Stochastic Electrochemical Measurement of a Biofouling Layer on Gold.

Adsorption of a biofouling layer on the surface of biosensors decreases the electrochemical activity and hence shortens the service life of biosensors, particularly implantable and wearable biosensors. Real-time quantification of the loss of activity is important for in situ assessment of performance while presenting an opportunity to compensate for the loss of activity and recalibrate the sensor to extend the service life. Here, we introduce an electrochemical noise measurement technique as a tool for the quantification of the formation of a biofouling layer on the surface of gold. The technique uniquely affords thermodynamic and kinetic information without applying an external bias (potential and/or current), hence allowing the system to be appraised in its innate state. The technique relies on the analysis of non-faradaic current and potential fluctuations that are intrinsically generated by the interaction of charged species at the electrode surface, i.e., gold. An analytical model is extended to explain the significance of parameters drawn from statistical analysis of the noise signal. This concept is then examined in buffered media in the presence of albumin, a common protein in the blood and a known source of a fouling layer in biological systems. Results indicate that the statistical analysis of the noise signal can quantify the loss of electrochemical activity, which is also corroborated by impedance spectroscopy as a complementary technique.

Approaches to Improving the Selectivity of Nanozymes.

Nanozymes mimic enzymes and that includes their selectivity. To achieve selectivity, significant inspiration for nanoparticle design can come from the geometric and molecular features that make enzymes selective catalysts. The two central features enzymes use are control over the arrangement of atoms in the active site and the placing of the active site down a nanoconfined substrate channel. The implementation of enzyme-inspired features has already been shown to both improve activity and selectivity of nanoparticles for a variety of catalytic and sensing applications. The tuning and control of active sites on metal nanoparticle surfaces ranges from simply changing the composition of the surface metal to sophisticated approaches such as the immobilization of single atoms on a metal substrate. Molecular frameworks provide a powerful platform for the implementation of isolated and discrete active sites while unique diffusional environments further improve selectivity. The implementation of nanoconfined substrate channels around these highly controlled active sites offers further ability to control selectivity through altering the solution environment and transport of reactants and products. Implementing these strategies together offers a unique opportunity to improve nanozyme selectivity in both sensing and catalysis.

Spiers Memorial Lecture. Next generation nanoelectrochemistry: the fundamental advances needed for applications.

Nanoelectrochemistry, where electrochemical processes are controlled and investigated with nanoscale resolution, is gaining more and more attention because of the many potential applications in energy and sensing and the fact that there is much to learn about fundamental electrochemical processes when we explore them at the nanoscale. The development of instrumental methods that can explore the heterogeneity of electrochemistry occurring across an electrode surface, monitoring single molecules or many single nanoparticles on a surface simultaneously, have been pivotal in giving us new insights into nanoscale electrochemistry. Equally important has been the ability to synthesise or fabricate nanoscale entities with a high degree of control that allows us to develop nanoscale devices. Central to the latter has been the incredible advances in nanomaterial synthesis where electrode materials with atomic control over electrochemically active sites can be achieved. After introducing nanoelectrochemistry, this paper focuses on recent developments in two major application areas of nanoelectrochemistry; electrocatalysis and using single entities in sensing. Discussion of the developments in these two application fields highlights some of the advances in the fundamental understanding of nanoelectrochemical systems really driving these applications forward. Looking into our nanocrystal ball, this paper then highlights: the need to understand the impact of nanoconfinement on electrochemical processes, the need to measure many single entities, the need to develop more sophisticated ways of treating the potentially large data sets from measuring such many single entities, the need for more new methods for characterising nanoelectrochemical systems as they operate and the need for material synthesis to become more reproducible as well as possess more nanoscale control.

Fabrication of biodegradable HA/Mg-Zn-Ca composites and the impact of heterogeneous microstructure on mechanical properties, in vitro degradation and cytocompatibility.

Due to their desirable elastic modulus and density that are similar to natural bone, non-toxic element containing magnesium alloys are regarded as promising bio-degradable materials. A biodegradable HA-particle-reinforced magnesium-matrix composite Mg-3Zn-0.2Ca-1HA (wt%) was fabricated for biomedical application by a combination of high shear solidification (HSS) and hot extrusion technology. The microstructure, mechanical properties, corrosion resistance and cell biocompatibility of the composite were subsequently investigated. In comparison with the matrix alloy, the as-cast Mg-3Zn-0.2Ca-1HA composite obtained by HSS technology exhibited a uniform and fine grained structure, further refined after a hot extrusion ratio of 36:1. The yield strength (0.2%YS), ultimate tensile strength and elongation of the extruded composite were 322 MPa, 341 MPa and 7.6%, respectively. The corrosion rate of the as-extruded Mg-3Zn-0.2Ca-1HA composite was measured to be 1.52 mm/y. Electrochemical and immersion tests showed that the corrosion resistance of the composite is slightly improved comparing to that of the matrix alloy.

Cytocompatible tantalum films on Ti6Al4V substrate by filtered cathodic vacuum arc deposition.

Tantalum films were deposited on negatively biased Ti6Al4V substrates using filtered cathodic vacuum arc deposition to enhance the corrosion resistance of the Ti6Al4V alloy. The effect of substrate voltage bias on the microstructure, mechanical and corrosion properties was examined and the cytocompatibility of the deposited films was verified with mammalian cell culturing. The Ta films deposited with substrate bias of -100V and -200V show a mixture of predominantly ß phase and minority of α phase. The Ta/-100V film shows adhesive failure at the Ti/Ta interface and a cohesive fracture is observed in Ta/-200V film. The Ta/-100V showed a significant improvement in corrosion resistance, which is attributed to the stable oxide layer. The in-vitro cytocompatibility of the materials was investigated using rat bone mesenchymal stem cells, and the results show that the Ta films have no adverse effect on mammalian cell adhesion and spreading proliferation.

Atomically Thin Hexagonal Boron Nitride Nanofilm for Cu Protection: The Importance of Film Perfection.

Outstanding protection of Cu by high-quality boron nitride nanofilm (BNNF) 1-2 atomic layers thick in salt water is observed, while defective BNNF accelerates the reaction of Cu toward water. The chemical stability, insulating nature, and impermeability of ions through the BN hexagons render BNNF a great choice for atomic-scale protection.

Electrical stimulation using conductive polymer polypyrrole promotes differentiation of human neural stem cells: a biocompatible platform for translational neural tissue engineering.

Conductive polymers (CPs) are organic materials that hold great promise for biomedicine. Potential applications include in vitro or implantable electrodes for excitable cell recording and stimulation and conductive scaffolds for cell support and tissue engineering. In this study, we demonstrate the utility of electroactive CP polypyrrole (PPy) containing the anionic dopant dodecylbenzenesulfonate (DBS) to differentiate novel clinically relevant human neural stem cells (hNSCs). Electrical stimulation of PPy(DBS) induced hNSCs to predominantly ß-III Tubulin (Tuj1) expressing neurons, with lower induction of glial fibrillary acidic protein (GFAP) expressing glial cells. In addition, stimulated cultures comprised nodes or clusters of neurons with longer neurites and greater branching than unstimulated cultures. Cell clusters showed a similar spatial distribution to regions of higher conductivity on the film surface. Our findings support the use of electrical stimulation to promote neuronal induction and the biocompatibility of PPy(DBS) with hNSCs and opens up the possibility of identifying novel mechanisms of fate determination of differentiating human stem cells for advanced in vitro modeling, translational drug discovery, and regenerative medicine.