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Nanoparticles that catalyze biochemically relevant reactions are promoted as alternative enzymes. The application of such artificial enzymes is severely restricted by poor selectivity in biological fluids; mainly because the reactions occur at active sites on the exterior surface of the nanoparticle. Enzymes in contrast typically have their active sites down a nanoconfined substrate channel where the reaction occurs in different solution conditions to bulk solution which aids in achieving selectivity for the substrate. Herein the same 3D structure of enzymes is mimicked in nanoparticles to allow selective reactions in biological fluids. This is achieved using a gold nanoparticle coated in a conducting mesoporous carbon shell where isolated nanochannels lead to the gold surface. It can detect glucose in whole blood with no interference from other species. This is achieved by electrochemically pulsing the artificial enzymes to generate the locally required alkalinity for an effective electrocatalytic reaction in the nanochannels, as well as expelling fouling agents that will otherwise passivate the electrocatalytic reaction. The artificial enzymes are shown to be capable of detecting glucose in biological fluids, without loss of signal, for several months. This study shows how nanoconfinement in nanoparticles can be exploited to potentially allow a broad range of species to be selectively detected in biological fluids with stability that can exceed that of enzymes. [ABSTRACT FROM AUTHOR]

This study presents the combination of electrochemical cell based biosensor and fluorescence microscopy on a single platform to track biomolecular processes contributing to the morphology changes of the cells. Initial experiments demonstrate that using interdigitated electrodes where the gold microfingers were comparable in width and spacing to a single cell have the optimal sensitivity in the final electrochemical cell based‐sensing device. This was determined by measuring the cell index, based on the impedance analysis of bare and cell‐covered microelectrodes. The fabrication of the electrodes on a glass substrate enabled the capture of high‐resolution fluorescence microscopy images of single cells and related intracellular calcium release inside the HeLa cells via a window incorporated into the gold microelectrode design. As an illustration of the enhanced capability of the combined approach over traditional impedance cellular assay, the opto‐electric assay was utilized as a functional readout for G protein couple receptor activation. The simultaneous examinations of cells stimulated with histamine demonstrated an association between time courses of changes in cytosolic calcium concentration and reductions in cell‐cell adhesions. [ABSTRACT FROM AUTHOR]

Herein is explored a dual optical and electrical cell based biosensor that can provide insights into cellular events. The fabrication steps along with the electrical characterization of the microelectrodes is described. Initial experiments show that the ability of indium tin oxide (ITO) to detect biological cells at the electrode‐cell layer interface mainly depends on the size of sensing area. Following this, the impact of conductivity was also explored to assess the real time impedance signal during the adhesion of a non‐confluent layer of the cells on different substrates. Electrodes with a higher conductivity than ITO gave much higher senstivity of impedance changes which allowed the dynamics of subtle cellular morphology changes to be monitored at densities far lower than a confluent layer of cells. Finally, the capability of ITO and gold microelectrode as a functional readout for G protein couple receptor activation were determined. These set of analyses highlighted the challenges and opportunities of ITO substrate as a dual cell‐based assay for quantitative analysis of subtle changes in cell morphology. [ABSTRACT FROM AUTHOR]

Impact experiments enable single particle analysis for many applications. However, the effect of the trajectory of a particle to an electrode on impact signals still requires further exploration. Here, we investigate the particle impact measurements versus motion using micromotors with controllable vertical motion. With biocatalytic cascade reactions, the micromotor system utilizes buoyancy as the driving force, thus enabling more regulated interactions with the electrode. With the aid of numerical simulations, the dynamic interactions between the electrode and micromotors are categorized into four representative patterns: approaching, departing, approaching‐and‐departing, and departing‐and‐reapproaching, which correspond well with the experimentally observed impact signals. This study offers a possibility of exploring the dynamic interactions between the electrode and particles, shedding light on the design of new electrochemical sensors. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The use of nanoparticles and nanostructured electrodes are abundant in electrocatalysis. These nanometric systems contain elements of nanoconfinement in different degrees, depending on the geometry, which can have a much greater effect on the activity and selectivity than often considered. In this Review, we firstly identify the systems containing different degrees of nanoconfinement and how they can affect the activity and selectivity of electrocatalytic reactions. Then we follow with a fundamental understanding of how electrochemistry and electrocatalysis are affected by nanoconfinement, which is beginning to be uncovered, thanks to the development of new, atomically precise manufacturing and fabrication techniques as well as advances in theoretical modeling. The aim of this Review is to help us look beyond using nanostructuring as just a way to increase surface area, but also as a way to break the scaling relations imposed on electrocatalysis by thermodynamics. [ABSTRACT FROM AUTHOR]

Bimetallic silver‐copper electrocatalysts are promising materials for electrochemical CO2 reduction reaction (CO2RR) to fuels and multi‐carbon molecules. Here, we combine Ag core/porous Cu shell particles, which entrap reaction intermediates and thus facilitate the formation of C2+ products at low overpotentials, with gas diffusion electrodes (GDE). Mass transport plays a crucial role in the product selectivity in CO2RR. Conventional H‐cell configurations suffer from limited CO2 diffusion to the reaction zone, thus decreasing the rate of the CO2RR. In contrast, in the case of GDE‐based cells, the CO2RR takes place under enhanced mass transport conditions. Hence, investigation of the Ag core/porous Cu shell particles at the same potentials under different mass transport regimes reveals: (i) a variation of product distribution including C3 products, and (ii) a significant change in the local OH‐ activity under operation. [ABSTRACT FROM AUTHOR]

Producing stable but active materials is one of the enduring challenges in electrocatalysis and other types of catalysis. Producing branched nanoparticles is one potential solution. Controlling the number of branches and branch size of faceted branched nanoparticles is one of the major synthetic challenges to achieve highly active and stable nanocatalysts. Herein, we use a cubic‐core hexagonal‐branch mechanism to synthesize branched Ru nanoparticles with control over the size and number of branches. This structural control is the key to achieving high exposure of active {10–11} facets and optimum number of Ru branches that enables improved catalytic activity for oxygen evolution reaction while maintaining high stability. [ABSTRACT FROM AUTHOR]

Recent advances in CRISPR based biotechnologies have greatly expanded our capabilities to repurpose CRISPR for the development of biomolecular sensors for diagnosing diseases and understanding cellular pathways. The key attribute that allows CRISPR to be widely utilized is the programmable and highly selective mechanism. In this Minireview, we first illustrate the molecular principle of CRISPR functioning process from sensing to actuating. Next, the CRISPR based biosensing strategies for nucleic acids, proteins and small molecules are summarized. We highlight some of recent advances in applications for in vitro detection of biomolecules and in vivo imaging of cellular networks. Finally, the challenges with, and exciting prospects of, CRISPR based biosensing developments are discussed. [ABSTRACT FROM AUTHOR]

Here we report a light‐assisted variant of click chemistry suitable for chemical patterning of semiconducting surfaces. Using a visible light beam to illuminate desired locations of an electrode surface, localized electrogeneration of the Cu(I) click catalyst was achieved. It was demonstrated that surface click reactions were correlated with a user‐defined 2D light pattern projected on a silicon photoelectrode. This new process is mask‐free and parallel, i. e. separate discrete regions of a semiconducting surface can be simultaneously reacted with a range of functional molecules. The covalent patterning of azido‐poly (ethylene glycol) molecules (PEG) over alkyne‐functionalized electrodes was employed as a proof‐of‐principle. By modulating the exposed chemical group of the clicked azido‐PEGs, the adhesion of antibodies and cells was further possible with spatial control. The use of structured light, instead of physical masks, drastically reduces patterning time to a couple of hours. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Controlling the formation of nanosized branched nanoparticles with high uniformity is one of the major challenges in synthesizing nanocatalysts with improved activity and stability. Using a cubic‐core hexagonal‐branch mechanism to form highly monodisperse branched nanoparticles, we vary the length of the nickel branches. Lengthening the nickel branches, with their high coverage of active facets, is shown to improve activity for electrocatalytic oxidation of 5‐hydroxymethylfurfural (HMF), as an example for biomass conversion. [ABSTRACT FROM AUTHOR]

We define, experimentally, the effect of intramolecular electric fields, generated from the positive charge of ferricenium cations, over the oxidation potential of 2,2,6,6‐tetramethyl‐1‐piperdinyloxy (TEMPO). We synthesized a TEMPO derivative, where the nitroxide is linked to a ferrocene unit. We have used this molecule to study the influence on the electrostatic cross‐talk between positively charged ferriceniums and TEMPO units by solvent dielectric, level of electrolytic support, and Lewis acid/base character of electrolyte ions. The magnitude of thermodynamic anodic shift of the TEMPO oxidation, after the ferrocene unit is converted to a ferricenium cation, increases with decreasing dielectric constant of the solvent, electrolytic concentration, and Lewis basicity strength (i. e. between ferriceniums and electrolyte anions). This work demonstrates an approach to use electrostatic forces, here delivered by intramolecular charged cations, to tune the oxidation energy for nitroxides in ionic solutions. [ABSTRACT FROM AUTHOR]

The electrocatalysis of the oxygen evolution reaction (OER) at the surface of oxidized metal electrocatalysts is highly dependent on the structure and composition of the surface oxide. Here, Au core‐ Co branched nanoparticles were synthesized using a cubic‐core hexagonal‐branch growth approach in a slow reductive solution synthesis, resulting in highly crystalline metallic hcp Co branches. Electrochemical surface oxidation of the Co branched nanoparticles resulted in formation of Co(OH)2 that enable the formation of a higher number of active sites under OER conditions compared to Co3O4. Differently from polycrystalline spherical Au−Co core‐shell nanoparticles, the oxidized structure on the Co branched nanoparticle surface is retained with electrochemical cycling, resulting in improved OER activity and stability. [ABSTRACT FROM AUTHOR]

The tremendous impact of UV radiation on every individual has resulted in massive interest in development of new sensor technologies to effectively monitor the solar exposure. However, there is no comprehensive review that critically discusses the advances made in the field of wearable UV sensor technologies and to position them as next‐generation mass‐deployable wearable devices. Herein, this gap is addressed by first classifying UV detection technologies into photoelectric and photochromic systems and summarizing their unique strengths and drawbacks. This is followed by a discussion on the integration of novel materials and design concepts with these technologies to develop wearable UV sensors. Then, the commercially available wearable UV sensors are examined thoroughly together with their limitations. Toward the end, a highly critical future outlook is provided, wherein the role of technological and regulatory interventions in assisting the development and integration of wearable UV sensors in the day‐to‐day activities is discussed. More importantly, the purpose of this review is not only to provide an in‐depth understanding of the underlying UV detection mechanism, design principles, and wearable technologies but also to act as a roadmap for those interested in the development and regulation of commercially deployable wearable UV sensors. [ABSTRACT FROM AUTHOR]

Monitoring of human serum albumin (HSA) in a point‐of‐care fashion is urgently needed in particular for elderly or chronically ill patients. Herein, a dual‐state emissive chalcone probe having the feature of aggregation‐induced emission was designed and synthesized. The concentration of HSA can be evaluated by the ratios of emission from probes in aggregated and monomeric state, which gives a visually discernible red‐to‐green color change. A simple, portable paper‐based analytical device have been fabricated by integration of the recognition probe in the detection pad and employed for HSA test using the whole blood samples. This paper‐based assay shows the analytical capability comparable to the standard testing methods but is in a point‐of‐care fashion, providing a promising tool for at‐home HSA detection and HSA‐related disease diagnosis. [ABSTRACT FROM AUTHOR]

The electrochemical formation of oxide on metallic surfaces often changes their electrocatalytic performance. In this work, we have studied this effect on the methanol oxidation reaction by systematically controlling the PdO formation/reduction potential using Au−Pd core‐shell nanocrystals with different Pd shell thicknesses. AuPd0.4 core‐shell nanocrystals have a 150 mV positive shift in the PdO reduction potential with respect to Pd nanocrystals and 2.9 and 8.8 times higher charge density in the anodic and cathodic scan of cyclic voltammetry respectively. The origin of the higher activity comes predominantly from electronic effects caused by the Au core that results in higher availability of Pd sites at more positive potentials. [ABSTRACT FROM AUTHOR]

Alexa Fluor 647 is a widely used fluorescent probe for cell bioimaging and super‐resolution microscopy. Herein, the reversible fluorescence switching of Alexa Fluor 647 conjugated to bovine serum albumin (BSA) and adsorbed onto indium tin oxide (ITO) electrodes under electrochemical potential control at the level of single protein molecules is reported. The modulation of the fluorescence as a function of potential was observed using total internal reflectance fluorescence (TIRF) microscopy. The fluorescence intensity of the Alexa Fluor 647 decreased, or reached background levels, at reducing potentials but returned to normal levels at oxidizing potentials. These electrochemically induced changes in fluorescence were sensitive to pH despite that BSA‐Alexa Fluor 647 fluorescence without applied potential is insensitive to pH between values of 4–10. The observed pH dependence indicated the involvement of electron and proton transfer in the fluorescence switching mechanism. [ABSTRACT FROM AUTHOR]

Geneva), Johan Bobacka (Åbo Akademi Univ.), Philippe Bühlmann (Univ. Minnesota), Daniel Citterio (Keio Univ.), Justin Gooding (Univ. With much anticipation after a one-year delay caused by the COVID-19 pandemic, the Mátrafüred International Conference on Electrochemical Sensors was held June 12-17, 2022, in Visegrád, Hungary. Serge Lemay (Univ. Twente), Peter Lieberzeit (Univ. Vienna), Tom Lindfors (Åbo Akademi Univ.), Daniel Mandler (Hebrew Univ. Jerusalem), Agata Michalska (Univ. Warsaw), Karin Mölling (Univ. Zürich), Frieder Scheller (Univ. Potsdam), Joseph Wang (Univ. California San Diego). [Extracted from the article]

Rationale: The decolouration of brilliant blue FCF by the action of titanium dioxide (TiO2) under ultraviolet (UV) exposure has been recently reported as the basis of a paper‐based sensor for monitoring UV sun exposure. The mechanism of brilliant blue FCF photodegradation in the presence of the photocatalyst and the resulting photoproducts are thus far unknown. Methods: The UV‐initiated photodegradation of brilliant blue FCF in the presence of TiO2 for both the aqueous and the solid state was investigated. Degradation in the solid state was observed using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐MS). Decomposition of the dye in the aqueous state was analyzed using liquid chromatography/mass spectrometry (LC/MS) and ultraviolet–visible (UV–Vis) spectroscopy. Results: After UV radiation exposure, the brilliant blue FCF base peak [M1 + NH4]+ (m/z calc. 766.194 found 766.194) decreased in the LC/MS chromatogram with a concomitant appearance of BB‐FCF decomposition products involving the sequential loss of the N‐ethyl and N‐methylbenzene sulfonate (MBSA) groups, assigned as [M2 + H]+ (‐MBSA, calc. 579.163 found 579.162), [M3 + H]+ (‐MBSA, −Et, calc. 551.131 found 551.131), [M4 + H]+ (‐2MBSA, calc. 409.158 found 409.158), [M5 + H]+ (‐2MBSA, −Et, calc. 381.127 found 381.127). Ions [M2 + H]+ and [M3 + H]+ were also identified in the photodegradation products using MALDI‐MS. Observation by UV–Vis indicated a decrease in the solution absorbance maxima and an associated blue‐shift upon UV exposure in solution. Conclusions: The LC/MS analysis indicated two main oxidation processes. The most obvious was attack of the N‐methylene, eliminating either ethyl or MBSA groups. The presence of the hydroxylated decomposition product M13 ([M13 + H]+, calc. 595.157 found 595.157) supported this assignment. In addition, the detection of photoproduct M8, proposed to be 3‐((ethylamino)methyl)benzenesulfonic acid ([M8 + H]+, calc. 216.069 found 216.069), indicates an aryl‐oxidative elimination. The absence of the aryl‐hydroxy products normally expected to accompany the formation of M8 is proposed to be due to TiO2‐binding catechol‐like derivatives, which are then removed upon filtration. [ABSTRACT FROM AUTHOR]

The reaction of hydrogen‐terminated Si(100) with 1,8‐nonadiyne was previously shown to afford robust surfaces where oxidation of the substrate is not evident. Here, the experimental conditions required for reacting hydrogen‐terminated Si(100) with α,ω‐diynes of different lengths is explored via thermal hydrosilylation of 1,6‐heptadiyne, 1,8‐nonadiyne, 1,10‐undecadiyne and 1,15‐hexadecadiyne. X‐ray photoelectron spectroscopy indicated monolayers were successfully formed with oxide levels below the XPS detection limit for molecules with lengths varying from 7 to 11 carbons. It was observed that the apparent rate of electron transfer (ket) was affected not only by the SAM thickness, but also by hopping between ferrocene moieties where the presence of tiny oxidative defects act as electron transfer hotspots. Electron transfer on monolayer protected silicon: SAM thickness plays a major influence on electron transfer kinetics. However, on silicon, the process is also affected by the presence of SiOx hotspots and by the surface coverage of tethered redox species. The consequence is SAMs with a higher‐coverage of redox species on 9 or 11 carbons length displaying faster ket than SAMs with a lower‐coverage of redox species on 7 carbons length. [ABSTRACT FROM AUTHOR]

We report here on a light addressable potassium (K+) sensor where light illumination of a semiconducting silicon electrode substrate results in a localized activation of the faradaic electrochemistry at the illuminated spot. This allows one, by electrochemical control, to oxidize surface bound ferrocene moieties that in turn trigger K+ transfer from the overlaid K+‐selective film to the solution phase. The resulting voltammetric response is shown to be K+‐selective, where peak position is a direct function of K+ activity at the surface of electrode. This concept was used to measure extracellular K+ concentration changes by stimulating living breast cancer cells. The associated decrease of intracellular K+ level was confirmed with a fluorescent K+ indicator. In contrast to light addressable potentiometry, the approach introduced here relies on dynamic electrochemistry and may be performed in tandem with other electrochemical analysis when studying biological events on the electrode. K+ sensing: A light‐addressable electrochemical K+ sensor is introduced that consists of a thin polymer film containing an ionophore deposited on a semiconducting silicon electrode. Ferrocene is covalently attached to oxide‐free silicon and the electrode exhibits surface confined electrochemistry under light illumination. The sensor exhibits a Nernstian response to [K+] in a light‐defined spatial region. Changes in extracellular [K+] associated with living cells upon stimulation are monitored electrochemically. [ABSTRACT FROM AUTHOR]

Summary: Acute respiratory tract infections are a major cause of morbidity and mortality and represent a significant burden on the health care system. Laboratory testing is required to definitively distinguish infecting influenza virus from other pathogens, resulting in prolonged emergency department (ED) visits and unnecessary antibiotic use. Recently available rapid point‐of‐care tests (POCT) may allow for appropriate use of antiviral and antibiotic treatments and decrease patient lengths of stay. We undertook a systematic review to assess the effect of POCT for influenza on three outcomes: (1) antiviral prescription, (2) antibiotic prescription, and (3) patient length of stay in the ED. The databases Medline and Embase were searched using MeSH terms and keywords for influenza, POCT, antivirals, antibiotics, and length of stay. Amongst 245 studies screened, 30 were included. The majority of papers reporting on antiviral prescription found that a positive POCT result significantly increased use of antivirals for influenza compared with negative POCT results and standard supportive care. A positive POCT result also led to decreased antibiotic use. The results of studies assessing the effect of POCT on ED length of stay were not definitive. The studies assessed in this systematic review support the use of POCT for diagnosis of influenza in patients suffering an acute respiratory infection. Diagnosis using POCT may lead to more appropriate prescription of treatments for infectious agents. Further studies are needed to assess the effect of POCT on the length of stay in ED. [ABSTRACT FROM AUTHOR]

Abstract: Achieving stability with highly active Ru nanoparticles for electrocatalysis is a major challenge for the oxygen evolution reaction. As improved stability of Ru catalysts has been shown for bulk surfaces with low‐index facets, there is an opportunity to incorporate these stable facets into Ru nanoparticles. Now, a new solution synthesis is presented in which hexagonal close‐packed structured Ru is grown on Au to form nanoparticles with 3D branches. Exposing low‐index facets on these 3D branches creates stable reaction kinetics to achieve high activity and the highest stability observed for Ru nanoparticle oxygen evolution reaction catalysts. These design principles provide a synthetic strategy to achieve stable and active electrocatalysts. [ABSTRACT FROM AUTHOR]

Abstract: A core–satellite nanotheranostic agent with pH‐dependent photothermal properties, pH‐triggered drug release, and H2O2‐induced catalytic generation of radical medicine is fabricated to give a selective and effective tumor medicine with three modes of action. The nanocomplex (core–satellite mesoporous silica–gold nanocomposite) consists of amino‐group‐functionalized mesoporous silica nanoparticles (MSN‐NH2) linked to L‐cysteine‐derivatized gold nanoparticles (AuNPs‐Cys) with bridging ferrous iron (Fe2+) ions. The AuNPs‐Cys serve as both removable caps that control drug release (doxorubicin) and stimuli‐responsive agents for selective photothermal therapy. Drug release and photothermal therapy are initiated by the cleavage of Fe2+ coordination bonds at low pH and the spontaneous aggregation of the dissociated AuNPs‐Cys. In addition, the Fe2+ is able to catalyze the decomposition of hydrogen peroxide abundant in cancer cells by a Fenton‐like reaction to generate high‐concentration hydroxyl radicals (·OH), which then causes cell damage. This system requires two tumor microenvironment conditions (low pH and considerable amounts of H2O2) to trigger the three therapeutic actions. In vivo data from mouse models show that a tumor can be completely inhibited after two weeks of treatment with the combined chemo‐photothermal method; the data directly demonstrate the efficiency of the MSN–Fe–AuNPs for tumor therapy. [ABSTRACT FROM AUTHOR]

Abstract: A common electrode construct for electrochemical DNA biosensors consists of tethering a redox‐label‐modified single stranded DNA to the electrode and comparing the electrochemical response of a redox probe before and after hybridization. Despite the analytical advantages of this construct, contradictory results are found in the literature regarding to the effect of redox‐labeling position on the charge transfer process happening at a DNA interface. Herein a contribution to this discussion is made by investigating how a methylene blue redox label placed at different positions along a probe strand of DNA affects the DNA hybridization efficiency. For that, a second redox label, a ferrocene molecule, was attached to the target DNA at a fixed position such that upon hybridization it is positioned at the distal end of the DNA monolayer. The dual label strategy allowed us to explore, for each methylene blue labeling position, how the binding‐induced diminution in the methylene blue signaling is associated with the appearance of the ferrocene signaling after hybridization. It was found that the location of the methylene blue redox label in the DNA interface can affect the hybridization efficiency. [ABSTRACT FROM AUTHOR]

We provide complex capacitance studies which show that the tethering of negatively-charged DNA molecules to p-doped silicon (111), without intervening oxide layer, leads to changes of the electric field in the underlying silicon. We proposed, that the tethering of the DNA leads to the formation of surface states that, from the electronic point of view, resemble the major carriers of p-type silicon, i.e. holes. This effect is enhanced by the formation of double-stranded (ds)DNA molecules and hence is the premise to label-free detection of the DNA hybridization. Overall, our studies provide a promising alternative to design a biosensor to detect the hybridization of DNA molecules on the silicon surface. [ABSTRACT FROM AUTHOR]

Measurement science has been converging to smaller and smaller samples, such that it is now possible to detect single molecules. This Review focuses on the next generation of analytical tools that combine single-molecule detection with the ability to measure many single molecules simultaneously and/or process larger and more complex samples. Such single-molecule sensors constitute a new type of quantitative analytical tool, as they perform analysis by molecular counting and thus potentially capture the heterogeneity of the sample. This Review outlines the advantages and potential of these new, quantitative single-molecule sensors, the measurement challenges in making single-molecule devices suitable for analysis, the inspiration biology provides for overcoming these challenges, and some of the solutions currently being explored. [ABSTRACT FROM AUTHOR]

Fortschritte in der Messtechnik ermöglichen immer kleinere Probenmengen, sodass mittlerweile der Nachweis einzelner Moleküle möglich ist. Schwerpunkt dieses Aufsatzes ist die nächste Generation von Analysewerkzeugen, die die Einzelmolekül ‐ Detektion mit der simultanen Messung vieler Einzelmoleküle kombinieren und/oder größere und komplexere Probenmengen bearbeiten können. Solche Einzelmolekül ‐ Sensoren sind eine neue Art quantitativer Analysewerkzeuge, da die Untersuchung durch Molekülzählung erfolgt und dadurch die Heterogenität der Probe bestimmt werden kann. Der Aufsatz gibt eine Übersicht über die Vorteile und das Potential dieser neuen, quantitativen Einzelmolekül ‐ Sensoren, die messtechnischen Herausforderungen bei der Herstellung von Einzelmolekül ‐ Instrumenten für die Analyse, die Anregungen aus der Biologie zur Bewältigung dieser Herausforderungen sowie einige der derzeit untersuchten Lösungsansätze. Fortschritte in der Messtechnik ermöglichten eine schrittweise Verringerung von Probengrößen, sodass heute Einzelmolekül ‐ Messungen zu den gängigen Methoden gehören. Erwartet wird nun eine neue Generation von Sensoren, mithilfe derer vielzählige Einzelmolekül ‐ Ereignisse zur quantitativen Analyse genutzt werden können. Herausforderungen, Möglichkeiten und neuere Entwicklungen im Bereich quantitativer Einzelmolekül ‐ Sensoren werden diskutiert. [ABSTRACT FROM AUTHOR]

Immobilisation of enzymes onto surfaces with defined orientation is of particular importance in order to optimise their activity and capacity to dock electron-transfer partners. Local characterisation methods are thus crucial to understanding the activity-orientation relationship of immobilised enzymes for long-term storage and applications. Herein, cytochrome c (cyt c) is chemoselectively immobilised through a cysteine functional group with a maleimide-functionalised gold surface, thus controlling cyt c orientation. X-ray photoelectron spectroscopy confirmed successful cyt c immobilisation. Scanning electrochemical microscopy methodologies were developed to quantify the activity of immobilised cyt c and cytochrome c peroxidase (C cP). The results suggest optimal enzymatic activities and docking ability for surface-tethered cyt c are obtained through the cysteine-maleimide linkage, in comparison to conventional indiscriminate lysine-carboxyl linkages. This study reveals the strong influence of cyt c orientation, as a result of linking strategy, upon the docking ability of redox-electron partner C cP. [ABSTRACT FROM AUTHOR]

Gold-coated magnetic nanoparticles (Au@MNPs) have attracted significant interest in electrochemistry in recent years. This is especially the case with their application as dispersible electrodes where modified Au@MNPs are dispersed into a solution, selectively bind to the analyte of interest and are then brought to an electrode via application of a magnetic field for measurement. This paper characterizes four types of Au@MNPs with different sizes, shapes, and method of synthesis as dispersible electrodes. The Au@MNPs were characterized by transmission electron microscopy and X-ray photoelectron spectroscopy and scanning electron microscopy. In addition, the electrochemical behaviour of Au@MNPs was investigated using cyclic voltammetry. The four sorts of Au@MNPs were evaluated with regards to the three main features required in the dispersible electrodes approach, well-defined morphology, well-defined electrochemistry and fast response to a magnetic field. The Cubic-Au@MNPs, which presents the simplest synthetic route, showed the best electrochemical stability and performance, responding quickly to a magnet and had a well defined shape. [ABSTRACT FROM AUTHOR]

Considerable attention has been dedicated to developing feasible point-of-care tests for cancer diagnosis and prognosis. An ideal biomarker for clinical use should be easily assayed with minimally invasive medical procedures but possess high sensitivity and specificity. The role of microRNAs ( miRNAs) in the regulation of different cellular processes, the unique altered patterns in cancer patients and presence in body fluids in the stable form, points to their clinical utility as blood-based biomarkers for diagnosis, prognosis, and treatment of cancer. Although a variety of selective and sensitive laboratory-based methods are already exist for the detection of circulating miRNA, having a simple, low-cost and rapid assay, which could be routinely used in clinical practice, is still required. Among different approaches that have developed for circulating miRNA detection, biosensors, due to the high sensitivity, ease of use, short assay time, non-toxic experimental steps, and adaptability to point-of-care testing, exhibit very attractive properties for developing portable devices. With this view, we present an overview of some of the challenges that still need to be met to be able to use circulating miRNAs in clinical practice, including their clinical significance, sample preparation, and detection. In particular, we highlight the recent advances in the rapidly developing area of biosensors for circulating miRNA detection, along with future prospects and challenges. WIREs Nanomed Nanobiotechnol 2015, 7:580-592. doi: 10.1002/wnan.1324 For further resources related to this article, please visit the . [ABSTRACT FROM AUTHOR]

Polymersomes provide a good platform for targeted drug delivery and the creation of complex (bio)catalytically active systems for research in synthetic biology. To realize these applications requires both spatial control over the encapsulation components in these polymersomes and a means to report where the components are in the polymersomes. To address these twin challenges, we synthesized the protein-polymer bioconjugate PNIPAM- b-amilFP497 composed of thermoresponsive poly( N-isopropylacrylamide) (PNIPAM) and a green-fluorescent protein variant (amilFP497). Above 37 °C, this bioconjugate forms polymersomes that can (co-)encapsulate the fluorescent drug doxorubicin and the fluorescent light-harvesting protein phycoerythrin 545 (PE545). Using fluorescence lifetime imaging microscopy and Förster resonance energy transfer (FLIM-FRET), we can distinguish the co-encapsulated PE545 protein inside the polymersome membrane while doxorubicin is found both in the polymersome core and membrane. [ABSTRACT FROM AUTHOR]

Polymersomes provide a good platform for targeted drug delivery and the creation of complex (bio)catalytically active systems for research in synthetic biology. To realize these applications requires both spatial control over the encapsulation components in these polymersomes and a means to report where the components are in the polymersomes. To address these twin challenges, we synthesized the protein-polymer bioconjugate PNIPAM- b-amilFP497 composed of thermoresponsive poly( N-isopropylacrylamide) (PNIPAM) and a green-fluorescent protein variant (amilFP497). Above 37 °C, this bioconjugate forms polymersomes that can (co-)encapsulate the fluorescent drug doxorubicin and the fluorescent light-harvesting protein phycoerythrin 545 (PE545). Using fluorescence lifetime imaging microscopy and Förster resonance energy transfer (FLIM-FRET), we can distinguish the co-encapsulated PE545 protein inside the polymersome membrane while doxorubicin is found both in the polymersome core and membrane. [ABSTRACT FROM AUTHOR]

In this study we have modified indium tin oxide (ITO) by electrografting phenylphosphorylcholine (PPC) and evaluated its protein-resistance performance using electrochemical impedance spectroscopy. During electrografting, significant amounts of PPC gets physically adsorbed on the surface, which cannot be removed by simply rinsing with water or buffer, and as a consequence the electrochemical response of such electrode is quite unstable. We have developed a simple protocol to remove the physically adsorbed PPC such that a stable interface is produced. It was found that such a stable surface, with appropriate amount of PPC, can dramatically reduce nonspecific adsorption of protein, giving us a platform of performing both electrochemical and spectroscopic studies in biological fluids. [ABSTRACT FROM AUTHOR]

Despite the rapid development of drug delivery vehicles that react to a specific biological environment, the complexity of triggering drug release in a particular target area remains an enduring challenge. Here, the engineering of bioresponsive polymer-mesoporous silica nanoparticles (MSNs) with function akin to an AND logic gate is described. Polycaprolactone (esterase degradable) is immobilized into the core of MSNs while polyacrylic acid (PAA), which is pH responsive, covered the outside of the MSNs to create a PAA-PCL-MSNs construct. Fluorescence spectroscopy indicates that the construct releases the payload (doxorubicin, cancer drugs) in the presence of, and only in the presence of, both low pH AND esterase. Confocal microscopy and fluorescence lifetime microscopy (FLIM) demonstrate uptake of the intact construct and subsequent intracellular doxorubicin (DOX) delivery into the nucleus. Further in vitro IC50 studies demonstrate the AND logic gate delivery system results in more than an eightfold efficacy against neuroblastoma (SK-N-BE(2)) cells in comparison with normal fibroblasts (MRC-5). These results demonstrate the utility of MSN-polymer construct to create an AND gate capable of selectively delivering a drug payload. [ABSTRACT FROM AUTHOR]

The article focuses on the use of single entity electrochemistry techniques for mammalian cell counting. Topics discussed include the use of fluorescence-activated cell sorting (FACS) for red blood cells counting, application of the nanoparticle collision in experiments as a subject and the use of hemocytometer to diagnose blood disorder by counting red blood cells.

Rote Blutkörperchen wurden in einem elektrochemischen Aufprallexperiment gemessen, das von Compton und Mitarbeitern kürzlich vorgestellt wurde. Wenn eine Zelle auf die Elektrode prallt, wird sie lysiert und ein Stromsignal aus der Reduktion des Sauerstoffs aus dem Zellinneren wird gemessen. [ABSTRACT FROM AUTHOR]

Low impedance, antifouling coatings on gold electrodes based on three new zwitterionic phenyl phosphorylcholine (PPC)-based layers namely 1) reductively adsorbed PPC diazonium salt, 2) dithiocarbamate PPC SAM and 3) lipoamide PPC SAM (PPC coupled to α-lipoic acid) were evaluated. The layers were assessed for their ability to limit nonspecific adsorption of proteins to electrode surface with some significant differences observed compared with previously studied PPC diazonium salts reductively adsorbed on glassy carbon. Fluorescence microscopy and electrochemical impedance spectroscopy results suggest that protein adsorption is sensitive to the difference in the structure of the PPC molecules and the charge neutrality of the layers. The lipoamide PPC SAM was shown to be the most effective at resisting nonspecific protein adsorption and this layer was as effective as the 'gold standard' of oligo(ethylene oxide) SAMs on gold and PPC diazonium salts reductively adsorbed on glassy carbon. [ABSTRACT FROM AUTHOR]

Biofouling on surfaces can deleteriously affect the function of electrochemical sensor used in a biological fluid. The demand is thus to develop a sensor operatable in complex matrices. Herein, we concisely review the technologies developed to date to minimize fouling of electrochemical interfaces by blood-based fluids with an emphasis on affinity biosensing. The methods toward this sensor fabrication that are discussed here include approaches where; chemically modified surfaces with antifouling layers such as ethylene oxides, zwitterionics and some alternative antifouling agents; physical forces such as fluidic systems; electrode surface topography, prevent biofouling, as well as recent approaches where biofouling does not interfere with the response (aptasensors). Furthermore, the important emerging field of implantable biosensors, originated from such fabrication procedures is discussed. [ABSTRACT FROM AUTHOR]

The influence of graphene on the electrical communication through organic layers fabricated on graphite and gold electrodes is investigated. These layers were prepared by in situ reductive adsorption of 4-aminobenzoic acid in the presence of NaNO2 and HCl to have surface bound carboxylic acid functionalities, followed by covalent attachment of 1-aminopyrene via an amide coupling reaction to have surface bound pyrene groups for graphene immobilization via noncovalent ππ stacking interaction. The coverage of the layers created via reductive adsorption on graphite electrodes was found to be much higher than that on gold electrodes. It was revealed that graphene significantly enhances the electrical communication through the layers on graphite electrodes but on gold electrodes the enhancement effect through the layers was only minor. However, when gold electrodes were modified with a self-assembled monolayer (SAM) of propanethiol the subsequent immobilization of graphene resulted in a significant enhancement of the electrical communication. It is also found that immobilization of graphene could affect the electron transfer between the redox probe, pyrene and the underlying electrodes. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to characterize the graphene sheets. Cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS) were also used to characterize the stepwise modified electrodes. [ABSTRACT FROM AUTHOR]