Scientific publications

Hybrid materials of core–shell particles and cellulose nanowhiskers (CNWs) were synthesized to produce opal films with increasing tensile strength. After the incorporation of CNWs into the processed particle films, differences in the mechanical and optical properties were noticeable, which stemmed from the adhesion forces between the cellulose and the particles’ shell material. Two different particle compositions were compared, using polystyrene as cores, and either poly(ethyl acrylate) (PEA) or a copolymer of ethyl acrylate and 3 wt % of 2-hydroxyethyl methacrylate (HEMA) as the shell material. Stronger interactions between the particles containing HEMA and the CNWs were displayed via atomic force microscopy particle manipulation experiments, where higher forces were required to deliberately move P(EA-co-HEMA) particles on a CNW substrate compared to PEA particles. The stronger interaction behaviors increased the disorder of the particles within the opal films toward photonic glasses with angle-independent structural colors. Also, the increase in tensile strength from <1 MPa at a cellulose content of 0 wt % to 6 MPa at the optimal CNW content of 15 wt % was more pronounced compared to the particle-cellulose mixture with only PEA in the particle shell. Thus, the presence of the hydroxy groups in the particles’ shell material on the molecular level significantly influenced the optical and mechanical properties on the macroscopic level.

Uric acid (UA) is one of the most electroactive low molecular weight compounds that can be electrochemically oxidized on the surfaces of numerous noble and non-noble electrocatalysts under applied polarization. Consequently, enzymatic determination of UA in model and real samples is complicated by possible interference between electrochemical and biochemical routes. Herein, a novel strategy for amperometric enzymatic hydrogen peroxide independent UA sensing at low concentrations (e.g., below 50 µM) is proposed. The UA-sensitive strategy relies on the use of screen printed electrodes modified by an electrodeposited hybrid functional sensing film comprising a non-noble electrocatalyst, a bioorganic layer containing enzyme uricase (UOx), and data acquisition enabling the biochemical transformation of UA to be distinguished from the electrochemical oxidation route. Performed selectivity test utilizing adenine, xanthine, urea, ascorbic acid, ethanol and glycerol did not reveal interferences during detection of UA. This proposed approach was tested for UA detection in model and fermentation samples. The quantitative results obtained in fermentation samples were validated through optical oxygen mini sensor studies and fluorescence-based bioassays.

Nine different derivatives of piperidino alanes of the general formula (CH2)5N-AlXY [X=Y=Cl (1), Br (2), I (3); X=(CH2)5N, Y=Cl (4), Br (5), I (6); X=H, Y=Cl (7), Br (8), I (9)] have been synthesized and compared with respect to their structures. All molecules form dimers with an Al2N2 central cycle and aluminum and nitrogen atoms in distorted tetrahedral environments as determined from X-ray diffraction. The three dihalide derivatives 1, 2 and 3 have C2h (2/m) symmetries in solution of which they maintain the Centro symmetry in the crystal lattice. The bis(piperidino) derivatives 4, 5 and 6 have either C1 (1) symmetry with the bridging piperidino cycles oriented in the same direction (4, 5) or Ci (ī) point symmetry as found for 6 (in solution at least one other isomer is present). Whereas the chlorine derivative 7 has crystallographic Ci (ī) symmetry, the bromine 8 has almost C2 and the iodine 9 crystallographic C2 (2) point symmetry. In solution all derivatives 7, 8, 9 show equilibria between cis (C2) and trans (Ci) isomeric forms (27Al NMR). The longest Al−N bond lengths within the rings are found for 5 (1.969(4) Å) and the shortest for 8 (1.940(4) Å). The ratio of Al⋅⋅⋅Al to N⋅⋅⋅N non-bonding distances in the almost square rings vary with the bulkiness of the terminal ligands at aluminum.

PeCa is a rare entity with rising incidence rates due to increased infections with human papillomaviruses (HPV). The distinct subtypes of PeCa with an individual pathogenesis demand biomarkers for a precise patient risk assessment regarding disease progression and therapeutic susceptibility. We recently identified promising candidates associated with an HPV-instructed tumor microenvironment (TME) using HPV-positive PeCa cell lines and tissue microarrays (TMA). The capacity of HPV + p63 + PeCa cells to release neutrophil-attracting CXCL-8 provided a molecular link explaining the infiltration of CD15 + myeloid cells in PeCa specimens. The candidate biomarkers HPV, p63, CD15, DKK1, and CD147 linked a tumor-promoting TME with a higher TNM classification reflecting more aggressive and metastasizing cancers. Based on immune-reactive scores (IRS) from TMA staining for these biomarkers, we calculated correlations and conducted association analyses to assess the degree of relationship between all biomarkers. We then conducted Kaplan–Meier survival estimates and Cox regression analyses to delineate the impact on PeCa patient survival. There is a notable predictive potential regarding the survival of patients with biomarker profiles beyond the potency of the individual biomarker. From all candidate biomarkers and biomarker profiles, the combination of CD147 and infiltrating CD15 + cells linked to an active HPV-driven transformation displayed cancer-immune dynamics with dismal prognosis for patients. After deciphering relevant interdependencies, the HPV + CD147 + CD15 + status was the most potent profile predicting metastasis-free survival of PeCa patients. The results of this report underscore the need for analysis of the TME and the development of multi-parameter composite scores that reflect fundamental cancer-immune relationships to tailor therapeutic interventions based on actual cancer immune dynamics.

Stinger-like structures in living organisms evolved convergently across taxa for both defensive and offensive purposes, with the main goal being penetration and damage. Our observations over a broad range of taxa and sizes, from microscopic radiolarians to narwhals, reveal a self-similar geometry of the stinger extremity: the diameter (d) increases along the distance from the tip (x) following a power law  , with the tapering exponent varying universally between 2 and 3. We demonstrate, through analytical and experimental mechanics involving three-dimensional (3D) printing, that this geometry optimizes the stinger’s performance; it represents a trade-off between the propensity to buckle, for n smaller than 2, and increased penetration force, for n greater than 3. Moreover, we find that this optimal tapering exponent does not depend on stinger size and aspect ratio (base diameter over length). We conclude that for Nature’s stingers, composed of biological materials with moduli ranging from hundreds of megapascals to ten gigapascals, the necessity for a power-law contour increases with sharpness to ensure sufficient stability for penetration of skin-like tissues. Our results offer a solution to the puzzle underlying this universal geometric trait of biological stingers and may provide a new strategy to design needle-like structures for engineering or medical applications.

Neutrophils play a crucial role in the tumor microenvironment (TME) of head and neck squamous cell carcinomas (HNSCC) and significantly influence treatment outcomes. Phenotypic and functional properties of neutrophils adapt to the TME with distinct subsets modulating disease progression and therapeutic interventions. Here, we evaluated phenotypic and functional differences of neutrophils derived from HNSCC patients and healthy donors. We observed significant phenotypic differences between neutrophils from healthy donors and HNSCC patient-derived neutrophils. Gender and tumor stage influenced neutrophil phenotypes and their ability to lyse tumor cells through antibody-dependent cell-mediated cytotoxicity (ADCC). Patients with advanced HNSCC and males may benefit less from neutrophil-centered immunotherapy. An engineered IgA2 antibody specific for the epidermal growth factor receptor (EGFR) demonstrated superior efficacy in activating neutrophils for ADCC compared to Panitumumab using healthy and patient-derived neutrophils, underscoring the potential of the IgA isotype as a therapeutic alternative. The distinct behavior and antibody-isotype dependent ADCC competence of CD177+/- neutrophils of healthy but not HNSCC donors warrants further exploration. Our study emphasizes the importance of personalized immunotherapy treatments that consider the characteristics of neutrophils, patient demographics, and the type of antibody to improve ADCC and ultimately enhance treatment outcomes for HNSCC.

Silver nanowires (AgNW) find use in transparent conductive electrodes with applications in solar cells, touch screens, and wearables. Unprotected AgNW are prone to atmospheric corrosion and lose conductivity over time. Known passivation techniques either require submersion of pre-deposited AgNW in liquid compounds or the modification of AgNW inks prior to deposition, which alters viscosity and complicates deposition. Here, new possibilities for stabilization of pre-deposited AgNW networks without need for submersion are explored. It is demonstrated that AgNW networks can be stabilized either by argon or hydrogen plasma treatment or by solvent vapor annealing with ethanol, methanol, or ethyl acetate. These treatments yielded stable electrical resistance over at least nine weeks, whereas untreated or thermally annealed AgNW layers quickly lost conductivity. The potential of solvent vapor annealing is further explored by demonstrating a new processing technique for stable polymer matrix composites containing AgNW. Co-deposited layers of AgNW with polystyrene microbeads are annealed in ethyl acetate vapor to stabilize the AgNW while at the same time merging polymer beads into a closed film around the AgNW. The resulting composites maintained stable resistance and transmittance for at least seven weeks.

Recently it was predicted, on the basis of a lattice gas model, that scalar active matter in a gravitational field would rise against gravity up a confining wall or inside a thin capillary—in spite of repulsive particle-wall interactions [Phys. Rev. Lett. 124, 048001 (2020)]. In this paper we confirm this prediction with sedimenting active Brownian particles (ABPs) in a box numerically and elucidate the mechanism leading to the formation of a meniscus rising above the bulk of the sedimentation region. The height of the meniscus increases with the activity of the system, algebraically with the Péclet number. The formation of the meniscus is determined by a stationary circular particle current, a vortex, centered at the base of the meniscus, whose size and strength increase with the ABP activity. The origin of these vortices can be traced back to the confinement of the ABPs in a box: already the stationary state of ideal (noninteracting) ABPs without gravitation displays circular currents that arrange in a highly symmetric way in the eight octants of the box. Gravitation distorts this vortex configuration downward, leaving two major vortices at the two side walls, with a strong downward flow along the walls. Repulsive interactions between the ABPs change this situation only as soon as motility induced phase separation (MIPS) sets in and forms a dense, sedimented liquid region at the bottom, which pushes the center of the vortex upwards towards the liquid-gas interface. Self-propelled particles therefore represent an impressive realization of scalar active matter that forms stationary particle currents being able to perform visible work against gravity or any other external field, which we predict to be observable experimentally in active colloids under gravitation.

Many biological active agents respond to gradients of environmental cues by redirecting their motion. In addition to the well-studied prominent examples such as phototaxis and chemotaxis, there has been considerable recent interest in topotaxis, i.e., the ability to sense and follow topographic environmental cues. A trivial topotaxis is achievable through a spatial gradient of obstacle density, though over limited length scales. Here, we introduce a type of topotaxis based on sliding of particles along obstacles—as observed, e.g., in bacterial dynamics near surfaces. We numerically demonstrate how imposing a gradient in the angle of sliding along pillars breaks the spatial symmetry and biases the direction of motion, resulting in an efficient topotaxis in a uniform pillar park. By repeating blocks of pillars with a strong gradient of sliding angle, we propose an efficient method for guiding particles over arbitrary long distances. We provide an explanation for this spectacular phenomenon based on effective reflection at the borders of neighboring blocks. Our results are of technological and medical importance for design of efficient taxis devices for living agents.

Hybrid hydrogels are hydrogels that exhibit heterogeneity in the network architecture by means of chemical composition and/or microstructure. The different types of interactions, together with structural heterogeneity, which can be created on different length scales, determine the mechanical properties of the final material to a large extent. In this work, the microstructure–mechanical property relationships for a hybrid hydrogel that contains both electrostatic and covalent interactions are investigated. The hybrid hydrogel is composed of a microphase-separated polyelectrolyte complex network (PEC) made of poly(4-styrenesulfonate) and poly(diallyldimethylammonium chloride) within a soft and elastic polyacrylamide hydrogel network. The system exhibits a granular structure, which is attributed to the liquid–liquid phase separation into complex coacervate droplets induced by the polymerization and the subsequent crowding effect of the polyacrylamide chains. The coacervate droplets are further hardened into PEC granules upon desalting the hydrogel. The structure formation is confirmed by a combination of electron microscopic imaging and molecular dynamics simulations. The interpenetration of both networks is shown to enhance the toughness of the resulting hydrogels due to the dissipative behavior of the PEC through the rupture of electrostatic interactions. Upon cyclic loading–unloading, the hydrogels show recovery of up to 80% of their original dissipative behavior in less than 300 s of rest with limited plasticity. The granular architecture and the tough and self-recoverable properties of the designed hybrid networks make them good candidates for applications, such as shape-memory materials, actuators, biological tissue mimics, and elastic substrates for soft sensors.