Randomized double-blind clinical studies of ularitide and other vasoactive substances in acute decompensated heart failure: a systematic review and meta-analysis.

AIMS: Acute decompensated heart failure (ADHF) has a poor prognosis and limited treatment options. No direct comparisons between ularitide-a synthetic natriuretic peptide being evaluated in ADHF-and other vasoactive substances are available. The aim of this meta-analysis was to determine haemodynamic effect sizes from randomized double-blind trials in ADHF. METHODS AND RESULTS: Eligible studies enrolled patients with ADHF requiring hospitalization and haemodynamic monitoring. Patients received 24-48 h of infusion with a vasoactive substance or comparator. Primary outcome measure was pulmonary artery wedge pressure (PAWP). Treatment effects were quantified as changes from baseline using mean differences between study drug and comparator. Results were analysed using random-effects (primary analysis) and fixed-effects meta-analyses. Twelve randomized, double-blind studies were identified with data after 3, 6, and 24 h of treatment (n = 622, 644, and 644, respectively). At 6 h, significant PAWP benefits for ularitide over placebo were seen (Hedges' g effect size, -0.979; P < 0.0001). On meta-analysis, treatment difference between ularitide and pooled other agents was statistically significant (-0.501; P = 0.0303). Effect sizes were numerically higher with ularitide than other treatments at 3 and 24 h. After 6 h, a significant difference in effect size between ularitide and all other treatments was observed for right atrial pressure (Hedges' g, -0.797 for ularitide and -0.304 for other treatments; P = 0.0274). CONCLUSIONS: After 6 h, ularitide demonstrated high effect sizes for PAWP and right atrial pressure. Improvements in these parameters were greater with ularitide vs. pooled data for other vasoactive drugs.

Revealing the Cell-Material Interface with Nanometer Resolution by Focused Ion Beam/Scanning Electron Microscopy.

The interface between cells and nonbiological surfaces regulates cell attachment, chronic tissue responses, and ultimately the success of medical implants or biosensors. Clinical and laboratory studies show that topological features of the surface profoundly influence cellular responses; for example, titanium surfaces with nano- and microtopographical structures enhance osteoblast attachment and host-implant integration as compared to a smooth surface. To understand how cells and tissues respond to different topographical features, it is of critical importance to directly visualize the cell-material interface at the relevant nanometer length scale. Here, we present a method for in situ examination of the cell-to-material interface at any desired location, based on focused ion beam milling and scanning electron microscopy imaging to resolve the cell membrane-to-material interface with 10 nm resolution. By examining how cell membranes interact with topographical features such as nanoscale protrusions or invaginations, we discovered that the cell membrane readily deforms inward and wraps around protruding structures, but hardly deforms outward to contour invaginating structures. This asymmetric membrane response (inward vs outward deformation) causes the cleft width between the cell membrane and the nanostructure surface to vary by more than an order of magnitude. Our results suggest that surface topology is a crucial consideration for the development of medical implants or biosensors whose performances are strongly influenced by the cell-to-material interface. We anticipate that the method can be used to explore the direct interaction of cells/tissue with medical devices such as metal implants in the future.

MEAs and 3D nanoelectrodes: electrodeposition as tool for a precisely controlled nanofabrication.

Microelectrode arrays (MEAs) are gaining increasing importance for the investigation of signaling processes between electrogenic cells. However, efficient cell-chip coupling for robust and long-term electrophysiological recording and stimulation still remains a challenge. A possible approach for the improvement of the cell-electrode contact is the utilization of three-dimensional structures. In recent years, various 3D electrode geometries have been developed, but we are still lacking a fabrication approach that enables the formation of different 3D structures on a single chip in a controlled manner. This, however, is needed to enable a direct and reliable comparison of the recording capabilities of the different structures. Here, we present a method for a precisely controlled deposition of nanoelectrodes, enabling the fabrication of multiple, well-defined types of structures on our 64 electrode MEAs towards a rapid-prototyping approach to 3D electrodes.

The Influence of Supporting Ions on the Electrochemical Detection of Individual Silver Nanoparticles: Understanding the Shape and Frequency of Current Transients in Nano-impacts.

We report the influence of electrolyte composition and concentration on the stochastic amperometric detection of individual silver nanoparticles at microelectrode arrays and show that the sensor response at certain electrode potentials is dependent on both the conductivity of the electrolyte and the concentration of chloride ions. We further demonstrate that the chloride concentration in solution heavily influences the characteristic current spike shape of recorded nanoparticle impacts: While typically too short to be resolved in the measured current, the spike widths are significantly broadened at low chloride concentrations below 10 mm and range into the millisecond regime. The analysis of more than 25 000 spikes reveals that this effect can be explained by the diffusive mass transport of chloride ions to the nanoparticle, which limits the oxidation rate of individual silver nanoparticles to silver chloride at the chosen electrode potential.

Influence of Self-Assembled Alkanethiol Monolayers on Stochastic Amperometric On-Chip Detection of Silver Nanoparticles.

We investigate the influence of self-assembled alkanethiol monolayers at the surface of platinum microelectrode arrays on the stochastic amperometric detection of citrate-stabilized silver nanoparticles in aqueous solutions. The measurements were performed using a microelectrode array featuring 64 individually addressable electrodes that are recorded in parallel with a sampling rate of 10 kHz for each channel. We show that both the functional end group and the total length of the alkanethiol influence the charge transfer. Three different terminal groups, an amino, a hydroxyl, and a carboxyl, were investigated using two different molecule lengths of 6 and 11 carbon atoms. Finally, we show that a monolayer of alkanethiols with a length of 11 carbon atoms and a carboxyl terminal group can efficiently block the charge transfer of free nanoparticles in an aqueous solution.

Interfacing electrogenic cells with 3D nanoelectrodes: position, shape, and size matter.

An in-depth understanding of the interface between cells and nanostructures is one of the key challenges for coupling electrically excitable cells and electronic devices. Recently, various 3D nanostructures have been introduced to stimulate and record electrical signals emanating from inside of the cell. Even though such approaches are highly sensitive and scalable, it remains an open question how cells couple to 3D structures, in particular how the engulfment-like processes of nanostructures work. Here, we present a profound study of the cell interface with two widely used nanostructure types, cylindrical pillars with and without a cap. While basic functionality was shown for these approaches before, a systematic investigation linking experimental data with membrane properties was not presented so far. The combination of electron microscopy investigations with a theoretical membrane deformation model allows us to predict the optimal shape and dimensions of 3D nanostructures for cell-chip coupling.

Matrix elasticity, replicative senescence and DNA methylation patterns of mesenchymal stem cells.

Matrix elasticity guides differentiation of mesenchymal stem cells (MSCs) but it is unclear if these effects are only transient - while the cells reside on the substrate - or if they reflect persistent lineage commitment. In this study, MSCs were continuously culture-expanded in parallel either on tissue culture plastic (TCP) or on polydimethylsiloxane (PDMS) gels of different elasticity to compare impact on replicative senescence, in vitro differentiation, gene expression, and DNA methylation (DNAm) profiles. The maximal number of cumulative population doublings was not affected by matrix elasticity. Differentiation towards adipogenic and osteogenic lineage was increased on soft and rigid biomaterials, respectively - but this propensity was no more evident if cells were transferred to TCP. Global gene expression profiles and DNAm profiles revealed relatively few differences in MSCs cultured on soft or rigid matrices. Furthermore, only moderate DNAm changes were observed upon culture on very soft hydrogels of human platelet lysate. Our results support the notion that matrix elasticity influences cellular behavior while the cells reside on the substrate, but it does not have major impact on cell-intrinsic lineage determination, replicative senescence or DNAm patterns.

On chip guidance and recording of cardiomyocytes with 3D mushroom-shaped electrodes.

The quality of the recording and stimulation capabilities of multielectrode arrays (MEAs) substantially depends on the interface properties and the coupling of the cell with the underlying electrode area. The purpose of this work was the investigation of a three-dimensional nanointerface, enabling simultaneous guidance and recording of electrogenic cells (HL-1) by utilizing nanostructures with a mushroom shape on MEAs.

Printed carbon microelectrodes for electrochemical detection of single vesicle release from PC12 cells.

We present a disposable system for recording neurotransmitter release from individual cells in vitro. A simple yet reliable microelectrode fabrication process is introduced using screen-printed carbon paste. It allows rapid fabrication of devices at low costs without standard clean-room technology. We demonstrate functionality of the system by real-time observation of vesicle release from single PC12 (rat pheochromocytoma) cells. The cells are cultured directly on the chip and can be used for immediate or long-term in vitro experiments. Thus, our approach may serve as a platform for pharmacological cell culture studies.