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1.    Name：Mass and charge transport in highly mesostructured polyelectrolyte/ electroactive-surfactant multilayer films

Authors：Esteban Piccinini, Graciela A.González, Omar Azzaroni and Fernando Battaglini

Journal：Journal of Colloid and Interface Science

DOI: 10.1016/j.jcis.2020.07.060

Abstract：

Hypothesis

Dimensionally stable electroactive films displaying spatially addressed redox sites is still a challenging goal due to gel-like structure. Polyelectrolyte and surfactants can yield highly mesostructured films using simple buildup strategies as layer-by-layer. The use of redox modified surfactants is expected to introduce order and an electroactive response in thin films.

Experiments

The assembly of polyacrylic acid and different combinations of redox-modified and unmodified hexadecyltrimethylammonium bromide yields highly structured and electroactive thin films. The growth, viscoelastic properties, mass, and electron transport of these films were studied by combining electrochemical and quartz crystal balance with dissipation experiments.

Findings

Our results show that the films are highly rigid and poorly hydrated. The mass and charge transport reveal that the ingress (egress) of the counter ions during the electrochemical oxidation (reduction) is accompanied with a small amount of water, which is close to their hydration sphere. Thus, the generated mesostructured films present an efficient charge transport with negligible changes in their structures during the electron transfer process. The control over the meso-organization and its stability represents a promising tool in the construction of devices where the vectorial transfer of electrons, or ions, is required.

Link：https://www.sciencedirect.com/science/article/abs/pii/S0021979720309383

2.    Name：Selective solvent filters for non-aqueous phase liquid separation from water

Authors：Tatianna Marshall, Klaudine M. Estepa, Maria Corradini, Alejandro G. Marangoni, Brent Sleep and Erica Pensini

Journal：Scientific Reports

DOI: 10.1038/s41598-020-68920-4

Abstract：Injectable filters permeable to water but impermeable to non-polar solvents were developed to contain non-aqueous phase liquids (NAPL) in contaminated aquifers, hence protecting downstream receptors during NAPL remediation. Filters were produced by injecting aqueous solutions of 0.01% chitosan, hydroxyethylcellulose and quaternized hydroxyethylcellulose into sand columns, followed by rinsing with water. Polymer sorption onto silica was verified using a quartz-crystal microbalance with dissipation monitoring. Fluorescence and gas chromatography mass spectroscopy showed low ppm range concentrations of non-polar solvents (e.g., hexane and toluene) in water eluted from the filters (in the absence of emulsifiers). The contact angles between polymer-coated surfaces and hexane or toluene were > 90°, indicating surface oleophobicity. Organic, polar solvents (e.g. tetrahydrofuran and tetrachloroethylene, TCE) were not separated from water. The contact angles between polymer-coated surfaces and TCE was also > 90°. However, the contact area with polymer coated surfaces was greater for TCE than non-polar solvents, suggesting higher affinity between TCE and the surfaces. Emulsifiers can be used to facilitate NAPL extraction from aquifers. Emulsion separation efficiency depended on the emulsifier used. Emulsions were not separated with classical surfactants (e.g. Tween 20 and oleic acid) or alkaline zein solutions. Partial emulsion separation was achieved with humic acids and zein particles.

Link：https://www.nature.com/articles/s41598-020-68920-4

3.    Name：Responsive Polymer Brush Design and Emerging Applications for Nanotheranostics

Authors：Danyang Li, Lizhou Xu, Jing Wang, and Julien E. Gautrot

Journal：Advanced Healthcare Materials

DOI: 10.1002/adhm.202000953.

Abstract：Responsive polymer brushes are a category of polymer brushes that are capable of conformational and chemical changes in response to external stimuli. They oer unique opportunities for the control of bio−nano interactions due to the precise control of chemical and structural parameters such as the brush thickness, density, chemistry, and architecture. The design of responsive brushes at the surface of nanomaterials for theranostic applications has developed rapidly. These coatings can be generated from a very broad range of nanomaterials, without compromising their physical, photophysical, and imaging properties. Although the use of responsive brushes for nano theragnostic remains in its early stages, in this review, the aim is to present how the systems developed to date can be combined to control sensing, imaging, and controlled delivery of therapeutics. The recent developments for such design and associated methods for the synthesis of responsive brushes are discussed. The responsive behaviors of homo polymer brushes and brushes with more complex architectures are briefly reviewed, before the applications of responsive brushes as smart delivery systems are discussed. Finally, the recent work is summarized on the use of responsive polymer brushes as novel biosensors and diagnostic tools for the detection of analytes and biomarkers.

Link：https://www.pubfacts.com/detail/32893474/Responsive-Polymer-Brush-Design-and-Emerging-Applications-for-Nanotheranostics

4.    Name：Current research progress of mammalian cellbased biosensors on the detection of foodborne pathogens and toxins

Authors：Xin Lu, Yongli Ye, Yinzhi Zhang, Xiulan Sun

Journal：Critical Reviews In Food Science And Nutrition

DOI: 10.1080/10408398.2020.1809341

Abstract：Foodborne diseases caused by pathogens and toxins are a serious threat to food safety and human health; thus, they are major concern to society. Existing conventional foodborne pathogen or toxin detection methods, including microbiological assay, nucleic acid-based assays, immunological assays, and instrumental analytical method, are time-consuming, labor-intensive and expensive. Because of the fast response and high sensitivity, cell-based biosensors are promising novel tools for food safety risk assessment and monitoring. This review focuses on the properties of mammalian cell-based biosensors and applications in the detection of foodborne pathogens (bacteria and viruses) and toxins (bacterial toxins, mycotoxins and marine toxins). We discuss mammalian cell adhesion and how it is involved in the establishment of 3D cell culture models for mammalian cell-based biosensors, as well as evaluate their limitations for commercialization and further development prospects.

Link：https://www.tandfonline.com/doi/full/10.1080/10408398.2020.1809341?scroll=top&needAccess=true

5.    Name：Whey protein gel — mechanical cleaning capability through modelling and experimental testing including compression and wire cutting investigation

Authors：Jintian Liu, Manuel Helbig, Jens-Peter Majschak, Markus Böl

Journal：Journal of Food Engineering

DOI: 10.1016/j.jfoodeng.2020.110324

Abstract：Whey protein has been used extensively to investigate the efficiency of procedures for cleaning dairy production equipment owing to the chemical reaction it undergoes at high temperature, similar to the formation of fouling deposits during heat treatment. In addition to the chemical and thermal aspects, a detailed understanding of the fundamental mechanical and fracture mechanisms that significantly influence the success of the cleaning procedure is indispensable. Consequently, to determine the basis for the mechanical detachment of whey protein isolate, in the present study, the mechanical characteristics and fracture properties of whey protein gels (WPGs) with a protein content of 15% and a treatment temperature of 80 ◦C were determined. For purely mechanical characterization, axial compression and compression relaxation experiments were performed. The results suggest a non-linear stress–stretch behaviour combined with time-dependent mechanical characteristics. To characterize the fracture properties of WPGs, wire cutting experiments were performed. Based on a viscoelastic numerical model and the corresponding parameters identified from the experimental investigations, the cutting procedure of WPGs was simulated by assigning a fracture criterion, and the critical stress was determined based on the measured cutting forces.

Link：https://www.sciencedirect.com/science/article/pii/S0260877420304118

6.    Name：Self-Immobilized Putrescine Oxidase Biocatalyst System Engineered with a Metal Binding Peptide

Authors：Nilan J. B. Kamathewatta, Dwight O. Deay, Banu Taktak Karaca, Steve Seibold, Tyler M. Nguyen, Brandon Tomás, Mark L. Richter, Cindy L. Berrie, and Candan Tamerler

Journal：Langmuir

DOI: 10.1021/acs.langmuir.0c01986

Abstract：Flavin oxidases are valuable biocatalysts for the oxidative synthesis of a wide range of compounds, while at the same time reduce oxygen to hydrogen peroxide. Compared to other redox enzymes, their ability to use molecular oxygen as an electron acceptor offers a relatively simple system that does not require a dissociable coenzyme. As such, they are attractive targets for adaptation as cost-effective biosensor elements. Their functional immobilization on surfaces offers unique opportunities to expand their utilization for a wide range of applications. Genetically engineered peptides have been demonstrated as enablers of the functional assembly of biomolecules at solid material interfaces. Once identified as having a high affinity for the material of interest, these peptides can provide a single step bio assembly process with orientation control, acritical parameter for functional immobilization of the enzymes. In this study, forthe first time, we explored the bio assembly of a putrescine oxidase enzyme using a gold binding peptide tag. The enzyme was genetically engineered to incorporate a gold binding peptide with an expectation of an effective display of the peptide tag to interact with the gold surface. In this work, the functional activity and expression were investigated, along with the selectivity of the binding of the peptide-tagged enzyme. The fusion enzyme was characterized using multiple techniques, including protein electrophoresis, enzyme activity, and microscopy and spectroscopic methods, to verify the functional expression of the tagged protein with near-native activity. Binding studies using quartz crystal microbalance (QCM),nanoparticle binding studies, and atomic force microscopy studies were used to address the selectivity of the binding through the peptide tag. Surface binding AFM studies show that the binding was selective for gold. Quartz crystal microbalance studies show a strong increase in the affinity of the peptide-tagged protein over the native enzyme, while activity assays of protein bound to nanoparticles provide evidence that the enzyme retained catalytic activity when immobilized. In addition to showing selectivity, AFM images show significant differences in the height of the molecules when immobilized through the peptide tag compared to immobilization of the native enzyme, indicating differences in orientation of the bound enzyme when attached via the affinity tag. Controlling the orientation of surface-immobilized enzymes would further improve their enzymatic activity and impact diverse applications, including oxidative biocatalysts, biosensors, biochips, and biofuel production.

Link：https://pubs.acs.org/doi/abs/10.1021/acs.langmuir.0c01986

7.    Name：Synthesis of a Three-Dimensional Interconnected Oxygen-, Boron-, Nitrogen-, and Phosphorus Tetratomic-Doped Porous Carbon Network as Electrode Material for the Construction of a Superior Flexible Supercapacitor

Authors：Lina Ma, Zhijie Bi, Wei Zhang, Zehua Zhang, Yue Xiao, Haijun Niu, and Yudong Huang

Journal：ACS Appl. Mater. Interfaces

DOI: 10.1021/acsami.0c13454

Abstract：To construct a high-performance next-generation carbon-based flexible supercapacitor, high porosity, large mass density, and high flexibility are three significant challenging goals. However, one side always affects another. Herein, high-density tetratomic-doped porous composite carbon derived from sustainable biomaterials is achieved via two-step processes of carbonization and acid-washing treatment. The assembled carbon-based electrodes are highly doped with various heteroatoms (B, O, N, and P) for33.59 atom %, resulting in abundant porosity, high densities, high pseudocapacitive contribution for 84.5%, and superior volumetric capacitive performance. The fabricated flexible electrode exhibits high flexibility, high mass loading (316 mg cm−3), and remarkable tensile strength (44.6 MPa). Generally, the volumetric performance is key and a significant parameter to appraise the electrochemical characteristics of flexible supercapacitors within a limited space. The aqueous symmetric supercapacitor demonstrates a high volumetric energy density and an excellent power density of 2.08 mWh cm−3 and 498.4 mW cm−3, respectively, along with 99.6%capacitance retention after 20 000 cycles, making it competitive to even some pseudo capacitors.

Link: https://pubs.acs.org/doi/abs/10.1021/acsami.0c13454

8.    Name：Wood hemicelluloses exert distinct biomechanical contributions to cellulose fibrillar networks

Authors：Jennie Berglund, Deirdre Mikkelsen, Bernadine M. Flanagan, Sushil Dhital,Stefan Gaunitz, Gunnar Henriksson, Mikael E. Lindström, Gleb E. Yakubov, Michael J. Gidley &Francisco Vilaplana

Journal：Nature Communications

DOI: 10.1038/s41467-020-18390-z

Abstract：Hemicelluloses, a family of heterogeneous polysaccharides with complex molecular structures, constitute a fundamental component of lignocellulosic biomass. However, the contribution of each hemicellulose type to the mechanical properties of secondary plant cell walls remains elusive. Here we homogeneously incorporate different combinations of extracted and purified hemicelluloses (xylans and glucomannans) from softwood and hardwood species into self-assembled networks during cellulose biosynthesis in a bacterial model, without altering the morphology and the crystallinity of the cellulose bundles. These composite hydrogels can be therefore envisioned as models of secondary plant cell walls prior to lignification. The incorporated hemicelluloses exhibit both a rigid phase having close interaction ns with cellulose, together with a flexible phase contributing to the multiscale architecture of the bacterial cellulose hydrogels. The wood hemicelluloses exhibit distinct biomechanical contributions, with glucomannans increasing the elastic modulus in compression, and xylans contributing to a dramatic increase of the elongation at break under tension. These diverging effects cannot be explained solely from the nature of their direct interactions with cellulose, but can be related to the distinct molecular structure of woodxylans and mannans, the multiphase architecture of the hydrogels and the aggregative effects amongst hemicellulose-coated fibrils. Our study contributes to understanding the specific roles of wood xylans and glucomannans in the biomechanical integrity of secondary cell walls in tension and compression and has significance for the development of lignocellulosic materials with controlled assembly and tailored mechanical properties.

Link：https://www.nature.com/articles/s41467-020-18390-z

9.    Name：Dynamic Adsorption of Functionalized Zwitterionic Copolymers on Carbonate Surfaces under Extreme Reservoir Conditions

Authors：Mohammed Kawelah, Yuan He, Haleema Alamri, Ayrat Gizzatov, Timothy M. Swager,

and S. Sherry Zhu

Journal：Energy & Fuels

DOI: 10.1021/acs.energyfuels.0c01423

Abstract：The injection of aqueous polymer solutions into reservoirs for enhanced oil recovery has attracted considerable interest in the petroleum industry. Polymers increase the viscosity of the fluids and thereby improve the volumetric sweep efficiency. However, significant polymer retention in reservoirs by adsorption to surfaces limits the propagation through the reservoir and canreduce the efficiency of the polymer flooding. To explore the structure−property relationships that can direct improvements in future polymer designs, we have investigated the dynamic adsorption of a model system of five zwitterionic copolymers using a quartz crystal microbalance with dissipation and core-flooding experiments at high temperatures and salinities. The results indicate that the degree of dynamic polymer retention is sensitive to a low percentage of functional comonomers on the polymer backbone. The concept of using a small fraction of comonomers to tune the adsorption of polymers is an attractive cost-effective method for modifying the properties of the polymers employed in the oil and gas industry.

Link：https://pubs.acs.org/doi/abs/10.1021/acs.energyfuels.0c01423

10. Name：Effects of Electrokinetic Phenomena on Bacterial Deposition monitored by Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D)

Authors：Yongping Shan, Lu Liu, Yang Liu, Hauke Harms, and Lukas Y. Wick

Journal：Environmental Science & Technology

DOI: 10.1021/acs.est.0c04347

Abstract：Bacterial deposition is the first step in the formation of microbial biofilms in environmental technology, and there is high interest in controlling such deposition. Earlier work indicated that direct electric current (DC) fields could influence bacterial deposition in percolation columns. Here, a time-resolved quartz crystal microbalance with dissipation monitoring (QCM-D) and microscopy-based cell counting were used to quantify DC field effects on the deposition of bacterial strains Pseudomonas putida KT2440 and Pseudomonas fluorescens LP6a at varying electrolyte concentrations and weak electric field strengths (0-2 V cm-1). DC-induced frequency (Δf) shifts, dissipation energy (ΔD), and ratios thereof (Δf/ΔD) proved as good indicators of the rigidity of cell attachment. We interpreted QCM-D signals using a theoretical approach calculating the attractive DLVO-force and the shear and drag forces acting on a bacterium near collector surfaces in a DC electric field. We found that changes in DC-induced deposition of bacteria depended on the relative strengths of electrophoretic drag and electroosmotic shear forces. This could enable the prediction and electrokinetic control of microbial deposition on surfaces in natural and manmade ecosystems.

Link：https://pubs.acs.org/doi/abs/10.1021/acs.est.0c04347