Editorial: Smart Objects and Technologies for Social Good (GOODTECHS 2017)

Mobile Networks and Applications -     

Self‐Assembled pH‐Sensitive Fluoromagnetic Nanotubes as Archetype System for Multimodal Imaging of Brain Cancer

Fluoromagnetic systems are recognized as an emerging class of materials with great potential in the biomedical field. Here, it is shown how to fabricate fluoromagnetic nanotubes that can serve as multimodal probes for the imaging and targeting of brain cancer. An ionic self‐assembly strategy is used to functionalize the surface of synthetic chrysotile nanotubes with pH‐sensitive fluorescent chromophores and ferromagnetic nanoparticles. The acquired magnetic properties permit their use as contrast agent for magnetic resonance imaging, and enable the tracking of tumor cell migration and infiltration responsible for metastatic growth and disease recurrence. Their organic component, changing its fluorescence attitude as a function of local pH, targets the cancer distinctive acidity, and allows localizing and monitoring the tumor occurrence and progression by mapping the acidic spatial distribution within biopsy tissues. The fluoromagnetic properties of nanotubes are preserved from the in vitro to the in vivo condition and they show the ability to migrate across the blood brain barrier, thus spontaneously reaching the brain tumor after injection. The simplicity of the synthesis route of these geomimetic nanomaterials combined with their demonstrated affinity with the in vivo condition strongly highlights their potential for developing effective functional materials for multimodal theranostics of brain cancer.     

Polyformamidine‐Derived Non‐Noble Metal Electrocatalysts for Efficient Oxygen Reduction Reaction

A facile approach for the template‐free synthesis of highly active non‐noble metal based oxygen reduction reaction (ORR) electrocatalysts is presented. Porous Fe?N?C/Fe/Fe₃C composite materials are obtained by pyrolysis of defined precursor mixtures of polyformamidine (PFA) and FeCl₃ as nitrogen‐rich carbon and iron sources, respectively. Selection of pyrolysis temperature (700–1100 °C) and FeCl₃ loading (5–30 wt%) yields materials with differing surface areas, porosity, graphitization degree, nitrogen and iron content, as well as ORR activity. While the ORR activity of Fe‐free materials is limited (i.e., synthesized from pure PFA), a huge increase in activity is observed for catalysts containing Fe, revealing the participation of the metal dopant in the construction of active electrocatalytic sites. Further activity improvement is achieved via acid‐leaching and repeated pyrolysis, a result which is attributed to the creation of new active sites located at the surface of the porous nitrogen‐doped carbon by dissolution of the Fe and Fe₃C nanophases. The best performing catalyst, which was synthesized with a low Fe loading (i.e., 5 wt%) and at a pyrolysis temperature of 900 °C, exhibits high activity, excellent H₂O selectivity, extended stability, in both basic and acidic media as well as a remarkable tolerance toward methanol.     

Thermal stability of end‐capped and linear sulfonated polyimides,sulfonated polystyrene,and Nafion 117

The thermal stability of end‐caped and linear sulfonated polyimides (SPIs), sulfonated polystyrene (SPS), and a sulfonated perfluorinated hydrocarbon, Nafion 117, and the corresponding triethylammonium sulfonate salts was investigated by dynamic and isothermal thermogravimetric analysis (TGA). Gas chromatographic‐mass spectrographic analysis (GC/MS) of the sulfonated polymers and the salts to determine the volatiles released from acid and salt groups over a temperature range 200–275 °C was also investigated. GC/MS analysis reveals that water and sulfur dioxide volatiles are released from the sulfonic acids and water, sulfur dioxide and triethyl amine are released from the sulfonate salts. Dynamic and isothermal TGA studies based on weight loss revealed that the SPIs exhibited superior thermal stability than SPS and Nafion 117 sulfonic acids. However, dynamic TGA curves to determine the onset decomposition temperature of the sulfonic acid group reveal that Nafion 117 and SPS sulfonic acids exhibited greater thermal stabilities than the SPIs. The mechanisms of sulfonic acid and triethylammonium sulfonate salt decompositions based on GC/MS, ¹³C‐NMR, and dynamic TGA curves are proposed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45694.     

Effects of the Protonation State of Titratable Residues and the Presence of Water Molecules on Nocodazole Binding to β‐Tubulin

Regulation of microtubule assembly by antimitotic agents is a potential therapeutic strategy for the treatment of cancer, parasite infections, and neurodegenerative diseases. One of these agents is nocodazole (NZ), which inhibits microtubule polymerization by binding to β‐tubulin. NZ was recently co‐crystallized in Gallus gallus tubulin, providing new information about the features of interaction for ligand recognition and stability. In this work, we used state‐of‐the‐art computational approaches to evaluate the protonation effects of titratable residues and the presence of water molecules in the binding of NZ. Analysis of protonation states showed that residue E198 has the largest modification in its pK_a value. The resulting E198 pK_a value, calculated with pH‐REMD methodology (pK_a=6.21), was higher than the isolated E amino acid (pK_a=4.25), thus being more likely to be found in its protonated state at the binding site. Moreover, we identified an interaction between a water molecule and C239 and G235 as essential for NZ binding. Our results suggest that the protonation state of E198 and the structural water molecules play key roles in the binding of NZ to β‐tubulin.     

Challenging Google Search filter bubbles in social and political information: Disconforming evidence from a digital methods case study

This article engages in the debate on supposed online ‘filter bubbles’ by analysing a panel of Google users’ search results on a standardized set of socio-politically themed search queries. In general, the query results appear to be dominated by mainstream media sources, followed at a large distance by civil society and government resources. By means of mixed model regression analyses, with the prominence of different source types in the search results as dependent variables, it was tested whether search results vary across Google Search users. The results indicate that the inclusion of participants as a random effect does not explain variance when controlling for the different query keywords and the time at which the queries were ran. Hence, this study does not support the occurrence of ‘filter bubbles’ in Google Search results in the context of social and political information.     

Bacteria-hemocyte interactions and phagocytosis in marine bivalves

Marine bivalves (such as mussels, oysters, and clams) are widespread mollusks in coastal waters at different latitudes; due to their filter-feeding habits, they accumulate large numbers of bacteria from the harvesting waters and may act as passive carriers of human pathogens. To cope with this challenge, bivalves possess both humoral and cellular defense mechanisms with remarkably effective capabilities. The circulating cells, or hemocytes, are primarily responsible for defense against parasites and pathogens; microbial killing results from the combined action of the phagocytic process with humoral defense factors such as agglutinins (e.g., lectins), lysosomal enzymes (e.g., acid phosphatase, lysozyme), toxic oxygen intermediates, and various antimicrobial peptides. In this work, current knowledge of the mechanisms underlying the interactions between bacteria and the hemolymph components of marine bivalves is summarized. Bacterial susceptibility to hemolymph killing in different bivalve species may be a consequence of the different ability of bacterial products to attract phagocytes, the presence or absence of specific opsonizing molecules, the hemocyte capability to bind and engulf different bacteria, and the different bacterial sensitivity to intracellular killing. The role of soluble (e.g., agglutinins and opsonins) and surface-bound factors in bacterial phagocytosis by hemocytes of the most common marine bivalve species is described and the possibility that environmental temperatures and other seasonal factors may influence this process is considered. Moreover, the potential strategies used by bacteria to evade phagocytic killing by hemocytes are discussed. From the available data it is clear that several questions need further investigation; the elucidation of the factors influencing phagocytosis in bivalves and the fundamental strategies used by bacteria to escape hemolymph killing are important not only to understand bivalve immune defenses but also to explain the persistence of pathogenic bacteria in bivalve tissues and to predict the consequent impact on human health.     

Comparative analysis of dental enamel polyvinylsiloxane impression and polyurethane casting methods for SEM research

Dental casting is a very common procedure for making high-quality replicas of paleo-anthropological remains. Replicas are frequently used, instead of original remains, to study both fossil and extant Primate teeth in morphological and metrical analyses. Several commercial products can be used in molds. This study analyzed SEM image resolution and enamel surface feature definition of tooth molds at various magnification levels and obtained, with both Coltène and 3M low-viscosity body polyvinylsiloxane impression, materials and polyurethane casts. Results, through comparison with the original teeth, show that both the negative molds and the positive casts are highly reliable in replicating enamel surfaces. However, positive cast quality is optimal for SEM observation only till the fourth consecutive replica from the original mold, especially at high SEM magnification levels.     

Structure of His94->Asp carbonic anhydrase II in a new crystalline form reveals a partially occupied zinc binding site

The structure of histidine 94aspartate (H94D) carbonic anhydraseII (CAII) crystallized in an orthorhombic space group has beendetermined to 2.5 Å resolution. This crystal form is notisomorphous with monoclinic wild-type enzyme crystals or withthe monoclinic crystal form of H94D CAII reported earlier [Kiefer,L.L.,Ippolito,J.A., Fierke,C.A. and Christianson,D.W. (1993) J. Am.Chem. Soc., 115, 12581–12582]. In monoclinic H94D CAII,a fully occupied zinc ion is tetrahedrally coordinated by D94,H96, H119 and a water molecule. In orthorhombic H94D CAII, apartially occupied zinc ion is coordinated by H96 and H119 andonly weakly coordinated by a disordered D94 side chain.Thesedifferences are particularly surprising given that the two crystalforms co-precipitate in the same drop in the same experiment.Re-refinement of the orthorhombic crystal form of H94C CAIIand comparison with its corresponding monoclinic crystal formyield similar results. It appears that partial—but notfull—zinc dissociation accompanies the crystallizationof CAII variants in the orthorhombic crystal form, and significantdifferences on the protein surface presumably affect the relativestability of each crystal lattice. These results underscoreanunexpected ambiguity in this protein engineering experiment:which crystal structure of H94D CAII should be correlated withfunctional measurements made in solution?     

Nanoscale Mapping of the Conductivity and Interfacial Capacitance of an Electrolyte-Gated Organic Field-Effect Transistor under Operation

Probing nanoscale electrical properties of organic semiconducting materials at the interface with an electrolyte solution under externally applied voltages is key in the field of organic bioelectronics. It is demonstrated that the conductivity and interfacial capacitance of the active channel of an electrolyte-gated organic field-effect transistor (EGOFET) under operation can be probed at the nanoscale using scanning dielectric microscopy in force detection mode in liquid environment. Local electrostatic force versus gate voltage transfer characteristics are obtained on the device and correlated with the global current–voltage transfer characteristics of the EGOFET. Nanoscale maps of the conductivity of the semiconducting channel show the dependence of the channel conductivity on the gate voltage and its variation along the channel due to the space charge limited conduction. The maps reveal very small electrical heterogeneities, which correspond to local interfacial capacitance variations due to an ultrathin non-uniform insulating layer resulting from a phase separation in the organic semiconducting blend. Present results offer insights into the transduction mechanism at the organic semiconductor/electrolyte interfaces at scales down to ≈100 nm, which can bring substantial optimization of organic electronic devices for bioelectronic applications such as electrical recording on excitable cells or label-free biosensing.