Macromolecular Layer Research Articles

Behavior of protein-polysaccharide conjugate-stabilized food emulsions under various destabilization conditions.

The sensitivity of protein-stabilized emulsions to flocculation, coalescence, and phase separation under destabilization conditions (i.e., heating, aging, pH, ionic strength, and freeze-thawing) may limit the widespread use of proteins as effective emulsifiers. Therefore, there is a great interest in modulating and improving the technological functionality of food proteins by conjugating them with polysaccharides, through the Maillard reaction. The present review article highlights the current approaches of protein-polysaccharide conjugate formation, their interfacial properties, and the behavior of protein-polysaccharide conjugate stabilized emulsions under various destabilization conditions, including long-term storage, heating and freeze-thawing treatments, acidic conditions, high ionic strength, and oxidation. Protein-polysaccharide conjugates are capable of forming a thick and cohesive macromolecular layer around oil droplets in food emulsions and stabilizing them against flocculation and coalescence under unfavorable conditions, through steric and electrostatic repulsion. The protein-polysaccharide conjugates could be therefore industrially used to design emulsion-based functional foods with high physicochemical stability.

Flow-induced glycocalyx formation and cell alignment of HUVECs compared to iPSC-derived ECs for tissue engineering applications.

The relevance of cellular in vitro models highly depends on their ability to mimic the physiological environment of the respective tissue or cell niche. Static culture conditions are often unsuitable, especially for endothelial models, since they completely neglect the physiological surface shear stress and corresponding reactions of endothelial cells (ECs) such as alignment in the direction of flow. Furthermore, formation and maturation of the glycocalyx, the essential polysaccharide layer covering all endothelial surfaces and regulating diverse processes, is highly dependent on applied fluid flow. This fragile but utterly important macromolecular layer is hard to analyze, its importance is often underestimated and accordingly neglected in many endothelial models. Therefore, we exposed human umbilical vein ECs (HUVECs) and human induced pluripotent stem cell-derived ECs (iPSC-ECs) as two relevant EC models in a side-by-side comparison to static and physiological dynamic (6.6 dyn cm−2) culture conditions. Both cell types demonstrated an elongation and alignment along the flow direction, some distinct changes in glycocalyx composition on the surface regarding the main glycosaminoglycan components heparan sulfate, chondroitin sulfate or hyaluronic acid as well as an increased and thereby improved glycocalyx thickness and functionality when cultured under homogeneous fluid flow. Thus, we were able to demonstrate the maturity of the employed iPSC-EC model regarding its ability to sense fluid flow along with the general importance of physiological shear stress for glycocalyx formation. Additionally, we investigated EC monolayer integrity with and without application of surface shear stress, revealing a comparable existence of tight junctions for all conditions and a reorganization of the cytoskeleton upon dynamic culture leading to an increased formation of focal adhesions. We then fabricated cell sheets of EC monolayers after static and dynamic culture via non-enzymatic detachment using thermoresponsive polymer coatings as culture substrates. In a first proof-of-concept we were able to transfer an aligned iPSC-EC sheet to a 3D-printed scaffold thereby making a step in the direction of vascular modelling. We envision these results to be a valuable contribution to improvements of in vitro endothelial models and vascular engineering in the future.

Efficient hydrogenation catalyst designing via preferential adsorption sites construction towards active copper

Based on the experimental and DFT calculation results, here for the first time we built preferential adsorption sites for nitroarenes by modification of the supported Cu catalysts surface with 1,10-phenathroline (1,10-phen), by which the yield of aniline via reduction of nitroarene is enhanced three times. Moreover, a macromolecular layer was in-situ generated on supported Cu catalysts to form a stable macromolecule modified supported Cu catalyst, i.e., CuAlOx-M. By applying the CuAlOx-M, a wide variety of nitroarene substrates react smoothly to afford the desired products in up to > 99% yield with > 99% selectivity. The method tolerates a variety of functional groups, including halides, ketone, amide, and C = C bond moieties. The excellent catalytic performance of the CuAlOx-M can be attributed to that the 1,10-phen modification benefits the preferential adsorption of nitrobenzene and slightly weakens adsorption of aniline on the supported nano-Cu surface.

Heparanase inhibition preserves the endothelial glycocalyx in lung grafts and improves lung preservation and transplant outcomes

The endothelial glycocalyx (eGC) is considered a key regulator of several mechanisms that prevent vascular injury and disease. Degradation of this macromolecular layer may be associated with post-transplant graft dysfunction. In this study, we aimed to demonstrate the benefits of eGC protection via heparanase inhibition on graft quality. We established rat models of lung grafts with damaged or preserved eGC using ischemic insult and transplanted the grafts into recipients. Lung grafts were also subjected to normothermic ex vivo lung perfusion for detailed assessment under isolated conditions. Physiologic parameters and eGC-associated cellular events were assessed in grafts before and after reperfusion. Structurally degraded eGC and highly activated heparanase were confirmed in lungs with ischemic insult. After transplant, lungs with damaged eGC exhibited impaired graft function, inflammation, edema, and inflammatory cell migration. Increased eGC shedding was evident in the lungs after reperfusion both in vivo and ex vivo. These reperfusion-related deficiencies were significantly attenuated in lungs with preserved eGC following heparanase inhibition. Our studies demonstrated that eGC plays a key role in maintaining lung graft quality and function. Heparanase inhibition may serve as a potential therapeutic to preserve eGC integrity, leading to improved post-transplant outcomes.

Evident Enhancement of Efficiency and Stability in Perovskite Solar Cells with Triphenylamine-Based Macromolecules on the CuSCN Hole-Transporting Layer

The CuSCN-containing perovskite solar cells (PSCs) are presently of great research focus due to the high carrier mobility and well-aligned work function of the CuSCN hole-transporting layer. The improvement of photovoltaic performance and stability is still an important subject in the practical applications of CuSCN-containing PSCs. Herein, a facile approach to improve the efficiency and stability of CuSCN-containing PSCs is developed by spin-coating the triphenylamine-based macromolecules between the CuSCN hole-transporting layer and metallic electrode, such as linear macromolecule poly-TPD and branched macromolecule CRA-TPA. The maximum power conversion efficiency (PCE) of CuSCN-containing PSCs is increased by linear triphenylamine-based macromolecule poly-TPD to 10.36% while the PCE value of CuSCN-containing PSCs, being modified by branched triphenylamine-based macromolecule CRA-TPA, reaches up to 11.97%. Evidently, the PCE values are nearly two times higher than 5.95% of CuSCN-containing control device. The photovoltaic improvement of macromolecule-modified CuSCN-containing PSCs is mainly caused by the strong hole-transporting capacity of triphenylamine-based macromolecules inducing the reduction of charge recombination, which is derived from the reduced potential barrier of hole transportation including the flatness and coverage improvement in the triphenylamine-based macromolecular functional layer. In addition, the stability of macromolecule-modified CuSCN-containing PSCs is significantly improved due to the protection of triphenylamine-based macromolecular layer on the perovskite film, so that the unencapsulated macromolecule-modified CuSCN-containing PSC device can keep over 70–80% of initial PCE value after 20-day exposure under ambient environment (relative humidity (RH) = 50%, 25°C). This work provides a facile approach to enhance the efficiency and stability of CuSCN-containing PSCs through the modification of triphenylamine-based macromolecules between the CuSCN hole-transporting layer and metallic electrode.

Influence of environmental and biological macromolecules on aggregation kinetics of nanoplastics in aquatic systems

Nanoplastics derived from degradation of micro- or macroplastics are emerging contaminants in aquatic environments, where their fate and transport as well as toxicity are affected by aggregation. This study employed time-resolved dynamic light scattering to investigate the aggregation kinetics of polystyrene nanoplastics (PSNPs) in the presence of four macromolecules (sodium alginate (SA), bovine serum albumin (BSA), extracellular polymeric substance (EPS), and Suwannee River humic acid (HA)) in solutions containing monovalent (NaCl) and divalent (CaCl2) salts at different pH. Our results showed that the macromolecules enhanced PSNP stability in NaCl solutions but destabilized PSNPs in CaCl2 solutions at pH 6. In NaCl solutions, macromolecules inhibited PSNP aggregation due to steric hindrance originated from macromolecular layer adsorbed on PSNPs. The strongest stabilization effect was observed for BSA having the greatest hydrodynamic adsorption layer thickness of 21.9 nm, followed by HA, EPS, and SA. In CaCl2 solutions, SA significantly destabilized PSNPs via alginate bridging with Ca2+, which enhanced with concentrations of SA and CaCl2. The destabilization effects of other three macromolecules in CaCl2 solutions were governed by the interplay among molecular bridging, charge screening, and steric hindrance. An increased pH in NaCl or CaCl2 solutions containing macromolecules all stabilized PSNPs due to elevated electrostatic repulsion, except that SA destabilized PSNPs in CaCl2 solutions via enhanced molecular bridging. The stabilization effect of macromolecules may also compete with the destabilization effect under seawater condition. This study suggested that PSNP aggregation in aquatic environments could be strongly affected by macromolecules and solution chemistry.

Potential impact of CO2 injection into coal matrix in molecular terms

Coal seams are one of the targeted geological bodies for CO2 sequestration. Coal structure deformation is a significant feature of the interaction between CO2 and coal seams. The rearrangement of macromolecular structure is a recognized deformation mechanism whose process has not been quantified. We used a high-order coal macromolecular model to reveal specific processes of coal macromolecular rearrangement caused by CO2 injection through molecular dynamics. In addition, the potential impact of this injection on the sequestration and mechanical properties of CO2 in the coal matrix was investigated. The rearrangement of the coal macromolecular structure is accomplished through the mutual coupling of the pore structure and macromolecular ordering. The compression of closed pores and the expansion of open pores together cause the swelling of macromolecular volumes. The concentration of closed pores was an important indicator for the quantification of the rearrangement of macromolecular structure. The greater the content of closed pores in the coal, the higher the potential for macromolecular structure transformation after CO2 injection. Furthermore, the more disordered the direction of the coal macromolecular layer, the lower the peak strength of the coal matrix. The amount of CO2 sequestration in the coal matrix is gradually saturated near the critical pressure point. Our findings contribute to the study of CO2 sequestration in coal seams and CO2 leakage risk prediction.

Surface regeneration and reusability of label-free DNA biosensors based on weak polyelectrolyte-modified capacitive field-effect structures

The reusability of capacitive field-effect electrolyte-insulator-semiconductor (EIS) sensors modified with a cationic weak polyelectrolyte (poly(allylamine hydrochloride) (PAH)) for the label-free electrical detection of single-stranded DNA (ssDNA), in-solution- and on-chip-hybridized double-stranded DNA (dsDNA) has been studied. It has been demonstrated that via simply regeneration of the gate surface of the EIS sensor by means of an electrostatic adsorption of a new PAH layer, the same biosensor can be reused for at least five DNA-detection measurements. Because of the reversal of the charge sign of the outermost layer after each surface modification with the cationic PAH or negatively charged DNA molecules, the EIS-biosensor signal exhibits a zigzag-like behavior. The amplitude of the signal changes has a tendency to decrease with increasing number of macromolecular layers. The direction of the EIS-signal shifts can serve as an indicator for a successful DNA-immobilization or -hybridization process. In addition, we observed that the EIS-signal changes induced by each surface-modification step (PAH adsorption, immobilization of ssDNA or dsDNA molecules and on-chip hybridization of complementary target cDNA) is decreased with increasing the ionic strength of the measurement solution, due to the more efficient macromolecular charge-screening by counter ions. The results of field-effect experiments were supported by fluorescence-intensity measurements of the PAH- or DNA-modified EIS surface using various fluorescence dyes.

Surfactant-Induced Patterns in Polymer Brushes.

The properties of surfaces with grafted macromolecules are determined by a fine structure of the macromolecular layer, whereas the mixtures of macromolecules with surfactants are very rich in structure types. Using the scaling mean-field theory, we consider the self-assembly in polymer brushes into various patterns induced by interactions with low-molecular surfactants. The interaction energies of the parts of a surfactant molecule with the polymer units are assumed to be greatly different. With increasing the grafting density, the formation of lamellae perpendicular to the grafting plane, a continuous layer with oblong or round pores, or a homogeneous brush is predicted. The driving force of the pattern formation is a gain in the interaction energy of surfactant molecules oriented at the lateral surfaces of lamellae or pores. The process of pore formation in a homogeneous brush caused by a temperature change at definite grafting densities is described as the first-order phase transition. It is accompanied by a stepwise extension of the brush and by orientational ordering of surfactant molecules. The transitions between the other patterns are of the second order. The thickness of lamellae and the distance between pores are approximately twice the surfactant molecule size except for the extremely high grafting densities. The diagrams of brush patterns are presented and discussed.

Effect of endothelial glycocalyx layer redistribution upon microvessel poroelastohydrodynamics

The endothelial glycocalyx layer (EGL) is a macromolecular layer that lines the inner surface of blood vessels. It is believed to serve a number of physiological functions in the microvasculature, including protection of the vessel walls from potentially harmful levels of fluid shear, as a molecular sieve that acts to regulate transendothelial mass transport, and as a transducer of mechanical stress from the vessel lumen. To best fulfil some of its roles, it has been suggested that the EGL redistributes, so that it is thickest at the cell–cell junctions. It has also been suggested that the majority of mechanotransduction occurs through the solid phase of the EGL, rather than via its fluid phase. The difficulties associated with measuring the distribution of the EGL in vivo make these hypotheses difficult to confirm experimentally. Consequently, to gauge the impact of EGL redistribution from a theoretical standpoint, we compute the flow through a porous-lined microvessel, the endothelial surface of which has been informed by confocal microscopy images of a postcapillary venule. Following earlier studies, we model the poroelastohydrodynamics of the EGL using biphasic mixture theory, taking advantage of a recently developed boundary integral representation of these equations to solve the coupled poroelastohydrodynamics using the boundary element method. However, the low permeabilities of the EGL mean that viscous effects are confined to thin layers, thereby also enabling an asymptotic treatment of the dynamics in this limit. In this asymptotic regime, we also consider a two-layer Stokes flow model for the lumen flow to approximate the effect of red blood cells within the lumen. We demonstrate that redistribution of the EGL can have a substantial impact upon microvessel haemodynamics. We also confirm that the bulk of the mechanical stress is indeed carried through the solid phase of the EGL.

Colloidal and spherical mesoporous silica particles: synthesis and new technologies for delivery applications

Continuous research in prominent fields such as biotechnology, biomedicine and nanopharmaceutics has brought the development of a widespread class of materials, and studies for mesoporous materials have been exponentially growing lately. The purpose of this review is to provide a useful guide for different materials, methods and configurations that have been reported in the last 5 years for the synthesis of spherical mesoporous silica particles (MSP), in the colloidal size range (1–1000 nm). MSP exhibit several limitations that must be overcome in order to enable their medical and clinical use. Surface modification of these particles will allow getting new promising characteristics of these materials, including better drug release control and biocompatibility improvement. These modified MSP could be potentially used in many biomedical applications, especially for drug delivery systems. Emphasis is made on the pore size, diameter and shape of the final particles since these parameters will establish key characteristics, i.e., drug delivery profile, loading capacity and efficiency. Spreading the use of mesoporous silica particles in biomedicine is possible by the improvement of its inner characteristics through surface modification. This may be done by chemical functionalization or by coating with macromolecular layers or brushes, thus creating novel responsive core–shell hybrid composites to be used as carriers for drug delivery applications.

Submicron complex lipid carriers for curcumin delivery to intestinal epithelial cells: Effect of different emulsifiers on bioaccessibility and cell uptake

Submicrometric lipid-based carriers were developed to encapsulate curcumin and deliver it to intestinal epithelial cells.A lipid matrix comprising monoolein, sunflower oil and water at weight ratio 1:1:1 was selected, upon screening of different combinations of amphiphilic molecules, vegetable oils and water, because of its high encapsulations efficiency of curcumin, retained over time and relatively lower content of amphiphilic molecules.Upon dispersion in aqueous phase, the carriers were stabilized by: (a) whey protein isolates (WPI), alone and (b) in combination with modified starch (WPI-MS), or by (c) polysorbate 20 (T20).Whereas T20-stabilized systems exhibited extremely fine particles (120nm), WPI and WPI-MS stabilized carriers were characterized by a significantly larger mean particle size (270nm). The thicker macromolecular layer of WPI and WPI-MS enabled better (a) physical stability, (b) controlled shell degradation during simulated digestion, and (c) curcumin bioaccessibility targeted at the intestinal digestion phase than T20-systems.However, uptake studies in HT29 cell lines, simulating intestinal epithelial cells, showed that WPI and WPI-MS carriers exhibited after 24h a lower relative uptake than T20-stabilized systems (about 60% and 80%, respectively), as a consequence of smaller size and higher cell adherence of T20 carriers to the cell membrane.

New strategy to create ultra-thin surface layer of grafted amphiphilic macromolecules.

It was found first that macromolecules made of amphiphilic monomer units could form spontaneously an ultra-thin layer on the surface which the macromolecules are grafted to. The width of such layer is about double size of monomer unit consisting of hydrophilic A (repulsive) and hydrophobic (attractive) B beads. The hydrophilic A beads are connected in a polymer chain while hydrophobic B beads are attached to A beads of the backbone as side groups. Three characteristic regimes are distinguished. At low grafting density, the macromolecules form ultra-thin micelles of the shape changing with decrease of distance d between grafting points as following: circular micelles-prolonged micelles-inverse micelles-homogeneous bilayer. Those micelles have approximately constant height and specific top-down A-BB-A structure. At higher grafting density, the micelles start to appear above the single bilayer of amphiphilic macromolecules. The thickness of grafted layer in these cases is different in different regions of grafting surface. Only at rather high density of grafting, the height of macromolecular layer becomes uniform over the whole grafting surface. The study was performed by computer modeling experiments and confirmed in framework of analytical theory.

Layer-by-layer assembly of thin organic films on PTFE activated by cold atmospheric plasma

Abstract An air diffuse coplanar surface barrier discharge is used to activate the surface of polytetrafluoroethylene (PTFE) samples, which are subsequently coated with polyvinylpyrrolidone (PVP) and tannic acid (TAN) single, bi- and multilayers, respectively, using the dip-coating method. The surfaces are characterized by X-ray Photoelectron Spectroscopy (XPS), Attenuated Total Reflection – Fourier Transform Infrared Spectroscopy (ATR-FTIR) and Atomic Force Microscopy (AFM). The XPS measurements show that with plasma treatment the F/C atomic ratio in the PTFE surface decreases, due to the diminution of the concentration of CF2 moieties, and also oxygen incorporation through formation of new C–O, C=O and O=C–O bonds can be observed. In the case of coated samples, the new bonds indicated by XPS show the bonding between the organic layer and the surface, and thus the stability of layers, while the gradual decrease of the concentration of F atoms with the number of deposited layers proves the creation of PVP/TAN bi- and multi-layers. According to the ATR-FTIR spectra, in the case of PVP/TAN multilayer hydrogen bonding develops between the PVP and TAN, which assures the stability of the multilayer. The AFM lateral friction measurements show that the macromolecular layers homogeneously coat the plasma treated PTFE surface.

Polythiolactone-based redox-responsive layers for the reversible release of functional molecules.

The development of thin macromolecular layers with incorporated disulfide bonds that can be disrupted and formed again under redox stimulation is of general interest for drug release applications, because such layers can provide rapid and reversible responses to specific biological systems and signals. However, the preparation of such layers from polythiols remains difficult, because of the fast oxidation of thiol groups in ambient conditions. Here we propose water-soluble thiolactone-containing copolymers as stable precursors containing protected thiol groups, allowing us to produce on demand polythiol layers on gold substrates in the presence of amine derivatives. Electrochemical, water contact angle, X-ray photoelectron spectroscopy, and X-ray reflectometry measurements evidence the formation of uniform copolymer layers containing both anchored and free thiol groups. The number of free thiols increases with the content of thiolactone units in the copolymers. In a second step, a thiolated dye, used as a model drug, was successfully grafted on the free thiol groups through disulfide bonds using mild oxidizing conditions, as proved by fluorescence and quartz crystal microbalance measurements. Finally, the reversible release/regrafting of the dye under redox stimulation is demonstrated.

Macromolecular and pore structures of Chinese tectonically deformed coal studied by atomic force microscopy

In this study, the macromolecular and nanoscale pores of different types of tectonically deformed coals were characterized by AFM. The nanostructures of coal differed in terms of the metamorphism degree, deformation degree, and deformation properties. The macromolecular grid-like structure of low-rank bituminous coal was loosely reticular, and the round or elliptical pores between chains were largely isolated. The macromolecular reticular grid-like structure of high-rank bituminous coal was more compact than that of low-rank bituminous coal. The large molecules of anthracite exhibited enhanced polymerization with significant reductions in the spacing between macromolecular layers. The reticular grid-like structure of this coal was fairly compact, and the pores between the chains were squeezed flat. Flat micropores were the predominant pore morphology in this type of coal. Metamorphism generally increased the quantity of micropores in the coal. The macromolecular reticular grid-like structures and pore structures of coal varied according to their properties and deformation degree. Under brittle deformation, the ratio of the transitional pores and the interconnectivity of the pores increased with increasing deformation degree. This phenomenon was beneficial for gas diffusion. Under ductile deformation, the coal surface exhibited creep flow features, the surface pore morphology of the coal was irregularly developed, and the ratios of micropores and transitional pores in the coal increased.

Boundary lubrication by macromolecular layers and its relevance to synovial joints

We review here two recent works on boundary lubrication by macromolecules with the aim of obtaining an insight into the extremely efficient lubrication of mammalian joints. The first work emulates the structure of the cartilage superficial layer by reconstructing films of hyaluronan (HA) and of HA/aggrecan complexes stabilized by cartilage link protein and studies normal and shear interactions between two atomically smooth mica surfaces coated with such molecules using a surface force balance. These molecules have been conjectured to act as boundary lubricants while sliding past each other at the interface between the articular cartilage surfaces and the synovial fluid. It was discovered that the HA/aggrecan/link protein macromolecular complexes provide better boundary lubrication compared with HA alone, most likely as a result of the higher charge density allowing a more efficient hydration lubrication effect. However, the results suggest that such complexes by themselves cannot be responsible for the very efficient lubrication of synovial joints. On the other hand, in the second work, phosphatidylcholine vesicles were shown to provide extremely efficient lubrication at physiological pressures as long as the robustness of the layer is maintained. Normal and shear interactions between two surfaces bearing different phosphatidylcholine vesicles, having the same head group but varying acyl chain length, were studied systematically. In addition to hydration, robustness of the surface layer plays a major role in the lubrication efficiency of the system. Implications of the results of these studies to the lubrication mechanism of synovial joints are suggested. Copyright © 2014 John Wiley & Sons, Ltd.

Red blood cell dynamics in polymer brush-coated microcapillaries: A model of endothelial glycocalyx in vitro.

The confined flow of red blood cells (RBCs) in microvasculature is essential for oxygen delivery to body tissues and has been extensively investigated in the literature, both in vivo and in vitro. One of the main problems still open in microcirculation is that flow resistance in microcapillaries in vivo is higher than that in vitro. This discrepancy has been attributed to the glycocalyx, a macromolecular layer lining the inner walls of vessels in vivo, but no direct experimental evidence of this hypothesis has been provided so far. Here, we investigate the flow behavior of RBCs in glass microcapillaries coated with a polymer brush (referred to as "hairy" microcapillaries as opposed to "bare" ones with no coating), an experimental model system of the glycocalyx. By high-speed microscopy imaging and image analysis, a velocity reduction of RBCs flowing in hairy microcapillaries as compared to bare ones is indeed found at the same pressure drop. Interestingly, such slowing down is larger than expected from lumen reduction due to the polymer brush and displays an on-off trend with a threshold around 70 nm of polymer brush dry thickness. Above this threshold, the presence of the polymer brush is associated with an increased RBC deformation, and RBC velocity is independent on polymer brush thickness (at the same pressure drop). In conclusion, this work provides direct support to the hypothesis that the glycocalyx is the main factor responsible of the higher flow resistance found in microcapillaries in vivo.

Macromolecular shape and interactions in layer-by-layer assemblies within cylindrical nanopores

Layer-by-layer (LbL) deposition of polyelectrolytes and proteins within the cylindrical nanopores of anodic aluminum oxide (AAO) membranes was studied by optical waveguide spectroscopy (OWS). AAO has aligned cylindrical, nonintersecting pores with a defined pore diameter d0 and functions as a planar optical waveguide so as to monitor, in situ, the LbL process by OWS. The LbL deposition of globular proteins, i.e., avidin and biotinylated bovine serum albumin was compared with that of linear polyelectrolytes (linear-PEs), both species being of similar molecular weight. LbL deposition within the cylindrical AAO geometry for different pore diameters (d0 = 25–80 nm) for the various macromolecular species, showed that the multilayer film growth was inhibited at different maximum numbers of LbL steps (nmax). The value of nmax was greatest for linear-PEs, while proteins had a lower value. The cylindrical pore geometry imposes a physical limit to LbL growth such that nmax is strongly dependent on the overall internal structure of the LbL film. For all macromolecular species, deposition was inhibited in native AAO, having pores of d0 = 25–30 nm. Both, OWS and scanning electron microscopy showed that LbL growth in larger AAO pores (d0 > 25–30 nm) became inhibited when approaching a pore diameter of deff,n_max = 25–35 nm, a similar size to that of native AAO pores, with d0 = 25–30 nm. For a reasonable estimation of deff,n_max, the actual volume occupied by a macromolecular assembly must be taken into consideration. The results clearly show that electrostatic LbL allowed for compact macromolecular layers, whereas proteins formed loosely packed multilayers.

SANS contrast variation method applied in experiments on ferrofluids at MURN instrument of IBR-2 reactor

Separate determination of the nuclear and magnetic contributions to the scattering intensity by means of a contrast variation method applied in a small angle neutron scattering experiment of nonpolarized neutrons in ferrofluids in early 90 's at the MURN instrument is reviewed. The nuclear scattering contribution gives the features of the colloidal particle dimensions, surfactant shell structure and the solvent degree penetration to the macromolecular layer. The magnetic scattering part is compatible to the models where is supposed that the particle surface has a nonmagnetic layer. Details on experimental "Grabcev method" in obtaining separate nuclear and magnetic contributions to the small angle neutron scattering intensity of unpolarized neutrons are emphasized for the case of a high quality ultrastabile benzene-based ferrofluid with magnetite nanoparticles.