1,720,980 research outputs found
Electrically Powered Dissipative Hydrogel Networks Reveal Transient Stiffness Properties for Out-of-Equilibrium Operations
No full textLiving systems use dissipative processes to enable precise spatiotemporal control over various functions, including the transient modulation of the stiffness of tissues, which, however, is challenging to achieve in soft materials. Here, we report a new platform to program hydrogel films with tunable, time-dependent mechanical properties under out-of-equilibrium conditions, powered by electricity. We show that the lifetime of the transient network of a surface-confined hydrogel film can be effectively controlled by programming the generation of an electrochemically oxidized mediator in the presence of a chemical or photoreducing agent in solution. It is, therefore, electrically possible to direct the transient stiffening or softening of the hydrogel film, enabling high modularity of the material functions with precise spatiotemporal control. Temporally controlled operations of the hydrogel films are demonstrated for the on-demand, dose-controlled release of multiple model protein payloads from electrode arrays using the present electrically powered dissipative system. This demonstration of electrically driven transient modulation of the stiffness properties of hydrogel films represents an important step toward the engineering of dissipative materials for developing future biomedical applications that can harness the temporal, adaptive properties of this new class of materials
Nanozyme-Cellulose Hydrogel Composites Enabling Cascade Catalysis for the Colorimetric Detection of Glucose
Full text linkCatalytic cascades obtained from the combination of nanozymes, which are nanomaterials with enzyme-like activity, and natural enzymes have drawn much attention for biosensing and biomedical applications. A key consideration in the development of cascade reaction systems is the integration of nanozymes with enzymes to boost the overall catalytic performance. Here, we report an efficient one-pot approach for the preparation of an enzyme-nanozyme hydrogel composite for cascade catalysis. Prussian blue (PB) nanoparticles (NPs) were prepared by using mild synthetic conditions in a cellulose-based hydrogel network in the presence of glucose oxidase (GOx), resulting in the simultaneous immobilization of PB NPs and active GOx in the hydrogel. This integrated system not only displays peroxidase-like activity relative to the PB NPs but also reveals an enhanced cascade catalytic performance for the colorimetric detection of glucose due to the proximity effect of the enzyme-nanozyme system within the hydrogel matrix. Compared to the analogue mixture with GOx in solution, the composite hydrogel shows enhanced glucose detection and improved stability. The developed colorimetric assay was successfully applied for the analysis of glucose in human serum samples, demonstrating its potential in clinical diagnosis. The versatility of this one-pot protocol holds promise for the development of different multienzyme systems, leading to efficient cascade catalysis for sensing applications
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Spatially oriented and reversible surface assembly of single-walled carbon nanotubes: a strategy based on p-p interactions
Full text linkPorous hydrogel scaffolds integrating Prussian Blue nanoparticles: A versatile strategy for electrochemical (bio)sensing
No full textHydrogels have emerged as promising porous soft materials from which to develop a wide range of biosensing platforms due to the possibility to easily engineer their properties and to effectively immobilize enzymes and nanomaterials in their matrix. Despite their attractive properties, the ability to form stable hydrogel films integrating well–dispersed catalytic nanomaterials and enzymes on electrode surfaces is still required to enable their implementation into electrochemical biosensors. Here, we report a facile approach to prepare hydrogel films embedding Prussian Blue nanoparticles (PBNPs) and different enzymes on electrode surfaces for electrochemical biosensing. A one-pot strategy was employed for the synthesis, under mild conditions, of PBNPs and the simultaneous immobilization of enzymes in a highly functionalized carboxymethyl cellulose matrix, yielding homogeneous hydrogel composites. Highly porous hydrogel films were successfully prepared by drop casting the hydrogel composites on the surface of flexible screen–printed electrodes (SPEs). Due to the high loading of well–dispersed PBNPs, the hydrogel films demonstrated good electrocatalytic activity for both the oxidation of NADH and the reduction of hydrogen peroxide resulting in high detection sensitivity. Two amperometric biosensors for the rapid detection of glucose and ethanol in serum were realized by employing hydrogel composites integrating glucose oxidase and alcohol dehydrogenase. By combining the unique features of hydrogels on flexible electrochemical strips, our approach holds great promise for the development of portable electrochemical (bio)sensors, which are easy to fabricate and versatile for the detection of a variety of analytes
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Scleroglucan/borax gel based immobilization: a new tool for protein electron transfer characterization
No full textInsights into the Gelation Mechanism of Metal-Coordinated Hydrogels by Paramagnetic NMR Spectroscopy and Molecular Dynamics
Full text linkMetal-coordination complexes are attracting increasing attention as supramolecular cross-linkers to develop polymeric hydrogel networks with tunable and dynamic mechanical properties. Nonetheless, the rational design of these materials is still hindered by the limited mechanistic understanding of how metal-ligand interactions influence the structure and properties of the hydrogel. Here, we report a detailed mechanistic investigation using nuclear magnetic resonance (NMR) spectroscopy combined with molecular dynamics (MD) simulations to explore the formation of cellulose-based hydrogels induced by coordination with paramagnetic Fe3+ ions. We demonstrate how NMR paramagnetic relaxation enhancement can be used to probe the distances between the metal center and NMR active nuclei on the polymer chain, informing on the metal-ligand coordination network. Experimental results, together with supporting MD simulations, allow us to uncover a structuration of water around the cross-linked metals within the hydrogel, in addition to the establishment of different orientations of the chains governed by hydrogen bonds networks. Progress in understanding the gelation mechanism of metal-coordinated hydrogels will fuel their exploitation for a wide variety of biomedical applications
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