Sorption of oxytetracycline to microsized colloids under concentrated salt solution: A perspective on terrestrial-to-ocean transfer of antibiotics.

The sorption of antibiotics on soil minerals and their cotransport have been widely studied for the past few years; however, these processes in concentrated salt solutions (estuary-like conditions) are not fully understood. This study aims to determine the possible sorption of oxytetracycline (OTC) on various natural and synthesized microsized minerals (including haematite, goethite, kaolinite, bentonite, lateritic, kaolinitic and illitic soil clays) under conditions mimicking pure, fresh, brackish and sea waters. The sorption of OTC was found to decrease in surface charge (herein zeta potential), hence altering the colloidal properties of the materials used. The sorption capacities of soil clays for OTC follow the inequality illitic soil clay > kaolinitic soil clay > lateritic soil clay, and the sorption capacities were found to decrease at higher salt concentrations. Seawater can intensify the release of the sorbed OTC from soil clay surfaces while favouring the coaggregation of the remaining OTC with soil clays. This implies that the long-range transport of OTC or other similar antibiotics can be governed by the mineralogical composition/properties of the suspended particles. More importantly, increasing salt concentrations in estuaries may form a chemical barrier at which limited amounts of OTC/antibiotics can pass through, while the remaining OTC/antibiotics can be favoured to aggregate simultaneously with suspended mineral particles.

Combination of Milk and Plant Proteins to Develop Novel Food Systems: What Are the Limits?

In the context of a diet transition from animal protein to plant protein, both for sustainable and healthy scopes, innovative plant-based foods are being developing. A combination with milk proteins has been proposed as a strategy to overcome the scarce functional and sensorial properties of plant proteins. Based on this mixture were designed several colloidal systems such as suspensions, gels, emulsions, and foams which can be found in many food products. This review aims to give profound scientific insights on the challenges and opportunities of developing such binary systems which could soon open a new market category in the food industry. The recent trends in the formulation of each colloidal system, as well as their limits and advantages are here considered. Lastly, new approaches to improve the coexistence of both milk and plant proteins and how they affect the sensorial profile of food products are discussed.

Sorption of cosmetic and personal care polymer ingredients to iron oxides, clay minerals and soil clays: An environmental perspective.

The increasing daily use of cosmetic and personal care ingredients (CPCIs) requires improved understanding of the fate and impacts of CPCIs in environmental systems. Effects of CPCIs on colloidal properties of various geocolloids such as iron oxides (goethite, haematite), clay minerals (kaolinite, bentonite) and soil clays (kaolinitic-, illitic- and lateritic soil clays) were studied by tracking time-resolved changes in zeta potential (ζ) and observing suspended particle density. Two polymers representing anionic CPCIs, i.e., polyacrylate crosspolymer-11 (PC11) and cationic CPCIs, i.e., polyDADMAC (PD) show contrast effects on ζ and colloidal properties of the selected materials. While PC11 tended to associate with Fe oxides, PD can be adsorbed by clay minerals and soil clays. The neutralization due to the sorption of either PC11 or PD onto opposite-charge sign surface sites can lower the net surface charge of the materials, thereby enhancing electrostatic attraction, stimulating particle size growth, and eventually intensifying co-aggregation. The observed colloidal properties of iron oxides, clay minerals and soil clays under the presence of PC11 and PD may reflect what are happening in many aquatic environments where CPCIs co-exist with various mineral colloids. Therein, CPCIs likely delay the transport of the opposite-charge sign colloids, while they increase the dispersibility and transportability of the same-charge sign colloids. This implies that intensifying presence of a given CPCI could have selective effects on colloid systems. As a whole, CPCIs can change the fate and the final destination of mineral colloids and themselves; therefore, their effects and relevant treatment techniques need to be included into the future agenda.

Comparative effects of crystalline, poorly crystalline and freshly formed iron oxides on the colloidal properties of polystyrene microplastics.

Colloid-sized microplastics (MPs) are ubiquitous in aquatic environments and can share the same transport route together with various crystalline, poorly crystalline and freshly formed iron oxides. However, the colloidal interactions between these colloid constituents are not fully understood. This study was designed to investigate the colloidal properties of polystyrene microplastics (PSMPs) under the influence of haematite, goethite, ferrihydrite and freshly formed Fe oxide (FFFO). Dynamic light scattering was coupled with a test tube method to observe changes in the surface charge and colloidal dynamics of suspensions of PSMPs and Fe oxides. The overall effects on the aggregation of PSMPs are found to decrease in the following order: FFFO > ferrihydrite > goethite > haematite. The effects of these Fe oxides are found to strongly depend on pH. While the crystalline oxides play a dominant role in the acidic environment, poorly crystalline oxides show greater effects on PSMP aggregation in an alkaline environment. Heteroaggregation due to decreasing electrostatic interactions is the major mechanism that governs the colloidal dynamics of PSMPs and Fe oxides. It can be inferred that the copresence of Fe oxides and MPs can delay the transport of MPs or even change the destination for MPs.

Influence of Coating and Size of Magnetic Nanoparticles on Cellular Uptake for In Vitro MRI.

Iron oxide nanoparticles (IONPs) are suitable materials for contrast enhancement in magnetic resonance imaging (MRI). Their potential clinical applications range from diagnosis to therapy and follow-up treatments. However, a deeper understanding of the interaction between IONPs, culture media and cells is necessary for expanding the application of this technology to different types of cancer therapies. To achieve new insights of these interactions, a set of IONPs were prepared with the same inorganic core and five distinct coatings, to study their aggregation and interactions in different physiological media, as well as their cell labelling efficiency. Then, a second set of IONPs, with six different core sizes and the same coating, were used to study how the core size affects cell labelling and MRI in vitro. Here, IONPs suspended in biological media experience a partial removal of the coating and adhesion of molecules. The FBS concentration alters the labelling of all types of IONPs and hydrodynamic sizes ≥ 300 nm provide the greatest labelling using the centrifugation-mediated internalization (CMI). The best contrast for MRI results requires a core size range between 12-14 nm coated with dimercaptosuccinic acid (DMSA) producing R2* values of 393.7 s-1 and 428.3 s-1, respectively. These findings will help to bring IONPs as negative contrast agents into clinical settings.

Effects of different processing steps on the flavor and colloidal properties of cloudy apple juice.

BACKGROUND: Flavor loss is a common problem when manufacturing apple juice and is closely related to the properties of the colloidal pectin particles in cloudy juice. The flavor changes and particle properties of three varieties of apple juice ('Ralls', 'Golden Delicious' and 'Fuji') during processing were investigated. RESULTS: Compared with manually pressed juice, juice made by industrial pulping and filtration contained larger particles, resulting in the 'sweet and sour' taste of the juice being relatively weak and the diversity of aromas narrower, as determined by E-nose analysis. Pulping and filtration, however, released some important flavor esters, such as butyl butyrate, hexyl-2-methyl butyrate, and hexyl butyrate. The transformation of volatile compounds during apple juice processing was closely related to the apple cultivar but, in all three varieties, the content of 1-hexanal and (E)-2-hexenal in the juice gradually decreased during processing. Pectinase treatment reduced the colloid particle size and increased the ζ-potential of the juice, resulting in better uniformity and stability, as well as increasing the content of nonanal. After pasteurization, the colloidal particles tended to aggregate and the ζ-potential decreased. Many volatile compounds decreased in concentration or disappeared after heat treatment. CONCLUSION: The flavor and colloidal properties of cloudy apple juice changed markedly during processing and the effect of each processing step was different. © 2020 Society of Chemical Industry.

Colloidal interactions of micro-sized biochar and a kaolinitic soil clay.

Fine-sized biochars and clay minerals co-present in various circumstances, e.g., agricultural land and water treatment. Because both of these materials are scavengers for nutrients, agrochemicals and other toxicants, their dispersibility and transportability have received much attention. However, little is documented about their colloidal interactions and to what extent biochar particles can stimulate the dispersion of clay minerals. Here, the effect of engineered micro-sized biochar amendment on the surface charge (SC) and colloidal dynamics of the clay fraction of a kaolinite-rich soil was determined. The engineered biochars showed distinctive SC and colloidal properties depending on their pyrolysis conditions (e.g., oxygen level and temperature) and solution chemistry (i.e., pH and cation type). Two types of biochars prepared under non-biochar-oriented pyrolysis (open heating, 'O-biochar') and biochar-oriented pyrolysis (N2-supported heating, 'N2-biochar') showed contrasting effects on the colloidal dynamics of clay. The O-biochars provoked aggregation due to their higher content of soluble salts, which increased ionic strength and provided multivalent cations, inducing bridging between negatively charged colloids. In contrast, the N2 biochars low in soluble salts and rich in negatively charged burned organic matter compounds favoured the dispersion of clay. The adjustment of biochar production methods can therefore be highlighted as the way to customize biochar for specific uses or to reduce the risk of clay loss from soils in the short term. In the long term, when soluble salts are removed by leaching, it is likely that dispersion is facilitated and the risk for erosion increases.

Variability in Probiotic Formulations Revealed by Proteomics and Physico-chemistry Approach in Relation to the Gut Permeability.

Variability in the efficacy, safety, and quality of probiotic formulations depends on many factors, including process conditions used by manufacturers. Developing reliable analytical tools is therefore essential to quickly monitor manufacturing differences in probiotic samples for their quality assessment. Here, multi-strain probiotics from two production sites and countries were investigated by proteomics and physico-chemistry approaches in relation to the protective effect on gut barrier. Proteomic analyses showed differences in protein abundances, identities, and origins of two series of VSL#3 samples from different sites. Even though both formulations were qualitatively similar in thermal and colloidal profiles, significant differences were quantitatively observed in terms of maximum decomposition temperature Tmax (p < 0.05) and phase transition temperature Tm (p < 0.01). Such variability in physical and biochemical features impacts on probiotic functionalities and translates into a differential modulation of gut permeability in mice. Physico-chemical scans provide coherent data with proteomics and represent a new tool for time and cost effective quality control of probiotic-based products.

Diethylaminoethyl chitosan-hyaluronic acid polyelectrolyte complexes.

Polysaccharide-based polyelectrolyte complexes (PECs) are of great interest for the development of drug delivery systems, as they are easily prepared and exhibit a wide range of colloidal properties. The water-soluble diethylaminoethyl chitosan (DEAE-CS) was synthesized with various degrees of substitution (DS), ranging from 26 to 113%. Analysis of the substitution pattern of DEAE-CS by different NMR techniques revealed N- and O-substitution, as well as quaternization of the tertiary amino group of the DEAE substituent; the fraction of quaternary amino groups increased with the DS. Unlike the tertiary amino groups, the quaternary amino groups did not support increases in the ζ-potential of DEAE-CS with the DS and the complexation with hyaluronic acid (HA). The influence of the PEC composition, DS of DEAE-CS, and mixing order on the size and polydispersity of PEC nanoparticles was investigated by dynamic and static light scattering. Internal disordered heterogeneous PEC nanoparticles were formed by the aggregates of several primary PECs. Disordered and structurally heterogeneous spherical complexes were formed (Rg/Rh = 1.0 ± 0.3). The obtained PECs were metastable and their properties were influenced by mixing order. The high molecular weight component (HA), being a minor component, was more exposed on the surface than was the low molecular weight DEAE-CS.

Colloidal properties and stability of UV-transformed graphene oxide in aqueous solutions: The role of disorder degree.

Motivated by the use of ultraviolet (UV) radiation in the disinfection processes of drinking and waste water treatment plants, this study explores the colloidal properties and stability of UV irradiated graphene oxide (GO) by using the batch technique and time-resolved dynamic light scattering over a wide range of salt types (NaCl, MgCl2, and CaCl2) and ionic strength relevant to engineered and natural systems. The results show that the UV irradiation time has an important impact on the physicochemical properties of GO and consequently on its colloidal properties and stability. The aggregation kinetics, attachment efficiency and critical coagulation concentration (CCC) values of UV irradiated GO are obtained for the first time. By correlating CCC values with physicochemical properties, we find that the disorder degree plays a more important role in colloidal properties and stability of UV irradiated GO than oxygen containing functional groups. The findings are valuable for environmental fate assessments on various families of functionalized GO.

Quillaja Saponin Characteristics and Functional Properties.

Consumer concerns about synthetically derived food additives have increased current research efforts to find naturally occurring alternatives. This review focuses on a group of natural surfactants, the Quillaja saponins, that can be extracted from the Quillaja saponaria Molina tree. Quillaja saponins are triterpenoid saponins comprising a hydrophobic quillaic acid backbone and hydrophilic sugar moieties. Commercially available Quillaja saponin products and their composition and properties are described, and the technofunctionality of Quillaja saponins in a variety of food, cosmetic, and pharmaceutical product applications is discussed. These applications make use of the biological and interfacial activities of Quillaja saponins and their ability to form and stabilize colloidal structures such as emulsions, foams, crystallized lipid particles, heteroaggregates, and micelles. Further emphasis is given to the complexation and functional properties of Quillaja saponins with other cosurfactants to create mixed surfactant systems, an approach that has the potential to facilitate new interfacial structures and novel functionalities.

Interpenetrating Polymer Network Microgels in Water: Effect of Composition on the Structural Properties and Electrosteric Interactions.

Microgels of cross-linked interpenetrating polymer networks (IPNs) are very versatile systems combining the properties of colloids and polymers. Herein we study IPN microgels composed of poly(N-isopropylacrylamide) and poly(acrylic acid) to understand how weight composition and reactant concentrations affect their structural, conformational and electrosteric properties in water. The results show that it is possible to drive the formation of microgels with the desired properties by adjusting IPN composition and preparation method during the synthesis. During synthesis, the polymerization of acrylic acid triggers the merging among IPNs via covalent linking, giving rise to microgels with larger mass and size, the effect being larger for higher concentration of the reactants. In addition, a close relation between the microgel internal conformation and the colloidal stability is observed, due to the presence of screened groups inside the microgel.

Water-based fractionation of a commercial humic acid. Solid-state and colloidal characterization of the solubility fractions.

BACKGROUND AND HYPOTHESIS: Humic acid (HA) is of considerable environmental significance, being a major component of soil, as well as being considered for application in other technological areas. However, its structure and colloidal properties continue to be the subject of debate, largely owing to its molecular complexity and association with other humic substances and mineral matter. As a class, HA is considered to comprise supramolecular assemblies of heterogeneous species, and herein we consider a simple route for the separation of some HA sub-fractions. EXPERIMENTS: A commercial HA sample from Sigma-Aldrich has been fractionated into two soluble (S1, S2) and two insoluble (I1, I2) fractions by successive dissolution in deionized water at near-neutral pH. These sub-fractions have been characterized by solution and solid-state approaches. FINDINGS: Using this simple approach, the HA has been shown to contain non-covalently bonded species with different polarity and water solubility. The soluble and insoluble fractions have very different chemical structures, as revealed particularly by their solid-state properties (13C NMR and IR spectroscopy, and TGA); in particular, S1 and S2 are characterized by higher carbonyl and aromatic contents, compared with I1 and I2. As shown by solution SAXS measurements and AFM, the soluble fractions behave as hydrophilic colloidal aggregates of at least 50nm diameter.

High-concentration protein formulations: How high is high?

High-concentration protein formulation (HCPF) is a term that is used to describe protein formulations, mostly monoclonal antibody (mAb) drugs, at high protein concentration. The concentration is rarely defined, with typical ranges varying between 50 and 150mg/ml for mAbs. The term HCPF is meant to include and express specific solution properties of formulations that are prone to appear at high protein concentrations such as high viscosity, high opalescence, phase separation, gel formation or the increased propensity for protein particle formation. Thus the term HCPF can be understood as a descriptor of protein formulations, usually at high protein (monoclonal antibody) concentrations, which have specific solution, stability and colloidal properties that differ from formulations at low protein concentration (e.g. at 10mg/ml). The current paper highlights in brief the development challenges that might occur for high-concentration protein/monoclonal antibody formulations. In particular, the maximum concentration regimes achievable in HCPF remained unclear. Based on geometrical considerations involving packing of monoclonal antibodies in a lattice we map out a maximum concentration range that might be theoretically achievable. Different geometrical assumptions and packing models are compared and their relevance is critically discussed, in particular concerning the influence of the physicochemical properties of the monoclonal antibodies on their solubility, which is neglected in the simple geometrical model. According to our estimates, monoclonal antibody concentration above 500mg/ml will be very challenging to achieve. Our results have implications for setting up realistic drug product development strategies and for preparing convincing drug target product profiles for development.

Transglutaminase-set colloidal properties of wheat gluten with ultrasound pretreatments.

The low solubility of wheat gluten limits its accessibility. This work aimed to study the impact of ultrasonic pretreatments on the gelation of wheat gluten. The pretreatments included ultrasound combined with alkali, urea, Na2SO3, with or without the addition of transglutaminase (TGase). The gel strength of wheat gluten was 287g/cm2 after treatment with Na2SO3/ultrasound/TGase. The free sulfhydryl and disulfide bond content was significantly affected by ultrasound treatment. After treatments including TGase crosslinking, the molecular weight of wheat gluten complexes became larger. The network formed by the wheat gluten was transformed into a dense and homogenous structure after the pretreatment with Na2SO3/ultrasound/TGase. The content of random coil of wheat gluten increased. The gelation of wheat gluten could also be significantly enhanced by Na2SO3/ultrasound treatment followed by TGase treatment. Using physical and chemical pretreatments to allow TGase to enhance the gelation of wheat gluten may increase its uses as a food additive.

Suspension stability and mobility of Trap-Ox Fe-zeolites for in-situ nanoremediation.

With Trap-Ox Fe-zeolites we intend to develop a novel nanoremediation concept, which is based on in situ trapping of organic contaminants by adsorption and catalytic oxidation in combination with oxidants such as hydrogen peroxide. Within this study, colloidal properties including surface charge and suspension stability as well as mobility in porous media were studied under various conditions for two Trap-Ox Fe-zeolite representatives: Fe-BEA35 and Fe-MFI120. These Fe-zeolites can act as adsorbent for contaminants and as micro-reactors for their catalytic Fenton-like oxidation. Both Fe-zeolites under investigation show remarkable suspension stability in slightly alkaline suspension (pH 8-8.5) without any additional stabilizers, but not in acidic suspensions (pH 5.5). Mobility investigations in columns with clean sand and natural sand suggest high mobility at slightly alkaline conditions. Particle breakthrough through 20cm sand columns was >75% for the two zeolites when injected as 10g/L suspensions with a flow velocity of 10m/d. However, under acidic conditions in natural sediment, a long period of near-total deposition of particles is observed before high breakthrough occurs. The pH dependency is believed to be caused by charge inhomogeneity due to Fe-oxide clusters on the zeolites as well as on the sediment grains.

Influence of Temperature on the Colloidal Stability of Polymer-Coated Gold Nanoparticles in Cell Culture Media.

The temperature-dependence of the hydrodynamic diameter and colloidal stability of gold-polymer core-shell particles with temperature-sensitive (poly(N-isopropylacrylamide)) and temperature-insensitive shells (polyallylaminine hydrochloride/polystyrensulfonate, poly(isobutylene-alt-maleic anhydride)-graft-dodecyl) are investigated in various aqueous media. The data demonstrate that for all nanoparticle agglomeration, i.e., increase in effective nanoparticle size, the presence of salts or proteins in the dispersion media has to be taken into account. Poly(N-isopropylacrylamide) coated nanoparticles show a reversible temperature-dependent increase in size above the volume phase transition of the polymer shell when they are dispersed in phosphate buffered saline or in media containing protein. In contrast, the nanoparticles coated with temperature-insensitive polymers show a time-dependent increase in size in phosphate buffered saline or in medium containing protein. This is due to time-dependent agglomeration, which is particularly strong in phosphate buffered saline, and induces a time-dependent, irreversible increase in the hydrodynamic diameter of the nanoparticles. This demonstrates that one has to distinguish between temperature- and time-induced agglomerations. Since the size of nanoparticles regulates their uptake by cells, temperature-dependent uptake of thermosensitive and non-thermosensitive nanoparticles by cells lines is compared. No temperature-specific difference between both types of nanoparticles could be observed.

Particle size, charge and colloidal stability of humic acids coprecipitated with Ferrihydrite.

Humic acids (HA) have a colloidal character whose size and negative charge are strictly dependent on surface functional groups. They are able to complex large amount of poorly ordered iron (hydr)oxides in soil as a function of pH and other environmental conditions. Accordingly, with the present study we intend to assess the colloidal properties of Fe(II) coprecipitated with humic acids (HA) and their effect on Fe hydroxide crystallinity under abiotic oxidation and order of addition of both Fe(II) and HA. TEM, XRD and DRS experiments showed that Fe-HA consisted of Ferrihydrite with important structural variations. DLS data of Fe-HA at acidic pH showed a bimodal size distribution, while at very low pH a slow aggregation process was observed. Electrophoretic zeta-potential measurements revealed a negative surface charge for Fe-HA macromolecules, providing a strong electrostatic barrier against aggregation. Under alkaline conditions HA chains swelled, which resulted in an enhanced stabilization of the colloid particles. The increasing of zeta potential and size of the Fe-HA macromolecules, reflects a linear dependence of both with pH. The increase in the size and negative charge of the Fe-HA precipitate seems to be more affected by the ionization of the phenolic acid groups, than by the carboxylic acid groups. The main cause of negative charge generation of Fe/HA is due to increased dissociation of phenolic groups in more expanded structure. The increased net negative surface potential induced by coprecipitation with Ferrihydrite and the correspondent changes in configuration of the HA could trigger the inter-particle aggregation with the formation of new negative surface. The Fe-HA coprecipitation can reduce electrosteric repulsive forces, which in turn may inhibit the aggregation process at different pH. Therefore, coprecipitation of Ferrihydrite would be expected to play an important role in the carbon stabilization and persistence not only in organic soils, but also in waters containing dissolved organic matter.