Tunneling Electron Transfer across Cell Membrane via Au Nanoparticles in Single Living Cells.

Herein, we present a new and simple electrochemical method to detect the intracellular electroactive substances by utilizing the electron tunnelling processes at the metal nanoparticles inside the cells. Intriguing discrete oxidation and reduction current spikes are obtained when testing the cells with loaded Au nanoparticles at the ultramicroelectrodes, which should come from reactive oxygen species (ROS) inside the single cell. The charges enclosed in the current spikes represent the ROS content inside the living cells, as confirmed by the fluorescence studies. As this simple electron tunnelling approach needs no nanoelectrodes or nanotip penetration processes, we believe it could have great potential applications in electrochemical analysis of single living cells.

An Ultramicroelectrode Electrochemistry and Surface Plasmon Resonance Coupling Method for Cell Exocytosis Study.

Exocytosis of a single cell has been extensively researched in recent years due to its close association with numerous diseases. However, current methods only investigate exocytosis at either the single-cell or multiple-cell level, and a method for simultaneously studying exocytosis at both levels has yet to be established. In this study, a combined device incorporating ultramicroelectrode (UME) electrochemistry and surface plasmon resonance (SPR) was developed, enabling the simultaneous monitoring of single-cell and multiple-cell exocytosis. PC12 cells were cultured directly on the SPR sensing Au film, with a carboxylated carbon nanopipette (c-CNP) electrode employed for electrochemical detection in the SPR reaction cell. Upon exocytosis, the released dopamine diffuses onto the inner wall of c-CNP, undergoing an electrochemical reaction to generate a current peak. Concurrently, exocytosis can also induce changes in the refractive index of the Au film surface, leading to the SPR signal. Consequently, the device enables real-time monitoring of exocytosis from both single and multiple cells with a high spatiotemporal resolution. The c-CNP electrode exhibited excellent resistance to protein contamination, high sensitivity for dopamine detection, and the capability to continuously monitor dopamine exocytosis over an extended period. Analysis of both SPR and electrochemical signals revealed a positive correlation between changes in the SPR signal and the frequency of exocytosis. This study introduces a novel method and platform for the simultaneous investigation of single-cell and multiple-cell exocytosis.

Revealing Hydrogen Spillover on 1T/2H MoS2 Heterostructures for an Enhanced Hydrogen Evolution Reaction by Scanning Electrochemical Microscopy.

The in situ characterization of the heterostructure active sites during the hydrogen evolution reaction (HER) process and the direct elucidation of the corresponding catalytic structure-activity relationships are essential for understanding the catalytic mechanism and designing catalysts with optimized activity. Hence, exploring the underlying reasons behind the exceptional catalytic performance necessitates a detailed analysis. Herein, we employed scanning electrochemical microscopy (SECM) to in situ image the topography and local electrocatalytic activity of 1T/2H MoS2 heterostructures on mixed-phase molybdenum disulfide (MoS2) with 20 nm spatial resolution. Our measurements provide direct data about HER activity, enabling us to differentiate the superior catalytic performance of 1T/2H MoS2 heterostructures compared to other active sites on the MoS2 surface. Combining this spatially resolved electrochemical information with density functional theory calculations and numerical simulations enables us to reveal the existence of hydrogen spillover from the 1T MoS2 surface to 1T/2H MoS2 heterostructures. Furthermore, it has been verified that hydrogen spillover can significantly enhance the electrocatalytic activity of the heterostructures, in addition to its strong electronic interaction. This study not only contributes to the future investigation of electrochemical processes at nanoscale active sites on structurally complex electrocatalysts but also provides new design strategies for improving the catalytic activity of 2D electrocatalysts.

Dynamic and Asymmetrical Ion Concentration Polarization in Dual Nanopipettes.

Dual nanopipettes with two channels have been receiving great attention due to the convenient experimental setup and multiple measuring channels in sensing applications at nanoscale, while the involved dynamic and asymmetrical ion transport processes have not been fully elucidated. In this paper, both experimental and simulation methods are used to investigate the dynamic mass transport processes inside dual nanopipettes with two well-separated channels. The results present that the ion transport resistance through the two channels (R12) is always the add-up of the individual ones (R13 + R23) with respect to the bulk solutions, at various ionic strengths and scan rates. A constant zero-current potential is obtained when loading an asymmetrical electrolyte concentration in the two channels, and the zero-potential current displays a good linear relationship with the bulk concentration outside the pipet. Besides revealing the dynamic and asymmetrical concentration polarization in the dual nanopipettes, these results would also further promote the better usage of dual nanopipettes in electrochemical sensing and imaging applications.

Elucidating the Shape of Current Transients in Electrochemical Resistive-Pulse Sensing of Single Liposomes.

Electrochemical resistive-pulse (ERP) sensing with conductive carbon nanopipettes (CNPs) has recently been developed and employed for the detection of single liposomes and biological vesicles, and for the analysis of redox molecules contained in such vesicles. However, the origins of different shapes of current transients produced by the translocation of single vesicles through the CNP remain poorly understood. Herein, we report extensive finite-element simulations of both portions of an ERP transient, the current blockage by a vesicle approaching and passing through the pipet orifice and the faradaic current spike due to oxidation/reduction of redox species released from a vesicle on the carbon surface, for different values of parameters defining the geometry and dynamics of the vesicle/CNP system. The effects of the pipet geometry, surface charge, transport, vesicle trajectory, and collision location on the shape of current transients are investigated. The possibility of quantitative analysis of experimental ERP transients produced by translocations of liposomes and extracellular vesicles by fitting them to simulated curves is demonstrated. The developed theory can enable a more reliable interpretation of complicated ERP signals and characterization of the size and contents of single biological and artificial vesicles.

FOXM1/NCAPH activates glycolysis to promote colon adenocarcinoma stemness and 5-FU resistance.

Chemotherapy using 5-fluorouracil (5-FU) is currently considered the most effective treatment for advanced colon adenocarcinoma (COAD). However, drug resistance remains a major obstacle in treating COAD. Non-SMC condensin I complex subunit H ( NCAPH ) is known to have a certain impact on the development of COAD, but its precise involvement in the mechanism of 5-FU resistance has not been demonstrated. Bioinformatics analysis was utilized to assay the expression of NCAPH and Forkhead box M1 ( FOXM1 ) in COAD tumor tissues, which was then verified in COAD cell lines. The resistance of COAD cells to 5-FU was measured by CCK-8 assay, stemness was tested by cell sphere formation assay, and glycolysis ability was measured by cellular energy analysis metabolism. Chromatin Immunoprecipitation and dual-luciferase reporter assays were done to confirm the specific interaction between FOXM1 and NCAPH . The expression levels of FOXM1 and NCAPH were significantly upregulated in COAD tissues and cells, and they were involved in regulating the glycolytic signaling pathway. Inhibition of the glycolytic pathway could reverse the effect of NCAPH overexpression on COAD stemness and resistance. FOXM1 was identified as a transcription factor of NCAPH , and it regulated COAD glycolysis, cell stemness, and 5-FU resistance by activating NCAPH expression. FOXM1-mediated upregulation of NCAPH expression promoted COAD cell stemness and resistance via the glycolytic pathway. This study provides a possible mechanism for the FOXM1/NCAPH axis in the glycolytic pathway, cell stemness, and resistance in COAD.

The role of prophylactic antibiotics in elective inguinal tension-free hernia repair: A systematic review and meta-analysis.

Whether to use antibiotics to prevent surgical site infection in elective inguinal tension-free hernia repair has been controversial. To systematically evaluate the effect of prophylactic antibiotic application in elective inguinal tension-free hernia repair, we identified all published randomised controlled trials of the effect of prophylactic antibiotic application on elective inguinal tension-free hernia repair were collected by computer retrieval from the China National Knowledge Infrastructure; VIP Database; Wanfang Database; China Biomedical Literature Database; and PubMed, EMBASE and Cochrane Library databases. Meta-analysis was performed by RevMan 5.3 software. The meta-analysis showed that the total incidence of surgical site infections [P = 0.003] and the incidence of superficial surgical site infections [P = 0.004] in the antibiotic group (AG) were lower than those in the non-antibiotic group (NAG). There was no significant difference in the total incidence of postoperative infections [P = 0.06], deep surgical site infections [P = 0.26] and seroma [P = 0.52] between the AG and the NAG. Based on current evidence, the application of prophylactic antibiotics in elective inguinal tension-free hernia repair can prevent the total incidence of surgical site infections and that of superficial surgical site infections but cannot prevent the total incidence of postoperative infection events, incidence of deep surgical site infections and incidence of seroma.

Electrochemical Molecule Trap-Based Sensing of Low-Abundance Enzymes in One Living Cell.

Measuring the activity of low-abundance enzymes, down to a few molecules in one living cell, is important but challenging to elucidate their biological function. Here, an electrochemical molecule trap is established at the tip of a nanopipette with an electrochemical detector, in which the diffusion of the molecules away from the electrochemical detector is prevented by electro-osmotic flow (EOF). Accordingly, a limited amount of enzymes is trapped to continuously catalyze the conversion of the substrate to generate a sufficient amount of the byproduct hydrogen peroxide for electrochemical measurements. The resistive pulse sensing of the enzymes in single liposomes validates the detection sensitivity down to 15 molecules. Using this ultrasensitive electrochemical strategy, the activity of 60 sphingomyelinase molecules inside single unstimulated living J774 cells is measured, which was hardly detected by previous methods. The established electrochemical molecule trap-based sensing approach opens the door toward single-molecule electrochemical detection in one living cell. This success will solve the long-standing problem regarding the study of the activity of low-abundance proteins in cells in their native physiological state and greatly enhance the understanding of the roles of proteins in cellular behavior.

Nanoconfined Electrochemical Collision and Catalysis of Single Enzyme inside Carbon Nanopipettes.

Revealing the electrocatalytic features of single redox enzyme is significant to both fundamental biological processes and practical catalysis and sensing applications. Herein, we directly reveal the electrocatalytic current from a single enzyme inside the carbon nanopipettes via electrochemical collision strategies, based on the increased activity at nanoscale confinement. Besides the staircase current steps from surface blockage, discrete H2O2 oxidation and reduction current transients catalyzed by a single enzyme are also displayed and analyzed. The carbon nanopipette would increase the catalytic activities of enzymes and lead to a detectable current response, thus opening a new way to investigate the fundamental enzymatic mechanisms at the single enzyme level.

Scanning Electrochemical Microscopy Featuring Transient Current Signals in Carbon Nanopipets with Dilute or No Redox Mediator.

Herein, we report a sensitive scanning electrochemical microscopy (SECM) method based on the high transient current signals in carbon nanopipets (CNPs) under step potential waveforms. Taking advantage of the transient peak current, the approach curve can be conducted with very dilute (1 µM) or even no redox mediator and fitted by the scanning ion conductance microscopy (SICM) theory. In addition, a trace amount of electroactive species generated at the substrate can also be directly revealed from the transient current at the CNP tips. With the established feedback and generation/collection methods, we present the constant-height topography and electroactivity imaging of the substrates with only 1 µM K4Fe(CN)6. The developed new SECM method would allow the usage of CNPs to achieve both high sensitivity and spatial resolution with dilute or no redox mediator and thus find great potential applications in biological and electrocatalytic studies.

Electrodeposition of Metal Nanoparticles inside Carbon Nanopipettes for Sensing Applications.

Conductive nanopipettes offer promising confined spaces to enable advanced electrochemical sensing applications in small spaces. Herein, a series of metal-decorated carbon nanopipettes (CNPs) were developed, in which Au, Ag, and Pt are modified at the inner walls of CNPs by a simple electrodeposition method. The fabricated tips show good sensing performances for a variety of important analytes, such as glucose, hydrogen peroxide, and chloride and hydrogen ions in biological and catalytic systems. This simple and effective approach can be further extended to prepare other functionalized nanopipette electrodes toward more versatile and powerful measurements in electrochemical sensing and imaging applications.

Three-Mediator Enhanced Collisions on an Ultramicroelectrode for Selective Identification of Single Saccharomyces cerevisiae.

Selective detection of colliding entities, especially cells and microbes, is of great challenge in single-entity electrochemistry. Herein, based on the different cellular electron transport pathways between microbes and mediators, we report a three-mediator system [K3Fe(CN)6, K4Fe(CN)6, and menadione] to achieve redox activity analysis and selective identification of single Saccharomyces cerevisiae without the usage of antibodies. K4Fe(CN)6 in the three-mediator system will oxidize near the electrode surface and increase the local concentration of K3Fe(CN)6, which will promote the redox reaction of S. cerevisiae. The hydrophobic mediator─menadione─can selectively penetrate through the S. cerevisiae membrane and get access to its intracellular redox center and can further react with K3Fe(CN)6 in the bulk solution. In contrast, the mediator can only get access to the bacterial membranes of Escherichia coli and Staphylococcus aureus, which results in different electrochemical collision signals between the above microbes. In the three-mediator system, upward step-like collision signals were observed in S. cerevisiae suspension, which are related to their microbial redox activity. In comparison, E. coli or S. aureus only generated downward current steps because the blockage effect of mediator diffusion suppresses their redox activities. When S. cerevisiae co-existed with E. coli or S. aureus, transients generated by both blockage and redox activity were observed. The approach enables us to trace the collision behaviors of different microbes and distinguish their simultaneous collisions, which is the foundation for further application of electrochemical collision technique in the specific identification of single biological entities.

Spatial Analysis of Reactive Oxygen Species in a 3D Cell Model Using a Sensitive Nanocavity Electrode.

The analysis of biomolecules in a 3D cell model is crucial for the collection of spatial information close to the actual organ. In this work, a highly sensitive platinized open carbon nanocavity electrode is fabricated to investigate reactive oxygen species (ROS) in three regions (proliferating zone, quiescent zone, and necrotic core) of a 3D CT26 cell model. The presence of a nanocavity permits more frequent collisions of ROS on the Pt surface, accelerating electron transfer, and thus pushes the detection limit down to 1 nM. This improved detection sensitivity guarantees the spatial investigation of the ROS distribution in a 3D cell sphere, including a high concentration in the outer proliferating layer even without any external stimulus, a low concentration in the quiescent layer, and almost no ROS at the center. The observation of ROS in the cell sphere without the stimulus reveals the presence of oxygen stress in the 3D cancer cell model, which is obviously different from the previous observation in living cultured 2D cells. This discovery provides direct evidence about the discrepancy about the metabolism in 2D and 3D cells, which could also direct a new study in cell electroanalysis to achieve more actual molecular information in life study.

Meta-analysis of arbidol versus lopinavir/ritonavir in the treatment of coronavirus disease 2019.

OBJECTIVES: To systematically evaluate the efficacy and safety of arbidol and lopinavir/ritonavir (LPV/r) in the treatment of coronavirus disease 2019 (COVID-19) using a meta-analysis method. METHODS: The China Knowledge Network, VIP database, WanFang database PubMed database, Embase database, and Cochrane Library were searched for a collection of comparative studies on arbidol and lopinavir/ritonavir in the treatment of COVID-19. Meta-analysis was used to evaluate the efficacy and safety of Arbidol and lopinavir/ritonavir in the treatment of COVID-19. RESULTS: The results of the systematic review indicated that Arbidol had a higher positive-to-negative conversion rate of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleic acid on Day 7 (p = 0.03), a higher positive-to-negative conversion rate of SARS-CoV-2 nucleic acid on Day 14 (p = 0.006), a higher improvement rate of chest computed tomography on Day 14 (p = 0.02), a lower incidence of adverse reactions (p = 0.002) and lower rate of mortality (p = 0.007). There was no difference in the rate of cough disappearance on Day 14 (p = 0.24) or the rate of severe/critical illness (p = 0.07) between the two groups. CONCLUSIONS: Arbidol may be superior to lopinavir/ritonavir in the treatment of COVID-19. However, due to the small number of included studies and the number of patients, high-quality multicenter large-sample randomized double-blind controlled trials are still needed for verification.

Does a long interval between neoadjuvant chemoradiotherapy and surgery benefit the clinical outcomes of locally advanced rectal cancer? A systematic review and meta analyses.

PURPOSE: The study aims to systematically evaluate the clinical efficacy after 8 weeks (long interval, LI) between neoadjuvant chemoradiotherapy and surgery for locally advanced rectal cancer. METHODS: The PubMed database, EMBASE database, and the Cochrane Library (deadline: September 25, 2021) were searched to select clinical studies that compared two intervals between neoadjuvant chemoradiotherapy and surgery for locally advanced rectal cancer: after 8 weeks (long interval, LI) and within 8 weeks (short interval, SI). The included studies were screened and evaluated according to the inclusion and exclusion criteria, and meta-analysis was performed by RevMan 5.3 software. RESULTS: Eighteen studies were included, with 9070 cases in the LI group and 14,207 cases in the SI group. The analysis results showed that the pathologic complete response (PCR) rate in the LI group was higher than that in the SI group (P < 0.00001). There was no significant difference in the R0 resection rate (P = 0.85), anal preservation rate (P = 0.89), morbidity rate (P = 0.60), anastomotic leakage rate (P = 0.06), operation time (P = 0.58), local recurrence rate (P = 0.56), distant metastasis rate (P = 0.32), or overall survival (OS) rate (P = 0.17) between the two groups. CONCLUSION: A longer interval between neoadjuvant chemoradiotherapy and surgery can improve the PCR rate; however, it has no significant impact on the clinical efficacy or long-term prognosis. Due to some limitations in the number and quality of the studies, these findings still need to be further verified by multicenter, large-sample high-quality RCTs in the future.

Direct high-resolution mapping of electrocatalytic activity of semi-two-dimensional catalysts with single-edge sensitivity.

The catalytic activity of low-dimensional electrocatalysts is highly dependent on their local atomic structures, particularly those less-coordinated sites found at edges and corners; therefore, a direct probe of the electrocatalytic current at specified local sites with true nanoscopic resolution has become critically important. Despite the growing availability of operando imaging tools, to date it has not been possible to measure the electrocatalytic activities from individual material edges and directly correlate those with the local structural defects. Herein, we show the possibility of using feedback and generation/collection modes of operation of the scanning electrochemical microscope (SECM) to independently image the topography and local electrocatalytic activity with 15-nm spatial resolution. We employed this operando microscopy technique to map out the oxygen evolution activity of a semi-2D nickel oxide nanosheet. The improved resolution and sensitivity enables us to distinguish the higher activities of the materials' edges from that of the fully coordinated surfaces in operando The combination of spatially resolved electrochemical information with state-of-the-art electron tomography, that unravels the 3D complexity of the edges, and ab initio calculations allows us to reveal the intricate coordination dependent activity along individual edges of the semi-2D material that is not achievable by other methods. The comparison of the simulated line scans to the experimental data suggests that the catalytic current density at the nanosheet edge is ∼200 times higher than that at the NiO basal plane.

Revealing Electrical Double-Layer Potential of Substrates by Hysteresis Ion Transport in Scanning Ion Conductance Microscopy.

The electrical double layer (EDL) at solid-liquid interfaces is key to interfacial transport and reaction processes and numerous emerging applications exploiting such processes. Herein, by studying hysteresis ion-transport processes in nanopipettes near charged substrates, we found the resulting cross-point potential (Vcp) to represent the surface potential of both nanopipettes and substrates. After the subtraction of Vcp in bulk solution, the remaining ΔVcp shows excellent exponential decay with respect to the separation distance from the substrates and agrees very well with the classical double-layer theory. The revealed new hysteresis ion transport in nanopipettes would provide a new way for the simple and direct EDL imaging of various interfaces of interest with nanoscale resolution in scanning ion conductance microscopy.

Electrochemical Collision of Single Silver Nanoparticles in Carbon Nanopipettes.

Exploring the electrochemical collision features at nanoelectrodes is highly desirable for revealing new physical insights and further expanding its applications at smaller spaces. Herein, we study the collision processes of single silver nanoparticles (AgNPs) inside carbon nanopipettes (CNPs). Results show that AgNPs undergo multiple collision and oxidation processes prior to fully oxidation after entering into the CNPs. Different from the disk electrodes, the produced Ag+ cannot immediately diffuse away from the cavity and will be reduced once switching to reductive potentials. More intriguingly, we observe discrete cathodic spikes from the Ag+ reduction, which are presumably due to the negatively charged carbon surface confined in the CNPs. The elucidated collision features in a CNP would enable its better usage for single entity measurements at confined spaces.

Self-Referenced Nanopipette for Electrochemical Analysis of Hydrogen Peroxide in the Nucleus of a Single Living Cell.

In a typical intracellular electroanalytical measurement, a nanoelectrode is located inside a living cell and a reference electrode outside the cell. This setup faces a problem to drop a certain potential across the cellular plasma membrane that might interrupt the cellular activity. To solve this problem, a self-referenced nanopipette is assembled by incorporating a reference electrode inside the nanocapillary, with a Pt ring at the tip as the electrochemical surface. The potential applied between the Pt ring and the reference electrode is restricted inside the capillary and thus has a negligible effect on the surrounding cellular environment. Using this new setup, the nanopipette pierces into the nucleus of a single living cell for the measurement of hydrogen peroxide under oxidative stress. It is found that a lesser amount of hydrogen peroxide is measured in the nucleus compared with the cytoplasm, revealing uneven oxidative stress inside the cell. The result will not only greatly improve the current setup for intracellular electrochemical analysis but also provide biological information of the compartment inside the living cell.

Enhancement in serum (1-3)-ß-D-glucan level by cutaneous alternariosis: A case report and literature review.

Contamination with the fungus Alternaria spp. is often considered to have originated from laboratory sources, which occasionally causes infection in immunocompromised patients, termed as phaeohyphomycosis. Here, we have reported a case of cutaneous alternariosis caused by Alternaria alternata. This diagnosis was based on microscopic examination and mycological culturing of patient's vesicular lesions, with the use of 5 molecular markers (namely, ITS, ATPase, Actin, rpb2, and tef1) for strain identification. We noted that Alternaria infection caused an increase in the serum level of (1-3)-ß-D-glucan (BG) in the patients. To the best of our knowledge, no such finding has been reported in previously in the literature.