Kidney diseases are a major global health burden, underscoring the need for new strategies to support renal repair. Biomimetic materials that recapitulate extracellular matrix functions can provide structural support while presenting biochemical cues that guide epithelial behavior. Here, we engineered self-assembled collagen type I microenvironments incorporating levan, sulfated levan (sLevan), pea starch (PEA), and sulfated PEA (sPEA) as a sustainable, non-animal-derived class of glycosaminoglycan (GAG) mimetics. Chemical sulfation of levan and starch introduced negative charge, enhanced solubility, and generated derivatives with moderate anti-factor Xa activity compared with heparin. Biochemical assays demonstrated that all polysaccharides were stably incorporated into collagen networks without hindering enzymatic degradability, while sulfation and polymer type modulated fibril assembly kinetics and coating morphology. In solution and when presented within collagen coatings, sPEA starch consistently reduced human kidney epithelial cell (HK-2) metabolic activity and cell numbers, indicating antiproliferative effects. In contrast, sLevan-containing microenvironments supported HK-2 proliferation under basal and hyperglycemic conditions comparable to heparin-containing controls. Notably, sLevan-functionalized coatings significantly suppressed secretion of the pro-inflammatory cytokine interleukin (IL)-6 and prevented glucose-induced increases in latent transforming growth factor (TGF)-β1, two mediators implicated in tubular inflammation and fibrotic remodeling. Together, these findings indicate that sulfation critically governs the bioactivity of levan- and starch-based GAG mimetics. Collagen/sLevan microenvironments combine tunable matrix assembly, moderate anticoagulant activity, and favorable epithelial growth and cytokine profiles under hyperglycemic stress, highlighting their potential as renewable GAG-mimetic platforms for renal tissue engineering and in vitro disease modeling.

Biofilm formation is the most effective pathway for electron transfer to anodes in bioelectrochemical systems. However, the mechanisms triggering biofilm formation under anoxic conditions, as well as the architectural and compositional factors that positively influence current generation, are not well understood. Recent findings have shown that riboflavin can function similarly to a quorum sensing molecule in the γ-proteobacterium Shewanella oneidensis. Enhanced biofilm formation induced by riboflavin correlates with increased current densities. Only a limited number of candidate proteins were found to have altered concentrations due to this quorum sensing mechanism. This study demonstrates that the catalytic functions of the UDP-N-acetylglucosamine C4 epimerase WbpP and UDP-N-acetyl-D-glucosamine 6-dehydrogenase WbpA affect biofilm formation and lead to increased current density. Using optical coherence tomography, we found that the expression of each protein individually causes specific, quantifiable changes in biofilm architecture, including biovolume, height, and porosity. However, the current density did not significantly differ when these proteins were expressed alone compared to the control. In contrast, co-expression of WbpP and WbpA resulted in a doubling of current density, closely resembling the increases observed with riboflavin-mediated quorum sensing. We hypothesize that riboflavin-based quorum sensing may lead, through several intermediary steps, to the overproduction of WbpA and WbpP, resulting in better attachment to graphite anodes and thus higher current densities.

In contact with saliva, tooth enamel is covered by biomolecules forming an initial biofilm. Microorganisms attach to the initial biofilm and form the bacterial biofilm, which can provoke diseases. Therefore, dental biofilms are the focus of preventive research. Enamel consists mainly of hydroxyapatite (HAP). Yet, the composition of dental apatite differs between individuals and influences enamel properties. Standardized surfaces might therefore be useful for biofilm research. Synthetic enamel-like HAP pellets perfectly meet the criteria for such well-defined samples. However, systematic investigations of synthetic HAP on oral biofilm formation have never been performed, especially not in comparison to enamel. Therefore, we systematically compared the in situ biofilm formation on synthetic HAP and enamel to investigate the suitability of HAP as a substitute for natural enamel in biofilm formation studies. We observed no differences in formation kinetics, microstructure and subject-specificity of the initial biofilm on both materials. Furthermore, at the proteome level the development of the biofilm on HAP follows the formation patterns observed for enamel. Formation kinetics and morphology of the bacterial biofilm were also subject-dependent and not distinguishable between the two materials. However, the bacterial viability on HAP was higher than on enamel. For bacterial biofilm viability studies, synthetic HAP may therefore even be the preferred substrate as it is more beneficial for identifying antimicrobial agents. In summary, the results prove synthetic HAP as perfect substrate for dental biofilm studies.

Staphylococcus aureus is a major cause of implant-associated infections (IAIs). The ability of this Gram-positive bacterium to cause IAIs is closely related to its capacity to attach to and to form biofilms on the implant material. Biofilm formation of S. aureus on artificial surfaces is usually mimicked in the laboratory by simple microplate-based in vitro assays and often involves type culture collection preserved laboratory strains such as SA113 (ATCC 35556), Newman (NCTC 8178), and Newman D2C (NCTC 10833, ATCC 25904). The latter two strains are phylogenetically closely related and often inadvertently indicated as strain “Newman” in publications, albeit of the fact that strain Newman D2C harbors among others mutations in the global regulatory loci agr and sae, which strongly impact the phenotypic behavior of this strain. Wondering how the genetic differences between strains Newman and Newman D2C alter the biofilm formation capacities of these two strains in vitro and in vivo, we tested here the adhesion behavior and biofilm formation capacities of both strains on different kinds of artificial surfaces (tissue culture-treated bottoms of 96-well polystyrene microplates and polyurethane-based peripheral venous catheter [PVC] tubing). Additionally, we determined their ability to cause infection in a foreign body-related murine infection model. Our studies revealed that the Newman and Newman D2C derivatives kept at Saarland University, Germany, differ significantly in their abilities to attach to microplate well bottoms and PVC tubing, and to form biofilms in various static and dynamic in vitro assays. However, when the biofilm formation capacities of both strains were determined in an in vivo infection model, rather comparable bacterial loads were observed. These findings suggest that biofilm formation capacities of S. aureus strains may differ substantially in vitro and in vivo. Additionally, researchers working with strains Newman and Newman D2C should be aware that both strains differ substantially in their phenotypic behavior, and that both strains should be indicated correctly to allow for a better comparison of data obtained with these strains in different laboratories.

Staphylococcus aureus (S. aureus) is one of the bacterial species capable of forming multilayered biofilms on implants. Such biofilms formed on implanted medical devices often require the removal of the implant in order to avoid sepsis or, in the worst case, even the death of the patient. To address the problem of unwanted S. aureus biofilm formation, its first step, i.e., adhesion, must be understood and prevented. Thus, the development of adhesion-reducing surface coatings for implant materials is of utmost importance. In this work, we used single-cell force spectroscopy to analyze the adhesion of the biofilm-forming S. aureus strain SA113 on naive and protein-coated silicon surfaces (SiO2). In addition to the wild type, we used the SA113 ΔdltA knockout mutant to further investigate the effect of d-alanylation of lipoteichoic acids of the cell wall. In order to examine how the surface charge affects adhesion, we coated silanized SiO2 surfaces with amphiphilic class II hydrophobins. The naturally occurring hydrophobin HFBI was used as well as the HFBI variant D40Q/D43N, which is less negatively charged at physiological pH due to the exchange of two acidic aspartate residues. These two types of hydrophobin-coated surfaces resemble each other in roughness and wettability but differ only in charge. By measurement of the forces with which each S. aureus strain binds to hydrophobin-coated surfaces, we show that the adhesion of S. aureus at surfaces can be influenced by the charges exposed by the target surfaces. Therefore, in addition to hydrogen bonding, electrostatic interactions between the cell and the hydrophilic surface govern adhesion on these surfaces. Moreover, we found that for both HFBI coatings, the adhesion strength of S. aureus is reduced by nearly a factor of 30 compared to silanized SiO2 surfaces. Therefore, hydrophobin coatings are of great interest for further use in the field of biomedical surface coating.

For smooth surfaces, chemical composition can be readily analyzed using various spectroscopic techniques, a prominent example is X‐ray photoelectron spectroscopy (XPS), where the relative proportions of the elements are mainly determined by the intensity ratio of the element‐specific photoelectrons. However, this analysis becomes more complex for nanorough surfaces like black silicon (b‐Si) due to the geometry's steep slopes, which mimic local variations in emission angles. In this study, this effect is explicitly quantified through an integral geometric analysis using Minkowski tensors, correlating XPS chemical data with topographical information from Atomic Force Microscopy (AFM). This approach yields reliable estimates of layer thicknesses for nanorough surfaces. For b‐Si, it is found that the oxide layer is ≈50%–80% thicker than the native oxide layer on a standard Si wafer. This study underscores the significant impact of nanoscale geometries on chemical property analysis.

Cellular adhesion and contractility are essential for cell movement. In this study, we investigated the effects of actin stabilization on adhesion properties, contractility, and cell migration. For this, we used the recently synthesized actin stabilizer miuraenamide A (MiuA), which has been discussed as a more reliable alternative to the otherwise commonly used actin stabilizer jasplakinolide. We investigated the number and size of focal adhesions in RPE-1 cells and used single-cell force spectroscopy to evaluate the adhesion properties of those cells after MiuA treatment. We showed that MiuA increases the number of focal adhesions while decreasing their size and reduces adhesion energy and force. Additionally, we investigated its effects on the contractility of RPE-1 cells by measuring their contractile energy using pattern-based contractility screening (PaCS). We found no significant change in contractility after MiuA treatment. Finally, we confined RPE-1 cells in PDMS microchannels and analyzed their migration after treatment with MiuA, showing that neither their speed nor their persistence is affected by MiuA. To check that these effects are not specific to RPE-1 cells, we also analyzed the effects of MiuA treatment in MEF cells and neutrophils. Both MEF cells and neutrophils showed the same results as the RPE-1 cells. Our measurements indicate that, although altering focal adhesions significantly reduces adhesion, it does not impact cell contractility. This finding also clarifies why amoeboid migration, which operates independently of adhesion, remains unaffected. Additionally, it explains the previously observed reduction in mesenchymal migration, which relies on adhesion-based mechanisms.

Phosphate plays a vital role in spider silk spinning and has been utilized in numerous artificial silk spinning attempts to replicate the remarkable mechanical properties of natural silk fiber. Its application in artificial processes has, however, yielded varying outcomes. It is thus necessary to investigate the origins and mechanisms behind these differences. By using recombinant silk protein SC-ADF3 derived from the garden spider Araneus diadematus, here, we describe its conformational changes under various conditions, elucidating the effect of phosphate on SC-ADF3 silk protein properties and interactions. Our results demonstrate that elevated phosphate levels induce the irreversible conformational conversion of SC-ADF3 from random coils to β-sheet structures, leading to decreased protein solubility over time. Furthermore, exposure of SC-ADF3 to phosphate stiffens already formed structures and reduces the ability to form new interactions. Our findings offer insights into the underlying mechanism through which phosphate-induced β-sheet structures in ADF3-related silk proteins impede fiber formation in the subsequent phases. From a broader perspective, our studies emphasize the significance of silk protein conformation for functional material formation, highlighting that the formation of β-sheet structures at the initial stages of protein assembly will affect the outcome of material forming processes.

Brass, along with other copper-based alloys, exhibits advantageous antibacterial properties that can be further enhanced by altering the surface topography to increase bacterial adhesion. This enhancement is achievable through a higher contact area created by precise periodic structures, each approximately the size of a single bacterial cell. One method for generating these structures is ultrashort pulsed direct laser interference patterning (USP-DLIP). However, this process may induce chemical alterations in addition to topographical changes, depending on the substrate’s composition. To mitigate unfavorable chemical alterations, brass with a 15% zinc content was selected for this study. The antibacterial effectiveness of the modified surfaces was tested against Escherichia coli, providing initial insights into the interaction between bacteria and the substrate. The results indicate that modified brass with a 15% zinc content shows improved antibacterial activity. Overall, this research demonstrates that by modifying a surface with the appropriate chemical composition, effective bacterial elimination through contact can be achieved.

Understanding and controlling microbial adhesion is a critical challenge in biomedical research, given the profound impact of bacterial infections on global health. Many facets of bacterial adhesion, including the distribution of adhesion forces across the cell wall, remain poorly understood. While a recent 'patchy colloid' model has shed light on adhesion in Gram-negative Escherichia coli cells, a corresponding model for Gram-positive cells has been elusive. In this study, we employ single cell force spectroscopy to investigate the adhesion force of Staphylococcus aureus. Normally, only one contact point of the entire bacterial surface is measured. However, by using a sine-shaped surface and recording force-distance curves along a path perpendicular to the rippled structures, we can characterize almost a hemisphere of one and the same bacterium. This unique approach allows us to study a greater number of contact points between the bacterium and the surface compared to conventional flat substrata. Distributed over the bacterial surface, we identify sites of higher and lower adhesion, which we call 'patchy adhesion', reminiscent of the patchy colloid model. The experimental results show that only some cells exhibit particularly strong adhesion at certain locations. To gain a better understanding of these locations, a geometric model of the bacterial cell surface was created. The experimental results were best reproduced by a model that features a few (5-6) particularly strong adhesion sites (diameter about 250 nm) that are widely distributed over the cell surface. Within the simulated patches, the number of molecules or their individual adhesive strength is increased. A more detailed comparison shows that simple geometric considerations for interacting molecules are not sufficient, but rather strong angle-dependent molecule-substratum interactions are required. We discuss the implications of our results for the development of new materials and the design and analysis of future studies.

FluidFM-based detachment of single Giardia duodenalis trophozoites from a flat glass surface revealed a unique detachment characteristic and adhesion mode for this type of parasite, compared to yeast cells or human keratinocytes.

Biofilm formation by Shewanella oneidensis has been extensively studied under oxic conditions; however, relatively little is known about biofilm formation under anoxic conditions and how biofilm architecture and composition can positively influence current generation in bioelectrochemical systems. In this study, we utilized a recently developed microfluidic biofilm analysis setup with automated 3D imaging to investigate the effects of extracellular electron acceptors and synthetic modifications to the extracellular polymeric matrix on biofilm formation. Our results with the wild type strain demonstrate robust biofilm formation even under anoxic conditions when fumarate is used as the electron acceptor. However, this pattern shifts when a graphite electrode is employed as the electron acceptor, resulting in biofilm formation falling below the detection limit of the optical coherence tomography imaging system. To manipulate biofilm formation, we aimed to express BpfG with a single amino acid substitution in the catalytic center (C116S) and to overexpress bpfA. Our analyses indicate that, under oxic conditions, overarching mechanisms predominantly influence biofilm development, rather than the specific mutations we investigated. Under anoxic conditions, the bpfG mutation led to a quantitative increase in biofilm formation, but both strains exhibited significant qualitative changes in biofilm architecture compared to the controls. When an anode was used as the sole electron acceptor, both the bpfA and bpfG mutations positively impacted mean current density, yielding a 1.8-fold increase for each mutation.

One of the most important properties of membranes is their permeability to water and other small molecules. A targeted change in permeability allows the passage of molecules to be controlled. Vesicles made of membranes with low water permeability are preferable for drug delivery, for example, because they are more stable and maintain the drug concentration inside. This study reports on the very low water permeability of pure protein membranes composed of a bilayer of the amphiphilic protein hydrophobin HFBI. Using a droplet interface bilayer setup, we demonstrate that HFBI bilayers are essentially impermeable to water. HFBI bilayers withstand far larger osmotic pressures than lipid membranes. Only by disturbing the packing of the proteins in the HFBI bilayer is a measurable water permeability induced. To investigate possible molecular mechanisms causing the near-zero permeability, we used all-atom molecular dynamics simulations of various HFBI bilayer models. The simulations suggest that the experimental HFBI bilayer permeability is compatible neither with a lateral honeycomb structure, as found for HFBI monolayers, nor with a residual oil layer within the bilayer or with a disordered lateral packing similar to the packing in lipid bilayers. These results suggest that the low permeabilities of HFBI and lipid bilayers rely on different mechanisms. With their extremely low but adaptable permeability and high stability, HFBI membranes could be used as an osmotic pressure-insensitive barrier in situations where lipid membranes fail such as desalination membranes.

Nanocomposite materials consist of nanometer-sized quantum objects such as atoms, molecules, voids or nanoparticles embedded in a host material. These quantum objects can be exploited as a super-structure, which can be designed to create material properties targeted for specific applications. For electromagnetism, such targeted properties include field enhancements around the bandgap of a semiconductor used for solar cells, directional decay in topological insulators, high kinetic inductance in superconducting circuits, and many more. Despite very different application areas, all of these properties are united by the common aim of exploiting collective interaction effects between quantum objects. The literature on the topic spreads over very many different disciplines and scientific communities. In this review, we present a cross-disciplinary overview of different approaches for the creation, analysis and theoretical description of nanocomposites with applications related to electromagnetic properties.

In recent decades, antibiotic resistance has become a crucial challenge for human health. One potential solution to this problem is the use of antibacterial surfaces, i.e., copper and copper alloys. This study investigates the antibacterial properties of brass that underwent topographic surface functionalization via ultrashort pulsed direct laser interference patterning. Periodic line-like patterns in the scale range of single bacterial cells were created on brass with a 37% zinc content to enhance the contact area for rod-shaped Escherichia coli (E. coli). Although the topography facilitates attachment of bacteria to the surface, reduced killing rates for E. coli are observed. In parallel, a high-resolution methodical approach was employed to explore the impact of laser-induced topographical and chemical modifications on the antibacterial properties. The findings reveal the underlying role of the chemical modification concerning the antimicrobial efficiency of the Cu-based alloy within the superficial layers of a few hundred nanometers. Overall, this study provides valuable insight into the effect of alloy composition on targeted laser processing for antimicrobial Cu-surfaces, which facilitates the thorough development and optimization of the process concerning antimicrobial applications.

Research into materials for medical application draws inspiration from naturally occurring or synthesized surfaces, just like many other research directions. For medical application of materials, particular attention has to be paid to biocompatibility, osseointegration, and bacterial adhesion behavior. To understand their properties and behavior, experimental studies with natural materials such as teeth are strongly required. The results, however, may be highly case-dependent because natural surfaces have the disadvantage of being subject to wide variations, for instance in their chemical composition, structure, morphology, roughness, and porosity. A synthetic surface which mimics enamel in its performance with respect to bacterial adhesion and biocompatibility would, therefore, facilitate systematic studies much better. In this study, we discuss the possibility of using hydroxyapatite (HAp) pellets to simulate the surfaces of teeth and show the possibility and limitations of using a model surface. We performed single-cell force spectroscopy with single Staphylococcus aureus cells to measure adhesion-related parameters such as adhesion force and rupture length of cell wall proteins binding to HAp and enamel. We also examine the influence of blood plasma and saliva on the adhesion properties of S. aureus. The results of these measurements are matched to water wettability, elemental composition of the samples, and the change in the macromolecules adsorbed over time on the surface. We found that the adhesion properties of S. aureus were similar on HAp and enamel samples under all conditions: Significant decreases in adhesion strength were found equally in the presence of saliva or blood plasma on both surfaces. We therefore conclude that HAp pellets are a good alternative for natural dental material. This is especially true when slight variations in the physicochemical properties of the natural materials may affect the experimental series.

FGF2 is a cell survival factor involved in tumor-induced angiogenesis that is secreted through an unconventional secretory pathway based upon direct protein translocation across the plasma membrane. Here, we demonstrate that both PI(4,5)P2-dependent FGF2 recruitment at the inner plasma membrane leaflet and FGF2 membrane translocation into the extracellular space are positively modulated by cholesterol in living cells. We further revealed cholesterol to enhance FGF2 binding to PI(4,5)P2-containing lipid bilayers. Based on extensive atomistic molecular dynamics (MD) simulations and membrane tension experiments, we proposed cholesterol to modulate FGF2 binding to PI(4,5)P2 by (i) increasing head group visibility of PI(4,5)P2 on the membrane surface, (ii) increasing avidity by cholesterol-induced clustering of PI(4,5)P2 molecules triggering FGF2 oligomerization, and (iii) increasing membrane tension facilitating the formation of lipidic membrane pores. Our findings have general implications for phosphoinositide-dependent protein recruitment to membranes and explain the highly selective targeting of FGF2 toward the plasma membrane, the subcellular site of FGF2 membrane translocation during unconventional secretion of FGF2.

Fibroblast growth factor 2 (FGF2) is a cellular survival factor involved in tumor-induced angiogenesis. It is one of the most prominent examples of extracellular proteins that lack signal peptides and are secreted by ER/Golgi-independent secretory pathways. Biochemical reconstitution experiments and imaging in living cells have shown that FGF2 is secreted by direct translocation across the plasma membrane. This process is initiated by PI(4,5)P2-dependent FGF2 recruitment at the inner plasma membrane leaflet.

2D nanomaterials have provided an extraordinary palette of mechanical, electrical, optical, and catalytic properties. Ultrathin 2D nanomaterials are classically produced via exfoliation, delamination, deposition, or advanced synthesis methods using a handful of starting materials. Thus, there is a need to explore more generic avenues to expand the feasibility to the next generation 2D materials beyond atomic and molecular-level covalent networks. In this context, self-assembly of atomically precise noble nanoclusters can, in principle, suggest modular approaches for new generation 2D materials, provided that the ligand engineering allows symmetry breaking and directional internanoparticle interactions. Here the self-assembly of silver nanoclusters (NCs) capped with p-mercaptobenzoic acid ligands (Na4 Ag44 -pMBA30 ) into large-area freestanding membranes by trapping the NCs in a transient solvent layer at air-solvent interfaces is demonstrated. The patchy distribution of ligand bundles facilitates symmetry breaking and preferential intralayer hydrogen bondings resulting in strong and elastic membranes. The membranes with Young's modulus of 14.5 ± 0.2 GPa can readily be transferred to different substrates. The assemblies allow detection of Raman active antibiotic molecules with high reproducibility without any need for substrate pretreatment.

The adhesion of Staphylococcus aureus to abiotic surfaces is crucial for establishing device-related infections. With a high number of single-cell force spectroscopy measurements with genetically modified S. aureus cells, this study provides insights into the adhesion process of the pathogen to abiotic surfaces of different wettability. Our results show that S. aureus utilizes different cell wall molecules and interaction mechanisms when binding to hydrophobic and hydrophilic surfaces. We found that covalently bound cell wall proteins strongly interact with hydrophobic substrates, while their contribution to the overall adhesion force is smaller on hydrophilic substrates. Teichoic acids promote adhesion to hydrophobic surfaces as well as to hydrophilic surfaces. This, however, is to a lesser extent. An interplay of electrostatic effects of charges and protein composition on bacterial surfaces is predominant on hydrophilic surfaces, while it is overshadowed on hydrophobic surfaces by the influence of the high number of binding proteins. Our results can help to design new models of bacterial adhesion and may be used to interpret the adhesion of other microorganisms with similar surface properties.