Hydrodynamic Diameter Measurements Research Articles

Molecular Dynamics and In Vitro Studies Elucidating the Tunable Features of Reconfigurable Nanodiscs for Guiding the Optimal Design of Curcumin Formulation.

In this study, we advance our exploration of Apolipoprotein A-I (apoA-I) peptide analogs (APAs) for their application in nanodisc (ND) assembly, focusing on the dynamic conformational characteristics and the potential for drug delivery. We explore APA-ND interactions with an emphasis on curcumin encapsulation, utilizing molecular dynamic simulations and in vitro assessments to evaluate the efficacy of various APA-ND formulations as drug carriers. The methodological approach involved the generation of three unique apoA-I α-11/3 helical mimics, resulting in fifteen distinct APAs. Their structural integrity was rigorously assessed using ColabFold-AF2, with particular attention to pLDDT and pTM scores. Extensive molecular dynamics simulations, covering 1.7 μs across 17 ND systems, were conducted to investigate the influence of APA sequence variations on ND stability and interactions. This study reveals that the composition of APAs, notably the presence of Proline, Serine, and Tryptophan, significantly impacts ND stability and morphology. Oligomeric APAs, in particular, demonstrated superior stability and distinct interaction patterns compared to their monomeric counterparts. Additionally, hydrodynamic diameter measurements over eight weeks indicated sequence-dependent stability, highlighting the potential of specific APA configurations for sustained colloidal stability. In vitro study successfully encapsulated curcumin in [AA]3/DMPC ND formulations, revealing concentration-dependent stability and interaction dynamics. The findings underscore the remarkable capability of APA-NDs to maintain structural integrity and efficient drug encapsulation, positioning them as a promising platform for drug delivery. The study concludes by emphasizing the tunability and versatility of APA-NDs in drug formulation, potentially revolutionizing nanomedicine by enabling customized APA sequences and ND properties for targeted drug delivery.

Lactose-Functionalized Carbosilane Glycodendrimers Are Highly Potent Multivalent Ligands for Galectin-9 Binding: Increased Glycan Affinity to Galectins Correlates with Aggregation Behavior.

Galectins, the glycan binding proteins, and their respective carbohydrate ligands represent a unique fundamental regulatory network modulating a plethora of biological processes. The advances in galectin-targeted therapy must be based on a deep understanding of the mechanism of ligand-protein recognition. Carbosilane dendrimers, the well-defined and finely tunable nanoscaffolds with low toxicity, are promising for multivalent carbohydrate ligand presentation to target galectin receptors. The study discloses a synthetic method for two types of lactose-functionalized carbosilane glycodendrimers (Lac-CS-DDMs). Furthermore, we report their outstanding, dendritic effect-driven affinity to tandem-type galectins, especially Gal-9. In the enzyme-linked immunosorbent assay, the affinity of the third-generation multivalent dendritic ligand bearing 32 lactose units to Gal-9 reached nanomolar values (IC50 = 970 nM), being a 1400-fold more effective inhibitor than monovalent lactose for this protein. This demonstrates a game-changing impact of multivalent presentation on the inhibitory effect of a ligand as simple as lactose. Moreover, using DLS hydrodynamic diameter measurements, we correlated the increased affinity of the glycodendrimer ligands to Gal-3 and Gal-8 but especially to Gal-9 with the formation of relatively uniform and stable galectin/Lac-CS-DDM aggregates.

Investigation of Cubic and Spherical IONPs’ Rheological Characteristics and Aggregation Patterns from the Perspective of Magnetic Targeting

Based on our prior research, we synthesized iron-oxide nanoparticles (IONPs) in two shapes (spherical and cubic) and sized them for the current inquiry. This research examined the magnetic, rheological, and sedimentation properties of the suspensions containing PEG-coated IONPs, considering that both produced particles are intended to be employed for magnetic targeting applications. The saturation magnetization of both IONPs was lower than the magnetite domain magnetization of 92 emu/g due to the surfactant and the dead surface magnetic layer. Under each investigated magnetic field (0, 34 and 183 mT), the shear viscosity behaviour of the MNP suspensions of both kinds was comparable. Shear thinning behaviour was seen for both particle suspensions in the low shear rate area (0.1 s−1 to 1 s−1). The rheological curves from this paper show that the suspensions present a higher viscosity at lower shear rates for spherical and cubic PEG-coated nanoparticles when a magnetic field is applied. The aggregation behaviour demonstrates that cubic-shaped IONPs are more stable throughout time, with hydrodynamic diameter measurements showing a relatively slow variation of the DLS size distribution from 250 nm to 210 nm in the first 600 s; contrarily, the hydrodynamic diameter of spherical IONPs fluctuated significantly, from 855 nm to 460 nm. Another key finding relates to the sedimentation profile, specifically that PEG-coated IONPs with spherical shapes have a stronger tendency to sediment than those with cubic forms, which are more stable.

Comprehensive study upon physicochemical properties of bio-ZnO NCs

In this study, for the first time, the comparison of commercially available chemical ZnO NCs and bio-ZnO NCs produced extracellularly by two different probiotic isolates (Latilactobacillus curvatus MEVP1 [OM736187] and Limosilactobacillus fermentum MEVP2 [OM736188]) were performed. All types of ZnO formulations were characterized by comprehensive interdisciplinary approach including various instrumental techniques in order to obtain nanocomposites with suitable properties for further applications, i.e. biomedical. Based on the X- ray diffraction analysis results, all tested nanoparticles exhibited the wurtzite structure with an average crystalline size distribution of 21.1 nm (CHEM_ZnO NCs), 13.2 nm (1C_ZnO NCs) and 12.9 nm (4a_ZnO NCs). The microscopy approach with use of broad range of detectors (SE, BF, HAADF) revealed the core–shell structure of bio-ZnO NCs, compared to the chemical one. The nanoparticles core of 1C and 4a_ZnO NCs are coated by the specific organic deposit coming from the metabolites produced by two probiotic strains, L. fermentum and L. curvatus. Vibrational infrared spectroscopy, photoluminescence (PL) and mass spectrometry (LDI-TOF-MS) have been used to monitor the ZnO NCs surface chemistry and allowed for better description of bio-NCs organic coating composition (amino acids residues). The characterized ZnO formulations were then assessed for their photocatalytic properties against methylene blue (MB). Both types of bio-ZnO NCs exhibited good photocatalytic activity, however, the effect of CHEM_ZnO NCs was more potent than bio-ZnO NCs. Finally, the colloidal stability of the tested nanoparticles were investigated based on the zeta potential (ZP) and hydrodynamic diameter measurements in dependence of the nanocomposites concentration and investigation time. During the biosynthesis of nano-ZnO, the increment of pH from 5.7 to around 8 were observed which suggested possible contribution of zinc aquacomplexes and carboxyl-rich compounds resulted in conversion of zinc tetrahydroxy ion complex to ZnO NCs. Overall results in present study suggest that used accessible source such us probiotic strains, L. fermentum and L. curvatus, for extracellular bio-ZnO NCs synthesis are of high interest. What is important, no significant differences between organic deposit (e.g. metabolites) produced by tested strains were noticed—both of them allowed to form the nanoparticles with natural origin coating. In comparison to chemical ZnO NCs, those synthetized via microbiological route are promising material with further biological potential once have shown high stability during 7 days.

Obtaining Medical Textiles Based on Viscose and Chitosan/Zinc Nanoparticles with Improved Antibacterial Properties by Using a Dielectric Barrier Discharge.

This study aimed to obtain functional viscose textiles based on chitosan coatings with improved antibacterial properties and washing durability. For that reason, before functionalization with chitosan/zinc nanoparticles (NCH+Zn), the viscose fabric was modified by nonthermal gas plasma of dielectric barrier discharge (DBD) to introduce into its structure functional groups suitable for attachment of NCH+Zn. NCH+Zn were characterized by measurements of hydrodynamic diameter and zeta potential and AFM. DBD-plasma-modified and NCH+Zn-functionalized fabrics were characterized by zeta potential measurements, ATR-FTIR spectroscopy, the calcium acetate method (determination of content of carboxyl and aldehyde groups), SEM, breaking-strength measurements, elemental analysis, and ICP-OES. Their antibacterial activity was determined under dynamic contact conditions. In addition to SEM, the NCH+Zn distributions on viscose fabrics were also indirectly characterized by measuring their absorbent capacities before and after functionalization with NCH+Zn. Washing durability was monitored through changes in the zeta potential, chitosan and zinc content, and antibacterial activity after 1, 3, and 5 washing cycles. The obtained results showed that DBD plasma modification contributed to the simultaneous improvement of NCH+Zn sorption and antibacterial properties of the viscose fabric functionalized with NCH+Zn, and its washing durability, making it suitable for the production of high-value-added medical textiles.

Dispersion stability of zinc oxide nanoparticles in an electroless bath with various surfactants

Stable dispersion of nanoparticles in electrolytes is essential for preparing a wide range of advanced electroless nanocomposites. However, nanoparticles agglomerate if the van der Waals attractive forces prevail over the electrostatic repulsive forces. As a result, various surfactants (anionic, cationic, and non-ionic) were used to prevent nanoparticle agglomeration in the electroless plating bath. This study specifically examines the dispersion stability of zinc oxide (ZnO) nanoparticles in an electroless bath with different surfactants, including anionic sodium dodecyl sulfate (SDS), cationic cetyltrimethylammonium bromide (CTAB), and non-ionic polyvinylpyrrolidone (PVP). The zeta potential and hydrodynamic diameter measurements were utilized as an indicator of nanodispersion stability. The results showed a better-dispersed state of ZnO nanoparticles with SDS surfactant with a small average size of the agglomerate. Surfactants SDS and CTAB improved stability by electrostatic repulsion between ZnO nanoparticles whereas PVP by steric inhibition towards other particles. In addition, ultraviolet–visible absorbance spectroscopy (UV–Vis) was used to examine the dispersion stability of ZnO nanoparticles with different surfactants. The nano-ZnO distributed with SDS displayed a maximum percentage of absorbance, suggesting the homogeneous dispersion of ZnO nanoparticles.

Investigation of the Behavior and Mechanism of Action of Ether-Based Polycarboxylate Superplasticizers Absorption on Large Bibulous Stone Powder.

The aim of this paper is to study the adsorption behavior of polycarboxylate superplasticizers (PCE) on coarse aggregates with a property of high water consumption (above 2%). The coarse aggregates were ground into a powder to create large bibulous stone powder, and it was observed that significant amounts of the ether-based PCE were absorbed onto large bibulous stone powder. The adsorption rate immediately reached a maximum after 5 min and then gradually decreased until an equilibrium absorption was established after 30 min. Zeta potential, infrared spectroscopy, and thermogravimetric analysis (TGA) measurements confirmed that the polycarboxylate superplasticizer adsorbed on the surface of the stone powder. Hydrodynamic diameter measurements showed that the polycarboxylate superplasticizer molecules were smaller than pore size, and the surface area and pore volume were reduced by the polymer incorporation in the pores.

Silver Nanoparticles Surface-Modified with Carbosilane Dendrons as Carriers of Anticancer siRNA.

Gene therapy is a promising approach in cancer treatment; however, current methods have a number of limitations mainly due to the difficulty in delivering therapeutic nucleic acids to their sites of action. The application of non-viral carriers based on nanomaterials aims at protecting genetic material from degradation and enabling its effective intracellular transport. We proposed the use of silver nanoparticles (AgNPs) surface-modified with carbosilane dendrons as carriers of anticancer siRNA (siBcl-xl). Using gel electrophoresis, zeta potential and hydrodynamic diameter measurements, as well as transmission electron microscopy, we characterized AgNP:siRNA complexes and demonstrated the stability of nucleic acid in complexes in the presence of RNase. Hemolytic properties of free silver nanoparticles and complexes, their effect on lymphocyte proliferation and cytotoxic activity on HeLa cells were also examined. Confocal microscopy proved the effective cellular uptake of complexes, indicating the possible use of this type of silver nanoparticles as carriers of genetic material in gene therapy.

Poly(lysine) Dendrimers Form Complexes with siRNA and Provide Its Efficient Uptake by Myeloid Cells: Model Studies for Therapeutic Nucleic Acid Delivery.

The disruption of the cellular pathways of protein biosynthesis through the mechanism of RNA interference has been recognized as a tool of great diagnostic and therapeutic significance. However, in order to fully exploit the potential of this phenomenon, efficient and safe carriers capable of overcoming extra- and intracellular barriers and delivering siRNA to the target cells are needed. Recently, attention has focused on the possibility of the application of multifunctional nanoparticles, dendrimers, as potential delivery devices for siRNA. The aim of the present work was to evaluate the formation of dendriplexes using novel poly(lysine) dendrimers (containing lysine and arginine or histidine residues in their structure), and to verify the hypothesis that the use of these polymers may allow an efficient method of siRNA transfer into the cells in vitro to be obtained. The fluorescence polarization studies, as well as zeta potential and hydrodynamic diameter measurements were used to characterize the dendrimer:siRNA complexes. The cytotoxicity of dendrimers and dendriplexes was evaluated with the resazurin-based assay. Using the flow cytometry technique, the efficiency of siRNA transport to the myeloid cells was determined. This approach allowed us to determine the properties and optimal molar ratios of dendrimer:siRNA complexes, as well as to demonstrate that poly(lysine) dendrimers may serve as efficient carriers of genetic material, being much more effective than the commercially available transfection agent Lipofectamine 2000. This outcome provides the basis for further research on the application of poly(lysine) dendrimers as carriers for nucleic acids in the field of gene therapy.

An enzyme-free electrochemical sandwich DNA assay based on the use of hybridization chain reaction and gold nanoparticles: application to the determination of the DNA of Helicobacter pylori.

An ultrasensitive enzyme-free electrochemical sandwich DNA biosensor is described for the detection of ssDNA oligonucleotides. A DNA sequence derived from the genom of Helicobacter pylori was selected as a model target DNA. The DNA assay was realized through catching target DNA on capture DNA immobilized gold electrode; then labeling the target DNA with reporter DNA (rpDNA) and initiator DNA (iDNA) co-modified gold nanoparticles (AuNPs). The high density of iDNAs serves as one of the amplification strategies. The iDNA triggers hybridization chain reaction (HCR) between two hairpins. This leads to the formation of a long dsDNA concatamer strand and represents one amplification strategy. The electrochemical probe [Ru(NH3)5L]2+, where L stands for 3-(2-phenanthren-9-ylvinyl)pyridine, intercalated into dsDNA chain. Multiple probe molecules intercalate into one dsDNA chain, serving as one amplification strategy. The electrode was subjected to differential pulse voltammetry for signal acquisition, and the oxidation peak current at -0.28V was recorded. On each AuNP, 240 iDNA and 25 rpDNA molecules were immobilized. Successful execution of HCR at the DNA-modified AuNPs was confirmed by gel electrophoresis and hydrodynamic diameter measurements. Introduction of HCR significantly enhances the DNA detection signal intensity. The assay has two linear ranges of different slopes, one from 0.01 fM to 0.5 fM; and one from 1 fM to 100 fM. The detection limit is as low as 0.68 aM. Single mismatch DNA can be differentiated from the fully complementary DNA. Conceivably, this highly sensitive and selective assay provides a general method for detection of various kinds of DNA. Graphical abstractSchematic representation of the detection and the amplification principles of the electrochemical sandwich DNA assay. Purple curl: Captured DNA; Green curl: Reporter DNA; Orange curl: HCR initiator DNA; Yellow solid-circle: Gold nanoparticle; H1 and H2: Two hairpin DNA; [Ru(NH3)5L]2+: Signal probe.

Green approach for the activation and functionalization of jute fibers through ball milling

As well known, cellulose fibers, defibrillated/activated in different degrees or even chemically modified, can be employed as additives in matrixes of different nature with the aim of modulating some properties such as the mechanical resistance, rheological behavior or hydrophobicity of the product. Consequently, there is an increasing interest in the incorporation of these materials in a wide variety of products, being necessary the development of green methodologies for their chemical modification. The objective of this work is the use of the ball milling technology as tool for the activation and chemical modification of cellulose fibers, specifically of cellulosic material from jute. The traditional method used to date for the NCO-functionalization of cellulose fibers requires a solvent as reaction medium, the action of a catalyst and a previous stage of mercerization to boost the reactivity of the fibers. Accordingly to the former, jute fibers were NCO-functionalized, on one side, evading previous mercerization and, on other side, applying two different alkali-based activation pre-treatments that lead to materials with different crystallinity index. In addition to this, and after having optimized milling conditions, both activation and NCO-functionalization were successfully carried out in a planetary ball mill avoiding solvent, catalyst and previous alkalization. Cellulose fibers esterification was successfully implemented over already ball milled cellulosic material, showing that activation and chemical modification do not need to be performed at the same time. Fourier transform infrared spectroscopy provided the follow-up of each reaction and the impact of ball milling on the fibers was analyzed by hydrodynamic diameter measurements. Thus, it is demonstrated that ball milling can be proposed as an efficient and environmentally friendly methodology for the activation and/or functionalization of cellulose fibers.

Controlling Size, Defectiveness, and Fluorescence in Nanoparticle UiO-66 Through Water and Ligand Modulation.

UiO-66, a zirconium(IV) metal-organic framework (MOF) comprised of six-metal clusters and terephthalic acid ligands, displays excellent thermal and chemical stability and has functions in gas storage, catalysis, selective adsorption, and drug delivery. Though the stability of UiO-66 is highly advantageous, simultaneous synthetic control over particle size and defectiveness of UiO-66 remains difficult to attain. Using an acid-free solvothermal synthesis, we demonstrate that particle size, defectiveness, and inherent fluorescence of UiO-66 can be precisely tuned using the molar ligand to metal ratio, quantified water content, and reaction time during synthesis. These three synthetic handles allow for reproducible modulation of UiO-66 defectiveness between 0 and 12% and particle size between 20 to 120 nm, while maintaining high crystallinity in the nanoparticles that were formed. We also find that particle defectiveness is linked to common over-estimation of particle size measurements obtained via dynamic light scattering (DLS) and propose a model to correct elevated hydrodynamic diameter measurements. Finally, we report inherent fluorescence of non-functionalized UiO-66, which exhibits peak fluorescence at a wavelength of 390 nm following excitation at 280 nm and is maximized in large, defect-free particles. Overall, this synthetic approach and characterization of defect, size, and fluorescence represent new opportunities to tune the physiochemical properties of UiO-66.

Improved emulsion stability and resveratrol encapsulation by whey protein/gum arabic interaction at oil-water interface

This work studied the effects of different concentrations of gum arabic (GA) on the interfacial adsorption kinetics of whey protein (WP) at the oil–water interface, the possibility of emulsion stabilized by WP/GA mixtures, and use of such emulsions as resveratrol delivery systems. Dynamic interface pressure measurements indicated that the change of GA concentration significantly affected the diffusion, penetration and rearrangement of WP at the oil–water interface, while measurements of hydrodynamic diameter and ζ-potential indicated electrostatic and hydrophobic interactions between WP and GA. The rheological measurements of the emulsions supported the above observations and indicated that different GA concentrations affected the viscoelastic properties of the emulsion. Adding resveratrol into oil influenced the adsorption of WP at the oil–water interface, thus affecting the emulsion stability and the encapsulation efficiency of resveratrol. The emulsions stabilized by WP and WP/GA mixtures have encapsulation efficiencies of >50% for resveratrol, while emulsions showed the best stability at a GA concentration of 0.2%. These results indicate that GA could effectively improve the emulsifying capacity of WP, while the emulsions prepared by WP/GA mixtures have the potential to serve as carriers for bioactive components.

Preparation, Characterization and Rheological Behavior of Glutathione-Chitosan Conjugates in Aqueous Media

Abstract Glutathione-chitosan conjugates are adequate carriers for anticancer treatment due to their ability for inhibition of efflux pumps, improved mucoadhesivity and in-situ gelling. These conjugates were obtained via carbodiimide at different reaction times in order to get different thiolation degrees (i.e., 4.4!, 5.1! and 7.0!) and their behavior in aqueous media at a pH of 4, 5 and 6 was assessed by measurements of hydrodynamic diameter, zeta potential and rheological analyses at a pH ranging from 4 to 6. Data examination was conducted by principal component analysis (PCA) which in turn explained 73.1! of data variability. All samples showed a Newtonian flow and thiolation rendered materials with a highly pronounced temperature-dependent behavior and a gel-like structure. In turn, the phase shift angle was the most prominent rheological change especially at a pH of 5.0 and 6.0 due to the formation of disulfide bonds. The thiolation degree was the most influential factor and it was inversely related to particle charge and consistency index.

Characterization of engineered nanoparticles in commercially available spray disinfectant products advertised to contain colloidal silver

Given the potential for human exposure to silver nanoparticles from spray disinfectants and dietary supplements, we characterized the silver-containing nanoparticles in 22 commercial products that advertised the use of silver or colloidal silver as the active ingredient. Characterization parameters included: total silver, fractionated silver (particulate and dissolved), primary particle size distribution, hydrodynamic diameter, particle number, and plasmon resonance absorbance. A high degree of variability between claimed and measured values for total silver was observed. Only 7 of the products showed total silver concentrations within 20% of their nominally reported values. In addition, significant variations in the relative percentages of particulate vs. soluble silver were also measured in many of these products reporting to be colloidal. Primary silver particle size distributions by transmission electron microscopy (TEM) showed two populations of particles - smaller particles (<5nm) and larger particles between 20 and 40nm. Hydrodynamic diameter measurements using nanoparticle tracking analysis (NTA) correlated well with TEM analysis for the larger particles. Z-average (Z-Avg) values measured using dynamic light scattering (DLS); however, were typically larger than both NTA or TEM particle diameters. Plasmon resonance absorbance signatures (peak absorbance at around 400nm indicative of metallic silver nanoparticles) were only noted in 4 of the 9 yellow-brown colored suspensions. Although the total silver concentrations were variable among products, ranging from 0.54mg/L to 960mg/L, silver containing nanoparticles were identified in all of the product suspensions by TEM.

Thermoresponsive nanoparticle agglomeration/aggregation in salt solutions: Dependence on graft density

Gold nanoparticles with a graft density of 0.09, 0.30 and 0.40chains/nm2 of poly(N-isopropylacrylamide) were reproducibly synthesized by varying the ratio of disulfide terminated poly(N-isopropylacrylamide) to gold nanoparticle. The polymer coated nanoparticles were stable at room temperature in 50mM NaCl, yet agglomerated at 37°C. Previous studies have observed conflicting results as to the reversibility of this agglomeration. Particle agglomeration with three different graft densities was studied in 50mM NaCl by measurements of their localized surface plasmon resonance and hydrodynamic diameter, and imaging with electron microscopy. Agglomerates with a polymer graft density of 0.30 and 0.40chains/nm2 could be dispersed with sonication, while particles with a graft density of 0.09chains/nm2 irreversibly aggregated. The graft density dependence on whether agglomeration or aggregation occurred is due to changes in collapsed polymer steric effects. Localized surface plasmon resonance measurements of agglomerates were discordant with hydrodynamic diameter measurements in determining agglomeration reversibility, which shed light on reasons previous reports yielded different interpretations on the reversibility of this agglomeration. This work demonstrates how polymer graft density affects thermoresponsive nanoparticle stability in salt solutions and the need for use of complementary techniques when determining agglomeration.

On the stability of 3H and 63Ni Ultima Gold liquid scintillation sources

The stability of 3H and 63Ni samples, made with Ultima Gold and Ultima Gold AB using eight aqueous fractions ranging between 0.1% and 10%, was monitored over a period of 32 weeks. Counting rate losses were measured in all cases, but were found to be particularly severe for samples with low aqueous fractions. Hydrodynamic diameter measurements of the reverse micelles of 3H and 63Ni in Ultima Gold and Ultima Gold AB samples were performed with dynamic light scattering. For Ultima Gold, the micelle diameters were measured to be about 2nm and slightly dependent of the aqueous fraction, while for Ultima Gold AB they were found to vary strongly with the aqueous fraction and range between 1 and 4nm. The hypothesis that the counting rate instabilities derive from changes in the sizes of micelles was tested by measuring them four times over the monitoring period. The measurement results do not support this claim.

Formulation and characterization of food-grade microemulsions as carriers of natural phenolic antioxidants

Food-grade W/O microemulsions based on lecithin, caprylic/capric triglycerides, isopropyl myristate, alcohols and water were formulated and structurally characterized to be used as potential carriers of natural food antioxidants. Different well-known food antioxidants including gallic acid, p-hydroxybenzoic acid, protocatechuic acid and tyrosol were successfully encapsulated in the aqueous cores of the microemulsions. A pseudo-ternary phase diagram was constructed to determine the extent of the monophasic area that corresponds to an inverted type microemulsion. Apparent hydrodynamic diameter measurements of empty and loaded microemulsions were performed using dynamic light scattering (DLS) and swollen micelles with diameters smaller than 10 nm were detected. Interfacial properties of the microemulsions were studied by electron paramagnetic resonance (EPR) spectroscopy employing the nitroxide spin probe 5-doxylstearic acid (5-DSA). A small increase in spin probe mobility upon addition of the antioxidants was observed; whereas the rigidity of the surfactants was not affected. Cryogenic transmission electron microscopy (Cryo-TEM) indicated the existence of entangled thread-like reversed micelles. Finally, the investigated phenolics were assessed and compared for their radical scavenging activity using an EPR approach based on free radicals. The encapsulated gallic acid showed the highest antioxidant activity (0.93 mM trolox equivalents) as compared to other antioxidants assessed within the frame of this study.

Effects of groundwater solutes on colloidal stability of polymer-coated and bare nanosized zero-valent iron particles

Colloidal stabilities of polymer-coated nanosized zero-valent iron (pNZVI) and bare nanosized zero-valent iron (bNZVI) particles were investigated in the presence of groundwater solutes, such as Suwannee River natural organic matter (SRNOM), Pony Lake fulvic acid (PLFA), sodium ion, and calcium ion. Measurements of hydrodynamic diameter and zeta-potential showed that dissolved organic matters (SRNOM and PLFA) enhanced the stability of bNZVI particles, but that they did not affect the stability of pNZVI particles. These measurements also showed that the stability of pNZVI particles was inhibited by the cations but that the effect of the cations on bNZVI particles was inconclusive. The sedimentation test confirmed that the stability of pNZVI particles was inhibited by the sodium and calcium ions. The sedimentation test identified that the stability of bNZVI particles was inhibited only in the presence of calcium ion. The predictions on the stability of NZVI particles based on the Derjaguin–Landau–Verwey–Overbeek interaction energies were generally consistent with experimental observations. Energy barriers of bNZVI particles were estimated to be up to 7.5 and 91 kBT in the presence of PLFA and SRNOM, respectively. For pNZVI particles, energy barriers were present in all experimental conditions except for the suspension with calcium ion.

Study of the effect of nanoclay incorporation on the rheological properties and corrosion protection by a silane layer

The corrosion protection properties offered to galvanized steel by an aqueous based silane layer are studied after incorporation of different amounts of sodium montmorillonite nanoclays (Na MMT). The rheological behaviour of Na + nanoclays in aqueous suspensions was determined in order to select the appropriate sonication time and concentration for incorporation in the silane matrix. The effect of sonication on the disaggregation/exfoliation of platelets was evaluated by using different characterization methods such as using the methylene blue (MB) dye as a spectrophotometric probe (UV–vis), zeta potential and hydrodynamic diameter measurements. The corrosion protection conferred to galvanized steel substrate by the modified silane layer was evaluated by electrochemical impedance spectroscopy (EIS) in 0.1 M aerated sodium chloride solution. The barrier properties of the silane layer are significantly increased by addition of 2 wt.% of clay sonicated for 1 and 2 h.