Purely peptidic amphiphiles : understanding and controlling their self-assembled structures

Amphiphilic molecules spontaneously self-assemble into a variety of structures in solution. The term amphiphilic indicates that one part of the molecule is attracted to the solvent, while the other is not. Interactions such as between solute-solvent and solute-solute thus determine the organization. Understanding the self-assembly means understanding those interactions and their driving forces. In the first chapter an overview of the self-organization of amphiphilic molecules into supermolecuar aggregates of different morphologies is provided, with a focus on purely peptidic amphiphiles, i.e. amphiphiles which consist solely of a different amino acid sequence. In the second chapter the self-assembly of amphiphilic peptides with a specific amino acid sequence into micelles and spherical peptide nanoparticles is described. The undecamer peptide that was used features a repetitive L-tryptophan and D-leucine [LW-DL] motif, representing the hydrophobic block – which is a truncated version of gramicidin A (gA), named gT. The N-terminally attached hydrophilic section was either lysine (K) or acetylated lysine (X) and was optionally terminated with cysteine for post-functionalization of the thiol-group. The uncharged peptide AcC-X3-gT was demonstrated to assemble into micelles and subsequently into peptide particles, termed ‘peptide beads’. We hypothesize that the peptide beads consisted of micelles – a structure described as multicompartment micelles. Peptide beads using AcC-X3-gT and its analogues – including Ac-X3-gT-C, a new peptide with the cysteine residue on the C instead of the N-terminus – are further investigated in Chapter Three. We succeeded in creating highly ordered Ac-X3-gT-C – Au-NP composites, which allowed us to visualize the inner structure of the nanoparticles. The presented composite materials are expected to exhibit exceptional electrical and optical properties. In Chapter Four these amphiphilic peptides are studied with regard to the interaction within a lipid layer but also in pure peptide layers at the air-water interface. Results indicate the formation of a unimolecular, flat film. Peptide layers were successfully transferred onto a solid support or self-assembled peptide monolayers (SAMs) were created equally well via immersion and spin-coating. Preliminary mineralization experiments confirmed the successful creation of calcium phosphate crystals. The topic of the following chapter focuses on a peptide library that has been synthesized to correlate the primary sequence, its secondary structure and the resulting self-assembly. The peptide design includes three parts: (a) a charged lysine part, (b) an acetylated lysine part and (c) a constant hydrophobic rod-like helix, based on gramicidin A (gA). By stepwise replacement of free lysine (K) with acetylated lysine (X) we generated a library of a total of ten peptides Ac-X8-gA and KmX8-m-gA (m ranging from 0 to 8). By using point mutations, we adjusted the degree of acetylation (DA) and thus the overall amphiphilicity of the peptides, which led to a change in the secondary structure in the aqueous environment from a Beta-sheet to an Alpha-helix. This transition generated a significant change in the morphology of the self-assembled structures from fibers to micelles. The study is important precisely because it presents a first step towards molecular switches based on acetylation of a peptide, inspired by the example of phosphorylation of proteins or enzymes, which converts them into the active or inactive state by structural changes. Chapter Sseven focuses on essential parameters to successfully manage membrane formation from a purely peptidic system. A crucial step in the formation of peptide membranes appears to be dimerization, which originates from the introduction of intermolecular interactions, such as H-bonds or Pi-Pi stacking of aromatic rings. The formation of a stabilized membrane subunit, i.e. dimers in the lateral or perpendicular directions (relative to the membrane) produced stable, purely peptidic vesicles and may well apply to other peptidic systems. These novel peptidic systems offer hydrophilic and hydrophobic compartments to encapsulate and integrate different drugs or payloads and could be used for gene delivery, since the design includes charged moieties. In the last chapter, the achievements of the presented work are discussed and summarized. Furthermore, lines of research are suggested, which, from the present point of view, appear to be the most promising and should be the focus of subsequent experiments

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Memetic Graph Clustering

It is common knowledge that there is no single best strategy for graph clustering, which justifies a plethora of existing approaches. In this paper, we present a general memetic algorithm, VieClus, to tackle the graph clustering problem. This algorithm can be adapted to optimize different objective functions. A key component of our contribution are natural recombine operators that employ ensemble clusterings as well as multi-level techniques. Lastly, we combine these techniques with a scalable communication protocol, producing a system that is able to compute high-quality solutions in a short amount of time. We instantiate our scheme with local search for modularity and show that our algorithm successfully improves or reproduces all entries of the 10th DIMACS implementation challenge under consideration using a small amount of time

Embedded disposable functionalized electrochemical biosensor with a 3D-printed flow cell for detection of hepatic oval cells (HOCs)

Hepatic oval cells (HOCs) are considered the progeny of the intrahepatic stem cells that are found in a small population in the liver after hepatocyte proliferation is inhibited. Due to their small number, isolation and capture of these cells constitute a challenging task for immunosensor technology. This work describes the development of a 3D-printed continuous flow system and exploits disposable screen-printed electrodes for the rapid detection of HOCs that over-express the OV6 marker on their membrane. Multiwall carbon nanotube (MWCNT) electrodes have a chitosan film that serves as a scaffold for the immobilization of oval cell marker antibodies (anti-OV6-Ab), which enhance the sensitivity of the biomarker and makes the designed sensor specific for oval cells. The developed sensor can be easily embedded into the 3D-printed flow cell to allow cells to be exposed continuously to the functionalized surface. The continuous flow is intended to increase capture of most of the target cells in the specimen. Contact angle measurements were performed to characterize the nature and quality of the modified sensor surface, and electrochemical measurements (cyclic voltammetry (CV) and square wave voltammetry (SWV)) were performed to confirm the efficiency and selectivity of the fabricated sensor to detect HOCs. The proposed method is valuable for capturing rare cells and could provide an effective tool for cancer diagnosis and detection

Journal of Nanobiotechnology / Characterization of CurcuEmulsomes: nanoformulation for enhanced solubility and delivery of curcumin

Background: Curcumin is a polyphenolic compound isolated from the rhizomes of the plant Curcuma longa and shows intrinsic anti-cancer properties. Its medical use remains limited due to its extremely low water solubility and bioavailability. Addressing this problem, drug delivery systems accompanied by nanoparticle technology have emerged. The present study introduces a novel nanocarrier system, so-called CurcuEmulsomes, where curcumin is encapsulated inside the solid core of emulsomes. Results: CurcuEmulsomes are spherical solid nanoparticles with an average size of 286 nm and a zeta potential of 37 mV. Encapsulation increases the bioavailability of curcumin by up to 10,000 fold corresponding to a concentration of 0.11 mg/mL. Uptaken by HepG2 human liver carcinoma cell line, CurcuEmulsomes show a significantly prolonged biological activity and demonstrated therapeutic efficacy comparable to free curcumin against HepG2 in vitro - with a delay in response, as assessed by cell viability, apoptosis and cell cycle studies. The delay is attributed to the solid character of the nanocarrier prolonging the release of curcumin inside the HepG2 cells. Conclusions: Incorporation of curcumin into emulsomes results in water-soluble and stable CurcuEmulsome nanoformulations. CurcuEmulsomes do not only successfully facilitate the delivery of curcumin into the cell in vitro, but also enable curcumin to reach its effective concentrations inside the cell. The enhanced solubility of curcumin and the promising in vitro efficacy of CurcuEmulsomes highlight the potential of the system for the delivery of lipophilic drugs. Moreover, high degree of compatibility, prolonged release profile and tailoring properties feature CurcuEmulsomes for further therapeutic applications in vivo

Fully automatic segmentation of glottis and vocal folds in endoscopic laryngeal high-speed videos using a deep Convolutional LSTM Network

The objective investigation of the dynamic properties of vocal fold vibrations demands the recording and further quantitative analysis of laryngeal high-speed video (HSV). Quantification of the vocal fold vibration patterns requires as a first step the segmentation of the glottal area within each video frame from which the vibrating edges of the vocal folds are usually derived. Consequently, the outcome of any further vibration analysis depends on the quality of this initial segmentation process. In this work we propose for the first time a procedure to fully automatically segment not only the time-varying glottal area but also the vocal fold tissue directly from laryngeal high-speed video (HSV) using a deep Convolutional Neural Network (CNN) approach. Eighteen different Convolutional Neural Network (CNN) network configurations were trained and evaluated on totally 13,000 high-speed video (HSV) frames obtained from 56 healthy and 74 pathologic subjects. The segmentation quality of the best performing Convolutional Neural Network (CNN) model, which uses Long Short-Term Memory (LSTM) cells to take also the temporal context into account, was intensely investigated on 15 test video sequences comprising 100 consecutive images each. As performance measures the Dice Coefficient (DC) as well as the precisions of four anatomical landmark positions were used. Over all test data a mean Dice Coefficient (DC) of 0.85 was obtained for the glottis and 0.91 and 0.90 for the right and left vocal fold (VF) respectively. The grand average precision of the identified landmarks amounts 2.2 pixels and is in the same range as comparable manual expert segmentations which can be regarded as Gold Standard. The method proposed here requires no user interaction and overcomes the limitations of current semiautomatic or computational expensive approaches. Thus, it allows also for the analysis of long high-speed video (HSV)-sequences and holds the promise to facilitate the objective analysis of vocal fold vibrations in clinical routine. The here used dataset including the ground truth will be provided freely for all scientific groups to allow a quantitative benchmarking of segmentation approaches in future

Lupusnephritis und assoziierte thrombotische Mikroangiopathie

Die Lupusnephritis stellt die häufigste Manifestation eines systemischen Lupus an den soliden Organen dar und geht mit einem erhöhten Risiko für eine chronische Niereninsuffizienz einher. Das gleichzeitige Auftreten einer Lupusnephritis mit einer thrombotischen Mikroangiopathie wird als selten beschrieben, impliziert jedoch das Risiko fataler Organdysfunktionen. Wir berichten von drei Patienten, bei denen diese beiden Krankheitsentitäten parallel auftraten und eine intensivierte immunsuppressive Therapie auch mittels Komplementblockade notwendig machten