanotool accompanied by assessment of different drugs effects. This work has unveiled the ability of electrochemistry to probe intracellular RNA and opened new opportunities to study the gene expression and heterogeneous complexity under physiological conditions down to single‐cell level. [ABSTRACT FROM AUTHOR]

Here we report the studies on the electrochemical behaviors at a closed bipolar cell which is composed of two separated reaction cells containing a closed bipolar electrode (c-BPE) and its driving electrodes. The influence factors such as the concentration of the reagents, the size and material of the electrodes are studied experimentally and theoretically. And the experimental results fit with the theoretic calculation very well. Significantly, unlike the previous studies focusing on the coupling of the two c-BPE poles, this work also considers the effect of the reaction on the driving electrode on the electrochemical behavior. We believe that this research could deepen our understanding of bipolar chemistry and be useful for the future c-BPE-based applications. [ABSTRACT FROM AUTHOR]

Electrochemistry, Hybridization Chain Reaction, Nanopipette, RNA, Single Cell Analysis Keywords: Electrochemistry; Hybridization Chain Reaction; Nanopipette; RNA; Single Cell Analysis EN Electrochemistry Hybridization Chain Reaction Nanopipette RNA Single Cell Analysis 1 1 1 06/05/21 20210607 NES 210607 B Einzelzellanalyse b Eine auf einer duplexspezifischen Nuklease basierende Nanopipette wurde im Forschungsartikel auf S. 13352 von Wei-Wei Zhao, Jing-Juan Xu et al. hergestellt und zur Analyse der wirkstoffinduzierten Schwankung des miR-10b-Spiegels auf Einzelzellniveau verwendet. [Extracted from the article]

• Detection of epigenetic modifiers using electrochemical-based methods was reviewed. • Epigenetic modifiers includes nucleic modification and protein modification. • DNA modifications mean DNA methylation, hydroxymethylation and formylation. • Protein modifications mean phosphorylation and acetylation. • The research trends and challenges were discussed. Epigenetic modifications mainly includes nucleic modifications and histone modifications, which play crucial role in biological processes, such as gene and microRNA expression, DNA-protein interactions, suppression of transposable element mobility, etc. The abnormal expression of epigenetic modifiers is related to various diseases. Thus, the quantitative analysis of epigenetic modifiers is crucial to early diagnosis of disease, drug screening, prognosis of disease treatment, discovery of new biological function. Up to now, various methods have been developed for epigenetic modifier detection, including thin layer chromatography, northern blotting, microarray, chromatography-based technology, fluorescence, colorimetry, surface plasmon resonance, surface enhanced Raman spectroscopy, electrochemistry, etc. Among them, electrochemical-based techniques have received widespread attentions due to the merits of simple operation, fast response, radioactive labeling-free, low-dose reagent, inexpensive and portable instrument, high sensitivity. Therefore, in this paper, the application of electrochemical techniques for determining epigenetic biomarkers in last ten years are reviewed, in which the electrochemical techniques include electrochemistry, photoelectrochemistry and electrochemiluminescence, and the epigenetic modifiers contain DNA methylation (5-methylcytosine and 7-methylguanine), DNA hydroxymethylation (5-hydroxymethylcytosine), DNA formylation (5-formylcytosine), RNA methylation (N6-methyladenosine), protein phosphorylation and protein acetylation. In addition, application of these techniques for the determination of the relative enzymes is also reviewed. Moreover, the research trends and challenges in the development of electrochemical-based methods for monitoring epigenetic biomarkers were discussed. [ABSTRACT FROM AUTHOR]

Nanochannels have brought new opportunities for biosensor development. Herein, we present the novel concept of a nanochannels photoelectrochemical (PEC) biosensor based on the integration of a unique CuxO-nanopyramid-islands (NPIs) photocathode, an anodic aluminum oxide (AAO) membrane, and alkaline phosphatase (ALP) catalytic chemistry. The CuxO-NPIs photocathode possesses good performance, and further assembly with AAO yields a designed architecture composed of vertically aligned, highly ordered nanoarrays on top of the CuxO-NPIs film. After biocatalytic precipitation (BCP) was stimulated within the channels, the biosensor was used for the successful detection of ALP activity. This study has not only provided a novel paradigm for an unconventional nanochannels PEC biosensor, which can be used for general bioanalytical purposes, but also indicated that the new concept of nanochannel -- semiconductor heterostructures is a step toward innovative biomedical applications. [ABSTRACT FROM AUTHOR]