2020, Han, L., Zheng, Y., Luo, H., Feng, J., Engstler, R., Xue, L., Jing, G., Deng, X., del Campo, A., Cui, J.

A solid-to-hollow evolution in macroscopic structures is challenging in synthetic materials. A fundamentally new strategy is reported for guiding macroscopic, unidirectional shape evolution of materials without compromising the material's integrity. This strategy is based on the creation of a field with a “swelling pole” and a “shrinking pole” to drive polymers to disassemble, migrate, and resettle in the targeted region. This concept is demonstrated using dynamic hydrogels containing anchored acrylic ligands and hydrophobic long alkyl chains. Adding water molecules and ferric ions (Fe3+) to induce a swelling–shrinking field transforms the hydrogels from solid to hollow. The strategy is versatile in the generation of various closed hollow objects (for example, spheres, helix tubes, and cubes with different diameters) for different applications.

2020, Wu, H., Friedrich, H., Patterson, J.P., Sommerdijk, N.A.J.M., de Jonge, N.

Innovations in liquid-phase electron microscopy (LP-EM) have made it possible to perform experiments at the optimized conditions needed to examine soft matter. The main obstacle is conducting experiments in such a way that electron beam radiation can be used to obtain answers for scientific questions without changing the structure and (bio)chemical processes in the sample due to the influence of the radiation. By overcoming these experimental difficulties at least partially, LP-EM has evolved into a new microscopy method with nanometer spatial resolution and sub-second temporal resolution for analysis of soft matter in materials science and biology. Both experimental design and applications of LP-EM for soft matter materials science and biological research are reviewed, and a perspective of possible future directions is given.

2021, Buchheit, Roman, Kuttich, Björn, González-García, Lola, Kraus, Tobias

A new type of hybrid core-shell nanoparticle dielectric that is suitable for inkjet printing is introduced. Gold cores (dcore  ≈ 4.5 nm diameter) are covalently grafted with thiol-terminated polystyrene (Mn  = 11000 Da and Mn  = 5000 Da) and used as inks to spin-coat and inkjet-print dielectric films. The dielectric layers have metal volume fractions of 5 to 21 vol% with either random or face-centered-cubic structures depending on the polymer length and grafting density. Films with 21 vol% metal have dielectric constants of 50@1 Hz. Structural and electrical characterization using transmission electron microscopy, small-angle X-ray scattering, and impedance spectroscopy indicates that classical random capacitor-resistor network models partially describe this hybrid material but fail at high metal fractions, where the covalently attached shell prevents percolation and ensures high dielectric constants without the risk of dielectric breakdown. A comparison of disordered to ordered films indicates that the network structure affects dielectric properties less than the metal content. The applicability of the new dielectric material is demonstrated by formulating inkjet inks and printing devices. An inkjet-printed capacitor with an area of 0.79 mm2 and a 17 nm thick dielectric had a capacitance of 2.2±0.1 nF@1 kHz .

2021, Tian, Mi, Lennox, Matthew J., O’Malley, Alexander J., Porter, Alexander J., Krüner, Benjamin, Rudić, Svemir, Mays, Timothy J., Düren, Tina, Presser, Volker, Terry, Lui R., Rols, Stephane, Fang, Yanan, Dong, Zhili, Rochat, Sebastien, Ting, Valeska P.

Our investigations into molecular hydrogen (H2) confined in microporous carbons with different pore geometries at 77 K have provided detailed information on effects of pore shape on densification of confined H2 at pressures up to 15 MPa. We selected three materials: a disordered, phenolic resin-based activated carbon, a graphitic carbon with slit-shaped pores (titanium carbide-derived carbon), and single-walled carbon nanotubes, all with comparable pore sizes of <1 nm. We show via a combination of in situ inelastic neutron scattering studies, high-pressure H2 adsorption measurements, and molecular modelling that both slit-shaped and cylindrical pores with a diameter of ∼0.7 nm lead to significant H2 densification compared to bulk hydrogen under the same conditions, with only subtle differences in hydrogen packing (and hence density) due to geometric constraints. While pore geometry may play some part in influencing the diffusion kinetics and packing arrangement of hydrogen molecules in pores, pore size remains the critical factor determining hydrogen storage capacities. This confirmation of the effects of pore geometry and pore size on the confinement of molecules is essential in understanding and guiding the development and scale-up of porous adsorbents that are tailored for maximising H2 storage capacities, in particular for sustainable energy applications.

2020, Ho, D.-K., Murgia, X., De Rossi, C., Christmann, R., Hüfner de Mello Martins, A.G., Koch, M., Andreas, A., Herrmann, J., Müller, R., Empting, M., Hartmann, R.W., Desmaele, D., Loretz, B., Couvreur, P., Lehr, C.-M.

Elimination of pulmonary Pseudomonas aeruginosa (PA) infections is challenging to accomplish with antibiotic therapies, mainly due to resistance mechanisms. Quorum sensing inhibitors (QSIs) interfering with biofilm formation can thus complement antibiotics. For simultaneous and improved delivery of both active agents to the infection sites, self-assembling nanoparticles of a newly synthesized squalenyl hydrogen sulfate (SqNPs) were prepared. These nanocarriers allowed for remarkably high loading capacities of hydrophilic antibiotic tobramycin (Tob) and a novel lipophilic QSI at 30 % and circa 10 %, respectively. The drug-loaded SqNPs showed improved biofilm penetration and enhanced efficacy in relevant biological barriers (mucin/human tracheal mucus, biofilm), leading to complete eradication of PA biofilms at circa 16-fold lower Tob concentration than Tob alone. This study offers a viable therapy optimization and invigorates the research and development of QSIs for clinical use.

2021, Trenkenschuh, Eduard, Richter, Maximilian, Heinrich, Eilien, Koch, Marcus, Fuhrmann, Gregor, Friess, Wolfgang

Extracellular vesicles (EV) are an emerging technology as immune therapeutics and drug delivery vehicles. However, EVs are usually stored at −80 °C which limits potential clinical applicability. Freeze-drying of EVs striving for long-term stable formulations is therefore studied. The most appropriate formulation parameters are identified in freeze-thawing studies with two different EV types. After a freeze-drying feasibility study, four lyophilized EV formulations are tested for storage stability for up to 6 months. Freeze-thawing studies revealed improved colloidal EV stability in presence of sucrose or potassium phosphate buffer instead of sodium phosphate buffer or phosphate-buffered saline. Less aggregation and/or vesicle fusion occurred at neutral pH compared to slightly acidic or alkaline pH. EVs colloidal stability can be most effectively preserved by addition of low amounts of poloxamer 188. Polyvinyl pyrrolidone failed to preserve EVs upon freeze-drying. Particle size and concentration of EVs are retained over 6 months at 40 °C in lyophilizates containing 10 mm K- or Na-phosphate buffer, 0.02% poloxamer 188, and 5% sucrose. The biological activity of associated beta-glucuronidase is maintained for 1 month, but decreased after 6 months. Here optimized parameters for lyophilization of EVs that contribute to generate long-term stable EV formulations are presented. © 2021 The Authors. Advanced Healthcare Materials published by Wiley-VCH GmbH

2021, Pearson, Samuel, Feng, Jun, del Campo, Aránzazu

Photoresponsive biomaterials are experiencing a transition from in vitro models to in vivo demonstrations that point toward clinical translation. Dynamic hydrogels for cell encapsulation, light-responsive carriers for controlled drug delivery, and nanomaterials containing photosensitizers for photodynamic therapy are relevant examples. Nonetheless, the step to the clinic largely depends on their combination with technologies to bring light into the body. This review highlights the challenge of photoactivation in vivo, and presents strategies for light management that can be adopted for this purpose. The authors’ focus is on technologies that are materials-driven, particularly upconversion nanoparticles that assist in “direct path” light delivery through tissue, and optical waveguides that “clear the path” between external light source and in vivo target. The authors’ intention is to assist the photoresponsive biomaterials community transition toward medical technologies by presenting light delivery concepts that can be integrated with the photoresponsive targets. The authors also aim to stimulate further innovation in materials-based light delivery platforms by highlighting needs and opportunities for in vivo photoactivation of biomaterials. © 2021 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH.

2021, Nair, Roshna V., Farrukh, Aleeza, del Campo, Aránzazu

The application of growth factor based therapies in regenerative medicine is limited by the high cost, fast degradation kinetics, and the multiple functions of these molecules in the cell, which requires regulated delivery to minimize side effects. Here a photoactivatable peptidomimetic of the vascular endothelial growth factor (VEGF) that allows the light-controlled presentation of angiogenic signals to endothelial cells embedded in hydrogel matrices is presented. A photoresponsive analog of the 15-mer peptidomimetic Ac-KLTWQELYQLKYKGI-NH2 (abbreviated PQK) is prepared by introducing a 3-(4,5-dimethoxy-2-nitrophenyl)-2-butyl (DMNPB) photoremovable protecting group at the Trp4 residue. This modification inhibits the angiogenic potential of the peptide temporally. Light exposure of PQK modified hydrogels provide instructive cues to embedded endothelial cells and promote angiogenesis at the illuminated sites of the 3D culture, with the possibility of spatial control. PQK modified photoresponsive biomaterials offer an attractive approach for the dosed delivery and spatial control of pro-angiogenic factors to support regulated vascular growth by just using light as an external trigger.

2020, Müller, Daniel W., Lößlein, Sarah, Terriac, Emmanuel, Brix, Kristina, Siems, Katharina, Moeller, Ralf, Kautenburger, Ralf, Mücklich, Frank

Copper (Cu) exhibits great potential for application in the design of antimicrobial contact surfaces aiming to reduce pathogenic contamination in public areas as well as clinically critical environments. However, current application perspectives rely purely on the toxic effect of emitted Cu ions, without considering influences on the interaction of pathogenic microorganisms with the surface to enhance antimicrobial efficiency. In this study, it is investigated on how antibacterial properties of Cu surfaces against Escherichia coli can be increased by tailored functionalization of the substrate surface by means of ultrashort pulsed direct laser interference patterning (USP-DLIP). Surface patterns in the scale range of single bacteria cells are fabricated to purposefully increase bacteria/surface contact area, while parallel modification of the surface chemistry allows to involve the aspect of surface wettability into bacterial attachment and the resulting antibacterial effectivity. The results exhibit a delicate interplay between bacterial adhesion and the expression of antibacterial properties, where a reduction of bacterial cell viability of up to 15-fold can be achieved for E. coli on USP-DLIP surfaces in comparison to smooth Cu surfaces. Thereby, it can be shown how the antimicrobial properties of copper surfaces can be additionally enhanced by targeted surface functionalization. © 2020 The Authors. Advanced Materials Interfaces published by Wiley-VCH GmbH

2021, Schüpfer, Dominique B., Badaczewski, Felix, Peilstöcker, Jan, Guerra-Castro, Juan Manuel, Shim, Hwirim, Firoozabadi, Saleh, Beyer, Andreas, Volz, Kerstin, Presser, Volker, Heiliger, Christian, Smarsly, Bernd, Klar, Peter J.

The preparation of carbons for technical applications is typically based on a treatment of a precursor, which is transformed into the carbon phase with the desired structural properties. During such treatment the material passes through several different structural stages, for example, starting from precursor molecules via an amorphous phase into crystalline-like phases. While the structure of non-graphitic and graphitic carbon has been well studied, the transformation stages from molecular to amorphous and non-graphitic carbon are still not fully understood. Disordered carbon often contains a mixture of sp3-, sp2-and sp1-hybridized bonds, whose analysis is difficult to interpret. We systematically address this issue by studying the transformation of purely sp3-hybridized carbons, that is, nanodiamond and adamantane, into sp2-hybridized non-graphitic and graphitic carbon. The precursor materials are thermally treated at different temperatures and the transformation stages are monitored. We employ Raman spectroscopy, WAXS and TEM to characterize the structural changes. We correlate the intensities and positions of the Raman bands with the lateral crystallite size La estimated by WAXS analysis. The behavior of the D and G Raman bands characteristic for sp2-type material formed by transforming the sp3-hybridized precursors into non-graphitic and graphitic carbon agrees well with that observed using sp2-structured precursors.