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Repair or regeneration of load-bearing bones has long been an incentive for the tissue engineering community to develop a plethora of synthetic bone scaffolds. Despite the key role of physical forces and the mechanical environment in bone regeneration, the mechanotransduction concept has rarely been incorporated in structural design of bone tissue scaffolds, particularly those made of bioactive materials such as hydrogels and bioceramics. Herein, we introduce a modular design strategy to fabricate a load bearing device that can support a wide range of hydrogel- and ceramic-based scaffolds against complex in-vivo loading conditions to induce desirable mechanical strains for bone regeneration within the scaffolds. The device is comprised of a fenestrated polymeric shell and ceramic structural pillars arranged in a sophisticated configuration to provide ample internal space for the scaffold, also enabling it to purposely regulate the levels of strains and stresses within the scaffolds. Utilizing this top-down design approach, we demonstrate that the failure load of alginate hydrogels increases 3200-fold in compression, 300-fold in shear and 75-fold in impact, achieving the values that enable them to withstand physiological loads in weight-bearing sites, while allowing generation of osteoinductive strains (i.e., 0.2-0.4%) in the hydrogel. This modular design approach opens a broad range of opportunities to utilize various bioactive but mechanically weak scaffolds for the treatment of load-bearing defects and exploiting mechanobiology strategies to improve bone regeneration. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Abstract: Carbon nanotubes have begun to attract enormous interest in electrochemistry because of their small size and good electrochemical properties. The vast majority of studies thus far have used ensembles of carbon nanotubes to nanostructure macroscopic electrodes either with randomly dispersed nanotubes or with aligned carbon nanotubes. The resultant nanotube modified electrodes have most frequently been used for electro-analytical purposes such as the development of biosensors. This review introduces carbon nanotubes and approaches to nanostructuring electrodes with carbon nanotubes, discusses what is known of their electrochemical properties and briefly outlines some of the exciting applications to which they are being targeted for use. [Copyright &y& Elsevier]

The label-free amperometric detection of a rabbit IgG antigen by an anti-rabbit IgG antibody is achieved by observing the electrochemistry at a glassy carbon electrode modified with antibody entrapped in an electrodeposited polypyrrole membrane. In a flow injection apparatus the electrode is pulsed between -0.2 and +0.4 V versus Ag/AgCl. The pulsing of the electrode switches the polypyrrole membrane between the oxidised and reduced states. When antigen is injected into the flow stream a change in current is observed at the electrode despite the antigen or antibody being redox inactive at the potentials employed. It is proposed that this current is due to a change in the flux of ions into and out of the polypyrrole matrix during a pulse when the poly-anionic antigen is present. The immunoreaction was reversible because the 200 ms pulse at each potential was too short to allow secondary bonding forces (hydrogen bonding and hydrophobic forces) which are responsible for the strength of the antibody–antigen complex to be established. The consequence of the reversibility of the antigen–antibody binding is a low apparent affinity constant but an easily regenerated recognition interface. [Copyright &y& Elsevier]

Harnessing triboelectricity is a promising form of energy harvesting technology. Unlike conventional triboelectric nanogenerators, which convert friction between insulators into alternating current, a sliding metal‒semiconductor contact converts small movements into direct current (d.c.), which can power electronic circuitry without the need of electrical rectification. The zero-bias d.c. output of a dynamic metal‒semiconductor contact is assumed to increase linearly with its area, posing restrictions on the miniaturization of this new type of power sources. By implementing silicon surfaces that are electrically heterogeneous, it is found that d.c. outputs are not steady-state, but instead peak when the metal contact slides across concave boundaries between highly and poorly rectifying silicon crystal facets. Sharp lateral changes in electrical rectification, coupled to a concave surface curvature, are more important to maximize current densities than applied normal force or surface friction. These findings help alleviating device-wear issues, as well as removing physical constraints to the miniaturization of sliding-diode nanogenerators. Image 1 • Direct-current produced by a sliding Schottky diode peaks at boundaries between highly and poorly rectifying crystal planes • Removing device wear: current outputs from out-of-equilibrium diodes do not necessarily scale with friction • Pressure effects on the flow of minority carrier are a path to maximize tribocurrents in sliding-diode nanogenerators [ABSTRACT FROM AUTHOR]

Electrochemical transduction of DNA hybridization based on the concept of long-range electron transfer using different types of intercalators is reported. This paper examines the performance of two classes of intercalators, based on their charge, that is positively and negatively charged intercalators. The DNA modified electrode was prepared using a two component self-assembled monolayer of thiolated 20-mer probe single-stranded DNA (ss-DNA) and mercaptohexanol (MCH). After hybridization with complementary target ss-DNA the duplex was incubated in an intercalator solution followed by voltammetric measurement in an intercalator free solution. The cations intercalate more rapidly than the anions. However, significant non-specific signals were observed for the cationic intercalators due to non-specific binding to the diluent layer. Anionic intercalator on the other hand showed negligible non-specific signals. [Copyright &y& Elsevier]

An oxygen-rich fill-and-flow channel biosensor has been developed for the measurement of glucose in wine. Glucose oxidase (GOD), immobilised in carbon paste (CP), was located in a well adjacent to a downstream detector electrode. When the analyte solution flows, hydrogen peroxide produced in the enzyme reaction is swept down to the detector electrode. Mineral oil and Kel-F oil (poly(chlorotrifluorethylene)) were used to prepare an enzyme layer of GOD within a CP. The hydrophobicity of the CP confined the reaction between the enzyme and its substrate to the surface of the enzyme layer. The oxidation current of hydrogen peroxide was sensitive to the enzyme loading but insensitive to mass transport variations such as flow rate. This response was, therefore, limited by the kinetics of the reaction between the enzyme and the substrate. For Kel-F oil, which can support a high concentration of dissolved oxygen, good reproducibility and greater dynamic range was obtained and the response did not decrease after degassing for 40 min with argon. Analysis of wine samples showed good agreement with the values obtained by spectrophotometric enzyme assay. [Copyright &y& Elsevier]

The detection principle of nanopore sensors relies on measuring changes in electrical signal as analyte molecules translocate through a nanoscale pore. There are two challenges with this experimental construct when using nanopores for quantitative sensing with low detection limits in complex samples. The first is getting the analyte to the nanopore in a reasonable time frame and the second is other species in the sample also translocating through the nanopore and generating erroneous signals. We have developed a nanopore blockade sensor that alleviates the limitations of diffusion-limited mass transport and non-specific signals. Antibody-modified magnetic nanoparticles are utilized to deliver analytes of interest extracted from sample to an array of antibody-modified nanopores under a controlled electromagnet, resulting in long-term nanopore blocking events due to the formation of sandwiched immunocomplexes. Herein, this study reports on understanding some of important parameters in determining the performance of nanopore blockade sensing system, where prostate-specific antigen (PSA) is used as a model analyte. We describe the characterization of nanopore blockade sensing of PSA by (1) tuning on/off the electromagnet, (2) varying nanopore number in a nanopore chip, and (3) deploying the sensor in human plasma. Results show that magnetophoresis effectively facilitates active delivery and selective sensing of PSA to the nanopore. Nanopore chips with a larger number of nanopores are shown to receive more nanopore blockades for a given concentration of analyte. Furthermore, identifiable blockade events accounted for successful detection of PSA in plasma, indicate the high specificity of the sensing system. • We report the evaluation of the sensing performance of nanopore blockade sensors. • Magnetophoresis effectively facilitates active delivery and selective sensing of PSA. • Nanopore blockade events detected are proportional to the number of nanopores. • Identifiable blockade events accounted for detecting PSA in plasma are observed. [ABSTRACT FROM AUTHOR]

Supercapacitors are attracting increasing research interest because they are expected to achieve battery-level energy density while having a long calendar life and a short charging time. However, the development of large-scale and cost-reasonable production methods for flexible, wearable and arbitrary-shaped supercapacitor devices still faces enormous challenges. Herein, a 3D-network, porous graphene/CoS 2 /Ni 3 S 4 (G/CoS 2 /Ni 3 S 4) composite electrode has been designed and synthesized through a combination of solvothermal and vulcanization methods. By combining the networked CoS 2 /Ni 3 S 4 nanoflakes with reduced graphene oxide (RGO) nanosheets, the as-prepared composite electrode exhibits good conductivity, a high density of electrochemically active sites and good cycling stability. The result is a high specific capacitance of 1739 F g−1 at a current density of 0.5 A g−1. Significantly, the arbitrary-shaped G/CoS 2 /Ni 3 S 4 ||GF hybrid supercapacitor devices can be printed directly on different substrates, which favorably combine mechanical flexibility, good cycling performance and high energy density. This methodology may be feasible to prepare fully-printable and wearable supercapacitors, and other electronic devices in large scale, thereby holding enormous potential for wearable technologies. Image 1 [ABSTRACT FROM AUTHOR]

The photoreduction of graphene oxide (GO) with titanium dioxide (TiO 2 ) was exploited to fabricate a UV sensor for real time monitoring of sun exposure. The sensor was fabricated by simultaneous deposition of GO sheets and TiO 2 nanoparticles onto interdigitated electrodes using an AC electrophoresis deposition method. Changes in the resistance of the GO sheets decorated with TiO 2 nanoparticles during repeated cycles of exposure to UV were measured to understand the sensitivity of this sensor to UV radiation. Current-time traces revealed that the fabricated UV sensor retains a memory of each cycle of UV exposure; regardless of whether the sensor is exposed to UV for one long cycle or several short cycles. This memory of the extent of UV exposure is a biomimetic approach, analogous to the response of the skin to sun, and means the sensor requires no power except when the data is read from the sensor. [ABSTRACT FROM AUTHOR]

Loop mediated isothermal amplification (LAMP) holds incredible promise for point – of – care molecular diagnostics because of its high sensitivity and isothermal amplification behaviour. The issues related to the spurious non-specific amplification caused by the template independent amplification of primers itself causes false positive detection. This can be exacerbated by the common indirect methods used for detection of LAMP. Developing robust and specific detection methods for LAMP is a challenge due to the complex nature of the LAMP amplicons. To see wider adaptation of LAMP, we employ locked nucleic acid bases in molecular beacon to provide the structural stability to the hairpin probes that enable specific and multiplex detection of LAMP. Locked nucleic acid (LNA) modification provides ultra – high thermal stability to the molecular beacons resulting in negligible background fluorescence in the closed state. In this study, various combinations of LNA modifications in the stem and loop region were used and characterized for their thermal stability and influence on hybridization efficiency. The sequence specificity and ultra – high thermal stability of the LNA bases was exploited to develop a multiplex LAMP assay for detection of clinically important antibiotic resistance in S.aureus in 30 min. Multiplex approaches hold a significant advancement in LAMP and would find widespread applications in molecular diagnostics. [ABSTRACT FROM AUTHOR]

High performance, hysteresis-free, low temperature n-i-p perovskite solar cells are successfully fabricated by solution processing using fullerene electron transport layer (ETL). PC 71 BM fullerene, with broader absorption spectrum and lower HOMO level, when incorporated in the perovskite solar cell yielded average power conversion efficiency (PCE) of 13.9%. This is the highest reported PCE in n-i-p perovskite solar cells with PC 71 BM ETL. The devices exhibited negligible hysteresis and high open-circuit voltage (V oc ). On the contrary, devices with PC 61 BM, a common fullerene ETL in perovskite solar cell, exhibited large hysteresis and lower V oc . The underlying mechanisms of superior performance of devices with PC 71 BM ETL were found to be correlated with fullerene surface wettability and perovskite grain size. The influence of fullerene ETL on the perovskite grain growth and subsequent photovoltaic performance was investigated by contact angle measurement, morphological characterization of the surface topography and electrochemical impedance analysis. [ABSTRACT FROM AUTHOR]

Semiconducting electrodes that are in depletion, can support appreciable electron transfer only when illuminated. This phenomenon has been implemented on silicon electrodes passivated by a protective organic self-assembled monolayer (SAM) to confine electrochemistry to microscale regions on an unstructured electrode surface by shining light only on those regions. This method, referred to as light-activated electrochemistry (LAE), has so far only been studied using electrodes with surface-bound redox mediators that are either covalently or electrostatically attached to a SAM-modified silicon electrode. In the current report, we extend LAE to redox species in solution using gold nanoparticles (AuNPs) attached to the SAM-modified silicon electrodes. Cyclic voltammetry showed that faradaic electron transfer to redox species in solution can be switched on/off using light. Furthermore, the modified silicon electrodes were stable to more than 650 redox cycles, even when scanning to anodic potentials, with negligible oxide growth and no noticeable change in the voltammograms. Using a variety of redox species in solution, it was shown that with n − -Si-SAM-AuNP electrodes negligible current was observed in the dark but appreciable faradaic electrochemistry was observed upon illumination. It was also shown that to ensure electron transfer proceeded via the AuNPs only, nonspecific adsorption of the redox species to the monolayer surface needed to be avoided. [ABSTRACT FROM AUTHOR]

The electrodeposition of noble metals, particularly gold, on semiconducting surfaces is a common step in the development of optoelectronic and catalytic devices. Theoretical models of electrodeposition transients can provide mechanistic insights on nucleation and growth of metal particles. Here we study to what extent these models can be applied to the growth of gold nanoparticles on semiconductor photoelectrodes, with the ultimate purpose of being able to control in two dimensions the electrodepostion process. We have examined current transients for the reduction of aurate salts at Si(100) photocathodes and have made adjustments both to the experimental parameters as well as to the available models so as to account for parallel adsorption steps. We have observed to what extent these models hold predictive power for a nucleation process on semiconducting photoelectrodes. We found that the hydrogen evolution reaction is significant even at very basic pH values, leading to a poor match between the modelled and actual outcomes in electrodeposition experiments. We have concluded that the catalytic activity of gold particles and semiconductor photoeffects make it difficult to rely on current transients alone to refine the experimental conditions for the growth of gold particles on Si(100) photocathodes. Specifically, it is proposed that hydrogen evolution causes turbulence leading to the displacement of particles and significant aggregation on the surface. A solution to this problem is to electrodeposit metals with high overpotentials for hydrogen evolution, such as copper, which allows us to control nucleation and ultimately to use illumination patterns to spatially address nanoparticle deposition on semiconducting surfaces. [ABSTRACT FROM AUTHOR]

Herein we show that faradaic electrochemistry can be confined to a discrete region of a monolithic semiconducting electrode by means of locally addressing the kinetics of electron transfer with a focused light-pointer. A Si(100) electrode is modified with a self-assembled monolayer to which ferrocene is attached. The extent to which a model heterogeneous electrochemical reaction can be addressed in two-dimensions was explored at Si(100) photoanodes using scanning electrochemical microscopy operating in surface-generation/tip-collection mode. The link between the experimental radial profile of the catalytic current around the site of illumination and the substrate thickness indicates an inverse relationship between thickness and spatial resolution. We show to which extent the diffusion of charge carriers in the substrate governs the light-addressability. A spatial resolutions for our electrocatalytic system can be as low as ca . 385 μm ( ca . 5-times the size of the light pointer) using a non-structured Si(100) photoanode configured as a single-wire device. [ABSTRACT FROM AUTHOR]

Light-activated electrochemistry is a powerful concept, where faradaic electrochemistry at a monolayer protected monolithic silicon electrode can be ‘turned on’ at any location with micron scale resolution simply by illuminating that region with light. The three requirements for light-activated electrochemistry are that i) the silicon must be protected from oxidation with a self-assembled monolayer (SAM), ii) the semiconducting electrode must be biased into depletion at the redox potential of the species of interest and iii) the redox couple must be covalently attached to the electrode. Herein it is shown that light-activated electrochemistry can be performed with solution species if they adsorb to the surface of the SAM. It is shown that redox species such as ferrocene and ruthenium hexamine adsorb onto the 1,8-nonadiyne modified silicon surface and undergo electron transfer upon illumination while potassium ferrocyanide does not. It is proposed this adsorption causes an increase in electronic coupling between the redox species and the silicon electrode such that appreciable electron transfer through the monolayer was achieved. Furthermore, it is demonstrated that light-activated electrochemistry can be used to rapidly switch between macroelectrode- and microelectrode-type voltammetry at the same interface by simple means of modulating the light intensity. This work expands our understanding of light-activated electrochemistry and its application for interrogating discrete regions on an electrode in a highly parallel way. [ABSTRACT FROM AUTHOR]

This work reports a simple and scalable method to convert stainless steel (SS) felt into an effective anode for bioelectrochemical systems (BESs) by means of heat treatment. X-ray photoelectron spectroscopy and cyclic voltammetry elucidated that the heat treatment generated an iron oxide rich layer on the SS felt surface. The iron oxide layer dramatically enhanced the electroactive biofilm formation on SS felt surface in BESs. Consequently, the sustained current densities achieved on the treated electrodes (1 cm 2 ) were around 1.5 ± 0.13 mA/cm 2 , which was seven times higher than the untreated electrodes (0.22 ± 0.04 mA/cm 2 ). To test the scalability of this material, the heat-treated SS felt was scaled up to 150 cm 2 and similar current density (1.5 mA/cm 2 ) was achieved on the larger electrode. The low cost, straightforwardness of the treatment, high conductivity and high bioelectrocatalytic performance make heat-treated SS felt a scalable anodic material for BESs. [ABSTRACT FROM AUTHOR]

We investigate the analytical performance of label free porous silicon Bloch surface wave (BSW) devices as protease sensors. Protease detection is based on the digestion of gelatin, which was covalently immobilized onto the surface modified PSi structure. Exposure to the protease enzyme, subtilisin initiates catalytic degradation of the gelatin gel network. The degradation of this network which is present in the top layer of the sensor, causes a blue shift in the spectral position of the Bloch surface mode. The magnitude of the resonance shift is directly proportional to the concentration of subtilisin and the digestion time. The lowest concentration of subtilisin detected was 370 pM. Secondary spectral features, such as band-edge modes, are relatively insensitive to refractive index changes in the superficial layers and thus can be utilised as an internal reference to exclude any nonspecific adsorption and bonding that may occur through the bulk of the film. The advantages of the system here include fast diffusion of digested product and self-referencing capability. [ABSTRACT FROM AUTHOR]

Abstract: Porous silicon has shown potential for various applications in biology and medicine, which require that the material (1) remain stable for the length of the intended application and (2) resist non-specific adsorption of proteins. Here we explore the efficacy of short oligo(ethylene glycol) moieties incorporated into organic layers via two separate strategies in achieving these aims. In the first strategy the porous silicon structure was modified in a single step via hydrosilylation of α-oligo(ethylene glycol)-ω-alkenes containing three or six ethylene glycol units. The second strategy employs two steps: (1) hydrosilylation of succinimidyl-10-undecenoate and (2) coupling of an amino hexa(ethylene glycol) species. The porous silicon photonic crystals modified by the two-step strategy displayed greater stability relative to the single step procedure when exposed to conditions of physiological temperature and pH. Both strategies produced layers that resist non-specific adsorption of proteins as determined with fluorescently labelled bovine serum albumin. The antifouling behaviour and greater stability to physiological conditions provided by this chemistry enhances the suitability of porous silicon for biomaterials applications. [Copyright &y& Elsevier]

Abstract: High-density, surface-mounted ferrocene has been prepared using covalent immobilisation of an alcohol substituted ferrocene derivative to a pre-assembled single-walled carbon nanotubes directly anchored to silicon(100) surface (SWCNTs-Si). The formation of these ferrocene-modified electrodes (Fc-SWCNTs-Si) has been followed using X-ray photoelectron spectroscopy and atomic force microscopy. Electrochemical results show the surface concentration of ferrocenemethanol molecules is 9.26×10−8 molcm−2, which is about 500–1000 times greater than the experimentally measured coverage of ferrocene directly attached to flat Si(100) surfaces. The reversible one-electron wave of the ferrocene/ferrocenium couple was observed at 490mV versus Ag+/Ag and the apparent rate constant of electron transfer, k app, was 21s−1. These results suggest these ferrocene-modified electrodes are excellent candidates for molecular memory devices. [Copyright &y& Elsevier]

Abstract: Porous polymer films show interesting properties as ion selective membranes. In this work, poly(1,2-diaminobenzene) and polytyramine were deposited from hexagonal liquid crystal templates using two different surfactants. Resulting films were investigated to find evidence of mesoporous structures. While templated poly(1,2-diaminobenzene) has already been described as charge selective in the past, electrochemical experiments in this work demonstrate that another mechanism (most likely, size selectivity) also contributes to its ion selective behaviour. Films were characterised using spectroscopic ellipsometry and impedance spectroscopy. Results provide further evidence for the porosity, thinness, and the presence of ions in the templated poly(1,2-diaminobenzene) films. It is demonstrated that the use of a low-cost surfactant (Brij 56) is sufficient for the templating process. In contrast, polytyramine gave no evidence of being templated by the liquid crystal. [Copyright &y& Elsevier]

Abstract: This paper studies the analytical performance and characterization of a peptide modified biosensor towards detection of Cu2+ ions. The peptide modified biosensor is developed by carbodiimide attachment of the Gly-Gly-His tripeptide onto a 3-mercaptopropionic acid (MPA) modified gold surface. X-ray photoelectron spectroscopy (XPS) was used to characterize the steps in the biosensor fabrication. Detection of Cu2+ ions are determined by cyclic and Osteryoung square wave voltammetry. The analytical performance of this biosensor is found to be affected by the pH, salt concentration, temperature and accumulation time of the test solution. Interference studies and investigations of the reusability of this biosensor have also been performed. [Copyright &y& Elsevier]