Adsorption and desorption of phenanthrene on carbon nanotubes in simulated gastrointestinal fluids

Influence of humic acid on the bioaccumulation, elimination, and toxicity of PFOS and TBBPA co-exposure in Mytilus unguiculatus Valenciennes

Tetrabromobisphenol A (TBBPA) and Perfluorooctane sulfonate (PFOS) are emerging contaminants which coexist in marine environments, posing significant risks to ecosystems and human health. The behavior of these contaminants in the presence of dissolved organic matter (DOM), specifically the co-contamination of TBBPA and PFOS, is not well understood. The bioaccumulation, distribution, elimination, and toxic effects of TBBPA and PFOS on thick-shell mussels (Mytilus unguiculatus V.), with the absence and presence of humic acid (HA), a typical DOM, were studied. The results showed that the uptake of TBBPA decreased and the uptake of PFOS increased when exposed to 1 mg/L HA. However, at higher concentrations of HA (5 and 25 mg/L), the opposite effect was observed. Combined exposure to HA, TBBPA, and PFOS resulted in oxidative stress in the digestive gland, with the severity of stress dependent on exposure time and HA dose. Histological analysis revealed a positive correlation between HA concentration and tissue damage caused by TBBPA and PFOS. This study provides insights into the influence of HA on the bioaccumulation-elimination patterns and toxicity of TBBPA and PFOS in marine bivalves, offering valuable data for ecological and health risk assessments of combined pollutants in aquatic environments rich in DOM.

Insight into the adsorption behaviors and bioaccessibility of three altered microplastics through three types of advanced oxidation processes

Advanced oxidation processes (AOPs) can significantly alter the structural properties, environmental behaviors and human exposure level of microplastics in aquatic environments. Three typical microplastics (Polyethylene (PE), polypropylene (PP), and polystyrene (PS)) and three AOPs (Heat-K2S2O8 (PDS), UV-H2O2, UV-peracetic acid (PAA)) were adopted to simulate the process when microplastics exposed to the sewage disposal system. 2-Nitrofluorene (2-NFlu) adsorption experiments found the equilibrium time decreased to 24 hours and the capacity increased up to 610 μg g-1, which means the adsorption efficiency has been greatly improved. The fitting results indicate the adsorption mechanism shifted from the partition dominant on pristine microplastic to the physical adsorption (pore filling) dominant. The alteration of specific surface area (21 to 152 m2 g-1), pore volume (0.003 to 0.148 cm3 g-1) and the particle size (123 to 16 μm) of microplastics after AOPs are implying the improvement for pore filling. Besides, the investigation of bioaccessibility is more complex, AOPs alter microplastic with more oxygen-containing functional groups and lower hydrophobicity detected by XPS and water contact angle, those modifications have increased the sorption concentration, especially in the human intestinal tract. Therefore, this indicates the actual exposure of organic compounds loaded in microplastic may be higher than in the pristine microplastic. This study can help to assess the human health risk of microplastic pollution in actual environments.

Adsorption of azoxystrobin and pyraclostrobin onto degradable and non-degradable microplastics: Performance and mechanism

Microplastics (MPs) exist after agricultural operations and thus present potential hazards to the environment and human health. However, the ecological risks posed by MPs carrying pesticides remain unclear. In this study, the adsorption and desorption behaviors of two pesticides, azoxystrobin and pyraclostrobin, on degradable and non-degradable MPs of poly(butylene adipate-co-terephthalate) (PBAT) and polyethylene (PE) were compared before and after UV aging. Additionally, the bioaccessibility of MPs carrying pesticides within a condition simulating gastrointestinal fluids was evaluated. The results showed that, after UV aging, the adsorption capacity of PBAT for pesticides decreased, while that of PE increased. Moreover, PBAT possessed higher adsorption ability towards both the pesticides due to its higher specific surface area, pore volume, contact angle, and lower crystallinity, as well as stronger van der Waals forces, electrostatic interactions, and hydrogen bonding indicated by theoretical calculation. Bioaccessibility experiments showed that azoxystrobin and pyraclostrobin had a higher risk of desorption from PBAT than PE, which is mainly dependent on the LogKow of pesticides according to the random forest analysis. In brief, the study highlights the potential risks of degradable MPs carrying pesticides to human health and the ecosystem, especially when compared to their non-degradable counterparts, manifesting that the ecological risk posed by degradable MPs should not be ignored.

The adsorption effects of biochar on carbofuran in water and the mixture toxicity of biochar-carbofuran in rats

Carbofuran, a widely used carbamate insecticide, is frequently detected in water. In this study, a high-performance adsorbent (WAB4) for carbofuran was obtained from laboratory-synthesized biochars. The maximum adsorption of carbofuran by WAB4 reaches 113.7 mg/g approximately. The adsorption of carbofuran by biochar was a multi-molecular layer and the adsorption process conforms to the pseudo-second-order kinetic model (R2 = 0.9984) and Freundlich isotherm model (R2 = 0.99). Importantly, an in vivo rat model was used to assess the combined toxicological effects of biochar-carbofuran complexes. The toxicity of the complexes (LD50 > 12 mg/kg) is lower than that of carbofuran (LD50 = 7.9 mg/kg) alone. The damage of biochar-carbofuran complex on rat liver and lung is significantly less than that of carbofuran. The Cmax and bioavailability of carbofuran were found to be reduced by 64% and 68%, respectively, when biochar was present, by UPLC-MS/MS analysis of carbofuran in rat plasma. Furthermore, it was confirmed that the biochar-carbofuran complex is relatively stable in the gastrointestinal tract, by performing a carbofuran release assay in artificial gastrointestinal fluids in vitro. Collectively, biochar is a bio-friendly material for the removal of carbofuran from water.

Natural aging and adsorption/desorption behaviors of polyethylene mulch films: Roles of film types and exposure patterns

Polyethylene (PE) mulch films are an important source of microplastics (MPs) in agricultural soils, which may further affect the bioavailability of coexisting pollutants. In this study, white (WM), black (BM), and silver-black (SM) PE mulch films were aged on the soil surface and under soil burial to simulate the two exposure patterns of abandoned mulch films in the field. Results indicated that the soil-surface exposure induced more pronounced aging characteristics, and WM seemed the most susceptible. Serious surface deterioration by aging led to a drastic decrease in the tensile properties of the films, suggesting the tendency to fragment. Oxygen-containing functional groups were generated on the film surfaces, with oxygen/carbon ratios increasing by up to 29 times, which contributed to the prominent increase in Pb adsorption on the film-derived MPs. Additionally, the film surface became more hydrophobic when exposed to the soil surface but more hydrophilic in the soil-burial exposure, which was in agreement with the change in triclosan adsorption, i.e., promotion and suppression, respectively. Aging generally decreased the desorption potential of the adsorbed pollutants in simulated gastrointestinal solutions due to increased interactions. By comparison, exposure patterns were revealed to be the critical factor for these changes, regardless of film types.

Nanoscale ZnO Improves the Amino Acids and Lipids in Tomato Fruits and the Subsequent Assimilation in a Simulated Human Gastrointestinal Tract Model

With the widespread use of nanoenabled agrochemicals, it is essential to evaluate the food safety of nanomaterials (NMs)-treated vegetable crops in full life cycle studies as well as their potential impacts on human health. Tomato seedlings were foliarly sprayed with 50 mg/L ZnO NMs, including ZnO quantum dots (QDs) and ZnO nanoparticles once per week over 11 weeks. The foliar sprayed ZnO QDs increased fruit dry weight and yield per plant by 39.1% and 24.9, respectively. It also significantly increased the lycopene, amino acids, Zn, B, and Fe in tomato fruits by 40.5%, 15.1%, 44.5%, 76.2%, and 12.8%, respectively. The tomato fruit metabolome of tomatoes showed that ZnO NMs upregulated the biosynthesis of unsaturated fatty acids and sphingolipid metabolism and elevated the levels of linoleic and arachidonic acids. The ZnO NMs-treated tomato fruits were then digested in a human gastrointestinal tract model. The results of essential mineral release suggested that the ZnO QDs treatment increased the bioaccessibility of K, Zn, and Cu by 14.8-35.1% relative to the control. Additionally, both types of ZnO NMs had no negative impact on the α-amylase, pepsin, and trypsin activities. The digested fruit metabolome in the intestinal fluid demonstrated that ZnO NMs did not interfere with the normal process of human digestion. Importantly, ZnO NMs treatments increased the glycerophospholipids, carbohydrates, amino acids, and peptides in the intestinal fluids of tomato fruits. This study suggests that nanoscale Zn can be potentially used to increase the nutritional value of vegetable crops and can be an important tool to sustainably increase food quality and security.

Desorption of sulfamethoxazole from polyamide 6 microplastics: Environmental factors, simulated gastrointestinal fluids, and desorption mechanisms

Microplastics (MPs) can enrich pollutants after being released into the environment, and the contaminants-loaded MPs are usually ingested by organisms, resulting in a potential dual biotoxic effect. In this paper, the adsorption behavior of Sulfamethoxazole (SMX) on Polyamide 6 (PA6) MPs was systematically investigated and simulated by the kinetic and isotherm models. The effect of environmental conditions (pH, salinity) on the adsorption process was studied, and the desorption behavior of SMX-loaded PA6 MPs was focused on simulating the seawater, ultrapure water, gastric and intestinal fluids. We found that lower pH and solubilization of SMX by gastrointestinal components (bovine serum albumin (BSA), sodium taurocholate (NaT), and pepsin) can reduce the electrostatic interaction between the surface charge of PA6 MPs and SMX. The result will lead to an increase in the desorption capacity of SMX-loaded PA6 MPs in gastrointestinal fluids and therefore will provide a reasonable mechanism for the desorption of SMX-loaded PA6 MPs in the gastrointestinal fluids. This study will provide a theoretical reference for studying the desorption behavior of SMX-loaded PA6 MPs under gastrointestinal conditions.

Synthesis and Assessment of Antimicrobial Composites of Ag Nanoparticles or AgNO3 and Egg Shell Membranes

Engineering research has been expanded by the advent of material fusion, which has led to the development of composites that are more reliable and cost-effective. This investigation aims to utilise this concept to promote a circular economy by maximizing the adsorption of silver nanoparticles and silver nitrate onto recycled chicken eggshell membranes, resulting in optimized antimicrobial silver/eggshell membrane composites. The pH, time, concentration, and adsorption temperatures were optimized. It was confirmed that these composites were excellent candidates for use in antimicrobial applications. The silver nanoparticles were produced through chemical synthesis using sodium borohydride as a reducing agent and through adsorption/surface reduction of silver nitrate on eggshell membranes. The composites were thoroughly characterized by various techniques, including spectrophotometry, atomic absorption spectrometry, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy, as well as agar well diffusion and MTT assay. The results indicate that silver/eggshell membrane composites with excellent antimicrobial properties were produced using both silver nanoparticles and silver nitrate at a pH of 6, 25 °C, and after 48 h of agitation. These materials exhibited remarkable antimicrobial activity against Pseudomonas aeruginosa and Bacillus subtilis, resulting in 27.77% and 15.34% cell death, respectively.

Aggregation kinetics of polystyrene nanoplastics in gastric environments: Effects of plastic properties, solution conditions, and gastric constituents

Nanoplastics are inevitably ingested into human gastric environment, wherein their aggregation kinetics and interactions with gastric constituents remain unclear. This study investigated the early-stage (20 min) and long-term (1-6 h) aggregation kinetics of four commonly-found polystyrene nanoplastics (PSNPs) including NP100 (100-nm), A-NP100 (100-nm, amino-modified), C-NP100 (100-nm, carboxyl-modified), and NP500 (500-nm) under gastric conditions. Five simulated human gastric fluids (SGFs) including SGF1-3 (0-3.2 g/L pepsin and 34.2 mM NaCl), SGF4 (400 mM glycine), and SGF5 (nine constituents), three pH (2, fasted state; 3.5, late-fed state; and 5, early-fed state), and 1-100 mg/L PSNPs were examined. Aggregation rates ranked NP100 > A-NP100 ≈ C-NP100 > NP500, SGF5 > SGF4 > SGF3 > SGF2 > SGF1, and pH 2 > 3.5 > 5. Increasing PSNP concentration enhanced aggregation rate up to 13.82 nm/s. Aggregation behavior generally followed the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Pepsin, glycine, and proteose-peptone strongly influenced PSNP stability via electrostatic interaction and steric hindrance imparted by protein corona. Freundlich isotherm suggested that PSNPs adsorbed organic constituents following lysozyme > porcine bile > proteose-peptone > pepsin > glycine > D-glucose, inducing changes in constituent structure and PSNP properties. These findings provide insights on the transport of nanoplastics in the gastric environments.

Adsorption of tetracycline and Cd(II) on polystyrene and polyethylene terephthalate microplastics with ultraviolet and hydrogen peroxide aging treatment

Microplastics (MPs) could serve as vectors of antibiotics and heavy metals through sorption and desorption. However, the combined adsorption process of antibiotics and heavy metals on aged MPs has rarely been studied. In this study, combined adsorption/desorption of tetracycline (TC) and Cd(II) on/from polystyrene (PS) and polyethylene terephthalate (PET) MPs, as well as ultraviolet (UV) and H₂O₂ aged MPs, was investigated. The specific surface areas of the MPs increased after UV and H₂O₂ aging. Adsorption experiments showed that the pseudo-second-order kinetic model and Freundlich model fitted adsorption of TC and Cd(II) on all of the MPs. The adsorption capacities of TC and Cd(II) were higher on aged MPs than on the pristine MPs, especially on H₂O₂ treated MPs. TC adsorption on the MPs was hardly affected by Cd(II), and Cd(II) adsorption was not significantly affected by TC when the solution pH value was below 8.0. Cd(II) slightly enhanced TC adsorption on the MPs at pH 8.0, especially on the aged MPs. The TC adsorption capacities increased with increasing pH, reaching a maximum at pH 5.0 or 6.0, and they then decreased, while the largest level of Cd(II) adsorption was at approximately pH 6.0. Adsorption of TC and Cd(II) on the pristine and aged MPs was thermodynamically favorable and spontaneous. The trend of the desorption rates of TC and Cd(II) from the MPs in different background solutions was ultrapure water < surface water < simulated gastric fluid. The desorption rates of TC and Cd(II) from the aged MPs were lower than those from the pristine MPs. The results revealed the mechanism of the TC and Cd(II) combined adsorption process on aged MPs, which will provide insight for understanding the aging process and its potential effects on sorption and desorption of antibiotics and heavy metals in the real environment.

Microplastics-sorbed phenanthrene and its derivatives are highly bioaccessible and may induce human cancer risks

Microplastics (MPs) are ubiquitous in environmental media and human diets and can enrich organic contaminants, including polycyclic aromatic hydrocarbons (PAHs) and their derivatives. The bioaccessibilities and triggering cancer risks of MP-sorbed PAHs and PAH derivatives are closely linked with human health, which, however, were rarely focused on. This study explored the sorption behaviors of phenanthrene (PHE) and PHE derivatives on polyethylene (PE), polypropylene (PP), and polystyrene (PS) MPs, and assessed their bioaccessibilities in gastrointestinal fluids as well as their inducing human cancer risks. PE MPs harbored the highest sorption capacity, secondly the PP MPs, then the PS ones. Sorption of PHE and PHE derivatives on MPs was positively correlated with their hydrophobicities. The bioaccessibilities of sorbed PHE and PHE derivatives could reach 53.59 %±0.46 %-90.28 %±0.92 % in gastrointestinal fluids and 81.34 %±0.77 %-98.72 %±1.44 % in gastrointestinal fluids with the addition of Tenax (more close to the bioavailability). The hydrophobicities also controlled the bioaccessibilities of PHE and PHE derivatives in gastric fluids, and those in intestinal fluids with Tenax for PS MPs. The incremental lifetime cancer risk (ILCR) values for PHE, PHE-Cl, and PHE-NO2 on MPs at tested concentrations were all higher than the USEPA-suggested safety limit (10-6), and most of them were even higher than 10-4, which thus indicates serious cancer risks. This study promoted our understanding of the potential health threats posed by organic pollutant-bearing MPs in the environment.

The simultaneous removal of co-contaminants pyrene and Cu (II) from aqueous solutions by Fe/Mn bimetallic functionalized mesoporous silica

In recent years, the co-contamination of heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) has attracted more and more attention, and finding efficient and coordinated removal method has been the hot focus. In this study, Fe/Mn-SBA15 bimetallic mesoporous silica adsorbent (Fe/Mn-SBA15) was prepared by hydrothermal method with the functional groups Fe and Mn simultaneously doped into the framework structure of SBA15. Fe/Mn-SBA15 was systematically characterized by XRD, TEM, and BET and used in removal of typical PAHs-pyrene and heavy metal-Cu (II) from aqueous solutions simultaneously. The single and binary adsorption behaviors were studied by kinetics, isotherm, pH, and ionic strength. The results showed that the functional groups of Fe and Mn were successfully loaded into the structure of SBA15 and the prepared adsorbent was still a typical mesoporous adsorbent. The adsorption of pyrene and Cu (II) onto Fe/Mn-SBA15 was fast and the adsorption equilibrium was achieved in 100 min. The Langmuir model fitted the adsorption isotherm better and the maximum adsorption capacities for pyrene and Cu (II) were 120 mg/g and 10.52 mg/g, respectively. The increase of ionic strength could enhance and decrease the adsorption capacity of pyrene and Cu (II), which may be attributed to salting-out effect and potassium competitive. With the increase of pH values, the negative charge on the surface of the adsorbent increased, resulting in the decrease and increase of adsorption capacity of pyrene and Cu (II) onto Fe/Mn-SBA15. In addition, Fe/Mn-SBA15 was found to have a synergistic effect on the adsorption of pyrene and Cu (II). This result is mainly due to the formation of hydration complex by pyrene-Cu (II) through cation-π interaction, which increases the adsorption capacity by occupying each other's adsorption sites of adsorbent. This study provides a new method for the synergistic removal of PAHs and HMs from aqueous solutions.

Bioaccessibility of Microplastic-Associated Antibiotics in Freshwater Organisms: Highlighting the Impacts of Biofilm Colonization via an In Vitro Protocol

Microplastics in the environment can be colonized by microbes capable of forming biofilms, which may act as reactive coatings to affect the bioaccessibility of pollutants in organisms. This study investigated the dynamic evolution of biofilm colonization on microplastics and its impacts and mechanisms on the bioaccessibility of microplastic-associated sulfamethazine (SMT) via microcosm incubation in surface water and sediment. After 60 days of incubation, the microbial communities formed in microplastics were distinct and more diverse than those untethered in surroundings, and photoaging treatment decreased the affinity of biofilms on microplastics due to decreased hydrophobicity. Biofilm formation further enhanced the desorption and bioaccessibility of microplastic-sorbed SMT in organisms. In vitro experiments indicated that the critical effects were mainly related to the stronger interaction of gastrointestinal components (i.e., pepsin, bovine serum albumin (BSA), and NaT) with biofilm components (e.g., extracellular polymer substances) than with the pure surface of microplastics, which competed for binding sites in microplastics for SMT more significantly. Photoaging decreased the enhancing effects of biofilms due to their lower accumulation in aged microplastics. This study is the first attempt to reveal the role of biofilms in the bioaccessibility of microplastics with associated antibiotics and provide insights into the combined risk of microplastics in the environment.

The Long Goodbye: Finally Moving on from the Relative Potency Approach to a Mixtures Approach for Polycyclic Aromatic Hydrocarbons (PAHs)

For the past several decades, a relative potency approach has been used to estimate the human health risks from exposure to polycyclic aromatic hydrocarbon (PAH) mixtures. Risk estimates are derived using potency equivalence factors (PEFs; also called relative potency factors [RPFs]), based on the ratio of selected PAHs to benzo[a]pyrene (BaP), expressed qualitatively by orders of magnitude. To quantify PEFs for 18 selected carcinogenic PAHs, a systematic approach with a priori and dose response criteria was developed, building on draft work by the US EPA in 2010 and its review by US EPA Science Advisory Board (SAB) in 2011. An exhaustive search for carcinogenicity studies that included both target PAHs and BaP with environmentally relevant exposure routes found only 48 animal bioassay datasets (mostly pre-1992 based on skin painting). Only eight datasets provided adequate low-response data, and of these only four datasets were appropriate for modeling to estimate PEFs; only benzo[b]fluoranthene and cyclopenta[c,d]pyrene had a PEF that could be quantified. Thus, current knowledge of PAH carcinogenicity is insufficient to support quantitative PEFs for PAH mixtures. This highlights the long-acknowledged need for an interdisciplinary approach to estimate risks from PAH mixtures. Use of alternative and short-term toxicity testing methods, improved mixture characterization, understanding the fate and bioavailability of PAH mixtures, and understanding exposure route-related differences in carcinogenicity are discussed as ways to improve the understanding of the risks of PAHs.

Effective Adsorption of Congo Red from Aqueous Solution Using Fe/Al Di-Metal Nanostructured Composite Synthesised from Fe(III) and Al(III) Recovered from Real Acid Mine Drainage

This study presents the first known exploration of Congo red dye (CR) adsorption by a polycationic Fe/Al Di-metal nanostructured composite (PDFe/Al) synthesised using Fe(III) and Al(III) recovered from authentic acid mine drainage (AMD). The PDFe/Al successfully removed CR from the aqueous solution. The mineralogical, microstructural, and chemical properties of the synthesised PDFe/Al adsorbent (before and after adsorption) were studied using state-of-the-art analytical instruments. The optimum conditions were observed to be 100 mg·L⁻¹ CR, 1 g of the PDFe/Al in 500 mL adsorbate solution, 20 min of shaking, pH = 3–8, and a temperature of 35 °C. At optimised conditions, the PDFe/Al showed ≥99% removal efficacy for CR dye and an exceptionally high Langmuir adsorption capacity of 411 mg·g⁻¹. Furthermore, a diffusion-limited adsorption mechanism was observed, with two distinct surfaces involved in the adsorption of CR from an aqueous solution. It was determined that the adsorption of CR induced internal strain and deformation within the matrices and interlayers of the PDFe/Al which resulted in a marked increase in the adsorbent pore surface area and pore volume. The remarkably high adsorption capacity could be attributed to the high surface area. A regeneration study showed that the adsorbent could be reused more than four times for the adsorption of CR. The findings from this study demonstrated the feasibility of recovering valuable minerals from toxic and hazardous AMD and demonstrated their potential for the treatment of industrial wastewaters.

Strong but reversible sorption on polar microplastics enhanced earthworm bioaccumulation of associated organic compounds

Sorption/desorption of two organic compounds (OCs), phenanthrene (PHE), and 1-nitronaphthalene (1-Nnap) on three polar and one nonpolar polypropylene (PP) microplastics (MPs) and earthworm bioaccumulation of MP associated PHE were systematically studied. Poly-butylene succinate (PBS) with the lowest glass transition temperature (T_g) showed the highest sorption toward PHE and 1-Nnap (K_d: 25,639 ± 276 and 1673 ± 28.8 L kg^-1, respectively), while polylactic acid (PLA) with the highest T_g showed the least sorption (182 ± 5 and near 0), confirming that hydrophobic partition was the main driving force of sorption. However, polar interactions also contributed to the preferential sorption of 1-Nnap on polar poly-hydroxyalkanoates (PHA). Moreover, small particle size favored the sorption of MPs and simulated weathering enhanced sorption on MPs with medium/high T_g. As for desorption, slight hysteresis was observed in most cases with near-zero hysteresis index (HI), and PHE generally had higher HI than 1-Nnap. The simulated digestive solution could further promote the desorption of PHE. The PHE concentrations in earthworms with the presence of 5% PBS or PP MPs in soil were 1.50-2.35 or 1.59-1.75 times that of the control without MPs; and PBS MPs with the smallest particle size showed the greatest enhancement. The results of this study confirmed that polar MPs could strongly but reversibly sorb both polar and nonpolar OCs and hence promote the bioaccumulation of OCs to soil organisms.

Polyamide microplastics in wastewater as vectors of cationic pharmaceutical drugs

Reported here is the first study to investigate the adsorption of pharmaceutical drugs to microplastics in wastewater. Wastewater is an environmental source of microplastics and pharmaceuticals, which is discharged as treated effluent or combined sewer overflows. In this study, adsorption of cationic pharmaceuticals, with a range of octanol-water distribution coefficients, to polyamide (Nylon 12) microplastics was investigated in real wastewater samples. Significant adsorption was observed for the more hydrophobic pharmaceuticals studied, propranolol, amitriptyline, and fluoxetine, with equilibrium reached within 24 h. Microplastic-wastewater distribution coefficients for these three pharmaceuticals were 191, 749 and 1020 L kg^-1, respectively. Favourable wastewater conditions for adsorption of pharmaceuticals to polyamide were at pH > 7, summer temperatures (20 °C), and no stormwater dilution. Adsorption of the more hydrophilic pharmaceuticals atenolol, pseudoephedrine, metoprolol, and tramadol was ≤7% under all conditions and considered insignificant. Limited desorption (7-17%) of propranolol, amitriptyline, and fluoxetine was observed in river water over 24 h. This suggests that microplastics may be able to transport adsorbed pharmaceuticals for considerable distances after discharge. In simulated gastric fluids their desorption increased to 24-27% and 40-58% in cold- and warm-blooded temperatures respectively. The findings demonstrate that wastewater microplastics could act as a vector of pharmaceutical drugs, from wastewater treatment plants to aquatic organisms. However, further research is needed to better appreciate the risks posed by pharmaceuticals adsorbed to microplastics in comparison to other organic particulates found in wastewater.

Contribution of aged polystyrene microplastics to the bioaccumulation of pharmaceuticals in marine organisms using experimental and model analysis

Microplastics (MPs) in the environment would undergo extensive weathering, which can act as a vector affecting the accumulation of pollutants in organisms. However, the risk of organic pollutants adsorbed on aged MPs to marine organisms is poorly understood. This study revealed the contribution of aged polystyrene (PS) MPs to the total bioaccumulation of atorvastatin (ATV) and amlodipine (AML), and assessed the environmental risks via experimental and model analysis. The results showed that pharmaceuticals were more easily released in gastrointestinal fluids from aged MPs relative to that in simulated seawater. The hydrophobic pharmaceuticals were more bioaccessible than hydrophilic ones by organisms. Model analysis showed that ingestion of water and food were the most important uptake routes for pharmaceuticals in marine fish and seabirds, while aged PS MPs could decrease the bioaccumulation of pharmaceuticals (contributed for -2.9% and -1.2% for the total uptake of ATV, and -25.8% and -4.4% for AML), indicating the cleaning effect of aged MPs, and the potential higher exposure risks of pharmaceuticals in warm-blooded organisms than that in cold-blooded ones via ingested MPs. The study revealed the effect of aged MPs to the bioaccumulation of pharmaceuticals in marine organisms, and highlighted the combined risks of aged MPs and pharmaceuticals in the environment.

Size-dependent adsorption of waterborne Benzophenone-3 on microplastics and its desorption under simulated gastrointestinal conditions

Microplastics (MPs) are global pollutants with heightened environmental and health concerns in recent years because of their worldwide distribution across aquatic environments, ability to load chemical contaminants and the potential for ingestion by animals, including human. In this study, three commonly used and environmentally detected plastics, i.e. polystyrene, polyethylene, polypropylene with sizes of 550, 250 and 75 μm, plus two submicron-sized polystyrene microplastics (5 and 0.5 μm) were assessed as solid adsorbents for a prevalent UV filter, benzophenone-3 (BP-3). The affinity and process of adsorption exhibited differentials among different sizes and types of MPs. Apparent desorption of BP-3 from MPs under simulated gastrointestinal conditions was not significantly enhanced, which might be due to the presence of the enzyme proteins, indicating potential risk of the contaminants carried by MPs. The desorption of BP-3 from MPs was affected by the size, type of MPs and the components of the gastrointestinal fluid.

Interfacial interaction between benzo[a]pyrene and pulmonary surfactant: Adverse effects on lung health

Inhaled polycyclic aromatic hydrocarbons (PAHs) can directly interact with the lung surfactant (PS) lining of alveoli, thereby affecting the normal physiological functions of PS, which is a serious threat to lung health. In spite of the extensive study of benzo[a]pyrene (BaP, a representative of PAHs), its potential biophysical influence on the natural PS is still largely unknown. In this study, the interfacial interaction between PS (extracted from porcine lungs) and BaP is investigated in vitro. The results showed that the surface tension, phase behavior, and interfacial structure of the PS monolayers were obviously altered in the presence of BaP. A solubilization test manifested that PS and its major components (dipalmitoyl phosphatidylcholine, DPPC; bovine serum albumin, BSA) could in turn accelerate the dissolution of BaP, which followed the order: PS > DPPC > BSA, and mixed phospholipids were significantly responsible for the solubilization of BaP by PS. In addition, solubilization of BaP also enhanced the consumption of hydroxyl radicals (·OH) in the simulated lung fluid, which could disturb the balance between oxidation and antioxidation.

High capacity Pb(II) adsorption characteristics onto raw- and chemically activated waste activated sludge

The Pb(II) adsorption characteristics of chemically activated waste activated sewage sludge (WAS) were compared to raw WAS. Adsorption kinetics and equilibrium isotherm parameters were fit using classic adsorption models. HCl and H₂SO₄ activation terminated any significant sludge-based adsorption. Raw and ZnCl₂ activated WAS displayed Langmuir adsorption capacities of 307 mg/g and 274 mg/g, respectively. Surface characterization revealed that chemical activation with ZnCl₂ increased the BET surface area for raw WAS from 0.97 m²/g to 1.78 m²/g, but did not significantly change the surface structure. FTIR analyzes and XPS were used to further investigate the nature of lead binding. The relationships between equilibrium ion concentration and Pb(II) adsorption suggest cationic exchange with hydrogen, calcium, and zinc as a significant mechanism of Pb(II) removal alongside electrostatic attraction. The pH_PZC was determined as 2.58 and 2.30 for ZnCl₂ activated WAS and raw WAS respectively. HNO₃ and Ca(NO₃)₂ demonstrated sufficient elution properties for WAS recovery. For authentic industrial effluent both raw and ZnCl₂ activated WAS displayed Pb(II) removal behavior comparable to simulated Pb(II) solutions. In comparison with modified and unmodified sludges from literature, this study demonstrates the auspicious potential of raw WAS as an effective Pb(II) adsorbent independent of pyrolytic or chemical activation.

Effective removal of arsenate from wastewater using aluminium enriched ferric oxide-hydroxide recovered from authentic acid mine drainage

This study explored an eco-friendly approach for the synthesis of novel aluminium enriched ferric oxide-hydroxide (Fe/AlO(OH)) from authentic acid mine drainage (AMD). The synthesized Fe/AlO(OH) was subsequently tested for arsenate removal capabilities. Fe/AlO(OH) was synthesized from bona fide AMD via selective precipitation, thermal activation, and vibratory ball milling. One-factor-at-a-time (OFAAT) method was used to optimize operational parameters, which include adsorbent dosage, concentration, pH, agitation time, and temperature. Optimized conditions were observed to be 150 ppm of As(V), Solid: Liquid ratio - 1 g: 250 mL, contact time of 60 min, and ambient temperature and pH. Limited temperature and pH effects on adsorption were observed. Equilibrium data fits using Langmuir-, Freundlich-, Two surface Langmuir-, Dubinin-Radushkevich-, and Dubinin-Astokov isotherm models showed highly favorable adsorption conditions, the highest known maximum adsorption capacity for As(V) of 102-129 mg g^-1, and coupled physisorption/diffusion limited adsorption. Thermodynamic analysis showed positive Gibbs free energy (ΔG°), negative enthalpy change (ΔH°), and positive entropy change (ΔS°) - likely a result of an inner sphere complexation of the As(V) with the Fe/Al surface. Considering the obtained results, valorization of AMD for the synthesis of Fe/AlO(OH) was viable and effective. This initiative could potentially minimize the footprints of AMD and arsenic pollution.

TiO2 nanoparticles enhanced bioaccumulation and toxic performance of PAHs via trophic transfer

Engineering nanoparticles (NPs) could act as accumulator and carrier of co-contaminants, affecting their fate and toxicity in environments. However, the effects of NPs on the bioaccumulation and trophic transfer of co-contaminants through the food chain and the ensuing effects on higher predators are unclear. In the present study, we investigated the effects of titanium dioxide nanoparticles (nTiO₂) on the trophic transfer of phenanthrene (Phe) from prey Artemia salina to predator Scophthalmus maximus. We also evaluated the ensuing toxic performance of Phe in S. maximus after been transferred from A. salina in the presence and absence of nTiO₂. The presence of nTiO₂ significantly (p < 0.05) increased Phe accumulation in A. salina with higher bioconcentration factor (BCF) up to 90.9 than that of 38.6 in Phe exposure along. After trophic transfer, nTiO₂ (1 mg/L) also promoted the bioaccumulation of Phe (1 μg/L) in predator S. maximus from 4.17 mg/kg to 7.85 mg/kg (dry weight). However, nTiO₂ did not enhance the trophic transfer of Phe from A. salina to S. maximus since the biological magnification factor (BMF) decreased from 0.13 to 0.08. Nevertheless, the nTiO₂-enhanced bioaccumulation of Phe did enhance Phe toxicity performance in predator S. maximus after trophic transfer, showing significant (p < 0.05) growth inhibition and changes of nutrient status in the predator, compared to those of the control. Further physio-biochemical investigations suggested that oxidative stress and inhibition of digestive functions might explain the growth inhibition in treatment with nTiO₂ + Phe. This study demonstrates the first evidence that NP-enhanced bioaccumulation and toxic performance of co-existing pollutants across trophic transfer, which poses potential risks to marine ecosystems, and ultimately human health by seafood consumption.

Co-adsorption of As(III) and phenanthrene by schwertmannite and Fenton-like regeneration of spent schwertmannite to realize phenanthrene degradation and As(III) oxidation

Co-contamination of arsenic and polycyclic aromatic hydrocarbons (PAHs) in groundwater is frequently reported, and it is thus necessary to develop efficient techniques to tackle this problem. Here, we evaluated the feasibility of utilizing schwertmannite to co-adsorb As(III) and phenanthrene from water solution and regenerating spent schwertmannite via a heterogeneous Fenton-like reaction to degrade adsorbed phenanthrene and meanwhile oxidize adsorbed As(III). The results suggested that schwertmannite with a hedgehog-like morphology was superior to that with a smooth surface for the adsorption removal of As(III) or phenanthrene because of the much higher BET surface area and hydroxyl proportion of the former one, and schwertmannite formed at 72 h incubation effectively co-adsorbed As(III) and phenanthrene from water solution. The adsorption of As(III) and phenanthrene on schwertmannite did not interfere with each other, while the acidic initial solution pH delayed the adsorption of As(III) on schwertmannite but enhanced the adsorption capacity for phenanthrene. The adsorption of As(III) on schwertmannite mainly involved its exchange with SO₄^2- (outer-sphere or inner-sphere) and its complexation with iron hydroxyl surface groups, and phenanthrene adsorption mainly occurred through cation-π bonding and OH-π interaction. During the adsorption-regeneration processes, schwertmannite adsorbed As(III) and phenanthrene firstly, and then it can be successfully regenerated via Fenton-like reaction catalyzed by itself to effectively degrade the adsorbed phenanthrene and meanwhile oxidize the adsorbed As(III) to As(V). Therefore, schwertmanite is an outstanding environmental adsorbent to decontaminate As(III) and phenanthrene co-existing in groundwater.

Food-Grade Titanium Dioxide Particles Decreased the Bioaccessibility of Vitamin D3 in the Simulated Human Gastrointestinal Tract

Food-grade titanium dioxide (E171) particles, as a "whiteness" additive, are often co-ingested with lipid-rich foods. Therefore, we explored the impact of E171 on lipid digestion and vitamin D₃ (VD₃) bioaccessibility encapsulated within oil-in-water emulsions in a simulated human gastrointestinal tract (GIT) model. VD₃ bioaccessibility significantly decreased from 80 to 74% when raising E171 from 0 to 0.5 wt %. The extent of lipid digestion was reduced by E171 addition in a dose-dependent manner. VD₃ bioaccessibility was positively correlated with the final amount of free fatty acids (FFAs) produced by lipid digestion (R² = 0.95), suggesting that the reduction in VD₃ bioaccessibility was due to the inhibition of lipid digestion by E171. Further experiments showed that E171 interacted with lipase and calcium ions, thereby interfering with lipid digestion. The findings of this study enhance our understanding toward the potential impact of E171 on the nutritional attributes of foods for human digestion health.

Sources, environmental levels, and health risks of PM2.5-bound polycyclic aromatic hydrocarbons in energy-producing cities in northern China

We collected 170 samples of airborne fine particulate matter from five coal-producing cities and one oil-producing city in northern China during both heating and non-heating periods to quantify the concentrations of 12 polycyclic aromatic hydrocarbons, estimate their bioaccessible fraction, and calculate the incremental lifetime cancer risk (ILCR) of this fraction. The major sources of the particulate matter were analyzed using the chemical mass balance model. We found that the main emission sources were coal combustion during the heating period and open sources during the non-heating period. The ILCR was initially calculated as 2.65 × 10^-9 for coal-producing cities and 4.60 × 10^-9 for the oil-producing city during the heating period and 1.17 × 10^-8 and 3.34 × 10^-8, respectively, during the non-heating period. When only the bioaccessible fraction was used, the ILCR in coal-producing cities and the oil-producing city decreased by 87.2% and 82.1%, respectively, for the heating period and by 89.0% and 80.1%, respectively, for the non-heating period. The findings suggest that bioaccessibility should be considered when assessing the carcinogenic risk of polycyclic aromatic hydrocarbons. This study provides insights into the contribution of major emission sources to air pollution related to the long-term exploitation, transportation, and use of coal and oil.

Transformations of Ag2S nanoparticles in simulated human gastrointestinal tract: Impacts of the degree and origin of sulfidation

Engineered silver sulfide nanoparticles (e-Ag₂S-NPs) are used in industry and can be released into the environment. Besides e-Ag₂S-NPs, transformed silver sulfide nanoparticles (t-Ag₂S-NPs) from silver nanoparticles are more likely to be the form that is widely distributed in the environment. Both e-Ag₂S-NPs and t-Ag₂S-NPs may be ingested and get into human gastrointestinal tract (GIT) through trophic transfer, posing a potential threat to human health. Nevertheless, knowledge of chemical stability of t-Ag₂S-NPs and e-Ag₂S-NPs in the human GIT is very limited. Herein e-Ag₂S-NPs and a series of t-Ag₂S-NPs with different degrees of sulfidation were selected as models for exposure to the simulated human GIT including mouth, stomach and small intestine phases under fed and fasted conditions. Silver ions were detected in the simulated saliva, gastric and small intestine fluids when t-Ag₂S-NPs or e-Ag₂S-NPs were incubated in the simulated GIT, but the amount (e.g., < 20 μg) of silver ion in each phase accounted for < 0.2‰ (w/w) of the silver added (i.e., 100 mg). Silver species of the residual particulate from each phase of the simulated GIT with t-Ag₂S-NPs or e-Ag₂S-NPs were thus analyzed through a developed analytical method that could selectively, successively and efficiently dissolve and quantify AgCl, Ag(0), and Ag₂S in particulates. Both e-Ag₂S-NPs and fully sulfidized t-Ag₂S-NPs were shown to be highly stable in the simulated human GIT. Conversely, partially sulfidized t-Ag₂S-NPs primarily underwent transformations in the mouth phase relative to stomach and small intestine phases regardless of fed or fasted status, wherein AgCl and Ag₂S were observed besides Ag(0). The amount of Ag₂S in the mouth phase negatively (r = -0.99, p <  0.001) correlated with the sulfidation degree of initial t-Ag₂S-NPs. This work improved our understanding of potential transformations of t-Ag₂S-NPs in the simulated human GIT, providing valuable information for future researches on evaluating health risks of ingested Ag₂S-NPs.

Kinetic and Equilibrium Studies of Doxorubicin Adsorption onto Carbon Nanotubes

This study provides deep insight into the adsorption process of doxorubicin onto different types of carbon nanotubes that have been proved to show attractive properties as a drug delivery system. The main aim of the work was to propose probable adsorption mechanisms and interactions between the anticancer drug and surface of modified and pristine carbon nanotubes at blood pH. The carbon nanotubes were oxidized to optimize the absorbance efficiency relative to that of pristine multiwalled carbon nanotubes. The adsorption isotherm of the modified system was well described by the Temkin equation. It confirms that the adsorption in the system studied involves also hydrogen and covalent bonding and is exothermic in nature. The experimental kinetic curves of adsorption were fitted to different mathematical models to check if the kinetics of doxorubicin adsorption onto the modified multiwalled carbon nanotubes follows a pseudo-second-order model and the chemical sorption is bound to be the rate-limiting. On the basis of the molecular dynamics simulation, it was shown that in vacuo the aggregation tendency of doxorubicin molecules is far more favorable than their adsorption on pristine carbon nanotubes (CNTs). It suggests that only functionalization of the nanotube surface can affect the interaction between doxorubicin and functional groups of the carriers and increases the efficiency of the drug loading process.

Microplastics Reduce Lipid Digestion in Simulated Human Gastrointestinal System

Microplastics (MPs) are unavoidably ingested by humans, and their gastrointestinal processes and impact on lipid digestion are unknown. In the present work, all five MP types used, including polystyrene (PS), polyethylene terephthalate, polyethylene, polyvinyl chloride, and poly(lactic-co-glycolic acid) (80 mg/L in small intestine), significantly reduced lipid digestion in the in vitro gastrointestinal system. PS MPs exhibited the highest inhibition (12.7%) among the five MPs. Lipid digestion decreased with increasing PS concentration, but independent of PS size (50 nm, 1 μm, 10 μm). PS MPs after photoaging by simulated sunlight also significantly decreased lipid digestion. Confocal imaging shows that PS MPs could interact with both lipid droplets and lipases. Two mechanisms underlying the PS-induced digestion inhibition were revealed using both experimental and molecular dynamics simulation approaches: (1) PS MPs decreased the bioavailability of lipid droplets via forming large lipid-MPs heteroaggregates due to the high MP hydrophobicity; and (2) PS MPs adsorbed lipase, and reduced its activity by changing the secondary structure and disturbing the essential open conformation. The first mechanism (MP-lipid interaction) played a more important role in lipid digestion reduction based on interaction energy calculation. These findings reveal potential risk of MPs to human digestion health and nutrient assimilation.

Key Physicochemical Properties Dictating Gastrointestinal Bioaccessibility of Microplastics-Associated Organic Xenobiotics: Insights from a Deep Learning Approach

A potential risk from human uptake of microplastics is the release of plastics-associated xenobiotics, but the key physicochemical properties of microplastics controlling this process are elusive. Here, we show that the gastrointestinal bioaccessibility, assessed using an in vitro digestive model, of two model xenobiotics (pyrene, at 391-624 mg/kg, and 4-nonylphenol, at 3054-8117 mg/kg) bound to 18 microplastics (including pristine polystyrene, polyvinyl chloride, polyethylene terephthalate, polypropylene, thermoplastic polyurethane, and polyethylene, and two artificially aged samples of each polymer) covered wide ranges: 16.1-77.4% and 26.4-83.8%, respectively. Sorption/desorption experiments conducted in simulated gastric fluid indicated that structural rigidity of polymers was an important factor controlling bioaccessibility of the nonpolar, nonionic pyrene, likely by inducing physical entrapment of pyrene in porous domains, whereas polarity of microplastics controlled bioaccessibility of 4-nonylphenol, by regulating polar interactions. The changes of bioaccessibility induced by microplastics aging corroborated the important roles of polymeric structures and surface polarity in dictating sorption affinity and degree of desorption hysteresis, and consequently, gastrointestinal bioaccessibility. Variance-based global sensitivity analysis using a deep learning neural network approach further revealed that micropore volume was the most important microplastics property controlling bioaccessibility of pyrene, whereas the O/C ratio played a key role in dictating the bioaccessibility of 4-nonylphenol in the gastric tract.

Competitive Adsorption of Polycyclic Aromatic Hydrocarbons to Carbon Nanotubes and the Impact on Bioavailability to Fathead Minnow (Pimephales promelas)

Recent studies investigating the influence of carbon nanotubes (CNTs) on the bioavailability of organic contaminants have mostly focused on single-solute systems; however, a more likely scenario in the natural environment is a multisolute system where chemical interactions at the surface of the CNT may alter the bioavailability of these chemicals. In the present study bisolute adsorption isotherms of pairs of chemically similar polycyclic aromatic hydrocarbons (PAHs) by multiwalled carbon nanotubes (MWCNTs) were established, in conjunction with quantifying the bioavailability of the 2 competing MWCNT-adsorbed PAHs to Pimephales promelas using bile analysis by high-performance liquid chromatography with fluorescence detection. The results showed that whereas adsorption and bioavailability of chemically similar PAHs (anthracene and phenanthrene, and fluoranthene and pyrene) were the same in a single-solute system, in bisolute systems, PAHs that could better align or flex with the MWCNT surface due to morphological characteristics would outcompete the more rigid or planar PAHs. The bioavailability of individual PAHs in bisolute solutions increased by as much as 50% compared with single-solute solutions. However, the relationship between adsorption (i.e., K_d ) and concentration of PAH in the fish bile was similar in single and bisolute systems. This finding indicates that competitive interactions at the surface of MWCNTs influence bioavailability by way of altering adsorption affinity in a moderately predictable manner. Environ Toxicol Chem 2020;39:1702-1711. © 2020 SETAC.

Assessing the Aflatoxins Mitigation Efficacy of Blueberry Pomace Biosorbent in Buffer, Gastrointestinal Fluids and Model Wine

Blueberry (BB) and cherry pomace were investigated as new biosorbents for aflatoxins (AFs) sequestration from buffered solutions, gastrointestinal fluids and model wine. Among the tested biosorbents, BB exhibited the maximum adsorption performance for AFs and hence was further selected for the optimization of experimental parameters like pH, dosage, time and initial concentration of AFs. Material characterizations via scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, N2 adsorption-desorption isothermal studies, thermogravimetric analysis (TGA) and X-ray photon spectroscopy (XPS) techniques revealed useful information about the texture and chemical composition of the biosorbents. The fitting of isothermal data with different models showed the model suitability trend as: Sips model > Langmuir model > Freundlich model, where the theoretical maximum adsorption capacity calculated from the Sips model was 4.6, 2.9, 2.7 and 2.4 mg/g for AFB1, AFB2, AFG1 and AFG2, respectively. Kinetics study revealed the fast AFs uptake by BB (50-90 min) while thermodynamics studies suggested the exothermic nature of the AFs adsorption from both, single as well as multi-toxin buffer systems, gastrointestinal fluids and model wine. Accrediting to the fast and efficient adsorption performance, green and facile fabrication approach and cost-effectiveness, the newly designed BB pomace can be counted as a promising contender for the sequestration of AFs and other organic pollutants.

Desorption of pharmaceuticals from pristine and aged polystyrene microplastics under simulated gastrointestinal conditions

Microplastics (MPs) in the environment usually undergo extensive weathering and can transport pollutants to organisms once being ingested. However, the transportation mechanism and effect of aging process are poorly understood. This study systematically investigated the desorption mechanisms of pharmaceuticals from pristine and aged polystyrene (PS) MPs under simulated gastric and intestinal conditions of marine organisms. Results showed that the increased desorption in stomach mainly depended on the solubilization of pepsin to pharmaceuticals and the competition for sorption sites on MPs via π-π and hydrophobic interactions. However, high desorption in gut relied on the solubilization of intestinal components (i.e. bovine serum albumin (BSA) and bile salts (NaT)) and the competitive sorption of NaT since the enhanced solubility increased the partition of pharmaceuticals in aqueous phase. Aging process suppressed the desorption of pharmaceuticals because aging decreased hydrophobic and π-π interactions but increased electrostatic interaction between aged MPs and pharmaceuticals, which became less affected by gastrointestinal components. Risk assessment indicated that the MP-associated pharmaceuticals posed low risks to organisms, and warm-blooded organisms suffered relatively higher risks than cold-blooded ones. This study reveals important information to understand the ecological risks of co-existed MPs and pollutants in the environment.

Consequential fate of bisphenol-attached PVC microplastics in water and simulated intestinal fluids

The ever-increasing prevalence of microplastics and different bisphenols made the presence of bisphenol-attached microplastics a critical concern. In this study, experiments were performed to examine desorption behaviors and cytotoxicity performance of contaminated microplastics in aquatic surroundings and intestinal environment after ingestion by organisms (cold-/warm-blooded). The kinetic study shows that the rate of desorption for bisphenols can be enhanced threefold under simulated warm intestinal conditions. The Freundlich isotherms indicate multiple-layer desorption of the bisphenols on the heterogeneous surfaces of polyvinyl chloride (PVC) microplastics. Hysteresis was detected in the adsorption/desorption of bisphenols in a water environment, but no adsorption/desorption hysteresis was observed in the simulated intestinal conditions of warm-blooded organisms. Due to enhanced bioaccessibility, the desorption results imply that the environmental risk of contaminated PVC microplastics may be significantly increased after ingestion at a high bisphenols dosage. Although with different IC₅₀, the five bisphenols released under the intestinal conditions of warm-blooded organisms can cause higher proliferation reduction in fish and human cell lines than the bisphenols released in water. This study helps elucidate the consequential fate and potential cytotoxicity of contaminated microplastics and the possible implications of the microplastics as a critical vector for bisphenols to increase the potential health risks.

Release of polycyclic aromatic hydrocarbons from biochar fine particles in simulated lung fluids: Implications for bioavailability and risks of airborne aromatics

Airborne carbonaceous fine particles, such as soot and biochar, represent a significant fraction of air particulate matter and have received widespread concern due to their health effects. Atmospheric carbonaceous particles can contain high concentration of polycyclic aromatic hydrocarbons (PAHs), and may pose significant health risks when carried into respiratory system from inhalation of particulates. In this study, the bioaccessibility of two PAH compounds, phenanthrene and pyrene, bound to biochar fine particles was assessed by examining their release in two simulated lung fluids: Gamble's solution and artificial lysosomal fluid (ALF). We observed that only 0.47 to 0.75% of biochar-bound PAHs were released in the simulated lung fluids, most likely due to the physical entrapment of PAH molecules in the micropore regimes of biochar, resulting in strong desorption hysteresis, even though apparent desorption equilibrium was reached within 30 min, well within the average clearance time of particulate matter in lung system. The inorganic and organic salts in the simulated lung fluids were found to inhibit the release of PAHs by exerting the pore blockage effect and salting-out effect. Moreover, the low molecular weight organic acids (LMWOAs) in the lung fluids further inhibited PAH release by increasing the micropore volume and surface area of biochar fine particles. When taking into account the inhibited release, the estimated carcinogenic risks of biochar-bound PAHs are typically low, even under extreme conditions wherein both biochar concentrations and PAH loadings on biochar are very high. An important implication is that contaminant bioavailability needs to be taken into account when assessing the risks of the contaminants bound to airborne carbonaceous materials.

Carbon Nanotubes as A High-Performance Platform for Target Delivery of Anticancer Quinones

BACKGROUND

In spite of considerable efforts of researchers the cancer deseases remain to be incurable and a percentage of cancer deseases in the structure of mortality increases every year. At that, high systemic toxicity of antitumor drugs hampers their effective use. Because of this fact, the development of nanosystems for targeted delivery of antitumor drugs is one of the leading problem in nanomedicine and nanopharmacy.

OBJECTIVE

To critically examine the modern strategies for carbon nanotubes (CNTs)-based delivery of anticancer quinones and to summarize the mechanisms which can provide high effectiveness and multifunctionality of the CNT-based quinone delivery platform.

RESULTS

Quinones, including anthracycline antibiotics - doxorubicin and daunorubicin, are among the most prospective group of natural and syntetic compounds which exhibit high antitumor activity against different type of tumors. In this review, we focus on the possibilities of using CNTs for targeted delivery of antitumor compounds with quinoid moiety which is ordinarily characterized by high specific interaction with DNA molecules. Quinones can be non-covalently adsorbed on CNT surface due to their aromatic structure and π-conjugated system of double bonds. The characteristic features of doxorubicine-CNT complex are high loading efficiency, pH-dependent release in acidic tumor microenviroment, enough stability in biological fluid. Different types of CNT functionalization, targeting strategies and designs for multifunctional CNT-based doxorubicine delivery platform are disscussed.

CONCLUSION

Nanosystems based on functionalized CNTs are very promising platform for quinone delivery resulting in significant enhancement of cancer treatment efficiency. Functionalization of CNTs with the polymeric shell, especially DNA-based shells, can provide the greatest affinity and mimicry with biological structures.

Adsorption and in vitro release study of curcumin form polyethyleneglycol functionalized multi walled carbon nanotube: kinetic and isotherm study

Polyethylene glycol functionalized with oxygenated multi-walled carbon nanotubes (O-PEG-MWCNTs) as an efficient nanomaterial for the in vitro adsorption/release of curcumin (CUR) anticancer agent. The synthesized material was morphologically characterized using scanning electron microscopy, Fourier transform infrared spectroscopy and transmission electron microscopy. In addition, the CUR adsorption process was assessed with kinetic and isotherm models fitting well with pseudo-second order and Langmuir isotherms. The results showed that the proposed O-PEG-MWCNTs has a high adsorption capacity for CUR (2.0 × 10³ mg/g) based on the Langmuir model. The in vitro release of CUR from O-PEG-MWCNTs was studied in simulating human body fluids with different pHs (ABS pH 5, intestinal fluid pH 6.6 and body fluid pH 7.4). Lastly, to confirm the success compliance of the O-PEG-MWCNT nanocomposite as a drug delivery system, the parameters affecting the CUR release such as temperature and PEG content were investigated. As a result, the proposed nanocomposite could be used as an efficient carrier for CUR delivery with an enhanced prolonged release property. Graphical Abstract ᅟ.

Removal of ciprofloxacin from aqueous solutions by ionic surfactant-modified carbon nanotubes

Ionic surfactants may impact removal efficiency of organic contaminants from aqueous solution, but research regarding the adsorption mechanisms on surfactant-modified carbon nanotubes (CNTs) was limited. In this study, three multi-walled and one single-walled CNTs were used as adsorbents to investigate the adsorption behavior and mechanisms of ciprofloxacin (CIP) on CNTs modified by ionic surfactants (cationic CTAB (Cetyltrimethylamnonium bromide) or anionic SDS (Sodium dodecyl sulfate)). More than 80% (82-88%) of the total removed CIP on CTAB-modified CNTs occurred within the first 6 h, much higher than that on SDS-modified CNTs (57-78%). Modeling adsorption kinetics demonstrated that CIP adsorption on surfactant-modified CNTs was controlled by multiple and faster processes, and both external mass transfer and intraparticle diffusion are limiting factors. Relative to SDS, CTAB was significantly (P < 0.001) concentration-dependent in suppressing CIP removal. Besides, the increase in 1/n values of Freundlich model with increasing CTAB concentration suggested that CTAB could be a stronger competitor for CIP adsorption. Hydrophobic interactions predominated zwitterionic CIP adsorption on all CNTs tested, while electrostatic interactions could help control ionizable CIP adsorption on surfactant-modified CNTs depending upon pH. CIP adsorption on modified SWCNTs significantly declined with increasing ionic strength from 1 mM to 100 mM relative to those multi-walled CNTs because the more favorable aggregation of SWCNTs reduced the CIP adsorption, irrespective of which surfactant was added. Significant desorption hysteresis of adsorbed CIP released by SDS and water was observed, but not by CTAB, by which 32.6-54.4% of adsorbed CIP were removed. For SDS-modified CNTs, the mean release ratio (RR) followed an order of MWCNTs (0.075) > MHCNTs (0.058) > SWCNTs (0.057) > MCCNTs (0.049), significantly (P < 0.001) lower than CTAB-CNTs (0.37-0.56). It can be predicted that the tested surfactants co-existing with CNTs depress removal efficiency of diverse contaminants similar to CIP in aqueous systems.

Accumulation, metabolite and active defence system responses of fluoxetine in zebrafish embryos: Influence of multiwalled carbon nanotubes with different functional groups

Studies on the bioavailability of organic contaminants adsorbed to nanomaterials are increasing. In this study, we investigated the interaction between fluoxetine (FLX) and three multiwalled carbon nanotubes (MWCNTs) with different functional groups in zebrafish (Danio rerio) embryos, focusing on the FLX accumulation, the formation of the metabolite norfluoxetine (NFLX), and the active defence system responses. The accumulation of FLX in zebrafish was intensified by MWCNTs (46-99%), which simultaneously facilitated the formation of the metabolite NFLX by 23-167%. The consistent enhancement revealed that the absorbed FLX is bioavailable in zebrafish. Moreover, the coexisting MWCNTs further promoted the influences of FLX on the active defence system in zebrafish (e.g. antioxidant and metabolic function), eliciting the defence function. The influences of MWCNTs on the bioavailability of FLX in zebrafish could be ordered as OH-MWCNTs > COOH-MWCNTs > pristine MWCNTs. The release of FLX from MWCNTs in biofluids may partially contribute to these significant alterations. In particular, MWCNTs themselves may also modulate the bioavailability of FLX in zebrafish by downregulating the gene expression of membrane ATP-binding cassette transporter (abcb4). These findings demonstrated that MWCNTs increased the bioavailability of FLX in zebrafish, especially the functionalized MWCNTs. The production of metabolites may be a useful bio-endpoint to evaluate the bioavailability of adsorbed contaminants on nanomaterials.

Bioaccessibility and exposure assessment of trace metals from urban airborne particulate matter (PM10 and PM2.5) in simulated digestive fluid

We describe a batch-extraction with simulated digestive fluid (salivary fluid, gastric fluid and intestinal fluid) to estimate the bioaccessibility of inhaled trace metals (TMs) in particulate matter less than 10 and 2.5 μm in aerodynamic diameter (PM₁₀ and PM_2.5). Concentrations of the assayed TMs (As, Cd, Cr, Ni, Mn, Cu, Zn, Sb, Hg and Pb) were determined in PM₁₀ and PM_2.5 samples by inductively coupled plasma-mass spectrometry. The TMs with the largest soluble fractions for airborne PM collected from winter and summer in saliva were Mn and Sb, respectively; in seasons this became Co in gastric fluid and Cu in intestinal fluid. Clearly, bioaccessibility is strongly dependent on particle size, the component of simulated digestive fluids (e.g., pH, digestive enzymes pepsin and trypsin), and the chemical properties of metal ions. The particle size and seasonal variation affected the inhaled bioaccessible fraction of PM-bound TMs during mucociliary clearance, which transported PM from the tracheal and the bronchial region to the digestive system. This study provides direct evidence for TMs in airborne PM being bioaccessible TMs are likely to possess an enhanced digestive toxic potential due to airborne PM pollution.

Dissolved organic matter affects both bioconcentration kinetics and steady-state concentrations of polycyclic aromatic hydrocarbons in zebrafish (Danio rerio)

Dissolved organic matter (DOM) is ubiquitous in natural aquatic ecosystems. The association of hydrophobic organic compounds (HOCs), such as polycyclic aromatic hydrocarbons (PAHs), with DOM may have a large impact on HOC fractions in water and their bioconcentration in fish. However, the effects of DOM on HOC bioconcentration in fish are not well understood, especially whether DOM will affect the bioconcentration steady-state concentrations of HOCs in fish is still confusing. Thus, this study investigated the effects of three DOM including gallic acid (GA), tannic acid (TA), and humic acid (HA) with molecular weights ranging from 170 Da to about 10 kDa at different concentrations (1, 5, and 15 mgOC L^-1) on the bioconcentration of PAHs including phenanthrene, anthracene, fluoranthene, and pyrene in zebrafish (Danio rerio), with the PAH freely dissolved concentrations maintained constant by passive dosing systems. The results revealed that the presence of DOM generally increased the bioconcentration steady-state concentrations of the PAHs in zebrafish (C_b-ss), with the increase ranging from 28.1% to 204.0%, and the increase of C_b-ss promoted by TA with middle molecular weight (1700 Da) was the highest among the studied DOM. Moreover, the C_b-ss increased with the concentrations of GA with low molecular weight and TA with middle molecular weight in water, whereas decreased with increasing concentrations of HA with high molecular weight. The uptake rate constants of the PAHs in zebrafish with DOM were higher than that without DOM. Ingestion of DOM and direct accumulation of PAHs associated with DOM might be primary influencing mechanisms of DOM on the C_b-ss, and whether the facilitated diffusive mass transfer by DOM will affect the C_b-ss needs to be further studied. This study suggested that DOM-associated HOCs should be considered in future HOC risk assessment in addition to the freely dissolved HOCs.

The interactions of fullerene C60 and Benzo(α)pyrene influence their bioavailability and toxicity to zebrafish embryos

This study aimed to assess the toxicological consequences related to the interaction of fullerene nanoparticles (C₆₀) and Benzo(α)pyrene (B(α)P) on zebrafish embryos, which were exposed to C₆₀ and B(α)P alone and to C₆₀ doped with B(α)P. The uptake of pollutants into their tissues and intra-cellular localization were investigated by immunofluorescence and electron microscopy. A set of biomarkers of genotoxicity and oxidative stress, as well as functional proteomics analysis were applied to assess the toxic effects due to C₆₀ interaction with B(α)P. The carrier role of C₆₀ for B(α)P was observed, however adsorption on C₆₀ did not affect the accumulation and localization of B(α)P in the embryos. Instead, C₆₀ doped with B(α)P resulted more prone to sedimentation and less bioavailable for the embryos compared to C₆₀ alone. As for toxicity, our results suggested that C₆₀ alone elicited oxidative stress in embryos and a down-regulation of proteins involved in energetic metabolism. The C₆₀ + B(α)P induced cellular response mechanisms similar to B(α)P alone, but generating greater cellular damages in the exposed embryos.

Concentration dependent adsorption of aromatic organic compounds by SWCNTs: Quantum-mechanical descriptors for nano-toxicological studies of biomolecules and agrochemicals

For evaluating the environmental risk associated using carbon nanotubes (CNTs), a successful prediction is desired for the adsorption of organic compounds (OCs) by CNTs at different adsorbate concentrations. This is most often achieved through poly-parameter linear solvation energy relationships (LSERs) based on solvatochromic descriptors. This study examines the real predictivity of the existing LSERs for predicting the adsorption of OCs by single-walled CNTs (SWCNTs) while comparing it with that of the models developed in the present work using quantum-mechanical descriptors. The real predictivity of the quantum-mechanical models and existing LSERs is compared using state-of-the-art statistical procedures employing an external prediction set of compounds not used in the model development. The quantum-mechanically computed mean polarizability, but originating from the interactions between electrons of parallel spin, is found to play an essential role in the adsorption of OCs by SWCNTs. Besides the solvatochromic descriptors (McGowan volume and molar excess refractivity), the instantaneous inter-electronic interactions, captured through electron-correlation based quantum-mechanical descriptors, are found to significantly affect the adsorption at varying adsorbate concentration. The models developed using a combination of quantum-mechanical and solvatochromic descriptors are found to be quite reliable. The models proposed were further employed to predict the adsorption of agrochemicals such as insecticides, pesticides, herbicides, as well as adsorption of endocrine disruptors and biomolecules such as nucleobases and steroid hormones. These are predicted to be strongly adsorbed by SWCNTs with Progesterone and Guanine exhibiting maximal interaction with the SWCNTs among biomolecules. The quantum-mechanical descriptors proposed in this work can be used for the risk assessment of SWCNTs in systems where adsorption is the primary process.

Impact of emerging, high-production-volume graphene-based materials on the bioavailability of benzo(a)pyrene to brine shrimp and fish liver cells

With increasing commercialization of high volume, two-dimensional carbon nanomaterials comes a greater likelihood of environmental release. In aquatic environments, black carbon binds contaminants like aromatic hydrocarbons, leading to changes in their uptake, bioavailability, and toxicity. Engineered carbon nanomaterials can also adsorb pollutants onto their carbon surfaces, and nanomaterial physicochemical properties can influence this contaminant interaction. We used 2D graphene nanoplatelets and isometric carbon black nanoparticles to evaluate the influence of particle morphology and surface properties on adsorption and bioavailability of benzo(a)pyrene, a model aromatic hydrocarbon, to brine shrimp (Artemia franciscana) and a fish liver cell line (PLHC-1). Acellular adsorption studies show that while high surface area carbon black (P90) was most effective at a given concentration, 2D graphene nanoplatelets (G550) adsorbed more benzo(a)pyrene than carbon black with comparable surface area (M120). In both biological models, co-exposure to nanomaterials lead to reduced bioavailability, with G550 graphene nanoplatelets cause a greater reduction in bioavailability or response than the M120 carbon black nanoparticles. However, on a mass basis the high surface area P90 carbon black was most effective. The trends in bioavailability and adsorption were consistent across all biological and acellular studies, demonstrating the biological relevance of these results in different models of aquatic organisms. While adsorption is limited by surface area, 2D graphene nanoplatelets adsorb more benzo(a)pyrene than carbon black nanoparticles of similar surface area and charge, demonstrating that both surface area and shape play important roles in the adsorption and bioavailability of benzo(a)pyrene to carbon nanomaterials.

Transformation and Speciation Analysis of Silver Nanoparticles of Dietary Supplement in Simulated Human Gastrointestinal Tract

Knowledge of the physicochemical properties of ingestible silver nanoparticles (AgNPs) in the human gastrointestinal tract (GIT) is essential for assessing their bioavailability, bioactivity, and potential health risks. The gastrointestinal fate of AgNPs and silver ions from a commercial dietary supplement was therefore investigated using a simulated human GIT. In the mouth, no dissolution or aggregation of AgNPs occurred, which was attributed to the neutral pH and the formation of biomolecular corona, while the silver ions formed complexes with biomolecules (Ag-biomolecule). In the stomach, aggregation of AgNPs did not occur, but extensive dissolution was observed due to the low pH and the presence of Cl^-. In the fed state (after meal), 72% AgNPs (by mass) dissolved, with 74% silver ions forming Ag-biomolecule and 26% forming AgCl. In the fasted state (before meal), 76% AgNPs dissolved, with 82% silver ions forming Ag-biomolecule and 18% forming AgCl. A biomolecular corona around AgNPs, comprised of mucin with multiple sulfhydryl groups, inhibited aggregation and dissolution of AgNPs. In the small intestine, no further dissolution or aggregation of AgNPs occurred, while the silver ions existed only as Ag-biomolecule. These results provide useful information for assessing the bioavailability of ingestible AgNPs and their subsequently potential health risks, and for the safe design and utilization of AgNPs in biomedical applications.

Bioaccessible trace metals in lip cosmetics and their health risks to female consumers

Females can be exposed to toxic elements in lip cosmetics following ingestion. The bioaccessibility of Cr, Mn, Co, Ni, Cu, Cd, Sb and Pb in lip cosmetics (n = 32) were assessed via the dilute HCl extraction method, In Vitro Gastrointestinal protocol (IVG) and the United States Pharmacopeia Methodology (USPM), and then health risks were characterized. The total concentrations of trace metals (TMs) in lip cosmetics were in the range of 15.55-111.97 mg/kg (Mean: 60.99 mg/kg). Cu, Pb and Cr were the three major TMs and accounting for >75% of the total concentrations. Except Sb and Pb in 4/32 and 4/32 samples were higher than the US FDA (Food and Drug Administration of the United States) limits, the other TMs were lower than that limits. Only bioaccessible Pb in all samples significantly exceeded the FDA limit 0.1 mg/kg in candy. Using IVG or USPM might be preferable for evaluating the TMs exposure over HCl since they better represent gastrointestinal physiology. The estimated average daily intake (ADI) of bioaccessible ∑TMs through lip cosmetics ingestion of career women and female college students were under safety level. The long-term exposure of bioaccessible TMs by lip cosmetics using would inevitably cause non-carcinogenic health risk. This is the first report on the in vitro tests used for evaluating bioaccessible TMs in lip cosmetics.

Enhanced Adsorption of p-Arsanilic Acid from Water by Amine-Modified UiO-67 as Examined Using Extended X-ray Absorption Fine Structure, X-ray Photoelectron Spectroscopy, and Density Functional Theory Calculations

p-Arsanilic acid ( p-ASA) is an emerging organoarsenic pollutant comprising both inorganic and organic moieties. For the efficient removal of p-ASA, adsorbents with high adsorption affinity are urgently needed. Herein, amine-modified UiO-67 (UiO-67-NH₂) metal-organic frameworks (MOFs) were synthesized, and their adsorption affinities toward p-ASA were 2 times higher than that of the pristine UiO-67. Extended X-ray absorption fine structure (EXAFS), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculation results revealed adsorption through a combination of As-O-Zr coordination, hydrogen bonding, and π-π stacking, among which As-O-Zr coordination was the dominant force. Amine groups played a significant role in enhancing the adsorption affinity through strengthening the As-O-Zr coordination and π-π stacking, as well as forming new adsorption sites via hydrogen bonding. UiO-67-NH₂s could remove p-ASA at low concentrations (<5 mg L^-1) in simulated natural and wastewaters to an arsenic level lower than that of the drinking water standard of World Health Organization (WHO) and the surface water standard of China, respectively. This work provided an emerging and promising method to increase the adsorption affinity of MOFs toward pollutants containing both organic and inorganic moieties, via modifying functional groups based on the pollutant structure to achieve synergistic adsorption effect.