Simple Method for the Preparation of Composites Based on PA6 and Partially Exfoliated Graphite

In the present work, the preparation of composite systems based on polyamide 6 (PA6) and exfoliated graphite was attempted by applying a simple procedure, which consists of a preliminary dispersion/exfoliation of graphite in the monomer, namely, ε- caprolactam (CL), and a subsequent polymerization of the above system. Atomic force microscopy (AFM) demonstrated specific interactions between CL and graphite surface. The dispersion of graphite in the monomer and polymer was assessed by scanning (SEM) and transmission (TEM) electron microscopy, while mechanical tests allowed to evaluate the influence of graphite on the polymer properties

Anchoring of Aminophosphonates on Titanium Oxide for Biomolecular Coupling

Aminophosphonates were chosen for a first step functionalization of TiO2 grown on titanium, as they possess a phosphonate group on one end, that can be exploited for coupling with the oxide surface, and an amino group on the other end to enable further functionalization of the surface. The deposition of aminophosphonates with different chain lengths (6 and 12 methylenes) was investigated. Oxygen plasma treatment proved useful in increasing the number of 12OH groups at the TiO2 surface, thus helping to anchor the aminophosphonates. By combining different surface-sensitive experimental techniques, we found the existence of a discontinuous monolayer where the molecules are covalently coupled to the TiO2 surface. For the molecules with longer chains, we find evidence of their covalent coupling to the surface through Ti\u2013O\u2013P bond formation, of the exposure of the amino groups at the outer surface, and of an increase in the order of the layer upon thermal annealing

spectroscopic ellipsometry meets afm nanolithography about hydration of bio inert oligo ethylene glycol terminated self assembled monolayers on gold

An accurate thickness determination provides insight into the complex vertical morphology of OEG-terminated SAMs

Heparin Strongly Enhances the Formation of β2-Microglobulin Amyloid Fibrils in the Presence of Type I Collagen

The tissue specificity of fibrillar deposition in dialysis-related amyloidosis is most likely associated with the peculiar interaction of beta2-microglobulin (beta2-m) with collagen fibers. However, other co-factors such as glycosaminoglycans might facilitate amyloid formation. In this study we have investigated the role of heparin in the process of collagen-driven amyloidogenesis. In fact, heparin is a well known positive effector of fibrillogenesis, and the elucidation of its potential effect in this type of amyloidosis is particularly relevant because heparin is regularly given to patients subject to hemodialysis to prevent blood clotting. We have monitored by atomic force microscopy the formation of beta2-m amyloid fibrils in the presence of collagen fibers, and we have discovered that heparin strongly accelerates amyloid deposition. The mechanism of this effect is still largely unexplained. Using dynamic light scattering, we have found that heparin promotes beta2-m aggregation in solution at pH 6.4. Morphology and structure of fibrils obtained in the presence of collagen and heparin are highly similar to those of natural fibrils. The fibril surface topology, investigated by limited proteolysis, suggests that the general assembly of amyloid fibrils grown under these conditions and in vitro at low pH is similar. The exposure of these fibrils to trypsin generates a cleavage at the C-terminal of lysine 6 and creates the 7-99 truncated form of beta2-m (DeltaN6beta2-m) that is a ubiquitous constituent of the natural beta2-m fibrils. The formation of this beta2-m species, which has a strong propensity to aggregate, might play an important role in the acceleration of local amyloid deposition

Adsorption of the rhNGF Protein on Polypropylene with Different Grades of Copolymerization

The surface properties of drug containers should reduce the adsorption of the drug and avoid packaging surface/drug interactions, especially in the case of biologically-derived products. Here, we developed a multi-technique approach that combined Differential Scanning Calorimetry (DSC), Atomic Force Microscopy (AFM), Contact Angle (CA), Quartz Crystal Microbalance with Dissipation monitoring (QCM-D), and X-ray Photoemission Spectroscopy (XPS) to investigate the interactions of rhNGF on different pharma grade polymeric materials. Polypropylene (PP)/polyethylene (PE) copolymers and PP homopolymers, both as spin-coated films and injected molded samples, were evaluated for their degree of crystallinity and adsorption of protein. Our analyses showed that copolymers are characterized by a lower degree of crystallinity and lower roughness compared to PP homopolymers. In line with this, PP/PE copolymers also show higher contact angle values, indicating a lower surface wettability for the rhNGF solution on copolymers than PP homopolymers. Thus, we demonstrated that the chemical composition of the polymeric material and, in turn, its surface roughness determine the interaction with the protein and identified that copolymers may offer an advantage in terms of protein interaction/adsorption. The combined QCM-D and XPS data indicated that protein adsorption is a self-limiting process that passivates the surface after the deposition of roughly one molecular layer, preventing any further protein adsorption in the long term

Genomic insights into the origin of farming in the ancient Near East

We report genome-wide ancient DNA from 44 ancient Near Easterners ranging in time between ~12,000 and 1,400 BC, from Natufian hunter–gatherers to Bronze Age farmers. We show that the earliest populations of the Near East derived around half their ancestry from a ‘Basal Eurasian’ lineage that had little if any Neanderthal admixture and that separated from other non-African lineages before their separation from each other. The first farmers of the southern Levant (Israel and Jordan) and Zagros Mountains (Iran) were strongly genetically differentiated, and each descended from local hunter–gatherers. By the time of the Bronze Age, these two populations and Anatolian-related farmers had mixed with each other and with the hunter–gatherers of Europe to greatly reduce genetic differentiation. The impact of the Near Eastern farmers extended beyond the Near East: farmers related to those of Anatolia spread westward into Europe; farmers related to those of the Levant spread southward into East Africa; farmers related to those of Iran spread northward into the Eurasian steppe; and people related to both the early farmers of Iran and to the pastoralists of the Eurasian steppe spread eastward into South Asia

Electrochemical Cu deposition on thiol covered Au(111) surfaces

The electrochemical deposition of Cu on Au(111) surfaces covered by self-assembled thiol monolayers has been followed in situ by electrochemical STM. Monolayers formed by thiols of different chain length have been chemisorbed on gold electrodes. The thiol molecules are organized in a quasi-crystalline structure characterized by a multi-domain ordering. The presence of the organic layer strongly influences the Cu deposition process. Cyclovoltammetry shows the absence of the underpotential deposition peaks observed on bare gold as well as a decrease of the electrochemical current in the overpotential regime. Independently of the chain length, in the UPD region we observe the formation of Cu nanoparticles 2-5 nm in diameter, one Cu atomic layer in height, uniformly distributed at the surface. The Cu cluster density reaches its maximum in the UPD regime. In the OPD region a chain length dependent behaviour is observed. Long thiol monolayers prevent any further growth of already existing clusters while on short thiol covered surfaces an almost 2D growth of Cu is observed

Scanning electron microscopy and atomic force microscopy of alkanethiol monolayers on gold

Alkanethiolates are adsorbed rapidly at gold and silver surfaces, forming monomolecular layers. These structures find applications in non-linear optics, molecular electronics, biosensors, adhesion and wetting. With the aim of studying the surface morphology of such structures at various magnifications, gold film surfaces covered with 1-octadecanethiol monolayers were inspected by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The evaporated gold films were covered using both the Langmuir-Blodgett (LB) and self-assembly methods. SEM images of films deposited by the vertical-dipping method show ridges roughly perpendicular to the dipping direction. The self-assembled (SA) monolayers have a more uniform aspect. Both LB and SA films can be distinguished from the gold surface by larger heap-shaped structures. Patchwork structures appear in films partially removed. AFM images with a magnification similar to that of the SEM images reveal more details of the surface morphology. Thioalkane monolayers appear less well defined than gold films, but the quantitative evaluation of the roughness of both surfaces brings about very similar results. Molecular resolution images of octadecanethiol monolayers show periodical structures attributed to vertically oriented alkane tails

Structural vs. electrochemical investigation of niobium oxide layers anodically grown in a Ca and P containing electrolyte

The growth of anodic oxide on niobium has been investigated as a function of the applied potential in a solution containing P and Ca-EDTA complexes. Anodizing below and above the breakdown potential has been explored via morphological (AFM and SEM) and compositional (XPS and EDX) analysis. Below the breakdown potential, thin (few hundreds of nanometers) and uniform oxide layers are formed, with negligible inclusions of electrolyte ions. Conversely, above the breakdown potential, in the so-called ASD regime, thicker and microporous oxide layers are observed, with a significant enrichment of the matrix with Ca and P. At potentials around 250 V the structure evolves towards a highly inhomogeneous and porous layer with the presence of some fractures, potentially affecting the oxide passivation properties. The corrosion resistance properties of the oxide layers have been investigated by electrochemical methods (OCP, anodic polarization and EIS). Data indicate that the corrosion resistance, initially increasing with the anodizing potential, weakens at potentials around 250 V. A potential of about 200 V represents, therefore, a good tradeoff between morphological and compositional properties and resistance to corrosion, which are important issues in view of osteoconductive properties for orthopaedic implant applications. (C) 2020 Elsevier B.V. All rights reserved

Morphological and Mechanical Characterization of DNA SAMs Combining Nanolithography with AFM and Optical Methods

The morphological and mechanical properties of thiolated ssDNA films self-assembled at different ionic strength on flat gold surfaces have been investigated using Atomic Force Microscopy (AFM). AFM nanoshaving experiments, performed in hard tapping mode, allowed selectively removing molecules from micro-sized regions. To image the shaved areas, in addition to the soft contact mode, we explored the use of the Quantitative Imaging (QI) mode. QI is a less perturbative imaging mode that allows obtaining quantitative information on both sample topography and mechanical properties. AFM analysis showed that DNA SAMs assembled at high ionic strength are thicker and less deformable than films prepared at low ionic strength. In the case of thicker films, the difference between film and substrate Young's moduli could be assessed from the analysis of QI data. The AFM finding of thicker and denser films was confirmed by X-Ray Photoelectron Spectroscopy (XPS) and Spectroscopic Ellipsometry (SE) analysis. SE data allowed detecting the DNA UV absorption on dense monomolecular films. Moreover, feeding the SE analysis with the thickness data obtained by AFM, we could estimate the refractive index of dense DNA films