1. Name：Role of lipopolysaccharides and lipoteichoic acids on C-Chrysophsin-1 interactions with model Gram-positive and Gram-negative bacterial membranes
Authors：Todd E. Alexander, Ian M. Smith, Zachary W. Lipsky, Lindsay D. Lozeau and Terri A. Camesano
Abstract：Antimicrobial peptides (AMPs) are attractive as biomaterial coatings because they have broad spectrum activity against different microbes, with a low likelihood of incurring antimicrobial resistance. Direct action against the bacterial membrane is the most common mechanism of action (MOA) of AMPs, with specific MOAs dependent on membrane composition, peptide concentration, and environmental factors that include temperature. Chrysophsin-1 (CHY1) is a broad spectrum salt-tolerant AMP that is derived from a marine fish. A cysteine modification was made to the peptide to facilitate attachment to a surface, such as a biomedical device. The authors used quartz crystal microbalance with dissipation monitoring to study how temperature (23 and 37 °C) and lipid composition influence the MOA of cysteine-modified peptide (C-CHY1) with model membranes comprised of supported lipid bilayers (SLBs). These two temperatures were used so that the authors could better understand the differences in behavior between typical lab temperatures and physiologic conditions. The authors created model membranes that mimicked properties of Gram-negative and Gram-positive bacteria in order to understand how the mechanisms might differ for different types of bacterial systems. SLB models of Gram-positive bacterial membranes were formed using combinations of phosphatidylcholine, phosphatidylglycerol (PG), and S. aureus-derived lipoteichoic acid (LTA). SLB models of Gram-negative bacterial membranes were formed using combinations of phosphatidylethanolamine (PE), PG, and E. coli-derived lipopolysaccharides (LPS). The molecules that distinguish Gram-positive and Gram-negative membranes (LTA and LPS) have the potential to alter the MOA of C-CHY1 with the SLBs. The authors’ results showed that the MOA for the Gram-positive SLBs was not sensitive to temperature, but the LTA addition did have an effect. Specifically, similar trends in frequency and dissipation changes across all overtones were observed, and the same mechanistic trends were observed in the polar plots at 23 and 37 °C. However, when LTA was added, polar plots showed an association between C-CHY1 and LTA, leading to SLB saturation. This was demonstrated by significant changes in dissipation, while the frequency (mass) was not increasing after the saturation point. For the Gram-negative SLBs, the composition did not have a significant effect on MOA, but the authors saw more differences between the two temperatures studied. The authors believe this is due to the fact that the gel-liquid crystal transition temperature of PE is 25 °C, which means that the bilayer is more rigid at 23 °C, compared to temperatures above the transition point. At 23 °C, a significant energetic shift would be required to allow for additional AMP insertion. This could be seen in the polar plots, where there was a steep slope but there was very little mass addition. At 37 °C, the membrane is more fluid and there is less of an energetic requirement for insertion. Therefore, the authors observed greater mass addition and fewer changes in dissipation. A better understanding of C-CHY1 MOA using different SLB models will allow for the more rational design of future therapeutic solutions that make use of antimicrobial peptides, including those involving biomaterial coatings.
2. Name：Acoustic methodology for selecting highly dissipative probes for ultra-sensitive DNA detection
Authors：Dimitra Milioni, Pablo Mateos-Gil, George Papadakis, Achilleas Tsortos, Olga Sarlidou and Electra Gizeli
Abstract：The objective of this work is to present a methodology for the selection of nanoparticles such as liposomes to be used as acoustic probes for the detection of very low concentrations of DNA. Liposomes, applied in the past as mass-amplifiers and detected through frequency measurement, are employed in the current work as probes for energy dissipation enhancement. Since the dissipation signal is related to the structure of the sensed nano-entity, a systematic investigation of the geometrical features of the liposome/DNA complex was carried out. We introduce the parameter of dissipation capacity by which several sizes of liposome and DNA structures were compared with respect to their ability to dissipate acoustic energy at the level of a single molecule/particle. Optimized 200 nm liposomes anchored to a dsDNA chain led to an improvement of the limit of detection (LoD) by 3 orders of magnitude when compared to direct DNA detection, with the new LoD being 1.2 fmol (or 23 fg/μl or 2 pM). Dissipation monitoring was also shown to be 8 times more sensitive than the corresponding frequency response. The high versatility of this new methodology is demonstrated in the detection of genetic biomarkers down to 1-2 target copies in real samples such as blood. This study offers new prospects in acoustic biosensing detection with potential use in real world diagnostics.
3. Name：Zwitterion Surface-functionalized Thermoplastic Polyurethane for Antifouling Catheter Applications
Authors：SP Nikam, peiru chen, K Nettleton, YH Hsu and ML Becker
Abstract：Immobilizing zwitterionic molecules on material surfaces has been a promising strategy for creating antifouling surfaces. Herein, we show the ability to surface derivatize an allyl ether functionalized thermoplastic polyurethane (TPU) with a zwitterionic thiol in a radically-induced thiol-ene reaction. The thermoplastic polyurethane was synthesized to have an allyl ether side functionality using a modified chain extender molecule. The Zwitterion surface-functionalization was achieved via thiol-ene reaction in aqueous conditions. The presence of chemically tethered zwitterion moieties on the TPU surface was confirmed using X-ray photoelectron spectroscopy (XPS). Protein adsorption experiments via quartz crystal microbalance (QCM) show reduced fibrinogen attachment for the zwitterion-derivatized TPU when compared to its unfunctionalized controls. The Zwitterion-TPU also showed a log scale reduction in bacterial adherence. For P. aeruginosa and S. epidermidis, the Zwitterion-TPU resulted in around a 40% and 50% lower bacterial biomass accumulation, respectively over the timescale of the experiment. The fibroblast cell viability of TPU remained unaffected by functionalization with zwitterion thiol. Results from our model experiments suggest a zwitterion modified TPU is a promising candidate for antifouling catheters.
4. Name：Adsorption behavior of anionic surfactants to silica surfaces in the presence of calcium ion and polystyrene sulfonate
Authors： Zilong Liu, Pegah Hedayati, Ernst J.R. Sudhölter, Robert Haaring, Abdur Rahman Shaik and Naveen Kumar
Journal：Colloids and Surfaces A: Physicochemical and Engineering Aspects
Abstract：Adsorption behavior of surfactants to rock surfaces is an important issue in oil recovery, especially in the process of surfactant flooding. The surfactant loss through adsorption to rock surfaces makes such process economically less feasible. Here, we investigated the adsorption behavior of anionic surfactants (alcohol alkoxy sulfate, AAS) onto silica with quartz crystal microbalance with dissipation monitoring. The results demonstrated that the surfactant adsorption followed the Langmuir adsorption isotherm. Up to solution pH 10, surfactant adsorption slightly increased with increasing pH. The higher pH leads to more anionic surface sites for binding with an anionic surfactant with the help of a calcium cation bridging. The amount of anionic surfactant binding also increases with increasing calcium ion concentration up to 50 mM. It was found that sodium ions were able to exchange calcium ions near the silica surface, which would reduce the affinity for surfactant adsorption. The effect of the polyanion polystyrene sulfonate (PSS) on the anionic AAS adsorption was investigated to learn the possible competitive adsorptions. Indeed, this was found. Upon addition of 50 ppm PSS to a 0.05 wt% AAS containing solution, the adsorption of AAS was reduced by about 85%. The obtained results show the interplay of different interacting species affecting the overall degree of anionic surfactant adsorption to silica surfaces. Optimal tuning of the process conditions according to these results will contribute to a more efficient use of anionic surfactants in enhanced oil recovery.
5. Name：In Situ Probing Unusual Protein Adsorption Behavior on Electrified Zwitterionic Conducting Polymers
Authors：Jhih‐Guang Wu, Shu‐Chen Wei and Shyh‐Chyang Luo
Journal：Advanced Materials Interface
Abstract：Understanding the phenomenon of protein adsorption on electrified conducting polymer‐based electrodes is an important issue in organic bioelectronics. To investigate both specific and nonspecific protein adsorption on electrified electrodes, C‐reactive protein (CRP) binding behavior is measured in situ and is compared with the nonspecific binding of bovine serum albumin and lysozyme on electrified phosphorylcholine‐functionalized poly(3,4‐ethylenedioxythiophene) (poly(EDOT‐PC)) by using an electrochemical quartz crystal microbalance with dissipation (EQCM‐D) and an electrochemical atomic force microscopy (EC‐AFM). According to the result of EQCM‐D, an unexpected enhancement is observed in the CRP binding on the electrified poly(EDOT‐PC) when both −0.5 and 0.5 V (versus Ag/AgCl) potentials are applied to poly(EDOT‐PC). Furthermore, an EC‐AFM is used to in situ map the surface topography and modulus of poly(EDOT‐PC) under the application of surface potentials. Together with EQCM‐D measurements, the large enhancement of CRP binding can be visualized as the formation of a loose and thick CRP multilayer of low surface modulus, high root‐mean‐square roughness, and high dissipation when a potential of 0.5 V is subjected to poly(EDOT‐PC). It is concluded that the enhancement in CRP binding is mainly attributed to the synergistic effect of specific protein recognition and electrostatic interaction between the CRP and poly(EDOT‐PC).
6. Name：Planar sucrose substrates for investigating interfaces found in molten chocolate
Authors：Iva Manasi, Tom Arnold, Joshaniel F.K.Cooper, Isabella Van Damme, Chuchuan Dong, Thomas Saerbeck, Gavin B.G.Stenning, James Tellam and Simon Titmuss
Abstract：We present planar substrates suitable for investigating the sucrose/triglyceride fat interfaces found in molten chocolate with surface science techniques. The planar sucrose substrates are produced by spin coating sucrose onto hydrophilic, silicon oxide-capped, silicon substrates from millimolar aqueous solutions of sucrose. We present the characterisation of the sucrose film thicknesses and crystallinity using X-ray reflectivity and grazing incidence X-ray diffraction, respectively. These sucrose-coated substrates can be used in flow cells for quartz crystal microbalance with dissipation (QCM-D) and neutron/X-ray reflectivity measurements, through which triglyceride oils containing the surfactants commonly used in chocolate manufacture can be flowed. This provides a well-defined, planar, sucrose/triglyceride interface, which can be used to probe the solid/liquid interfaces that are found in molten chocolate at the molecular level.
7. Name：Pickering high internal phase emulsion costabilized by a low amount of bio-based rigid surfactant with microsilica via depletion interaction and synergistic effect
Authors：Xiong Zhang, Kangle Jia, Lei Zhang, Junjie Zhang, Yongqiang Dai, Longfei Yu, Wu Wen and Yuliang Mai
Journal：Journal of Molecular Liquids
Abstract：A series of green bio-based polyether surfactant were synthesized based on dehydroabietic acid and used to construct Pickering high internal phase emulsions (HIPEs) with microsilica particles which the dispersed phase fraction could up to 90%. Such surfactants have a high surface activity so that the Pickering HIPEs could be stabilized stably at low concentrations with micron-size silica. The microstructure, droplet size and rheology property of Pickering HIPEs could be regulated by varying the microsilica content or dispersed phase fraction. The QCM-D measurements revealed that the nonionic surfactant could adsorb on surface of silica particles, giving rise to the change of wettability of the hydrophilic particles and rendering the particles surface-active. The coated particles were more likely to adsorb at the oil-water interface of droplets. The synergistic effects of hydrophilic silica particles and this nonionic surfactant promoted the formation of stable Pickering HIPEs. Moreover, the depletion interaction between droplets and hydrophilic particles was also the vital factor in the stability of the Pickering HIPEs. Once particles were adsorbed, particles at the interface were inhibited desorption by depletion attraction. This work suggests another possible mechanism for better stability of Pickering HIPEs in nonionic surfactant/particles system, and our strategy to preparing Pickering HIPEs is environmentally friendly by using a bio-based surfactant, which has wide potential application in cosmetics, pharmaceuticals, food, environmental protection, materials, and so on.
8. Name：Enzymatically degradable, starch-based layer-by-layer films: application to cytocompatible single-cell nanoencapsulation
Authors：Hee Chul Moon, Sol Han, João Borges, Tamagno Pesqueira, Hyunwoo Choi, Sang Yeong Han, Hyeoncheol Cho, Ji Hun Park, João F. Mano and Insung S. Choi
Abstract：The build-up and degradation of cytocompatible nanofilms in a controlled fashion have great potential in biomedical and nanomedicinal fields, including single-cell nanoencapsulation (SCNE). Herein, we report the fabrication of biodegradable films of cationic starch (c-ST) and anionic alginate (ALG) by electrostatically driven layer-by-layer (LbL) assembly technology and its application to the SCNE. The [c-ST/ALG] multilayer nanofilms, assembled either on individual Saccharomyces cerevisiae or on the 2D flat gold surface, degrade on demand, in a cytocompatible fashion, via treatment with α-amylase. Their degradation profiles are investigated, while systematically changing the α-amylase concentration, by several surface characterization techniques, including quartz crystal microbalance with dissipation monitoring (QCM-D) and ellipsometry. DNA incorporation in the LbL nanofilms and its controlled release, upon exposure of the nanofilms to an aqueous α-amylase solution, are demonstrated. The highly cytocompatible nature of the film-forming and -degrading conditions is assessed in the c-ST/ALG-shell formation and degradation of S. cerevisiae. We envisage that the cytocompatible, enzymatic degradation of c-ST-based nanofilms paves the way for developing advanced biomedical devices with programmed dissolution in vivo.
9. Name：Single-vesicle imaging reveals lipid-selective and stepwise membrane disruption by monomeric α-synuclein
Authors：Jonas K. Hannestad, Sandra Rocha, Björn Agnarsson, Vladimir P. Zhdanov, Pernilla Wittung-Stafshede and Fredrik Höök
Abstract：The interaction of the neuronal protein α-synuclein with lipid membranes appears crucial in the context of Parkinson’s disease, but the underlying mechanistic details, including the roles of different lipids in pathogenic protein aggregation and membrane disruption, remain elusive. Here, we used single-vesicle resolution fluorescence and label-free scattering microscopy to investigate the interaction kinetics of monomeric α-synuclein with surface-tethered vesicles composed of different negatively charged lipids. Supported by a theoretical model to account for structural changes in scattering properties of surface-tethered lipid vesicles, the data demonstrate stepwise vesicle disruption and asymmetric membrane deformation upon α-synuclein binding to phosphatidylglycerol vesicles at protein concentrations down to 10 nM (∼100 proteins per vesicle). In contrast, phosphatidylserine vesicles were only marginally affected. These insights into structural consequences of α-synuclein interaction with lipid vesicles highlight the contrasting roles of different anionic lipids, which may be of mechanistic relevance for both normal protein function (e.g., synaptic vesicle binding) and dysfunction (e.g., mitochondrial membrane interaction).
10. Name：Bubble attachment to cellulose and silica surfaces of varied surface energies: wetting transition and implications in foam forming
Authors：Annika E. Ketola, Wenchao Xiang, Tuomo Hjelt, Heikki Pajari, Tekla Tammelin, Orlando J. Rojas and Jukka Aukusti Ketoja
Abstract：To better understand the complex system of wet foams in the presence of cellulosic fibers, we investigate bubble-surface interactions by following the effects of surface hydrophobicity and surface tension on the contact angle of captive bubbles. Bubbles are brought into contact with model silica and cellulose surfaces immersed in solutions of a foaming surfactant (sodium dodecyl sulfate, SDS) of different concentrations. It is observed that bubble attachment is controlled by surface wetting but a significant scatter in the behavior occurs near the transition from partial to complete wetting. For chemically homogeneous silica surfaces, this transition during bubble attachment is described by the balance between energy changes of the immersed surface and the frictional surface tension of the moving three-phase contact line. The situation is more complex with chemically heterogeneous, hydrophobic trimethylsilyl cellulose (TMSC). TMSC regeneration, which yields hydrophilic cellulose, causes a dramatic drop in bubble contact angle. Moreover, a high interfacial tension is required to overcome the friction caused by microscopic (hydrophilic) pinning sites of the three-phase contact line during bubble attachment. A simple theoretical framework is introduced to explain our experimental observations.
11. Name：Antifouling and antimicrobial coatings based on sol–gel films
Authors：Tal Zada, Meital Reches and Daniel Mandler
Journal：Journal of Sol-Gel Science and Technology
Abstract：Biofouling is an undesirable process in which biological molecules and organisms adhere to a surface. This process causes severe negative effects in various fields including healthcare, water distillation, and marine transportation. Therefore, its prevention is highly explored. Here, the prevention of biofouling by thin films, based on different sol–gel precursors, was studied. Specifically, films were formed by methyltrimethoxysilane (MTMOS), phenyltrimethoxysilane (PTMOS), 3,3,3-trifluropropyltrimethoxysilane (FTMOS), or 3-aminopropyltrimethoxysilane (APTMS) using spin-coating on glass. We found that hydrophobicity alone showed a moderate effect on the number of adsorbed bacteria onto the surface. The APTMS film showed, as expected, antibacterial properties and its combination with FTMOS led to a significant prevention of protein and bacterial adsorption. These results emphasize that a dual effect of antifouling and antibacterial properties, is preferred in the prevention of biomass on surfaces.
12. Name：Preparation of debranched starch nanoparticles by ionic gelation for encapsulation of epigallocatechin gallate
Authors：Qing Liu, Wei Cai, Tianyuan Zhen, Na Ji, Lei Dai, Liu Xiong and Qingjie Sun
Journal：International Journal of Biological Macromolecules
Abstract：Starch nanoparticles are promising candidates for the delivery of active compounds or drugs. The purpose of this study was to prepare nanoparticles from debranched starch using an ionic gelation method. Negatively charged carboxymethyl debranched starch (CMDBS) was obtained by modification of debranched starch (DBS). The zeta potential value of CMDBS with a degree of substitution of 0.81 was approximately −26 mV. The starch nanoparticles formed from 2 mg mL−1 CMDBS and cationized DBS (CDBS) had particle sizes of 50 to 100 nm, as determined by transmission electron spectroscopy, and most nanoparticles were spherical in shape. Measurements with a quartz crystal microbalance with dissipation monitoring confirmed a successful adsorption interaction between the negatively charged CMDBS and positively charged CDBS. Epigallocatechin gallate (EGCG) was successfully incorporated into the nanoparticles with the highest encapsulation efficiency of 84.4%, and the resulting nanoparticles showed controlled release of EGCG into simulated gastric and intestinal fluids.
13. Name：Unraveling how nanoscale curvature drives formation of lysozyme protein monolayers on inorganic oxide surfaces
Authors： Abdul Rahim Ferhan, Bo Kyeong Yoon, Won-Yong Jeon, Joshua A.Jackman, and Nam-JoonCho
Journal：Applied Materials Today
Abstract：The development of nanostructured material interfaces is critical to various application areas spanning diverse fields such as medicine, energy, and sensing. One of the most promising areas involves nanomedicine and drug delivery and involves the formation of noncovalently adsorbed protein coatings on nanostructured surfaces such as inorganic nanoparticles. The coatings can form naturally as part of the so-called protein corona or be purposely incorporated as functional elements to evade immune recognition or to enable enzymatic function, for example. To date, most relevant studies have examined the underlying adsorption processes on planar surfaces while the effect of nanoscale curvature on protein adsorption is still being unraveled across many dimensions. Herein, we investigated the ionic strength-dependent adsorption of antibacterial lysozyme protein onto planar and nanostructured silicon oxide surfaces by employing the quartz crystal microbalance-dissipation and localized surface plasmon resonance sensing techniques. Our findings revealed that lysozyme undergoes greater adsorption-related denaturation and spreading on planar surfaces which led to multilayer formation, while nanoscale curvature effects suppress protein denaturation on nanostructured surfaces leading to monolayer formation. We discuss these findings within the context of protein-surface and protein-protein interactions and how subtle changes in adsorption pathways can drive the formation of distinct macromolecular assemblies. Looking forward, we also discuss how such measurement strategies can enable mechanistic insights into the formation of protein coatings on nanostructured surfaces with broad implications for nano-bio interface science.
14. Name：Role of surfactants in spontaneous displacement of high viscosity oil droplets from solid surfaces in aqueous solutions
Authors：Rui Li, Rogerio Manica, Yi Lu and Zhenghe Xu
Journal：Journal of Colloid and Interface Science
Displacement of oil droplets receding from solid surfaces in aqueous solutions plays a critical role in many household activities and industrial operations. Surfactants are often involved in these activities to control the displacement process. We hypothesize that the influence of surfactants on the displacement process of oil is highly dependent on the type and dosage of surfactants, with the mechanisms being elucidated by the analysis using appropriate dynamic wetting models.
We systematically investigated the spontaneous displacement of a high viscosity oil on curved hydrophilic glass surfaces in aqueous solutions of anionic sodium dodecylbenzene sulfonate, cationic hexadecyl trimethyl ammonium bromide, and nonionic TritonTM X-100 over a wide range of concentrations.
The rather different oil displacement behaviors were observed with different surfactant additions. The displacement dynamics of the receding oil droplet was found to be inhibited by surfactant additions and followed two distinct models quantitatively: the power-law model describing the temporal evolution of early-stage displacement, and the molecular kinetic model describing the dependence of the three-phase contact line displacement velocity on the dynamic contact angle at the late stage of oil displacement. The model-based data analysis provided insights on the role of surfactants in controlling the oil displacement dynamics.
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