2015, Moerz, Sebastian T., Kraegeloh, Annette, Chanana, Munish, Kraus, Tobias

Citrate-stabilized gold nanoparticles (AuNP) agglomerate in the presence of hemoglobin (Hb) at acidic pH. The extent of agglomeration strongly depends on the concentration ratio [Hb]/[AuNP]. Negligible agglomeration occurs at very low and very high [Hb]/[AuNP]. Full agglomeration and precipitation occur at [Hb]/[AuNP] corresponding to an Hb monolayer on the AuNP. Ratios above and below this value lead to the formation of an unexpected phase: stable, microscopic AuNP–Hb agglomerates. We investigated the kinetics of agglomeration with dynamic light scattering and the adsorption kinetics of Hb on planar gold with surface-acoustic wave-phase measurements. Comparing agglomeration and adsorption kinetics leads to an explanation of the complex behavior of this nanoparticle–protein mixture. Agglomeration is initiated either when Hb bridges AuNP or when the electrostatic repulsion between AuNP is neutralized by Hb. It is terminated when Hb has been depleted or when Hb forms multilayers on the agglomerates that stabilize microscopic clusters indefinitely.

2015, Silina, Yuliya E., Fink-Straube, Claudia, Hayen, Heiko, Volmer, Dietrich A.

In this study, we propose a simple and rapid technique for characterization of free fatty acids and triacylglycerides (TAG) based on palladium nanoparticular (Pd-NP) surface-assisted laser desorption/ionization (SALDI) mass spectrometry (MS). The implemented Pd-NP material allowed detection of free fatty acids and TAGs exclusively as [M + K]+ ions in positive ion mode. Under negative ionization conditions, unusual trimetric structures were generated for free fatty acids, while TAGs underwent irreproducible degradation reactions. Importantly, the mass spectra obtained from Pd-NP targets in positive ion mode were very clean without interferences from matrix-derived ions in the low m/z range and readily enabled the detection of intact TAGs in vegetable oils without major fragmentation reactions as compared to conventional MALDI-MS, requiring only a minimal amount of sample preparation.

2020, Ho, D.-K., Murgia, X., De Rossi, C., Christmann, R., Hüfner de Mello Martins, A.G., Koch, M., Andreas, A., Herrmann, J., Müller, R., Empting, M., Hartmann, R.W., Desmaele, D., Loretz, B., Couvreur, P., Lehr, C.-M.

Elimination of pulmonary Pseudomonas aeruginosa (PA) infections is challenging to accomplish with antibiotic therapies, mainly due to resistance mechanisms. Quorum sensing inhibitors (QSIs) interfering with biofilm formation can thus complement antibiotics. For simultaneous and improved delivery of both active agents to the infection sites, self-assembling nanoparticles of a newly synthesized squalenyl hydrogen sulfate (SqNPs) were prepared. These nanocarriers allowed for remarkably high loading capacities of hydrophilic antibiotic tobramycin (Tob) and a novel lipophilic QSI at 30 % and circa 10 %, respectively. The drug-loaded SqNPs showed improved biofilm penetration and enhanced efficacy in relevant biological barriers (mucin/human tracheal mucus, biofilm), leading to complete eradication of PA biofilms at circa 16-fold lower Tob concentration than Tob alone. This study offers a viable therapy optimization and invigorates the research and development of QSIs for clinical use.

2019, Taverno, I., Rodrigo, A.M., Kandziora, M., Kuntz, S., Dernedde, J., Trautwein, C., Tacke, F., Blas-Garcia, A., Bartneck, M.

Due to their importance for the outcome of the inflammatory response, the motile myeloid cells are a focus of novel treatment options. The interplay of selectins and their ligands with leukocytes and endothelial cells, which mediate endothelial attachment and transmigration of immune cells, can be modulated by selectin‐binding structures. Here, a library of selectin‐targeting ligands coupled to either gold, silver, iron oxide nanospheres, or quantum dots of 5–10 nm in size is used to systematically study their impact on immune cell motility. The multivalent presentation of the carbohydrate mimetics results in very low sub‐nanomolar binding to L ‐selectin. Using human primary monocytes, granulocytes, lymphocytes, and macrophages, it is shown that the ligands exhibit only minor effects on uptake, whereas the motility of leukocytes is critically affected as observed in migration assays evaluated by flow cytometry. The carbohydrate mimetic ring structure, sulfation, in particular, and the degree of ligand presentation, are constituents which cohere in this process. Specific carbohydrate ligands can thus selectively regulate leukocyte subsets. These data form the basis for advanced immunotherapy which inhibits the amplification of inflammation by restricting leukocyte influx to injured tissue sites. Furthermore, the targeting ligands may complement existing treatment options for inflammatory diseases.

2019, Wang, Y., Kang, V., Arzt, E., Federle, W., Hensel, R.

Recent advances in bio-inspired microfibrillar adhesives have resulted in technologies that allow reliable attachment to a variety of surfaces. Because capillary and van der Waals forces are considerably weakened underwater, fibrillar adhesives are however far less effective in wet environments. Although various strategies have been proposed to achieve strong reversible underwater adhesion, strong adhesives that work both in air and underwater without additional surface treatments have yet to be developed. In this study, we report a novel design - cupped microstructures (CM) - that generates strong controllable adhesion in air and underwater. We measured the adhesive performance of cupped polyurethane microstructures with three different cup angles (15, 30, and 45°) and the same cup diameter of 100 μm in dry and wet conditions in comparison to standard mushroom-shaped microstructures (MSMs) of the same dimensions. In air, 15°CM performed comparably to the flat MSM of the same size with an adhesion strength (force per real contact area) of up to 1.3 MPa, but underwater, 15°CM achieved 20 times stronger adhesion than MSM (∼1 MPa versus ∼0.05 MPa). Furthermore, the cupped microstructures exhibit self-sealing properties, whereby stronger pulls lead to longer stable attachment and much higher adhesion through the formation of a better seal. © 2019 American Chemical Society.

2020, Liu, Zhen, Zhang, Peng, Pyttlik, Andrea, Kraus, Tobias, Volmer, Dietrich A.

Gold nanoparticles (AuNP) are frequently used in surface‐assisted laser desorption/ionization mass spectrometry (SALDI‐MS) for analysis of biomolecules because they exhibit suitable thermal and chemical properties as well as strong surface plasmonic effects. Moreover, the structures of AuNP can be controlled by well‐established synthesis protocols. This was important in the present work, which studied the influence of the nanoparticles’ structures on atmospheric pressure (AP)‐SALDI‐MS performance. A series of AuNP with different core sizes and capping ligands were investigated, to examine the desorption/ionization efficiency (DIE) under AP‐SALDI conditions. The results showed that both the AuNP core size as well as the nature of the surface ligand had a strong influence on DIE. DIE increased with the size of the AuNP and the hydrophobicity of the ligands. Chemical interactions between ligand and analytes also influenced DIE. Moreover, we discovered that removing the organic ligands from the deposited AuNP substrate layer by simple laser irradiation prior to LDI further amplified DIE values. The optimized AuNP were successfully used to analyze a wide arrange of different low molecular weight biomolecules as well as a crude pig brain extract, which readily demonstrated the ability of the technique to detect a wide range of lipid species within highly complex samples.

2018, Sankaran, Shrikrishnan, Zhao, Shifang, Muth, Christina, Paez, Julieta, Del Campo, Aránzazu

Living materials are an emergent material class, infused with the productive,adaptive, and regenerative properties of living organisms. Property regulation in living materials requires encoding responsive units in the living components to allow external manipulation of their function. Here, an optoregulated Escherichia coli (E. coli)-based living biomaterial that can be externally addressed using light to interact with mammalian cells is demonstrated. This is achieved by using a photoactivatable inducer of gene expression and bacterial surface display technology to present an integrin-specific miniprotein on the outer membrane of an endotoxin-free E. coli strain. Hydrogel surfaces functionalized with the bacteria can expose cell adhesive molecules upon in situ light-activation, and trigger cell adhesion. Surface immobilized bacteria are able to deliver a fluorescent protein to the mammalian cells with which they are interacting, indicating the potential of such a bacterial material to deliver molecules to cells in a targeted manner.

2014, Wählisch, Felix C., Peter, Nicolas J., Torrents Abad, Oscar, Oliveira, Mariana V.G., Schneider, Andreas S., Schmahl, Wolfgang, Griesshaber, Erika, Bennewitz, Roland

We investigated the friction and wear behavior as well as the mechanical properties of the periostracum of Mytilus sp. Tribological properties were determined with a reciprocal sliding microtribometer, while mechanical characterization was performed using a nanoindenter. Measurements were performed in dry and wet conditions. On the dry periostracum we found a low friction coefficient of 0.078 ± 0.007 on the young parts and a higher one of 0.63 ± 0.02 on the old parts of the shell. Under wet, saline, conditions we only observed one average coefficient of friction of 0.37 ± 0.01. Microscopic ex situ analysis indicated that dry periostracum wore rather rapidly by plowing and fatigue, while it exhibited a high wear resistance when immersed in salt water. The Young’s modulus and hardness of the periostracum were also investigated in both dry and wet conditions. Under dry conditions the Young’s modulus of the periostracum was 8 ± 3 GPa, while under wet conditions it was 0.21 ± 0.05 GPa. The hardness of dry periostracum samples was 353 ± 127 MPa, whereas the hardness of wet samples was 5 ± 2 MPa. It was found that, in the wet state, viscous behavior plays a significant role in the mechanical response of the periostracum. Our results strongly indicate that the periostracum can provide an important contribution to the overall wear resistance of Mytilus sp. shell.

2020, Han, L., Zheng, Y., Luo, H., Feng, J., Engstler, R., Xue, L., Jing, G., Deng, X., del Campo, A., Cui, J.

A solid-to-hollow evolution in macroscopic structures is challenging in synthetic materials. A fundamentally new strategy is reported for guiding macroscopic, unidirectional shape evolution of materials without compromising the material's integrity. This strategy is based on the creation of a field with a “swelling pole” and a “shrinking pole” to drive polymers to disassemble, migrate, and resettle in the targeted region. This concept is demonstrated using dynamic hydrogels containing anchored acrylic ligands and hydrophobic long alkyl chains. Adding water molecules and ferric ions (Fe3+) to induce a swelling–shrinking field transforms the hydrogels from solid to hollow. The strategy is versatile in the generation of various closed hollow objects (for example, spheres, helix tubes, and cubes with different diameters) for different applications.

2011, Veith, Michael, Belot, Celine, Huch, Volker

In the mononuclear title compound, [Tb(C13H9OS3)3(C4H8O)3]·C4H8O, the lanthanide cation is located on a threefold rotation axis and is surrounded by electron-rich ligands in an approximately octahedral geometry. One of the thienyl groups and the bound THF are disordered with 0.5:0.5 occupancy. The free THF is disordered around the threefold axis.