Lipopolysaccharide (LPS), also referred to as endotoxin, is the major component of Gram-negative bacteria’s outer cell wall. It is one of the main types of pathogen-associated molecular patterns (PAMPs) that are known to elicit severe immune reactions in the event of a pathogen trespassing the epithelial barrier and reaching the bloodstream. Associated symptoms include fever and septic shock, which in severe cases, might even lead to death. Thus, the detection of LPS in medical devices and injectable pharmaceuticals is of utmost importance. However, the term LPS does not describe one single molecule but a diverse class of molecules sharing one common feature: their characteristic chemical structure. Each bacterial species has its own pool of LPS molecules varying in their chemical composition and enabling the aggregation into different supramolecular structures upon release from the bacterial cell wall. As this heterogeneity has consequences for bioassays, we aim to examine the great variability of LPS molecules and their potential to form various supramolecular structures. Furthermore, we describe current LPS quantification methods and the LPS-dependent inflammatory pathway and show how LPS heterogeneity can affect them. With the intent of overcoming these challenges and moving towards a universal approach for targeting LPS, we review current studies concerning LPS-specific binders. Finally, we give perspectives for LPS research and the use of LPS-binding molecules.

The core of the semi-synthetic magnetic nanoparticle magnetoferritin was doped with cobalt or zinc in order to evaluate its applicability as a nanoagent for intracellular target redistribution or localised heat dissipation via magnetic hyperthermia.

Magnetic nanoparticles (MNPs) are widely known as valuable agents for biomedical applications. Recently, MNPs were further suggested to be used for a remote and non-invasive manipulation, where their spatial redistribution or force response in a magnetic field provides a fine-tunable stimulus to a cell. Here, we investigated the properties of two different MNPs and assessed their suitability for spatio-mechanical manipulations: semisynthetic magnetoferritin nanoparticles and fully synthetic ‘nanoflower’-shaped iron oxide nanoparticles. As well as confirming their monodispersity in terms of structure, surface potential, and magnetic response, we monitored the MNP performance in a living cell environment using fluorescence microscopy and asserted their biocompatibility. We then demonstrated facilitated spatial redistribution of magnetoferritin compared to ‘nanoflower’-NPs after microinjection, and a higher magnetic force response of these NPs compared to magnetoferritin inside a cell. Our remote manipulation assays present these tailored magnetic materials as suitable agents for applications in magnetogenetics, biomedicine, or nanomaterial research.

Diffusion and immobilization of molecules in biomembranes are essential for life. Understanding it is crucial for biomimetic approaches where well-defined substrates are created for live cell assays or biomaterial development. Here, we present biomimetic model systems consisting of a supported lipid bilayer and membrane coupled proteins to study the influence of lipid–lipid and lipid–protein interactions on membrane mobility. To characterize the diffusion of lipids or proteins, the continuous photobleaching technique is used. Either Neutravidin coupled to DOPE-cap-Biotin lipids or GFP coupled to DOGS-NTA lipids is studied at 0.005–0.5 mol% concentration of the linker lipid. Neutravidin creates mobile obstacles in the membrane, while GFP coupling results in immobile obstacles. By actin filament coupling to Neutravidin-lipid complexes, obstacles are crosslinked, resulting in lipid mobility reduction along with the appearance of a membrane texture. Theoretical considerations accurately describe lipid diffusion changes at high obstacle concentration as a function of obstacle size and viscous effects. The mobility of membrane lipids depends on the concentration of protein-binding lipids and on the concentration and charge of the coupled protein. Next to diffusion and friction coefficients, we determine the effective obstacle size as well as a charge-dependent effect that dominates the decrease in lipid mobility.

Homopolymerization and cluster formation of cellular membrane receptors (MRs) are increasingly recognized as an essential facet of cell signaling and modulator of physiological responses. Yet, there is a lack of tools that can mediate precise stimulation to better understand the mechanisms and effects of clustering. Here, we designed fluorescent semisynthetic nanoparticles (NPs) based on the iron-storage protein ferritin and Staphylococcus aureus protein A to specifically target and activate distinct MRs, without causing side-effects. The NP exhibits high monodispersity and is readily equipped with a variety of antibodies with a K_D value below 5 nM. Specificity of the NP antigen recognition was evaluated for cells expressing transferrin receptor 1 (TfR1) or the death receptor CD95, both of which displayed NP-mediated cluster formation. Finally, our engineered NP acts as a natural ligand for TfR1 and induces apoptosis signaling solely by CD95 cluster formation in a ligand-independent manner.

We introduce superparamagnetic biomembranes as a novel, actively tunable hybrid platform. The superparamagnetic biomembranes are supported lipid bilayers (SLBs) with defined lipid composition and site-specific coupling of proteins and superparamagnetic nanoparticles (MNPs). 2 Application of magnetic field gradients induces rapid and fully reversible lateral transport of lipidanchored MNPs with forces in the femtonewton range. Using single magnetic tips as well as multiple magnetic tips and line structures, we achieve parallelized and spatially defined MNP patterning. Transition of the SLB from the liquid-crystalline to the gel phase enables reversible immobilization of the patterned MNP distributions. Local MNP accumulation displaces lipids and membrane-associated proteins, including Neutravidin, mEGFP, and CD19, thereby generating inverse molecular gradients that are recognized by living cells. This biocompatible substrate with dynamically controllable nanoparticle and molecular organization provides a versatile framework for applications in bio- and nanotechnology.