STRUCTURING OF ELECTRODE SURFACES WITH LIGAND-FREE NANOPARTICLES VIA ELECTROPHORETIC DEPOSITION- FUNDAMENTALS AND IN VIVO APPLICATIONS

Electrodes for neural stimulation and recording are highly relevant in modern medicine, e.g. for the treatment of movement disorders. As these electrodes have to be implanted directly into the patient´s brain, impaired biocompatibility as well as reduced performance due to increased impedance upon tissue contact are serious problems. Strategies to improve the efficiency of electrodes entail the implementation of defined nanoscopic structures to the electrode surface, which increase the surface area and improve the current flow by possible edge effects1. In this context electrophoretic deposition (EPD) of nanoparticles (NP) constitutes an efficient and feasible way for surface structuring as in contrast to e.g. ablative laser machining, electric field lines are naturally ordered perpendicular to the implant´s surface, so that electrophoretic deposition is well compatible to shaped implants and curved surfaces. In this work an EPD process for the structuring of Pt electrode surfaces with NP is systematically investigated. Reference NP from a modern synthesis route named pulsed laser ablation in liquids (PLAL)2 are utilized as they possess a high surface charge density in order to ease their movement in an electric field. The electrophoretic velocity of these NP was examined and found to be linearly-correlated with the electric field strength, while the slope is dictated by the NP´s surface charge density (zeta-potential).3, 4 On the other hand the PLAL-generated NP are, by design, completely free of organic ligand, which significantly affected their deposition in an EPD setup. It was found that the deposited mass linearly increased with process time, yielding a well scalable process, while on the other hand control experiments with ligands showed a saturation of the deposited mass due to electrochemical shielding of the surface by charged ligands.4 It was furthermore demonstrated that the EPD process with ligand-free NP could also be done in a continuous flow-through setup suitable for the parallel structuring of multiple electrodes.5 Interestingly, the deposition velocity was not size dependent as particle size distributions prior to and after EPD were identical.5 In consecutive experiments, the surface properties like coverage, oxidation, wettability6 and impedance of the electrode materials were evaluated and correlated with the EPD process parameters electric field strength, colloid concentration and deposition time. As a result a detailed map was obtained, which allows a defined tuning of Pt surface properties by Pt NP EPD. Finally, the impedance of electrodes coated with ligand-free Pt NP were evaluated in long term stimulation experiments with rats. The NP coating could stabilize the impedance of the electrodes in vivo, while it continuously increased in non-coated controls.7 Furthermore, the coated electrodes exhibited excellent biocompatibility similar to the controls7 while no significant NP desorption from the surface was found upon mechanical tear. 1. X. F. F. Wei and W. M. Grill, J. Neural Eng., 2005, 2, 139-147. 2. V. Amendola and M. Meneghetti, Phys. Chem. Chem. Phys., 2013, 15, 3027-3046. 3. A. Menendez-Manjon, J. Jakobi, K. Schwabe, J. K. Krauss and S. Barcikowski, J. Laser Micro Nanoeng., 2009, 4, 95-99. 4. C. Streich, S. Koenen, M. Lelle, K. Peneva and S. Barcikowski, Appl. Surf. Sci., 2015, 348, 92-99. 5. S. Koenen, R. Streubel, J. Jakobi, K. Schwabe, J. K. Krauss and S. Barcikowski, J. Electrochem. Soc., 2015, 162, D174-D179. 6. A. Heinemann, S. Koenen, K. Schwabe, C. Rehbock and S. Barcikowski, Key engineering materials, 2015, 654, 218-223. 7. S. D. Angelov, S. Koenen, J. Jakobi, H. E. Heissler, M. Alam, K. Schwabe, S. Barcikowski and J. K. Krauss, J. Nanobiotechnol., 2016, 14

Using the third state of matter: high harmonic generation from liquid targets

High harmonic generation on solid and gaseous targets has been proven to be a powerful platform for the generation of attosecond pulses. Here we demonstrate a novel technique for the XUV generation on a smooth liquid surface target in vacuum, which circumvents the problem of low repetition rate and limited shot numbers associated with solid targets, while it maintains some of its merits. We employed atomically smooth, continuous liquid jets of water, aqueous salt solutions and ethanol that allow uninterrupted high harmonic generation due to the coherent wake emission mechanism for over 8 h. It has been found that the mechanism of plasma generation is very similar to that for smooth solid target surfaces. The vapor pressure around the liquid target in our setup has been found to be very low such that the presence of the gas phase around the liquid jet could be neglected

Polysiloxane layers created by sol-gel and photochemistry: Ideal surfaces for rapid, low-cost and high-strength bonding of epoxy components to polydimethylsiloxane

In this article we introduce and compare three techniques for low-cost and rapid bonding of stereolithographically structured epoxy components to polydimethylsiloxane (PDMS). In short, we first create a polysiloxane layer on the epoxy surface via silane surface coupling and polymerization. Afterwards, the modified epoxy surface can be bonded to a PDMS component at room temperature using a handheld corona discharger, which is a commonly used low-cost technique for bonding two PDMS components. Using these methods bonds of desirable strength can be generated within half an hour. Depending on the epoxy resin, we found it necessary to modify the silanization procedure. Therefore, we provide a total of three different silanization techniques that allow bonding of a wide variety of stereolithographically structurable epoxy resins. The first technique is a UV-light induced silanization process which couples a silane that contains an epoxy-ring ((3-glycidoxypropyl)trimethoxysilane (GPTMS)). For surfaces that cannot be modified with this silane we use dimethoxydimethylsilane (DMDMS). This silane can either be coupled to the surface by a sol-gel process or UV-light induced polymerisation. The sol-gel process which is a heat induced surface modification technique results in high bond strengths. Because of the heat which triggers the sol-gel process, this technique is limited to epoxy polymers with high glass transition temperatures. For the majority of stereolithographically structured epoxy resins which typically have glass transition temperatures of around 60°C the light-induced bonding technique is preferable. For all three techniques we performed DIN EN-conform tensile testing demonstrating maximum bond strengths of up to 350 kPa which is comparable with bond strengths reported for PDMS-to-PDMS bonds. For all bond methods, long-term stability as well as hydrolytic stability was assessed

Calmodulin-like proteins localized to the conoid regulate motility and cell invasion by Toxoplasma gondii

Toxoplasma gondii contains an expanded number of calmodulin (CaM)-like proteins whose functions are poorly understood. Using a combination of CRISPR/Cas9-mediated gene editing and a plant-like auxin-induced degron (AID) system, we examined the roles of three apically localized CaMs. CaM1 and CaM2 were individually dispensable, but loss of both resulted in a synthetic lethal phenotype. CaM3 was refractory to deletion, suggesting it is essential. Consistent with this prediction auxin-induced degradation of CaM3 blocked growth. Phenotypic analysis revealed that all three CaMs contribute to parasite motility, invasion, and egress from host cells, and that they act downstream of microneme and rhoptry secretion. Super-resolution microscopy localized all three CaMs to the conoid where they overlap with myosin H (MyoH), a motor protein that is required for invasion. Biotinylation using BirA fusions with the CaMs labeled a number of apical proteins including MyoH and its light chain MLC7, suggesting they may interact. Consistent with this hypothesis, disruption of MyoH led to degradation of CaM3, or redistribution of CaM1 and CaM2. Collectively, our findings suggest these CaMs may interact with MyoH to control motility and cell invasion

Titanium based cranial reconstruction using incremental sheet forming

In this paper, we report recent work in cranial plate manufacturing using incremental sheet forming (ISF) process. With a typical cranial shape, the ISF process was used to manufacture the titanium cranial shape by using different ISF tooling solutions with and without backing plates. Detailed evaluation of the ISF process including material deformation and thinning, geometric accuracy and surface finish was conducted by using a combination of experimental testing and Finite Element (FE) simulation. The results show that satisfactory cranial shape can be achieved with sufficient accuracy and surface finish by using a feature based tool path generation method and new ISF tooling design. The results also demonstrate that the ISF based cranial reconstruction has the potential to achieve considerable lead time reduction as compared to conventional methods for cranial plate manufacturing. This outcome indicates that there is a potential for the ISF process to achieve technological advances and economic benefits as well as improvement to quality of life

Affimer proteins for F-actin: novel affinity reagents that label F-actin in live and fixed cells

Imaging the actin cytoskeleton in cells uses a wide range of approaches. Typically, a fluorescent derivative of the small cyclic peptide phalloidin is used to image F-actin in fixed cells. Lifeact and F-tractin are popular for imaging the cytoskeleton in live cells. Here we characterised novel affinity reagents called Affimers that specifically bind to F-actin in vitro to determine if they are suitable alternatives as eGFP-fusion proteins, to label actin in live cells, or for labeling F-actin in fixed cells. In vitro experiments showed that 3 out of the 4 Affimers (Affimers 6, 14 and 24) tested bind tightly to purified F-actin, and appear to have overlapping binding sites. As eGFP-fusion proteins, the same 3 Affimers label F-actin in live cells. FRAP experiments suggest that eGFP-Affimer 6 behaves most similarly to F-tractin and Lifeact. However, it does not colocalize with mCherry-actin in dynamic ruffles, and may preferentially bind stable actin filaments. All 4 Affimers label F-actin in methanol fixed cells, while only Affimer 14 labels F-actin after paraformaldehyde fixation. eGFP-Affimer 6 has potential for use in selectively imaging the stable actin cytoskeleton in live cells, while all 4 Affimers are strong alternatives to phalloidin for labelling F-actin in fixed cells

Functional characterization of the human myosin-7a motor domain

Myosin-7a participates in auditory and visual processes. Defects in MYO7A, the gene encoding the myosin-7a heavy chain, are causative for Usher syndrome 1B, the most frequent cause of deaf-blindness in humans. In the present study, we performed a detailed kinetic and functional characterization of the isolated human myosin-7a motor domain to elucidate the details of chemomechanical coupling and the regulation of motor function. A rate-limiting, slow ADP release step causes long lifetimes of strong actin-binding intermediates and results in a high duty ratio. Moreover, our results reveal a Mg2+-sensitive regulatory mechanism tuning the kinetic and mechanical properties of the myosin-7a motor domain. We obtained direct evidence that changes in the concentration of free Mg2+ ions affect the motor properties of human myosin-7a using an in vitro motility assay system. Our results suggest that in a cellular environment, compartment-specific fluctuations in free Mg2+ ions can mediate the conditional switching of myosin-7a between cargo moving and tension bearing modes

4° Intelligence

Berger D., Heissler N., Piéron Henri. 4° Intelligence. In: L'année psychologique. 1956 vol. 56, n°1. pp. 224-228