Soil colloids can significantly enhance spreading of polybromodiphenyl ethers in groundwater by serving as an effective carrier.

Polybromodiphenyl ethers (PBDEs), the widely used flame retardants, are common contaminants in surface soils at e-waste recycling sites. The association of PBDEs with soil colloids has been observed, indicating the potential risk to groundwater due to colloid-facilitated transport. However, the extent to which soil colloids may enhance the spreading of PBDEs in groundwater is largely unknown. Herein, we report the co-transport of decabromodiphenyl ester (BDE-209) and soil colloids in saturated porous media. The colloids released from a soil sample collected at an e-waste recycling site in Tianjin, China, contain high concentration of PBDEs, with BDE-209 being the most abundant conger (320 ± 30 mg/kg). The colloids exhibit relatively high mobility in saturated sand columns, under conditions commonly observed in groundwater environments. Notably, under all the tested conditions (i.e., varying flow velocity, pH, ionic species and ionic strength), the mass of eluted BDE-209 correlates linearly with that of eluted soil colloids, even though the mobility of the colloids varies markedly depending on the specific hydrodynamic and solution chemistry conditions involved. Additionally, the mass of BDE-209 retained in the columns also correlates strongly with the mass of retained colloids. Apparently, the PBDEs remain bound to soil colloids during transport in porous media. Findings in this study indicate that soil colloids may significantly promote the transport of PBDEs in groundwater by serving as an effective carrier. This might be the reason why the highly insoluble and adsorptive PBDEs are found in groundwater at some PBDE-contaminated sites.

Environmental colloid behaviors of humic acid - Cadmium nanoparticles in aquatic environments.

Humic acid (HA), a principal constituent of natural organic matter (NOM), manifests ubiquitously across diverse ecosystems and can significantly influence the environmental behaviors of Cd(II) in aquatic systems. Previous studies on NOM-Cd(II) interactions have primarily focused on the immobilization of Cd(II) solids, but little is known about the colloidal stability of organically complexed Cd(II) particles in the environment. In this study, we investigated the formation of HA-Cd(II) colloids and quantified their aggregation, stability, and transport behaviors in a saturated porous media representative of typical subsurface conditions. Results from batch experiments indicated that the relative quantity of HA-Cd(II) colloids increased with increasing C/Cd molar ratio and that the carboxyl functional groups of HA dominated the stability of HA-Cd(II) colloids. The results of correlation analysis between particle size, critical aggregation concentration (CCC), and zeta potential indicated that both Derjaguin-Landau-Verwey-Overbeek (DLVO) and non-DLVO interactions contributed to the enhanced colloidal stability of HA-Cd(II) colloids. Column results further confirmed that the stable HA-Cd(II) colloid can transport fast in a saturated media composed of clean sand. Together, this study provides new knowledge of the colloidal behaviors of NOM-Cd(II) nanoparticles, which is important for better understanding the ultimate cycling of Cd(II) in aquatic systems.

A screening model for predicting the potential of soil colloids-enhanced leaching of hydrophobic organic contaminants to groundwater at contaminated sites.

Modeling the fate and transport of organic pollutants at contaminated sites is critical for risk assessment and management practices, such as establishing realistic cleanup standards or remediation endpoints. Against the conventional wisdom that highly hydrophobic persistent organic pollutants (POPs) (e.g., polybrominated diphenyl ethers and polycyclic aromatic hydrocarbons) in surface soils are essentially immobile, mounting evidence has demonstrated the potential of these contaminants leaching into the groundwater, due to enhanced transport by soil colloids. Here, we develop a Colloids-Enhanced Transport (CET) model, which can be used as a simple screening tool to predict the leaching potential of POPs into groundwater, as mediated by soil colloids. The CET model incorporates several processes, including the release of POPs-bearing colloids into the porewater, the vertical transport of colloids and associated POPs in the vadose zone, the mixing of POPs-containing soil leachate with groundwater, and the migration of POPs-bearing colloids in saturated zone. Thus, using parameters that can be easily obtained (e.g., annual rainfall, soil type, and common hydrogeological properties of the subsurface porous media), the CET model can estimate the concentrations of POPs in the saturated zone from the observed POPs concentrations in surface or shallow subsurface zones. The CET model can also be used to derive soil quality standards or cleanup endpoints by back-calculating soil concentrations based on groundwater protection limits.

The Janus effect of colloidal self-assembly on the biological response of amphiphilic drugs.

In aqueous environment amphiphilic molecules organize themselves into supramolecular structures deeply affecting the chemo-physical properties. Supramolecular assemby is also crucial in the pharmaceutical development of bioactive lipophilic molecules whose attitude to self-aggregate is a recognized factor affecting the in vivo pharmacokinetic, but can also play a crucial role in the interaction with the biological targets in in vitro tests. In aqueous solution, amphiphilic drugs exist in a complex equilibrium involving free monomers, oligomers and larger supramolecular aggregates held together by noncovalent bonds. In this review we focus our attention on the dual effect of drugs self-assembly, which can both reduce the availability of active compounds and create multivalent scaffolds, potentially improving binding affinity and avidity to cellular targets. We examine the effect of aggregation on different classes of amphiphatic molecules with significant biological activities, such as immunomodulatory, anti-tumor, antiviral, and antibiotic. Our purpose is to provide a comprehensive overview of how supramolecular chemistry influences the pharmacological and biological responses of amphiphilic molecules, emphasizing the need to consider these effects in early-stage drug development and in vitro testing. By elucidating these phenomena, this review aims to offer insights into optimizing drug design and formulation to overcome challenges posed by self-aggregation.

Humic acid enhances the co-transport of colloids and phosphorus in saturated porous media.

Phosphorus (P) has been widely recognized as a substance that is difficult to transport due to its tendency to become easily fixed in the soil. However, many reports demonstrate that groundwater P pollution is rising in humus-rich areas. Research is urgently needed to confirm (or reject) the hypothesis that increased P pollution is related to humus, as there is currently limited quantitative research on this topic. In this study, we conducted a series of batch equilibrium adsorption-desorption experiments and column experiments to quantify the effects of montmorillonite colloids (MCs) and humic acids (HCs, the main components of humus) on the P transport behavior. The results indicate that P's adsorption and desorption behavior on MCs can be well simulated using the Langmuir and Temkin models (R2 > 0.91). Compared to the non-HC treatments, HCs significantly increased MCs' P adsorption and desorption capacity 5.18 and 7.21 times, respectively. Moreover, HCs facilitated the transport ability of the MC-P mixture through the saturated quartz sand column. In a 0.1 M NaCl solution, the MC-P mixture is nearly completely adsorbed on the surface of quartz sand, with a penetration rate of only 0.5%. In contrast, the HC-MC-P mixture can evidently penetrate further at a rate of 26.1%. The transport parameters fitted using HYDRUS-1D further indicated that the presence of humic acids significantly decreased the deposition coefficients of colloids, thereby enhancing the co-transport of colloids and P through the quartz sand porous medium. The potential mechanism of P pollution in humus-rich areas is likely enhanced by the formation of an HC-colloid-P mixture, which greatly increases the adsorption amount of P on colloids and enhances the electrostatic and spatial repulsion between colloids as well as between colloids and quartz sand. It reduces the aggregation and adsorption of colloids, ultimately transferring P into groundwater through colloid-facilitated co-transport. The findings of this study clarified the relationship between the transport of P, colloids, and HCs, which provides a theoretical basis for explaining the P pollution mechanism in humus-rich areas.

Nanoporous Polystyrene Inverse Opal Materials with Optical Interference Properties for Label-Free Biosensing.

Colloidal crystal nanomaterials have been proven to be valuable substrates for optical-based biosensing due to their ordered macroporous nanostructure and brilliant optical properties. In this work, silica colloidal crystal (SCC) thin films, as well as polystyrene-SCC composite films and inverse opal (IO) polystyrene films fabricated using SCC as templates, are investigated for their application as substrate materials in optical interferometric biosensors. The SCC films formed by the self-assembly of silica colloidal crystals have the most densely packed nano-3D structure, also known as the opal structure. IO films are fabricated by filling the opal pores of SCC with polystyrene and then removing the template, resulting in an interconnected nano-3D ordered macroporous structure, as indicated by the name inverse opal. The performance of the three materials was compared and discussed based on an ordered porous layer interferometry optical platform, focusing on refractive index response, protein adsorption response, and biomolecular interaction response. These results could potentially offer innovative material support for the advancement of label-free optical biosensors, which can be used for more biological/biochemical/biomolecular reaction monitoring studies.

Colloidal Hydrogel with Staged Sequestration and Release of Molecules Undergoing Competitive Binding.

Competitive binding of distinct molecules in the hydrogel interior can facilitate dynamic exchange between the hydrogel and the surrounding environment. The ability to control the rates of sequestration and release of these molecules would enhance the hydrogel's functionality and enable targeting of a specific task. Here, we report the design of a colloidal hydrogel with two distinct pore dimensions to achieve staged, diffusion-controlled scavenging and release dynamics of molecules undergoing competitive binding. The staged scavenging and release strategy was shown for CpG oligodeoxynucleotide (ODN) and human epidermal growth factor (hEGF), two molecules exhibiting different affinities to the quaternary ammonium groups of the hydrogel. Fast ODN scavenging from the ambient environment occurred via diffusion through submicrometer-size hydrogel pores, while delayed hEGF release from the hydrogel was governed by its diffusion through nanometer-size pores. The results of the experiments were in agreement with simulation results. The significance of staged ODN-hEGF exchange was highlighted by the dual anti-inflammation and tissue proliferation hydrogel performance.

Analytical and Numerical Investigation of Star Polymers in Confined Geometries.

The analysis of the impact of the star polymer topology on depletion interaction potentials, depletion forces, and monomer density profiles is carried out analytically using field theory methods and techniques as well as molecular dynamic simulations. The dimensionless depletion interaction potentials and the dimensionless depletion forces for a dilute solution of ideal star polymers with three and five legs (arms) in a Θ-solvent confined in a slit between two parallel walls with repulsive surfaces and for the case where one of the surfaces is repulsive and the other inert are obtained. Furthermore, the dimensionless layer monomer density profiles for ideal star polymers with an odd number (f˜ = 3, 5) of arms immersed in a dilute solution of big colloidal particles with different adsorbing or repelling properties in respect of polymers are calculated, bearing in mind the Derjaguin approximation. Molecular dynamic simulations of a dilute solution of star-shaped polymers in a good solvent with N = 901 (3 × 300 + 1 -star polymer with three arms) and 1501 (5 × 300 + 1 -star polymer with five arms) beads accordingly confined in a slit with different boundary conditions are performed, and the results of the monomer density profiles for the above-mentioned cases are obtained. The numerical calculation of the radius of gyration for star polymers with f˜ = 3, 5 arms and the ratio of the perpendicular to parallel components of the radius of gyration with respect to the wall orientation for the above-mentioned cases is performed. The obtained analytical and numerical results for star polymers with an odd number (f˜ = 3, 5) of arms are compared with our previous results for linear polymers in confined geometries. The acquired results show that a dilute solution of star polymer chains can be applied in the production of new functional materials, because the behavior of these solutions is strictly correlated with the topology of polymers and also with the nature and geometry of confined surfaces. The above-mentioned properties can find extensive practical application in materials engineering, as well as in biotechnology and medicine for drug and gene transmission.

Highly Specific Polyphenolic Colloids as Alternatives to Antimicrobials in Livestock Production.

The dispersion of antibiotics in livestock farming represents a health concern worldwide, contributing to the spread of antimicrobial-resistant bacteria through animals, the environment, and humans. Phenolic compounds could be alternatives to antibiotics, once drawbacks such as their low water solubility, bioavailability, and reduced stability are overcome. Although nano- or micro-sized formulations could counter these shortcomings, they do not represent cost-effective options. In this study, three phenolic compounds, obtained from wood-processing manufacturers, were characterized, revealing suitable features such as their antioxidant activity, size, and chemical and colloidal stability for in-field applications. The minimum inhibitory concentration (MIC) of these colloidal suspensions was measured against six bacterial strains isolated from livestock. These particles showed different inhibition behaviors: Colloidal chestnut was effective against one of the most threatening antibiotic-resistant pathogens, i.e., S. aureus, but ineffective toward E. coli. Instead, colloidal pine showed a weak effect on S. aureus but specificity toward E. coli. The present proof-of-concept points at colloidal polyphenols as valuable alternatives for antimicrobial substitutes in the livestock context.

Bioinspired colloidal crystal hydrogel pressure sensors with Janus wettability for uterus cervical canal tension perception.

The pursuit of flexible, sensitive, and cost-effective pressure sensors plays a pivotal role in medical diagnostics, particularly in the domain of cervical health monitoring. However, significant challenges remain in the economical production of flexible piezoresistive materials and the integration of microstructures aimed at enhancing sensor sensitivity. This urge highlights the use of innovative, stable hydrogel films that demonstrate robust adherence to soft biological tissues, thereby enabling prolonged bio-signal monitoring. In this study, we introduce an innovative integration of a flexible pressure electrical signal sensor with structural color hydrogel scaffolds. This integration leverages the tunability of the inverse opal structure to fine-tune the scaffold's adherence to the endocervical wall under varying environmental conditions and to amplify the sensitivity of pressure measurements. Our findings indicate that this novel approach holds promise for substantial enhancements in the manufacturing and functional capabilities of cervical pressure sensors, potentially revolutionizing personalized medical treatments and improving patient monitoring.

Do nanoparticles and colloids replenish soil phosphorus in the rhizosphere of winter wheat?

The rhizosphere is generally depleted in nutrients, but as a hotspot of microbial activity it fosters crop P uptake. We hypothesized that P contents of water extractable nanoparticles (<0.1 µm) and small sized colloids (<0.45 µm) differ between non-rhizosphere and rhizosphere soil. To test this hypothesis, rhizosphere and non-rhizosphere soils (Luvisol and Cambisol) were sampled at harvest period of winter wheat near Selhausen (Germany). Microaggregate and colloidal fractions in the size range of 53-250 µm, 20-53 µm, 0.45-20 µm, and <0.45 µm were separated by wet-sieving and centrifugation. Subsequently, the colloids <0.45 µm were further isolated in 0.66-20 nm, 20-100 nm and 100-450 nm fractions using asymmetric flow field flow fractionation (AF4) and directly analyzed by online coupled organic carbon detector (OCD) and inductively coupled plasma mass spectrometry (ICP-MS) for element composition. No significant differences (p > 0.05) were measured between rhizosphere and non-rhizosphere soil P contents of microaggregate fractions. The rhizosphere soil, however, showed ∼26 % depletion of average P content in the 0.66-20 nm fraction, which went along with an enrichment of P content of the 100-450 nm fraction by a factor of two. Apparently, P uptake by plants results in a redistribution of P in the rhizosphere, with small nanoparticles providing available P to plants while excess residual P is bound to fine colloids.

Colloidal photonic crystals towards biological applications.

Colloidal photonic crystals (CPCs), fabricated from the assembly of micro-/nano-particles, have attracted considerable interest due to their unique properties, such as structural color, slow-photon effect, and high specific surface area (SSA). Benefiting from these properties, significant progress has been made in the biological applications of CPCs. In this perspective, these properties and relative manipulation strategies are firstly discussed, building bridges between properties and biological applications of CPCs. Structural color endows CPCs with naked-eye sensing capability, which can be applied to physiological state assessment and diagnosis, as well as self-report of CPC-based diagnostic and therapeutic devices. The slow-photon effect contributes to enhanced fluorescence, surface-enhanced Raman scattering, and efficacy of photodynamic/photothermal therapy, when CPCs are combined with corresponding functional materials. High SSA provides CPCs with abundant binding sites and superior capabilities for loading, adsorption, delivery, etc. These properties can be utilized individually or synergistically to grant CPCs superior performance in biological applications. Next, the recent advancements of CPCs towards biological applications are summarized, including biosensors, wound dressings, cells-on-a-chip, and phototherapy. Finally, a perspective on the challenges and future development of CPCs for biological applications is presented.

Are nano-colloids controlling rare earth elements mobility or is it the opposite? Insight from A4F-UV-QQQ-ICP-MS.

Rare earth element (REE) mobility in the environment is expected to be controlled by colloids. Recent research has detailed the structure of iron-organic colloids (Fe-OM colloids), which include both large colloids and smaller nano-colloids. To assess how these nano-colloids affect REE mobility, their interactions with REE and calcium (Ca) were investigated at pH 4 and 6. Using Asymmetric Flow Field Flow Fractionation (A4F) combined with UV and Triple Quadrupole Inductively Coupled Plasma Mass Spectrometry (QQQ-ICP-MS), Fe-OM nano-colloids were separated from bulk Fe-OM colloids and their REE and Ca content were analyzed. Without REE and Ca, nano-colloids had an average diameter of approximately 25 nm. Their structure is pH-dependent, with aggregation increasing as pH decreases. At high REE loadings (REE/Fe ≥ 0.05), REE induced a size increase of nano-colloids, regardless of pH. Heavy REE (HREE), with their high affinity for organic matter, formed strong complexes with Fe-OM colloids, resulting in large aggregates. In contrast, light REE (LREE), which bind less strongly to organic molecules, were associated with the smallest nano-colloids. Low REE loading did not cause noticeable fractionation. Calcium further enhanced the aggregation process at both pH levels by neutralizing the charges on nano-colloids. These findings indicate that REE can act as aggregating agent controlling their own mobility, and regulating colloid transfer.

Evolution of self-assembled amphiphilic colloidal particles in strong-flavor Chinese baijiu.

This study proposed the evolution of self-assembled amphiphilic colloidal particles in Strong-Flavor (SF) Baijiu based on Ostwald ripening for the first time. The evolution process occurs in two stages: disordered amphiphilic molecules self-assemble into small colloidal particles and subsequently undergo Oswald ripening to form larger hydrophobic particles. Microscopic observations revealed the average size of oil-like spherical colloidal particles in Baijiu increased from 1.86 µm to 2.96 µm while the number of particles decreased by 39.50% during the 16-year cellaring process of SF Baijiu, consistent with the particle size trend observed via laser scattering. During fusion process, the charge-to-mass ratio of positively charged colloidal particles decreased, leading ζ-potential decreased from 23.7 mV to 4.66 mV within 16 years of storage. The electrochemical impedance spectroscopy approach tracked the unidirectional variation in the dielectric constant during evolution of SF Baijiu, reflecting the gradual expansion of colloidal particles, which aligns with the evolution trend observed in molecular dynamics simulations. By integrating direct microscopic observations of amphiphilic colloidal particles with electrochemical techniques, the evolution of Baijiu samples is capable to be evaluated in-situ, laying the foundation for intelligent Baijiu aging monitoring technology.

Quantitative analysis of intermolecular forces in cellulose microfibrils and hemicellulose with AFM nano-colloidal probes.

It is an interesting research topic to study the interfacial interactions between hemicellulose and cellulose, specifically how hemicellulose's structure affects its binding to cellulose nanofibers. Our research proposes that dispersion interaction play an important role in this interfacial interaction, more so than electrostatic forces when considering the adherence of cellulose to xylan. To quantify these interactions, the Atomic Force Microscope (AFM) colloidal probe technique is applied to measure the intermolecular forces between cellulose nanofibers, which are attached to the probe and xylan. These measured forces are then analyzed in relation to the length, diameter and functional groups of the nanocellulose, as well as the molecular weight and side chains of the xylan. Moreover, the predominance of dispersion forces by contrasting the adhesive forces before and after the grafting of a large nonpolar group onto xylan. This modification significantly reduces contact between the cellulose and xylan backbone, thereby markedly diminishing the dispersion interactions. Parallel to the AFM experiments, molecular dynamics (MD) simulations corroborate the experimental results and support our hypotheses. Collectively, these findings contribute to a deeper understanding of polysaccharide interactions within lignocellulose.

Current Thoughts on Burn Resuscitation.

The optimal treatment of burn shock is still unresolved. The problem of "fluid creep" continues despite modern devices that fail to improve outcomes over hourly urine output. Colloids, especially albumin, reduce fluid requirements. Albumin can be used either immediately at the start of resuscitation, or as a "rescue" when crystalloid use is excessive. Several studies confirm that when crystalloid resuscitation is "out of control" the majority of caregivers will add albumin to reduce fluid rates. A multi-center trial is underway comparing crystalloids with albumin to confirm the benefit of colloids. The next question is whether albumin or plasma is as the better colloid choice.

Hydrocolloid-based fruit fillings: A comprehensive review on formulation, techno-functional properties, synergistic mechanisms, and applications.

This study offers a comprehensive review of current developments regarding the utilization of diverse hydrocolloids in formulating fruit fillings across different fruit types, their impact on textural attributes, rheological properties, thermal stability, syneresis, and nutritional advantages of fillings and optimization of its characteristics to align with consumer preferences. The review also focuses on the various factors influencing fruit fillings, including the selection of fruits, processing methodologies, the inherent nature and concentration of hydrocolloids, and their synergistic interactions. In depth, scientific work on the impact of the parameters such as pH, total soluble solids, and sugar content within the fruit fillings was also discussed. Additionally, this article focuses on the utilization of the diverse fruit fillings developed by using hydrocolloids in bakery products including pastry, tartlet, muffins, cookies, and so forth. The review establishes that hydrocolloids offer a spectrum of techno-functional attributes conducive to strengthening both the structural and thermal stability of fruit fillings, consequently extending their shelf life. It further establishes that incorporating of hydrocolloids facilitates the development of healthier food products by mitigating the necessity of excessive sugar or various other less favorable ingredients. The incorporation of fruit fillings in bakery products significantly increases the value proposition of these baked goods, contributing to their overall enhancement of quality and sensory value.

Methods for the Characterization of the Colloidal Properties of Bacterial Membrane Vesicles.

Bacterial membrane vesicles (BMVs) are extracellular vesicles secreted by either Gram-positive or Gram-negative bacteria. These BMVs typically possess a diameter between 20 and 250 nm. Due to their size, when these BMVs are suspended in another medium, they could be constituents of a colloidal system. It has been hypothesized that investigating BMVs as colloidal particles could help characterize BMV interactions with other environmentally relevant surfaces. Developing a more thorough understanding of BMV interactions with other surfaces would be critical for developing predictive models of their environmental fate. However, this bio-colloidal perspective has been largely overlooked for BMVs, despite the wealth of methods and expertise available to characterize colloidal particles. A particular strength of taking a more colloid-centric approach to BMV characterization is the potential to quantify a particle's attachment efficiency (α). These values describe the likelihood of attachment during particle-particle or particle-surface interactions, especially those interactions which are governed by physicochemical interactions (such as those described by DLVO and xDLVO theory). Elucidating the influence of physical and electrochemical properties on these attachment efficiency values could give insights into the primary factors driving interactions between BMVs and other surfaces. This chapter details methods for the characterization of BMVs as colloids, beginning with size and surface charge (i.e., electrophoretic mobility/zeta potential) measurements. Afterward, this chapter will address experimental design, especially column experiments, targeted for BMV investigation and the determination of α values.

Influence of chirality and sequence in lysine-rich lipopeptide biosurfactants and micellar model colloid systems.

Lipopeptides can self-assemble into diverse nanostructures which can be programmed to incorporate peptide sequences to achieve a remarkable range of bioactivities. Here, the influence of peptide sequence and chirality on micelle structure and interactions is investigated in a series of lipopeptides bearing two lysine or D-lysine residues and tyrosine or tryptophan residues, attached to a hexadecyl lipid chain. All molecules self-assemble into micelles above a critical micelle concentration (CMC). Small-angle x-ray scattering (SAXS) is used to probe micelle shape and structure from the form factor and to probe inter-micellar interactions via analysis of structure factor. The CMC is obtained consistently from surface tension and electrical conductivity measurements. We introduce a method to obtain the zeta potential from the SAXS structure factor which is in good agreement with directly measured values. Atomistic molecular dynamics simulations provide insights into molecular packing and conformation within the lipopeptide micelles which constitute model self-assembling colloidal systems and biomaterials.