1. Influence of Aptamer Surface Coverage on Small Target Recognition: A SPR and QCM-D Comparative Study
Author: Hannah Macdonald, Hugues Bonnet, Angeline Van Der Heyden, Eric Defrancq, Nicolas Spinelli, Liliane Coche-Guerente, and Jerome Dejeu
Journal: Journal of Physical Chemistry C
DOI: 10.1021/acs.jpcc.9b00845
Abstract: Aptamers have emerged as promising biorecognition elements for the development of biosensors. The present work focused on the direct detection, by surface plasmon resonance (SPR) and quartz crystal microbalance with dissipation monitoring (QCM-D), of a low molecular weight (LMW) compound (less than 200 Da) with an aptamer receptor presented as an oriented monolayer on surface. These techniques are powerful for label-free, real-time characterization and quantification of molecular interactions at interfaces. Herein, we analyzed the influence of aptamer surface density on the recognition properties. A decrease of the surface concentration was shown to improve the recognition properties due to a higher kinetic association constant that could be explained by a limitation of the steric hindrance of the aptamer on the surface. An aptamer folding is produced upon recognition of the LMW target that gives rise to the modification of the layer on the surface. This induces a displacement of water acoustically coupled to the sensing layer, a thickness layer variation and a deviation of the refractive index increment (RII) of the target/aptamer complex from the sum of the RII of individual entities. We also demonstrated that the recognition signal is still detectable for low aptamer density (lower than 1 pmol.cm-2).

2. Adsorption Behavior and Nanotribology of Amine-Based Friction Modifiers on Steel Surfaces
Authors: Prathima C. Nalam, Alex Pham, R. Veronica Castillo, and Rosa M. Espinosa-Marzal
Journal: Journal of Physical Chemistry C
DOI: 10.1021/acs.jpcc.9b02097
Abstract: This work describes the effect of the adsorption behavior of fatty amine-based organic friction modifiers on their tribological performance. The adsorption of four different fatty amines with a varying number of amine functional groups (two vs. three) and different anchoring structures (straight vs. branched) on stainless steel surfaces in n-hexadecane was monitored using quartz crystal microbalance (QCM). It is shown that the fatty amines form weakly adsorbed and disordered boundary films and the molecules lay horizontally on the surface. A higher number of amine functional groups at the anchoring end of the fatty amines results in higher adsorbed masses, however, their larger steric hindrance results in slower adsorption kinetics. Atomic force microscopy shows that the loosely-packed adlayers decrease the adhesion between the tip and the stainless steel surface and yield a linear increase in friction force with load at low loads. Comparing adsorbed masses and adsorption kinetic constants with the coefficients of friction measured by lateral force microscopy reveals that faster surface-adsorption kinetics of the additive molecules enables a more effective healing of the worn track, which dictates the friction force in the boundary lubrication regime.

3. Building polyphenol and gelatin films as implant coating, evaluating from in vitro and in vivo performances
Authors: Shuoshuo Yang Yong Wang，Shan Luo，Chenjie Shan，Yibo Geng，Tinghong Zhang，Sunren Sheng and Xingjie Zan
Journal: Colloids and Surfaces B: Biointerfaces
DOI: 10.1016/j.colsurfb.2019.05.058
Abstract: Bone related implants have huge potential market in global. Improving the implant outcomes and probability of implant success are highly pursued to relieve the pain of patients and burden on native healthy system. There are growing evidence to support reactive oxygen species (ROS) directly involved in bone diseases and failure of implants. Taking advantage of the antioxidant property of tannic acid (TA) and biocompatibility of gelatin (Gel), the TA/Gel multilayer film was fabricated by layer by layer method, and the growing process of this film was monitored by QCM-D. The physical properties of TA/Gel film were further well characterized and modulated. In cellular test, TA/Gel multilayer film displayed good antioxidant properties under ROS stress environment (after H2O2 treatment flourscence intensity increased 38.9-fold for glasses, only ˜6-fold for (TA/Gel)8), facilitating cell attachment, fastening spreading at early stage and accelerating proliferation in beginning 2 day. Area per cell on (TA/ Gel)4-0.15M is 1.5-fold higher than that on glass at 2 h, while it became 2.3-fold higher at 4 h. Moreover, these films performed both enhanced osteogenesis in vitro test and bone formation in vivo in the animal bone implanting model. Our results supported discovered the antioxidant coating played the critical role one the success of bone related implants, which could be particularly noted in the future implant design. And the strategy applied here, utilizing the interactions between polyphenol and proteins to construct multilayer film, will pave the way to fabricating an antioxidant coating.

4. Understanding How Membrane Surface Charge Influences Lipid Bicelle Adsorption onto Oxide Surfaces
Authors: Tun Naw Sut, Joshua A. Jackman and Nam-Joon Cho
Journal: Langmuir
DOI: 10.1021/acs.langmuir.9b00570
Abstract: The adsorption of two-dimensional bicellar disks onto solid supports is an emerging fabrication technique to form supported lipid bilayer (SLBs) that is efficient and requires minimal sample preparation. To date, nearly all relevant studies have focused on zwitterionic lipid compositions and silica-based surfaces, and extending the scope of investigation to other lipid compositions and surfaces would improve our understanding of application possibilities and underpinning formation processes. Herein, using the quartz crystal microbalance-dissipation technique, we systematically investigated the adsorption of charged lipid bicelles onto silicon dioxide, titanium oxide, and aluminum oxide surfaces. Depending on the lipid composition and substrate, we observed different adsorption pathways, including (i) SLB formation via one- or two-step adsorption kinetics, (ii) monotonic adsorption without SLB formation, and (iii) negligible adsorption. On each substrate, SLB formation could be achieved with particular lipid compositions while the trend in adsorption pathways varied according to the substrate and could be controlled by adjusting the bicelle-substrate interaction strength. To rationalize these findings, we discuss how electrostatic and hydration forces affect bicelle-substrate interactions on different oxide surfaces. Collectively, our findings demonstrate the broad utility of lipid bicelles for SLB formation while revealing physicochemical insights into the role of interfacial forces in controlling bicelle adsorption pathways.

5. Supramolecular Self‐Assembly and Organization of Collagen at Solid/Liquid Interface: Effect of Spheroid‐and Rod‐Shaped TiO2 Nanocrystals
Authors: Mathieu Beauvais, Thomas Degabriel, Nesrine Aissaoui, Vincent Dupres, Elodie Colaço, Karim El Kirat, Rute F. Domingos, Dalil Brouri, Claire‐Marie Pradier, Jolanda Spadavecchia and Jessem Landoulsi
Journal: Advanced Materials Interfaces
DOI: 10.1002/admi.201900195
Abstract: The adsorption behavior of collagen on solid surfaces is a process that determines the role of this protein to mediate cell–material interaction. Herein, the mechanism of self‐assembly and organization of collagen on a model substrate is investigated in the presence of TiO2 nanoparticles. In solution, results show that nanoparticles do not alter the conformation of collagen (triple‐helix), and slightly delay the kinetics of its self‐assembly. In the adsorbed state, by exploring the dewetting patterns of collagen layers from atomic force microscopy (AFM) images, a method is developed to extract parameters describing the characteristics of collagen networks. It is shown that collagen layer is strongly impacted by the presence of nanoparticles in the medium. These results are consistent with the analysis of the protein layers in the hydrated state, showing a rigidification, as observed by quartz crystal microbalance with dissipation monitoring (QCM‐D), and the formation of shorter and/or less extended fibrillar structures with a lower surface density, as probed by AFM force spectroscopy. The approach described here provides a reconciliation between disparate views of collagen layers’ characterization in the dried and the hydrated states. It also offers new perspectives to assess the impact of nanoparticles on the organization of collagen during in vitro tests, particularly at the stage of cell adhesion.

6. Structure and Function in Antimicrobial Piscidins: Histidine Position, Directionality of Membrane Insertion, and pH-dependent Permeabilization
Authors: Mihaela Mihailescu, Mirco Sorci, Jolita Seckute, Vitalii I. Silin, Janet Hammer, B. Scott Perrin, Jr., Jorge I. Hernandez, Nedzada Smajic, Akritee Shrestha, Kimberly A. Bogardus, Alexander I Greenwood, Riqiang Fu, Jack Blazyk, Richard W. Pastor, Linda K. Nicholson, Georges Belfort and Myriam L. Cotten
Journal:  Journal of the American Chemical Society
DOI: 10.1021/jacs.9b00440
Abstract: Piscidins are histidine-enriched antimicrobial peptides that interact with lipid bilayers as amphipathic α-helices. Their activity at acidic and basic pH in vivo makes them promising templates for biomedical applications. This study focuses on p1 and p3, both 22-residue-long piscidins with 68% sequence identity. They share three histidines (H3, H4 and H11) but p1, which is significantly more permeabilizing, has a fourth histidine (H17). This study investigates how variations in amphipathic character associated with histidines affect the permeabilization properties of p1 and p3. First, we show that the permeabilization ability of p3, but not p1, is strongly inhibited at pH 6.0 when the conserved histidines are partially charged and H17 is predominantly neutral. Secondly, our neutron diffraction measurements performed at low water content and neutral pH indicate that the average conformation of p1 is highly tilted, with its C-terminus extending into the opposite leaflet. In contrast, p3 is surface bound with its N-terminal end tilted toward the bilayer interior. The deeper membrane insertion of p1 correlates with its behavior at full hydration: an enhanced ability to tilt, bury its histidines and C-terminus, induce membrane thinning and defects, and alter membrane conductance and viscoelastic properties. Furthermore, its pH-resiliency relates to the neutral state favored by H17. Overall, these results provide mechanistic insights into how differences in the histidine content and amphipathicity of peptides can elicit different directionality of membrane insertion and pH-dependent permeabilization. This work features complementary methods, including dye leakage assays, NMR-monitored titrations, X-ray and neutron diffraction, oriented CD, molecular dynamics, electrochemical impedance spectroscopy, surface plasmon resonance, and quartz crystal microbalance with dissipation.

7. Adsorption of Fibrinogen and Fibronectin on Elastomeric Poly(butylene Succinate) Copolyesters
Authors: Peter SobolewskiN. Sanjeeva MurthyJoachim Kohn and Miroslawa El Fray
Journal:  Langmuir
DOI: 10.1021/acs.langmuir.9b01119
Abstract: Proteins adsorbed onto biomaterial surfaces facilitate cell-material interactions, including adhesion and migration. Of particular importance are provisional matrix components, fibrinogen (Fg) and fibronectin (Fn), which play an important role in the wound healing process. Here, to assess the potential of a series of elastomeric poly(butylene succinate) copolymers for soft tissue engineering and regenerative medicine applications, we examined the adsorption of Fg and Fn. We prepared spin-coated thin films of poly(butylene succinate) homopolymer and a series of elastomeric poly(butylene succinate) copolymers with butylene succinate (PBS, hard segment) to succinate-dimer linoleic diol units (DLS, soft segments) weight ratios of 70:30, 60:40, and 50:50. X-ray diffraction was used to assess crystallinity, while the obtained thin films were characterized using quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM). Protein adsorption was assessed using QCM-D, followed by data analysis using viscoelastic modeling. On all three copolymers, we observed robust adsorption of both key provisional matrix proteins. Importantly, for both proteins, viscoelastic modeling determined that the adlayers were 30–40 nm thick and had low shear modulus values (<25 kPa), thus indicating soft orientations (end-on for Fg) or conformations (open for Fn) of the hydrated proteins. Overall, our results are very encouraging, as they predict excellent cell adhesion and migration, key features enabling tissue integration of potential PBS-DLS scaffolds.

8. Synergistic effect of lignin incorporation into polystyrene for producing sustainable superadsorbent
Authors: Nasim Ghavidel and Pedram Fatehi
Journal: RSC Advances
DOI: 10.1039/C9RA02526J
Abstract:  Lignin has gained intensive interest as an excellent raw material for the generation of advanced green products. Polystyrene (PS) is known for its worldwide application in water purification processes. To induce a sustainable PS, kraft lignin (KL) and polystyrene were polymerized via free radical polymerization in a facile aqueous emulsion process. KL enhanced surface area and porosity of PS. The physicochemical properties of induced KL–PS were analyzed, and the fate of lignin in KL–PS was discussed fundamentally. Wettability and surface energy analyses were implemented to monitor the surface properties of KL, PS and KL–PS. Incorporation of KL in PS (40 wt%) boosted its surface energy and oxygen content, which led to KL–PS with better compatibility than PS with copper ions in aqueous systems. A quartz crystal microbalance with dissipation (QCM-D) confirmed the noticeably higher adsorption performance of copper ion on KL–PS than on PS and KL. The sorption mechanism, which was revealed by FTIR studies, was primarily attributed to the coordination of Cu(II) and hydroxyl group of KL–PS as well as the quadrupolar system of KL–PS.

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