Functional Cell Adhesion Receptors (Integrins) in Polymeric Architectures.

Integrins, as transmembrane heterodimeric receptors, have important functions in cell adhesion, migration, proliferation, survival apoptosis and signal transduction, in many physio- as well as pathophysiological settings. Characterisation of integrins and their ligand/antagonist binding is notoriously difficult, due to high integrin redundancy and ubiquity. Bypassing the intrinsic difficulties of cell-based integrin expression, purification and reconstitution, we present for the first time the synthesis of a heterodimeric integrin receptor and its assembly into a block-copolymeric membrane mimic. We present comprehensive data to demonstrate the synthesis of functionally active integrin αv ß3, generated by in vitro membrane-assisted protein synthesis (iMAPS). This work represents the first step towards a robust and adaptable polymer-based platform for characterisation of integrin-ligand interactions.

The Piezo1 hypothesis of renal anemia.

Erythropoietin deficiency is an extensively researched cause of renal anemia. The etiology and consequences of shortened red blood cell (RBC) life span in chronic kidney disease (CKD) are less well understood. Traversing capillaries requires RBC geometry changes, a process enabled by adaptions of the cytoskeleton. These changes are mediated by transient activation of the mechanosensory Piezo1 channel, resulting in calcium influx. Importantly, prolonged Piezo1 activation shortens RBC life span, presumably through activation of calcium-dependent intracellular pathways triggering RBC death. Two Piezo1-activating small molecules, Jedi1 and Jedi2, share remarkable structural similarities with 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF), a uremic retention solute cleared by the healthy kidney. We hypothesize that in CKD the accumulation of CMPF leads to prolonged activation of Piezo1 (similar in effect to Jedi1 and Jedi2), thus reducing RBC life span. This hypothesis can be tested through bench experiments and, ultimately, by studying the effect of CMPF removal on renal anemia.

Mobility and fate of ligand stabilized semiconductor nanoparticles in landfill leachates.

Semiconductor quantum dots (QDs) are nanocrystals used in diverse optoelectronics. At the end of their useful life they are likely to end up in landfills, where they could be mobilzed by infiltrating rain water. In this work, spectroscopic and light scattering techniques were employed to investigate the environmental fate of QDs exposed to leachates from Austrian landfill sites containing municipal solid and bulky wastes. Brij-58-coated CdSe QDs, a model for surfactant stabilized hydrophobic nanoparticles, primarily sedimented before being degraded on a slower timescale in the course of 6 months. In contrast, N-acetyl-l-cystein-coated CdTe QDs, which represent electrostatically stabilized nanoparticles with a small covalently linked stabilizing molecule, mainly underwent a degradation mechanism that was accelerated by temperature. 71-95 % of this QD type was still dispersed in all leachates after 6 months at low temperature. Leachate temperature and composition, such as the DOC, as well as the used particle coating determined the mechanistic route of clearance of sedimentation versus degradation. Our study shows, that mechanistic investigations are necessary to determine the persistence of nanoparticles depending on their coatings in waste matrices which can be further used to assess hazardous risks of such nanowastes.

Fluorescent Magnetopolymersomes: A Theranostic Platform to Track Intracellular Delivery.

We present a potential theranostic delivery platform based on the amphiphilic diblock copolymer polybutadiene-block-poly (ethylene oxide) combining covalent fluorescent labeling and membrane incorporation of superparamagnetic iron oxide nanoparticles for multimodal imaging. A simple self-assembly and labeling approach to create the fluorescent and magnetic vesicles is described. Cell uptake of the densely PEGylated polymer vesicles could be altered by surface modifications that vary surface charge and accessibility of the membrane active species. Cell uptake and cytotoxicity were evaluated by confocal microscopy, transmission electron microscopy, iron content and metabolic assays, utilizing multimodal tracking of membrane fluorophores and nanoparticles. Cationic functionalization of vesicles promoted endocytotic uptake. In particular, incorporation of cationic lipids in the polymersome membrane yielded tremendously increased uptake of polymersomes and magnetopolymersomes without increase in cytotoxicity. Ultrastructure investigations showed that cationic magnetopolymersomes disintegrated upon hydrolysis, including the dissolution of incorporated iron oxide nanoparticles. The presented platform could find future use in theranostic multimodal imaging in vivo and magnetically triggered delivery by incorporation of thermorepsonsive amphiphiles that can break the membrane integrity upon magnetic heating via the embedded superparamagnetic nanoparticles.

Traceability of fluorescent engineered nanomaterials and their fate in complex liquid waste matrices.

The number of products containing engineered nanomaterials (ENMs) has increased due to their high industrial relevance as well as their use in diverse consumer products. At the end of their life cycle ENMs might be released to the environment and therefore concerns arise regarding their environmental impact. In order to track their fate upon disposal, it is crucial to establish methods to trace ENMs in complex environmental samples and to differentiate them from naturally-occurring nanoparticles. The goal of this study was to distinctively trace ENMs by (non-invasive) detection methods. For this, fluorescent ENMs, namely quantum dots (QDs), were distinctively traced in complex aqueous matrices, and were still detectable after a period of two months using fluorescence spectroscopy. In particular, two water-dispersible QD-species, namely CdTe/CdS QDs with N-acetyl-l-cysteine as capping agent (NAC-QDs) and surfactant-stabilized CdSe/ZnS QDs (Brij(®)58-QDs), were synthesized to examine their environmental fate during disposal as well as their potential interaction with naturally-occurring substances present in landfill leachates. When QDs were spiked into a leachate from an old landfill site, alteration processes, such as sorption, aggregation, agglomeration, and interactions with dissolved organic carbon (DOC), led to modifications of the optical properties of QDs. The spectral signatures of NAC-QDs deteriorated depending on residence time and storage temperature, while Brij(®)58-QDs retained their photoluminescence fingerprints, indicating their high colloidal stability. The observed change in photoluminescence intensity was mainly caused by DOC-interaction and association with complexing agents, such as fulvic or humic acids, typically present in mature landfill leachates. For both QD-species, the results also indicated that pH of the leachate had no significant impact on their optical properties. As a result, the unique spectroscopic fingerprints of QDs, specifically surfactant-stabilized QDs, allowed distinctive tracing in complex aqueous waste matrices in order to study their long-term behavior and ultimate fate.

Nanoscopic leg irons: harvesting of polymer-stabilized membrane proteins with antibody-functionalized silica nanoparticles.

Silica-based nanoparticles (SiNPs) are presented to harvest complex membrane proteins, which have been embedded into unilammelar polymersomes via in vitro membrane assisted protein synthesis (iMAP). Size-optimized SiNPs have been surface-modified with polymer-targeting antibodies, which are employed to harvest the protein-containing polymersomes. The polymersomes mimic the cellular membrane. They are chemically defined and preserve their structural-functional integrity as virtually any membrane protein species can be synthesized into such architecture via the ribosomal context of a cellular lysate. The SiNPs resemble 'heavy leg irons' catching the polymersomes in order to enable gravity-based generic purification and concentration of such proteopolymersomes from the crude mixture of cellular lysates.