Publikationen

Extracellular vesicles (EVs), lipid-enclosed structures released by virtually all life forms, have gained significant attention due to their role in intercellular and interorganismal communication. Despite their recognized importance in disease processes and therapeutic applications, fundamental questions about their primary function remain. Here, we propose a different perspective on the primary function of EVs, arguing that they serve as essential elements providing membrane area for long-distance, contact-dependent cellular communication based on protein-protein interaction. While EVs have been recognized as carriers of genetic information, additional unique advantages that they could provide for cellular communication remain unclear. Here, we introduce the concept that the substantial membrane area provided by EVs allows for membrane contact-dependent interactions that could be central to their function. This membrane area enables the lateral diffusion and sorting of membrane ligands like proteins, polysaccharides or lipids in two dimensions, promoting avidity-driven effects and assembly of co-stimulatory architectures at the EV-cell interface. The concept of vesicle-induced receptor sequestration (VIRS), for example, describes how EVs confine and focus receptors at the EV contact site, promoting a dense local concentration of receptors into signalosomes. This process can increase the signalling strength of EV-presented ligands by 10-1000-fold compared to their soluble counterparts. The speculations in this perspective advance our understanding of EV-biology and have critical implications for EV-based applications and therapeutics. We suggest a shift in perspective from viewing EVs merely as transporters of relevant nucleic acids and proteins to considering their unique biophysical properties as presentation platforms for long-distance, contact-dependent signalling. We therefore highlight the functional role of the EV membrane rather than their content. We further discuss how this signalling mechanism might be exploited by virus-transformed or cancer cells to enhance immune-evasive mechanisms.

The structure of supraparticles (SPs) is a key parameter for achieving advanced functionalities arising from the combination of different nanoparticle (NP) types in one hierarchical entity. However, whenever a droplet-assisted forced assembly approach is used, e.g., spray-drying, the achievable structure is limited by the inherent drying phenomena of the method. In particular, mixed NP dispersions of differently sized colloids are heavily affected by segregation during the assembly. Herein, the influence of the colloidal arrangement of Pt and SiO2 NPs within a single supraparticulate entity is investigated. A salt-based electrostatic manipulation approach of the utilized NPs is proposed to customize the structure of spray-dried Pt/SiO2 SPs. By this, size-dependent separation phenomena of NPs during solvent evaporation, that limit the catalytic performance in the reduction of 4-nitrophenol, are overcome by achieving even Pt NP distribution. Additionally, the textural properties (pore size and distribution) of the SiO2 pore framework are altered to improve the mass transfer within the material leading to increased catalytic activity. The suggested strategy demonstrates a powerful, material-independent, and universally applicable approach to deliberately customize the structure and functionality of multi-component SP systems. This opens up new ways of colloidal material combinations and structural designs in droplet-assisted forced assembly approaches like spray-drying.

Soft lithography, in particular microcontact printing (µCP), represents a well-established and widespread class of lithographic patterning techniques. It is based on a directed deposition of molecules or colloidal particles by a transfer process with a micro-structured stamp. A critical aspect of µCP is the adhesion cascade that enables the directed transfer of the objects. Here, the interfacial properties of a µCP-stamp are tuned electrochemically to modify the adhesion cascade. During the printing process, the µCP-stamp is submerged in an electrolyte solution and acted as a working electrode whose surface properties depended on the externally applied potential, thus enabling in situ rapid switching of its adhesion properties. As a proof of principle, defined particle patterns are selectively removed from a monolayer of colloidal particles. The adhesion at the particle/solid interface and the transfer mechanisms are determined by using the colloidal probe technique based on atomic force microscopy (AFM). In this case, a single particle is brought into contact with an electrode with the same surface chemistry as the µCP-stamp. Hence, it became possible to determine the electrochemical potential ranges suitable to establish an adhesion cascade.

The treatment of Parkinson’s disease has been moving into the focus of pharmaceutical development. Yet, the necessity for reliable model systems in the development phase has made research challenging and in vivo models necessary. We have established reliable, reproducible in vitro model systems to evaluate the binding and transport of dopamine-loaded PLGA nanoparticles for the treatment of Parkinson’s disease and put the results in context with comparable in vivo results. The in vitro models have provided similar results concerning the usability of the investigated nanoparticles as the previously used in vivo models and thus provide a good alternative in line with the 3R principles in pharmaceutical research.

Recycling of Waste from Electrical and Electronic Equipment (WEEE) is crucial in preventing resource depletion and promoting a circular economy. The increasing fraction of printed and in-mold electronics is particularly challenging. The combinations of polymers and printed metals are difficult to disassemble due to the strong interfaces that are formed to create reliable in-mold devices. The relatively low metal content makes recycling uneconomical and those valuable materials are then lost to landfill or incineration. Separation layers enable design-for-recycling with minimal modifications during the fabrication process, while preserving product performance and reliability. We present a scalable method for preparing polymer separation layers for printed and in-mold electronics. Slot-die coating is used to prepare water-soluble polymer films with a dry thickness of less than 10 μm on commodity polymer substrates. This separation layer improves the bending stability of inkjet- and screen-printed circuits. Furthermore, it is compatible with typical polymer processing methods, such as thermoforming and injection molding. Various methods, including plasma treatment, are presented to ensure adhesion of the modified interfaces. Finally, we investigate the material recovery and demonstrate the release of the integrated metal within a few minutes by dissolving the separation layer in water. This material recovery process can be readily integrated into current WEEE recycling processes.

We explore the potential of nanocrystals (a term used equivalently to nanoparticles) as building blocks for nanomaterials, and the current advances and open challenges for fundamental science developments and applications. Nanocrystal assemblies are inherently multiscale, and the generation of revolutionary material properties requires a precise understanding of the relationship between structure and function, the former being determined by classical effects and the latter often by quantum effects. With an emphasis on theory and computation, we discuss challenges that hamper current assembly strategies and to what extent nanocrystal assemblies represent thermodynamic equilibrium or kinetically trapped metastable states. We also examine dynamic effects and optimization of assembly protocols. Finally, we discuss promising material functions and examples of their realization with nanocrystal assemblies.

We undertake a numerical study of the ordering kinetics in the two-dimensional (2d) active Ising model (AIM), a discrete flocking model with a non-conserved scalar order parameter. We find that for a quench into the liquid-gas coexistence region and in the ordered liquid region, the characteristic length scale of both the density and magnetization domains follows the Lifshitz-Cahn-Allen (LCA) growth law: R(t)∼t1/2, consistent with the growth law of passive systems with scalar order parameter and non-conserved dynamics. The system morphology is analyzed with the two-point correlation function and its Fourier transform, the structure factor, which conforms to the well-known Porod's law, a manifestation of the coarsening of compact domains with smooth boundaries. We also find the domain growth exponent unaffected by different noise strengths and self-propulsion velocities of the active particles. However, transverse diffusion is found to play the most significant role in the growth kinetics of the AIM. We extract the same growth exponent by solving the hydrodynamic equations of the AIM.

Microfluidics plays a pivotal role in organ-on-chip technologies and in the study of synthetic cells, especially in the development and analysis of artificial cell models. However, approaches that use synthetic cells as integral functional components for microfluidic systems to shape the microenvironment of natural living cells cultured on-chip are not explored. Here, colloidosome-based synthetic cells are integrated into 3D microfluidic devices, pioneering the concept of synthetic cell-based microenvironments for organs-on-chip. Methods are devised to create dense and stable networks of silica colloidosomes, enveloped by supported lipid bilayers, within microfluidic channels. These networks promote receptor-ligand interactions with on-chip cultured cells. Furthermore, a technique is introduced for the controlled release of growth factors from the synthetic cells into the channels, using a calcium alginate-based hydrogel formation within the colloidosomes. To demonstrate the potential of the technology, a modular plug-and-play lymph-node-on-a-chip prototype that guides the expansion of primary human T cells by stimulating receptor ligands on the T cells and modulating their cytokine environment is presented. This integration of synthetic cells into microfluidic systems offers a new direction for organ-on-chip technologies and suggests further avenues for exploration in potential therapeutic applications.

Dr. Helmut Cölfen, an exceptional interdisciplinary scientist, mentor, colleague, and dear friend, passed away in November 2023 at the age of 58. His untimely departure is a profound loss for the fields of analytical ultracentrifugation, colloid, crystallization, and polymer research. This obituary pays tribute to Helmut, honoring his remarkable academic career and contributions to the study of nanochemistry, biophysics, and life sciences. Helmut was renowned for his pioneering research contributions in several key research areas: (1) Development of advanced analytical techniques: Helmut made major contributions to techniques such as analytical ultracentrifugation and field flow fractionation, which are widely utilized to characterize the structure of biomolecules and the growth of nanostructured crystalline materials; (2) Study of nucleation and crystallization processes: Helmut explored the early stages of crystallization which led to the discovery of pre-nucleation clusters and mesocrystal intermediates, in the presence of additives and templates; and (3) Investigation of structure and morphogenesis of mesocrystals, examining their molecular properties.

The tailored synthesis of copolymer architectures provides insights into fundamental structure–property relationships for the formation of complex morphologies through microphase separation. In this way, classical areas within the phase diagram can be specifically influenced and also adapted for important applications. The exploration of copolymer architectures also offers the possibility to discover entirely new morphologies. In this study, we design a symmetric dendrimer-like second generation block copolymer by anionic polymerization. The structural design of the polymers influences the curvature of the interfaces to produce, in particular, bicontinuous morphologies and is investigated based on molecular chain architecture. After extensive molecular analysis of the new dendrimer-like block copolymers, the resulting morphology is analyzed using transmission electron microscopy, atomic force microscopy, and small-angle X-ray scattering measurements. We further combine the experimentally obtained morphologies with Monte Carlo simulations to better understand the relationship between tailored polymer architecture and the observed morphology. By changing the volume ratio of the copolymers used and also mixing this complex polymer architecture with a linear block copolymer, we gain insights into the polymer behavior at the phase boundaries. This knowledge has an impact on the optical and mechanical properties of thermoplastic elastomers and their corresponding blends.