Functional Mesostructured Electrospun Polymer Nonwovens with Supramolecular Nanofibers.

Functional, hierarchically mesostructured nonwovens are of fundamental importance because complex fiber morphologies increase the active surface area and functionality allowing for the effective immobilization of metal nanoparticles. Such complex functional fiber morphologies clearly widen the property profile and enable the preparation of more efficient and selective filter media. Here, the realization of hierarchically mesostructured nonwovens with barbed wire-like morphology is demonstrated by combining electrospun polystyrene fibers, decorated with patchy worm-like micelles, with solution-processed supramolecular short fibers composed of 1,3,5-benzenetricarboxamides with peripheral N,N-diisopropylaminoethyl substituents. The worm-like micelles with a patchy microphase-separated corona are prepared by crystallization-driven self-assembly of a polyethylene based triblock terpolymer and deposited on top of the polystyrene fibers by coaxial electrospinning. The micelles are designed in a way that their patches promote the directed self-assembly of the 1,3,5-benzenetricarboxamide and the fixation of the supramolecular nanofibers on the supporting polystyrene fibers. Functionality of the mesostructured nonwoven is provided by the peripheral N,N-diisopropylaminoethyl substituents of the 1,3,5-benzenetricarboxamide and proven by the effective immobilization of individual palladium nanoparticles on the supramolecular nanofibers. The preparation of hierarchically mesostructured nonwovens and their shown functionality demonstrate that such systems are attractive candidates to be used for example in filtration, selective separation and heterogenous catalysis.

Reconstructing the Environmental Degradation of Polystyrene by Accelerated Weathering.

The fragmentation of macro- into microplastics (MP) is the main source of MP in the environment. Nevertheless, knowledge about degradation mechanisms, changes in chemical composition, morphology, and residence times is still limited. Here, we present a long-term accelerated weathering study on polystyrene (PS) tensile bars and MP particles using simulated solar radiation and mechanical stress. The degradation process was monitored by gel permeation chromatography (GPC), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), 13C magic-angle spinning (MAS) NMR spectroscopy, tensile testing, and Monte Carlo simulations. We verified that degradation proceeds in two main stages. Stage I is dominated by photooxidation in a near-surface layer. During stage II, microcrack formation and particle rupturing accelerate the degradation. Depending on the ratio and intensity of the applied stress factors, MP degradation kinetics and lifetimes vary dramatically and an increasing amount of small MP fragments with high proportions of carboxyl, peroxide, and keto groups is continuously released into the environment. The enhanced surface area for adsorbing pollutants and forming biofilms modifies the uptake behavior and interaction with organisms together with potential ecological risks. We expect the proposed two-stage model to be valid for predicting the abiotic degradation of other commodity plastics with a carbon-carbon backbone.

Polydepsipeptide Block-Stabilized Polyplexes for Efficient Transfection of Primary Human Cells.

The rational design of a polyplex gene carrier aims to balance maximal effectiveness of nucleic acid transfection into cells with minimal adverse effects. Depsipeptide blocks with an Mn ∼ 5 kDa exhibiting strong physical interactions were conjugated with PEI moieties (2.5 or 10 kDa) to di- and triblock copolymers. Upon nanoparticle formation and complexation with DNA, the resulting polyplexes (sizes typically 60-150 nm) showed remarkable stability compared to PEI-only or lipoplex and facilitated efficient gene delivery. Intracellular trafficking was visualized by observing fluorescence-labeled pDNA and highlighted the effective cytoplasmic uptake of polyplexes and release of DNA to the perinuclear space. Specifically, a triblock copolymer with a middle depsipeptide block and two 10 kDa PEI swallowtail structures mediated the highest levels of transgenic VEGF secretion in mesenchymal stem cells with low cytotoxicity. These nanocarriers form the basis for a delivery platform technology, especially for gene transfer to primary human cells.

Small but powerful: co-assembly of polyether-based triblock terpolymers into sub-30 nm micelles and synergistic effects on cellular interactions.

We introduce a versatile ABC triblock terpoly- mer platform based on poly(ethylene oxide)-block-poly(allyl glycidyl ether)-block-poly(tert-butyl glycidyl ether) (PEO-b-PAGE-b-PtBGE) and subsequent functionalization of the PAGE segment with thiogalactose (hydroxyl), cysteamine (amino), and 2-mercaptopropionic acid (carboxy) by thiol-ene chemistry. These materials are used to prepare core-shell-corona micelles with a PtBGE core, a PAGE shell, and a PEO corona and sizes below 30 nm in aqueous media. We investigate the influence of different functional groups on micelle formation and cellular uptake. Moreover, co-assembly of differently functionalized materials allows to create micelles with a mixed shell and adjustable charge and, in that way, important characteristics such as cell uptake or cytotoxicity can be controlled. Furthermore, we demonstrate that even the uptake mechanism depends on the substitution pattern of the underlying triblock terpolymer.

Poly(2-vinyl pyridine)-block-poly(ethylene oxide) featuring a furan group at the block junction-synthesis and functionalization.

Furfuryl glycidyl ether (FGE) represents a highly versatile monomer for the preparation of reversibly cross-linkable nanostructured materials via Diels-Alder reactions. Here, the use of FGE for the mid-chain functionalization of a P2VP-b-PEO diblock copolymer is reported. The material features one furan moiety at the block junction, P2VP68 -FGE-b-PEO390 , which can be subsequently addressed in Diels-Alder reactions using maleimide-functionalized counterparts. The presence of the FGE moiety enables the introduction of dyes as model labels or the formation of hetero-grafted brushes as shell on hybrid Au@Polymer nanoparticles. This renders P2VP68 -FGE-b-PEO390 , a powerful tool for selective functionalization reactions, including the modification of surfaces.

Composite Alginate Dialdehyde-Gelatin (ADA-GEL) Hydrogel Containing Short Ribbon-Shaped Fillers for Skeletal Muscle Tissue Biofabrication.

Skeletal muscle tissue can be severely damaged by disease or trauma beyond its ability to self-repair, necessitating the further development of biofabrication and tissue-engineering tools for reconstructive processes. Hence, in this study, a composite bioink of oxidized alginate (ADA) and gelatin (GEL) including cell-laden ribbon-shaped fillers is used for enhancing cell alignment and the formation of an anisotropic structure. Different plasma treatments combined with protein coatings were evaluated for the improvement of cell adhesion to poly(lactic-co-glycolic acid) (PLGA) ribbon surfaces. Oxygen plasma activation of 30 W for 5 min showed high immobilization of fibronectin as a protein coating on the PLGA ribbon surface, which resulted in enhanced cell adhesion and differentiation of muscle cells. Furthermore, the effect of various concentrations of CaCl2 solution, used for ionic cross-linking of ADA, on ADA-GEL physical and mechanical properties as well as encapsulated C2C12 cell viability and proliferation behavior was investigated. The pore area was measured via two approaches, cryofixation and lyophilization, which, in accordance with degradation tests and mechanical analysis, showed that 60 mM CaCl2 concentration is the optimum range for cross-linking of the formulation of ADA 2.5%w/v-GEL 3.75%w/v. These cross-linked hydrogels showed a compression modulus of 11.5 kPa (similar to the native skeletal muscle tissue), a high viability of C2C12 muscle cells (>80%), and a high proliferation rate during 7 days of culture. Rheological characterization of the ADA-GEL composite hydrogel containing short fillers (100 µm long) showed its suitability as a bioink with shear-thinning and flow behavior compared to ADA-GEL.

Elemental Compositions of Enamel or Dentin in Human and Bovine Teeth Differ from Murine Teeth.

Teeth with different chemical compositions can show vastly different physical properties, so knowledge of elemental composition is required to use animal teeth as substitutes for human teeth in research. In vitro, energy dispersive X-ray spectroscopy (EDX), improved by calibration standards and Si3N4-window material, enables determining local elemental compositions of inorganic and organic compounds without sample destruction. Six human molars, bovine incisors, murine incisors, and murine molars were analyzed. EDX-field scans and line scans were analyzed for elements Ca, P, O, C, N, F, Na, Mg, Fe, Cl, and S. Furthermore, Ca/P- and Ca/N-Ratios were calculated. The presence of iron in murine incisor enamel was investigated using additional wavelength dispersive X-ray spectroscopy measurements (WDX) near the enamel surface. Bovine and human enamel and dentin revealed close similarities regarding elemental composition. The median (25-75% percentiles) of At%Ca was 21.1 (20.8-21.3) in human enamel, 21.0 (20.7-21.2) in bovine enamel, and in murine enamel, 18.3 (17.85-18.88) for molars and 18.35 (18.00-18.75) for incisors. In dentin, murine teeth revealed a higher At%Ca compared to human and bovine teeth. Significant differences between human and bovine teeth were found for nitrogen in dentin, with a median of 4.5 (3.3-5) At%N for human dentin and 2.7 (2.3-3.2) At%N for bovine dentin. The Ca/P-Ratio was the highest in human and bovine enamel, which did not differ significantly. Enamel from murine molars had a higher Ca/P-Ratio than murine incisors and the highest Ca/P-Ratio in dentin was observed for human teeth and murine molars (1.49). WDX revealed iron in the outer 10 µm of pre- and post-eruptive enamel of murine incisors. Pre- and post-eruptive enamel on murine incisors only differed significantly in At%Ca (p = 0.041) and At%P (p = 0.026) with both At% higher in the pre-eruptive enamel. Murine teeth differ significantly from human and bovine teeth in terms of the elemental composition of enamel and dentin.

Heteroaggregation of PS microplastic with ferrihydrite leads to rapid removal of microplastic particles from the water column.

Microplastic (MP) particles are ubiquitous in aquatic environments. Therefore, understanding the processes that affect their removal from the water column, such as sedimentation, is critical for evaluating the risk they pose to aquatic ecosystems. We performed sedimentation experiments in which polystyrene (PS) and PS + ferrihydrite, a short-range ordered ferric (oxy)hydroxide, were analyzed in settling columns after 1 day and 1 week of settling time. The presence of ferrihydrite increased sedimentation rates of PS at all pH values studied (pH 3-11). At pH 6 we found that almost all PS particles were removed from the water column after only one day of exposure time. SEM/EDS imaging confirmed heteroaggregation between the PS particles and ferrihydrite. Zeta potential measurements indicated that at acidic pH values the negatively charged PS surface was coated with positively charged ferrihydrite particles leading to charge reversal. Our results demonstrate for the first time that ferric (oxy)hydroxides drive heteroaggregation and subsequent removal of MP from the water column, especially at typical pH values found in natural lake environments. Given their abundance in aquatic systems ferric (oxy)hydroxides need to be regarded as key scavengers of MP.

Degradation of low-density polyethylene to nanoplastic particles by accelerated weathering.

When plastics enter the environment, they are exposed to abiotic and biotic impacts, resulting in degradation and the formation of micro- and nanoplastic. Microplastic is ubiquitous in every environmental compartment. Nevertheless, the underlying degradation processes are not yet fully understood. Here, we studied the abiotic degradation of commonly used semi-crystalline, low-density polyethylene (LDPE) in a long-term accelerated weathering experiment combining several macro- and microscopic methods. Based on our observations, the degradation of LDPE proceeds in three stages. Initially, LDPE objects are prone to abrasion, followed by a period of surface cracking. A large number of secondary particles with a high degree of crystallinity are formed, with sizes down to the nanometer scale. These particles consist of highly polar oligomers leading to agglomeration in the final stage. We therefore suppose that weathered microplastic and nanoplastic particles will attach to colloidal environmental matter. This offers an explanation for the absence of free nanoplastic particles in natural samples.

Investigating the motion of diblock copolymer assemblies in ionic liquids by in situ electron microscopy.

The movement of individual block copolymer micelles in free-standing films of ionic liquids is investigated by transmission electron microscopy with the aim of providing an easily accessible high-resolution imaging tool for the in situ observation of particle movement in a liquid environment. A proof of concept and first studies on the behavior of individual particles in the fluid are demonstrated.