Topological States on the Gold Surface

Gold surfaces host special electronic states that have been understood as a prototype of Shockley surface states (SSs). These SSs are commonly employed to benchmark the capability of angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling spectroscopy. We find that these Shockley SSs can be reinterpreted as topologically derived surface states (TDSSs) of a topological insulator (TI), a recently discovered quantum state. Based on band structure calculations, the Z2 topological invariant can be well defined to characterize the nontrivial features of gold that we detect by ARPES. The same TDSSs are also recognized on surfaces of other well-known noble metals (e.g., silver, copper, platinum, and palladium). Besides providing a new understanding of noble metal SSs, finding topological states on late transition metals provokes interesting questions on the role of topological effects in surface-related processes, such as adsorption and catalysis.Comment: 21 pages, 3 figure

Development of Mass Spectrometric Methods for the Quantification of Membrane Lipids : Studies on Mitochondria, T Cells, Golgi Membranes and COPI Vesicles

Biological membranes contain more than thousand different lipid classes and lipid species that are far from being fully characterized. In order to understand molecular processes that are connected to membrane lipids a continuous development of analytical methods is required. In this thesis, nano-electrospray ionization tandem mass spectrometry (nano-ESI-MS/MS) was employed to establish methods for the quantification of cardiolipin (CL), diacylglycerol (DAG) and the phosphoinositides PIP and PIP2. The methods were applied for the analysis of mitochondria, Golgi membranes and T cells in order to address scientific questions: I. The quantitative analysis of CL in mitochondria, isolated from yeast mutants, showed that GEP genes (genetic interactors of prohibitins) are involved in the regulation of mitochondrial phospholipids CL and phosphatidylethanolamine. Strikingly, the mass spectrometric identification of the lipid intermediate phosphatidylglycerolphosphate (PGP) in mitochondria from delta gep4 mutants supported the identification of Gep4 as a novel PGP phosphatase required for CL biosynthesis. II. The quantitative analysis of DAG revealed that ilimaquinone (IQ)-induced vesiculation of the Golgi complex significantly affects the level of DAG. This result is consistent with previous observations that lipid-modifying enzymes, such as phospholipase D and PA phosphatase, are activated and suggests that membrane lipids play a critical role during the process of IQ-mediated Golgi vesiculation. III. The quantitative analysis of PIP, PIP2 and DAG in conventional T cells showed that T cell receptor (TCR)-induced stimulation significantly affects the level of signaling lipids. This result was an important readout to address the question whether regulatory T cells interfere with proximal lipid signaling events in conventional T cells. Furthermore, a lipidome analysis of Golgi membranes and COPI vesicles was performed. The generated data confirmed previous findings that sphingomyelin and cholesterol are segregated during the formation of COPI vesicles. Moreover, the lipid analysis revealed that COPI vesicles display a lipid composition similar to the endoplasmatic reticulum, with elevated levels of phosphatidylcholine and phosphatidylinositol. The characteristic lipid composition supports the scenario that COPI vesicle formation occurs at liquid-disordered domains in the Golgi complex

Thiol‐Click Based Polyglycerol Hydrogels as Biosensing Platform with In Situ Encapsulated Streptavidin Probes

An in situ streptavidin‐encapsulated hydrogel based on dendritic polyglycerol (dPG) which is functionalized with either an acrylate, allyl or acrylamide group and dithiolated polyethylene glycol (PEG) is constructed via a thiol‐click chemistry approach and is investigated for biosensing applications. The hydrogel platform is screened for the encapsulation and release efficiencies of the model protein streptavidin under varying physicochemical conditions, for example, crosslinking chemistry reactions, the molar ratio between the two gel components, macromonomer concentrations or pH‐values. By that, tailor‐made hydrogels can be developed, which are able to encapsulate or release the model protein for several days based on its modality. Furthermore, the accessible binding site of encapsulated streptavidin or in other words, the biotin‐binding performance is quantified, and the stability of the various hydrogel types is studied by rheology measurements, 1H NMR, gel permeation chromatography (GPC), and mass loss experiments

Repression of anti-proliferative factor Tob1 in osteoarthritic cartilage

Osteoarthritis is the most common degenerative disorder of the modern world. However, many basic cellular features and molecular processes of the disease are poorly understood. In the present study we used oligonucleotide-based microarray analysis of genes of known or assumed relevance to the cellular phenotype to screen for relevant differences in gene expression between normal and osteoarthritic chondrocytes. Custom made oligonucleotide DNA arrays were used to screen for differentially expressed genes in normal (n = 9) and osteoarthritic (n = 10) cartilage samples. Real-time polymerase chain reaction (PCR) with gene-specific primers was used for quantification. Primary human adult articular chondrocytes and chondrosarcoma cell line HCS-2/8 were used to study changes in gene expression levels after stimulation with interleukin-1β and bone morphogenetic protein, as well as the dependence on cell differentiation. In situ hybridization with a gene-specific probe was applied to detect mRNA expression levels in fetal growth plate cartilage. Overall, more than 200 significantly regulated genes were detected between normal and osteoarthritic cartilage (P < 0.01). One of the significantly repressed genes, Tob1, encodes a protein belonging to a family involved in silencing cells in terms of proliferation and functional activity. The repression of Tob1 was confirmed by quantitative PCR and correlated to markers of chondrocyte activity and proliferation in vivo. Tob1 expression was also detected at a decreased level in isolated chondrocytes and in the chondrosarcoma cell line HCS-2/8. Again, in these cells it was negatively correlated with proliferative activity and positively with cellular differentiation. Altogether, the downregulation of the expression of Tob1 in osteoarthritic chondrocytes might be an important aspect of the cellular processes taking place during osteoarthritic cartilage degeneration. Activation, the reinitiation of proliferative activity and the loss of a stable phenotype are three major changes in osteoarthritic chondrocytes that are highly significantly correlated with the repression of Tob1 expression

Dendritic Glycerol-Cholesterol Amphiphiles as Drug Delivery Systems: A Comparison between Monomeric and Polymeric Structures

The application of micelles as drug delivery systems has gained a great deal of attention as a means to overcome the current several drawbacks present in conventional cancer treatments. In this work, we highlight the comparison of polymeric and monomeric amphiphilic systems with a similar hydrophilic–lipophilic balance (HLB) in terms of their biocompatibility, aggregation behavior in aqueous solution, and potential in solubilizing hydrophobic compounds. The polymeric system consists of non-ionic polymeric amphiphiles synthesized via sequential RAFT polymerization of polyglycerol first-generation [G1] dendron methacrylate and cholesterol methacrylate to obtain poly(G1-polyglycerol dendron methacrylate)-block-poly(cholesterol methacrylate) (pG1MA-b-pCMA). The monomeric system is a polyglycerol second-generation [G2] dendron end-capped to a cholesterol unit. Both amphiphiles form spherical micellar aggregations in aqueous solution, with differences in size and the morphology in which hydrophobic molecules can be encapsulated. The polymeric and monomeric micelles showed a low critical micelle concentration (CMC) of 0.2 and 17 μg/mL, respectively. The results of our cytotoxicity assays showed that the polymeric system has significantly higher cell viability compared to that of the monomeric amphiphiles. The polymeric micelles were implemented as drug delivery systems by encapsulation of the hydrophobic small molecule doxorubicin, achieving a loading capacity of 4%. In summary, the results of this study reveal that using cholesterol as a building block for polymer synthesis is a promising method of preparation for efficient drug delivery systems while improving the cell viability of monomeric cholesterol

Tunable Polyglycerol-Based Redox-Responsive Nanogels for Efficient Cytochrome C Delivery

The sensitivity of therapeutic proteins is a challenge for their use in biomedical applications, as they are prone to degradation and opsonization, thus limiting their potential. This demands for the development of drug delivery systems shielding proteins and releasing them at the site of action. Here, we describe the synthesis of novel polyglycerol-based redox-responsive nanogels and report on their potential as nanocarrier systems for the delivery of cytochrome C (CC). This system is based on an encapsulation protocol of the therapeutic protein into the polymer network. NGs were formed via inverse nanoprecipitation using inverse electron-demand Diels–Alder cyclizations (iEDDA) between methyl tetrazines and norbornenes. Coprecipitation of CC led to high encapsulation efficiencies. Applying physiological reductive conditions of l-glutathione (GSH) led to degradation of the nanogel network, releasing 80% of the loaded CC within 48 h while maintaining protein functionality. Cytotoxicity measurements revealed high potency of CC-loaded NGs for various cancer cell lines with low IC50 values (up to 30 μg·mL−1), whereas free polymer was well tolerated up to a concentration of 1.50 mg·mL−1. Confocal laser scanning microscopy (CLSM) was used to monitor internalization of free and CC-loaded NGs and demonstrate the protein cargo’s release into the cytosol

Gram Scale Synthesis of Dual-Responsive Dendritic Polyglycerol Sulfate as Drug Delivery System

Biocompatible polymers with the ability to load and release a cargo at the site of action in a smart response to stimuli have attracted great attention in the field of drug delivery and cancer therapy. In this work, we synthesize a dual-responsive dendritic polyglycerol sulfate (DR-dPGS) drug delivery system by copolymerization of glycidol, ε-caprolactone and an epoxide monomer bearing a disulfide bond (SSG), followed by sulfation of terminal hydroxyl groups of the copolymer. The effect of different catalysts, including Lewis acids and organic bases, on the molecular weight, monomer content and polymer structure was investigated. The degradation of the polymer backbone was proven in presence of reducing agents and candida antarctica Lipase B (CALB) enzyme, which results in the cleavage of the disulfides and ester bonds, respectively. The hydrophobic anticancer drug Doxorubicin (DOX) was loaded in the polymer and the kinetic assessment showed an enhanced drug release with glutathione (GSH) or CALB as compared to controls and a synergistic effect of a combination of both stimuli. Cell uptake was studied by using confocal laser scanning microscopy with HeLa cells and showed the uptake of the Dox-loaded carriers and the release of the drug into the nucleus. Cytotoxicity tests with three different cancer cell lines showed good tolerability of the polymers of as high concentrations as 1 mg mL−1, while cancer cell growth was efficiently inhibited by DR-dPGS@Dox

Self-assembled nanosheets of biocompatible polymers as universal cell-membrane mimic to block viral infection

Viruses cause severe damage to society due to seasonal and pandemic outbreaks; therefore, developing new antivirals is urgently needed. Multivalent virus inhibitors are promising broad-spectrum antivirals, as they can block the initial step of viral infection by mimicking the structure of the cell receptors on the host cell membrane. Biocompatible supramolecular architectures are particularly well-suited for virus inhibition due to the numerous weak non-covalent bindings, resulting in strong yet dynamic multivalent interactions. Herein, we report on supramolecular nanosheets based on dendritic polyglycerol (dPG). The dPG core was functionalized with different ratios of sulfate and mercaptoundecanoic acid (MUA) groups. The MUA, as the hydrophobic part, triggers the self-assembly and -via the acid group-the supramolecular interaction with the virus, while sulfate groups mimic heparan sulfate proteoglycans (HSPG) on the cell membrane for virus interaction. The effect of polymer functionalization degree of MUA (ranging from 30 to 100 %) on the nanosheet size and morphology, as well as their interaction with viral particles, were monitored by cryo-transmission electron microscopy (cryo-TEM) and cryo-electron tomography (cryo-ET). Bio-functional assays such as plaque reduction, pre-infection inhibition, hemagglutination inhibition (HAI) and cell viability assays have been performed to assess the in vitro efficiency of supramolecular nanosheets against Influenza A virus and Herpes-simplex virus type 1. These studies revealed inhibitory activities against IAV (X31/H3N2) and HSV-1 with the half-inhibitory concentration (IC50) of 1 and 0.01 μg/mL in vitro, respectively, demonstrating its potential of being a universal virus inhibitor by dynamic multivalent interactions

Multivalent 2D- and 3D-nanogels as carbohydrate-lectin binders

The development of synthetic glycoarchitectures for targeted bacterial adhesion represents a promising strategy in anti-adhesion therapy. This study presents the synthesis and characterization of two distinct mannosylated nanogel architectures. First, a spherical 3D-nanogel was prepared via nanoprecipitation and functionalized with α- d -mannose units. This system demonstrated enhanced precipitation kinetics in turbidity measurements with Concanavalin A and exhibited single-site binding behavior comparable to monovalent reference compounds when tested with intact E. coli strain ORN 178 (FimH + ) via microscale thermophoresis. Cryo-TEM imaging revealed clear co-localization with bacterial pili, confirming specific bacterial interactions. The complementary sheet-like 2D-nanogel, synthesized using a removable graphene template and functionalized with α- d -mannose units, showed distinct dual binding characteristics with significantly different affinities in FimH binding studies. Notably, the high-affinity site of the 2D-nanogel maintained superior binding compared to the 3D architecture. Both architectures were extensively characterized using multiple analytical techniques, confirming their defined structures, sizes, and surface modifications. These findings provide fundamental insights into the influence of spatial ligand presentation on multivalent binding interactions, contributing to the rational design of glycoarchitectures for bacterial targeting

Modular Synthesis of Dendritic Oligo-Glycerol Cationic Surfactants for Enhanced Antibacterial Efficacy

Bacterial infections and antibiotic resistance present an ever-increasing threat to human health worldwide, and medicine urgently needs new alternatives for the successful treatment of bacterial infections. Cationic surfactants have proven to be effective antibacterial agents due to their ability to disrupt bacterial membranes, inhibit biofilm formation, and combat a broad spectrum of pathogens. We employed a orthogonal click chemistry strategy for the efficient modular synthesis of six novel cationic surfactants. Our results emphasize the strong correlation between the surfactant design and its antibacterial potential. Among these six cationic surfactants we identified a prime candidate, which possessed an impressive antibacterial effect against gram-positive and gram-negative bacteria, including drug-resistant strains. We found that our surfactant can prevent biofilm formation and eradicate already existing biofilms. Cryo-TEM imaging was used to reveal the membrane-disrupting properties of the surfactant. In-vivo wound healing experiments underline the surfactants’ ability to inhibit wound infections. Cationic surfactants often face the challenge of balancing strong antibacterial activity with minimal cytotoxicity. Our strategic design and orthogonal click chemistry approach have enabled precise fine-tuning of molecular structures to achieve an optimal balance between antibacterial efficacy and biocompatibility, effectively overcoming this critical limitation