Deposition of protein-coated multi-walled carbon nanotubes on oxide surfaces and the retention in a silicon micromodel

Migration of natural organic matter and Pseudomonas fluorescens-associated polystyrene on natural substrates in aquatic environments

This study investigated the migration behavior of microplastics (MPs) covered with natural organic matter (NOM) and biofilm on three substrates (silica, Pseudomonas fluorescent and Pseudomonas aeruginosa biofilms) in various ionic strengths, focusing on the alterations in surface properties based on surface energy theory that affected their deposition and release processes. Peptone and Pseudomonas fluorescens were employed to generate NOM-attached and biofilm-coated polystyrene (PS) (NOM-PS and Bio-PS). NOM-PS and Bio-PS both exhibited different surface properties, as increased roughness and particle sizes, more hydrophilic surfaces and altered zeta potentials which increased with ionic strength. Although the deposition of NOM-PS on biofilms were enhanced by higher ionic strengths and the addition of Ca2+, while Bio-PS deposited less on biofilms and more on the silica surface. Both types exhibited diffusion-driven adsorption on the silica surface, with Bio-PS also engaging in synergistic and competitive interactions on biofilm surfaces. Release tests revealed that NOM-PS and Bio-PS were prone to release from silica than from biofilms. The Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory furtherly demonstrated that mid-range electrostatic (EL) repulsion had significantly impacts on NOM-PS deposition, and structural properties of extracellular polymeric substances (EPS) and substrate could affect Bio-PS migration.

Facilitated transport of toluene and naphthalene with humic acid in high- and low-permeability systems: Role of ionic strength and cationic type

The occurrence of colloids on pollutants transport in groundwater has attracted more attention. However, the research on the regulation mechanism of colloids on combined pollutants transport in heterogeneous aquifers is limited. In this study, a series of tank experiments were conducted to systematically investigate the effects of ionic strength, and cation type on humic acid (HA) facilitated transport of toluene (TOL), and naphthalene (NAP) in high- and low-permeability systems. The results showed that HA facilitated pollutants transport in low Na+ solution. In Ca2+ solution, the presence of HA hindered pollutants transport, and the inhibition increased with the increase of ionic strength. Both in Na+ solution and low Ca2+ solution, the influence of heterogeneous structure on pollutant transport played a dominant role, and TOL and NAP had a greater transport potential in the high permeability zone (HPZ) due to the preferential flow. Whereas, deposition of HA aggregates, and electrostatic attractive interaction had negative effects on transport than groundwater flow in high Ca2+ solution. Pollutants were prone to accumulate at the bottom of the HPZ, and the top of the low permeability zone (LPZ). These new findings provide insights into the mechanism of colloids influence on the pollutants transport in heterogenous aquifer.

The transport and retention of CQDs-doped TiO2 in packed columns and 3D printed micromodels

CQDs-doped TiO₂ (C-TiO₂) has drawn increased attention in recent because of its excellent catalytic performance. Understanding the transport of C-TiO₂ in porous media is necessary for evaluating the environmental process of this new nanomaterial. Column experiments were used in this study to investigate ionic strength (IS), dissolved organic matter (DOM) and sand grain size on the transport of C-TiO₂. The mobility of C-TiO₂ was inhibited by the increased IS and decreased sand grain size, but was promoted by the increased DOM concentration. The promotion efficiency of DOM ranked as humic acid (HA) > alginate (Alg) > bovine serum albumin (BSA), which was in the same order as their ability to change surface charges. The micromodels of pore network were prepared via 3D printing to further reveal the deposition mechanisms and spatial/temporal distribution of C-TiO₂ in porous space. C-TiO₂ mainly attached to the upstream region of collectors because of interception. The collector ripening was observed after long-time deposition. The existence of DOM caused visible decrease of C-TiO₂ deposition in the pore network. HA caused the most remarkable reduce of deposition in the three types of DOM, which was consistent with the column experiment results. This research is helpful to predict the transport of C-TiO₂ in natural porous media.

Change of Cell Toxicity of Food-Borne Nanoparticles after Forming Protein Coronas with Human Serum Albumin

Nanoparticles (NPs) can form protein coronas with plasma proteins after entering the biological environment due to their surface adsorption ability. In this study, the effects of protein coronas of roast squid food-borne nanoparticles (FNPs) with human serum albumin (HSA) on the HepG-2 and normal rat kidney (NRK) cells were investigated. The hydrodynamic diameters of the HSA and HSA-FNPs were 8 and 13 nm, respectively. The cytotoxicity and cell membrane damage of FNPs to HepG-2 cells increased with the increase of roasting temperature. The presence of 4.78 × 10^-3 mol/L FNPs increased the numbers of cellular necrosis and prolonged the G₂ phase of the cell cycle. The formation of protein coronas of squid FNPs mitigated the autophagy phenomenon by FNPs on HepG-2 cells. Moreover, protein coronas reduced the mitochondrial membrane potential in the HepG-2 and NRK cells and the production of reactive oxygen species caused by FNPs. The abnormal contents of oxidative stress indicators such as glutathione, superoxide dismutase, malondialdehyde, and catalase in HepG-2 and NRK cells induced by FNPs were alleviated due to the presence of HSA. These results suggested that the protein coronas formed by HSA on FNPs mitigated the cytotoxicity compared with the bare FNPs, thus providing insights into the interaction of squid FNPs with HSA.

Effect of cavitation bubble on the dispersion of magnetorheological polishing fluid under ultrasonic preparation

In the ultrasonic dispersion process, the ultrasonic cavitation effect can seriously affect the dispersion efficiency of magnetorheological polishing fluid (MRPF), but the mechanism remains unclear now. Through considering the continuity equation and Vand viscosity equation of the suspension, a revised cavitation bubble dynamic model in the MRPF was developed and calculated. The effects of presence or absence of solid particles, the volume fraction of solid particles, and viscosity on the cavitation bubble motion characteristics in the MRPF were discussed. Settlement experiments of the MRPF under ultrasonic and mechanical dispersion were observed. Analysis of particle dispersion is made by trinocular biomicroscope and image processing of the microscopic morphology of the MRPF. The results show that the high volume fraction of carbonyl iron particle (CIP) will significantly weaken the cavitation effect, and the low volume fraction of green silicon carbide (GSC) has a negligible effect on the cavitation effect in the MRPF. When the liquid viscosity is greater than or equal to 0.1 Pa·s, it is inconvenient to produce micro-jets in the MRPF. The sedimentation rate of the MRPF prepared by ultrasonic dispersion is lower than mechanical dispersion when the volume fraction of CIP is between 1% and 25%. The dispersion ratio under ultrasonic dispersion is lower than that under mechanical dispersion. The experimental results fit the simulation well. It offers a theoretical basis for exploring the ultrasonic cavitation effect in the industrial application of the MRPF.

Aggregation and Deposition Kinetics of Polystyrene Microplastics and Nanoplastics in Aquatic Environment

Microplastics (MPs) and nanoplastics (NPs) attract widespread attention due to their final threats to human health. Here, 50 nm and 500 nm polystyrene particles (PS50 and PS500) were selected as the typical NPs and MPs, respectively. Their aggregation kinetics was monitored, and their deposition was investigated on silica and alumina surfaces using quartz crystal microbalance with dissipation monitoring (QCM-D). PS500 has higher critical coagulation concentration (CCC) values than PS50, because of the weaker Brownian diffusion, less particle number and lower collision chance. PS50 has smaller values of critical deposition concentration (CDC) than PS500, indicating the stronger adsorption on silica. Derjaguin-Landau-Verwey-Overbeek (DLVO) calculations explain that PS500 has weaker attachment on silica and slower deposition rate on alumina than PS50. Our results demonstrate that solution chemistry, particle size and mineral surfaces determine the transport and distribution of plastic particles together.

Transport of nanoparticles in porous media and its effects on the co-existing pollutants

Nanomaterials are widely used in daily life owing to their superior characteristics. The release and transport of nanoparticles (NPs) in the environment is inevitable during their entire life cycle, posing a risk to the aquatic environment. Thus, considerable attention has been focused on the fate and behavior of NPs in porous media, as well as the co-transport of NPs with other pollutants. In this review, current knowledge about the retention and transport behavior of NPs in porous media is summarized. NP transport in porous media is dominated by various internal and external factors, including the characteristics of NPs, porous media, and water flow. Generally, NPs with high density, small particle size, and surface coating are easily transported in porous media with the characteristics of large size, smooth surface, and low water saturation. Meanwhile, high pH and velocity, low temperature, and natural organic matter-containing fluids are also conducive to NP transport. Aggregation, adsorption, straining, and blocking are the primary mechanisms by which NPs affect the transport of co-existing pollutants in porous media. Current research on NP transport has been performed predominantly using modal porous media (e.g., sand and glass beads); however, there is a large gap between simulated and natural porous media. Further studies should focus on the transport, fate, and interaction of NPs and coexistent pollutants in natural porous media, as well as the coupling mechanisms under actual environmental conditions.

Protein corona formation of human serum albumin with carbon quantum dots from roast salmon

When food-borne nanoparticles enter biological systems, they can interact with various proteins to form protein coronas, which can affect their physicochemical properties and biological identity. In this study, the protein corona formation of carbon quantum dots (CQDs) from roast salmon with human serum albumin (HSA) was explored. Furthermore, the biological identity of the HSA-CQD coronas, in relation to cell apoptosis, energy, glucose and lipid metabolism and acute toxicity in mice, was also investigated. The HSA-CQD coronas were formed between HSA and CQDs via a static binding mechanism, and the binding site of CQDs on HSA was located at both Sudlow's site I and site II. After entering the cytoplasm, the HSA-CQD coronas became localized in the lysosomes and autolysosomes. Importantly, the HSA coronas reduced the cytotoxicity of the CQDs from 18.65% to 9.26%, and the energy metabolism was rectified by changing from glycolytic to aerobic metabolism. The glucose and lipid metabolite profile of cells exposed to the HSA-CQD coronas differed from that of those treated with CQDs, indicating that the HSA-CQD coronas rectified metabolic disturbances caused by CQDs. Histopathological and blood biochemical analysis revealed no statistically significant differences between the treated and control mice after a single CQDs dose of 2000 mg per kg body weight. Overall, the results confirmed the formation of protein coronas between HSA and food-borne fluorescent CQDs, and could be helpful for evaluating the safety of fluorescent CQDs in cooked food items.