Two-photon polymerization (2PP) allows 3D microfabrication of biomaterial scaffolds with user-defined geometry. This technique is highly promising for 3D cell culture and tissue engineering. However, biological applications of 2PP require photopolymerizable hydrogels with high reactivity and low cytotoxicity. This paper describes a novel hydrogel system based on hyaluronic acid vinyl esters (HA-VE), which enabled fast 2PP-fabrication of 3D hydrogel constructs with μm-scale accuracy. A series of HA-VE macromers with tunable degrees of substitution were synthesized by lipase-catalyzed transesterification. HA-VE gels were proved to be injectable, photocurable, enzymatically degradable and mechanically comparable to various soft tissues. Owing to the unique molecular design, degradation products of HA-VE gels through hydrolysis are non-toxic polyvinyl alcohol and adipic acid. Furthermore, HA-VE gels were systematically characterized and compared to HA-acrylates (HA-AC) and HA-methacrylates (HA-MA) gels including macromer cytotoxicity, photoreactivity, swelling, and gel stiffness. Cytotoxicity assay with L929 fibroblasts revealed that HA-VE was significantly less toxic than HA-AC (P < 0.01) and HA-MA (P < 0.05). Crosslinking efficiency of HA-VE was comparable to HA-AC and much higher than HA-MA. Although the reactivity of HA-VE for homopolymerization was insufficient for 2PP, it was demonstrated that thiol–ene chemistry could substantially improve its reactivity. This optimization led to 2PP-fabrication of a HA-VE hydrogel construct with μm-scale accuracy. Low cytotoxicity, high reactivity and good biodegradability makes HA-VE promising candidates for biological applications in cell culture and tissue engineering.

Transistors fabricated from ${\mathrm{C}}_{60}$ films grown by hot wall epitaxy at higher substrate temperature, showed an order of magnitude increased charge carrier mobility up to $6{\mathrm{cm}}^2∕\mathrm{V}\mathrm{s}$ . In this letter, the authors present an extensive study of morphology and crystallinity of the fullerene films using atomic force microscopy and grazing-incidence x-ray diffraction. A clear correlation of crystalline quality of the ${\mathrm{C}}_{60}$ film and charge carrier mobility was found. A higher substrate temperature leads to a single crystal-like faceted fullerene crystals. The high crystalline quality solely brings a drastic improvement in the charge carrier mobility. A gate voltage independent mobility is also observed in these devices which can be attributed to the highly conjugated nature of the ${\mathrm{C}}_{60}$ thin film.

We introduce a method, single-particle profiler, that provides single-particle information on the content and biophysical properties of thousands of particles in the size range 5–200 nm. We use our single-particle profiler to measure the messenger RNA encapsulation efficiency of lipid nanoparticles, the viral binding efficiencies of different nanobodies, and the biophysical heterogeneity of liposomes, lipoproteins, exosomes and viruses.

Surface reactive nanostructures were fabricated using stimulated emission depletion (STED) lithography. The functionalization of the nanostructures was realized by copolymerization of a bifunctional metal oxo cluster in the presence of a triacrylate monomer. Ligands of the cluster surface cross-link to the monomer during the lithographic process, whereas unreacted mercapto functionalized ligands are transferred to the polymer and remain reactive after polymer formation of the surface of the nanostructure. The depletion efficiency in dependence of the cluster loading was investigated and full depletion of the STED effect was observed with a cluster loading exceeding 4 wt %. A feature size by λ/11 was achieved by using a donut-shaped depletion beam. The reactivity of the mercapto groups on the surface of the nanostructure was tested by incubation with mercapto-reactive fluorophores.

AFM images show that chromatin reconstituted on methylated DNA (meDNA) is compacted when imaged under water. Chromatin reconstituted on unmethylated DNA is less compacted and less sensitive to hydration. These differences must reflect changes in the physical properties of DNA on methylation, but prior studies have not revealed large differences between methylated and unmethylated DNA. Quasi-elastic light scattering studies of solutions of methylated and unmethylated DNA support this view. In contrast, AFM images of molecules at a water/solid interface yield a persistence length that nearly doubles (to 92.5 ± 4 nm) when 9% of the total DNA is methylated. This increase in persistence length is accompanied by a decrease in contour length, suggesting that a significant fraction of the meDNA changes into the stiffer A form as the more hydrophobic meDNA is dehydrated at the interface. This suggests a simple mechanism for gene silencing as the stiffer meDNA is more difficult to remove from nucleosomes.