Adsorption of antibiotics on different microplastics (MPs): Behavior and mechanism

Reactive oxygen species drive aging-associated microplastic release in diverse infusion ingredients

Exposure routes and transport of microplastics (MPs) from the environment into the human bodies deserve considerable attention. Intravenous injection has been reported as a direct MP-intrusion pathway. However, it is unclear whether or how the infusion fluid composition influences polymer degradation and MP release. Here, we determined that the concentrations of MPs shed from infusion bags ranged from 522 to 5455 particles/L. The storage period, mechanical shaking, and storage temperature all contributed to MP release to some extent; however, the infusion fluid composition affected the formation of MPs more than any other factor. Infusion fluids containing moxifloxacin hydrochloride, etimicin sulfate, and sodium bicarbonate ringer's solution generated more reactive oxygen species than those containing sodium chloride, grape sugar, and glucose and sodium chloride. Specifically, the generation of reactive oxygen species (hydroxyl radicals, carbonate radicals, and single oxygen) facilitated oxygen-containing functional group formation and breaking of carbon chains on the surface of the polypropylene plastic, which increased aging and fragmentation. Overall, this study provides knowledge of the mechanisms underlying MP release from infusion bags during storage and transportation. This offers insight for optimizing the use and handling of infusion bags in medical settings to minimize contamination.

Integration of machine learning and meta-analysis reveals the behaviors and mechanisms of antibiotic adsorption on microplastics

Microplastics (MPs) can adsorb antibiotics (ATs) to cause combined pollution in the environment. Research on this topic has been limited to specific types of MPs and ATs, resulting in inconsistent findings, particularly for the influencing factors and adsorption mechanisms. Therefore, this study combined meta-analysis and machine learning to analyze a dataset comprising 6805 records from 123 references. The results indicated that polyamide has the highest adsorption capacity for ATs, which is primarily attributed to the formation of hydrogen bonds by its N-H groups, and MPs exhibited the strongest affinity for chlortetracycline because the CO and -Cl groups in chlortetracycline form hydrogen and halogen bonds with MPs. Moreover, the particle size, MP and AT concentrations, and pH were key factors affecting the adsorption process with notable interaction effects. Hydrogen bonding and electrostatic interaction were commonly involved in the adsorption of ATs onto MPs. Finally, an interactive graphical user interface was deployed to predict the adsorption amount, affinity constant, and maximum adsorption capacity of MPs for ATs, with results aligning well with the latest published data. This study provides crucial insights into the behavior of MPs carrying ATs, thereby facilitating accurate assessment of the combined environmental risks of them.

Effects of microplastics accumulation and antibiotics contamination in anaerobic membrane bioreactors for municipal wastewater treatment

Municipal wastewater treatment plants are the main collection points for plastics and antibiotics. Anaerobic membrane bioreactor (AnMBR) is one the most potential municipal wastewater treatment technologies. This study evaluated the impact of microplastic (aged polyvinyl chloride, aged PVC, 1.5 g/L), antibiotics (ciprofloxacin, CIP, 100 μg/L) and their interaction effect on AnMBR treatment performance and membrane fouling. Results showed that the inhibition of CIP on AnMBR organic removal and methane production was intensified, owing to the CIP adsorption on aged PVC. The enzyme activities of electron transport (ETS), adenosine triphosphate (ATP) and F420 were also significantly restrained by 47-52 % with combined exposure. The combined effects also significantly aggravated the membrane fouling of AnMBR, which shorted the membrane operational period by half due to more soluble microbial products (SMP) secretion. The microbial diversity analyses indicated that aged PVC and CIP addition can accumulate some main anaerobic fermentation bacteria but inhibit the archaea. The abundance of related enzyme in the acetoclastic and hydrogenotrophic methanogenesis decreased with the sole aged PVC and CIP addition and severely inhibited with their combine effect. The absolute abundance mcrA significantly reduced by 92 % with combined exposure, validating the negative impact on methanogenic activity. These findings provide valuable insight into the AnMBR implementation in complex wastewater treatment.

Protein corona as a mediator in antibiotic adsorption onto microplastics: Mechanisms and implications

Microplastics are emerging pollutants capable of adsorbing antibiotics in the environment through interactions mediated by biological molecules such as proteins, ultimately posing risks to human health. However, direct evidence demonstrating that microplastics and antibiotics form chemical-adsorption products has not been explored. One key mechanism contributing to their co-exposure risks during their transmission is biofilm formation, particularly the development of a protein corona, which may also serve as a potential virulence mechanism. In this study, the interactions and adsorption processes among microplastics, proteins, and antibiotics within biofilm formation were innovatively analysed using molecular docking. Hydrophobic interactions contributing to the formation of a stable protein corona have been evidenced even in vitro digestive simulations. Notably, the presence of a protein corona on microplastics enhances the maximum adsorption capacity of antibiotics by 51.9 ± 2.7 %-64.7 ± 3.5 %, without affecting the chemical adsorption mode on Site II or the heterogeneous diffusion mechanism. Furthermore, compared to previous studies, this research provides compelling evidence that sulfamethoxazole interacts with Glu 166 in Site II of bovine serum albumin with high accuracy. Overall, this study addresses a previously overlooked aspect of toxicological research by offering new insights into pollutant adsorption facilitated by the protein corona on microplastics.

Unraveling the toxic trio: Combined effects of thifluzamide, enrofloxacin, and microplastics on Mytilus coruscus

The presence of pesticides, antibiotics, and microplastics in aquatic environments poses a significant threat because of their persistence and potential harm to aquatic life and human health. However, few studies have explored their combined effects on bioaccumulation and toxicity in edible bivalves. This study examined the bioaccumulation and toxicological impacts of thifluzamide (TF) and enrofloxacin (ENR) on oxidative stress, neurotoxicity, detoxification, and metabolism in Mytilus coruscus after 4 weeks of exposure at the environmental level. The findings indicated that coexposure to TF and ENR or the presence of microplastic polystyrene (PS) increased TF and ENR accumulation in mussels and caused oxidative damage, as evidenced by elevated catalase and glutathione transferase activities and increased malondialdehyde (MDA) levels. Notably, compared with single exposures, coexposure to PS+TF, PS+ENR, or TF+ENR generally increased the MDA content, reduced acetylcholinesterase activity, and increased detoxification gene expression. Metabolomic analysis revealed that TF, ENR, and PS, either alone or combined, significantly disrupted multiple metabolic pathways by altering levels of glycerophospholipids, eicosanoids, amino acids, and nucleotides. Coexposure particularly worsened glycerophospholipid and arachidonic acid metabolism disturbances. These results suggest that combined exposure to TF, ENR or PS exacerbated the ecotoxicological effects of TF and ENR on M. coruscus. Taken together, the results of the present study could enhance our understanding of the environmental effects resulting from multipollutant interactions and their potential risks to seafood security.

Impact of the hydrated functional zone on the adsorption of ciprofloxacin to microplastics under the influence of UV aging

The inevitable UV aging of microplastics (MPs) is one of the key factors affecting their interaction with antibiotics. In this study, polyethylene (PE) and polystyrene (PS) MPs were aged with UV irradiation. The adsorption isotherms and kinetics of ciprofloxacin (CIP) to virgin and aged MPs were investigated through various models, and the effects of pH on the adsorption amount were explored. Characterization revealed that the surfaces of aged MPs became rougher, and the hydrophilicity increased. These aged MPs were still in the early stage of aging on the basis of their carbonyl index (CI) (<0.2) and O/C (<0.04) values. The adsorption isotherms indicated that the adsorption mechanism of aged PE was different from that of virgin PE. Compared with virgin PE, the adsorption amount of aged PE increased by 87.80-95.45%, and the adsorption rate decreased by 65.52-80.74%. However, aging did not significantly affect the equilibrium adsorption amount or adsorption rate of aged PS. The external diffusion rate (Kext) (about 2.29-0.36 h-1) was almost 30 times greater than the internal diffusion rate (Kint) in the film-pore mass transfer (FPMT) model, indicating that CIP adsorption rate was dominated by external diffusion. A hydrated functional zone is thought to form around aged MPs, thus changing the adsorption mechanism and adsorption amount of aged PE. Therefore, more attention should be given to alterations in the hydrated functional zone in the early stage of MPs aging.

Sorption kinetics of metallic and organic contaminants on micro- and nanoplastics: remarkable dependence of the intraparticulate contaminant diffusion coefficient on the particle size and potential role of polymer crystallinity

We developed a mechanistic diffusion model to describe the sorption kinetics of metallic and organic contaminants on nano- and micro-plastics. The framework implements bulk depletion processes, transient fluxes, and fully adaptable particle/water boundary conditions, i.e. not only the typically assumed simple linear Henry regime, which is not applicable to many contaminant-particle situations. Thus, our model represents a flexible and comprehensive theory for the analysis of contaminant sorption kinetics, which goes well beyond the traditional empirical pseudo first or second order kinetic equations. We applied the model to the analysis of a large body of literature data on the equilibrium and kinetic features of sorption of a wide range of contaminants by diverse types and sizes of plastic particles. Results establish the paramount importance of sorption boundary conditions (Henry, Langmuir, or Langmuir-Freundlich) and reveal interesting and often overlooked sorption features that depend on the plastic particle size and the extent to which the target compound is depleted in the bulk medium. The greater degree of polymer crystallinity reported for smaller particles may underlie our findings that the intraparticulate contaminant diffusion coefficient decreases with a decreasing particle size. We establish a universal law to predict the sorption kinetics and diffusion of any compound within any plastic phase, which has far reaching importance across many domains relevant to the environment and human health.

Colloid and Interface Science for Understanding Microplastics and Developing Remediation Strategies

Microplastics (MPs) originate from industrial production of <1 mm polymeric particles and from the progressive breakdown of larger plastic debris. Their environmental behavior is governed by their interfacial properties, which dominate due to their small size. This Perspective highlights the complex surface chemistry of MPs under environmental stressors and discusses how physical attributes like shape and roughness could influence their fate. We further identify wastewater treatment plants (WWTPs) as critical hotspots for MP accumulation, where the MPs are inadvertently transferred to sewage sludge and reintroduced into the environment. We emphasize the potential of colloid and interfacial science not only to improve our fundamental understanding of MPs but also to advance mitigation strategies in hotspots such as WWTPs.

Sorption behavior of oxytetracycline on microplastics and the influence of environmental factors in groundwater: Experimental investigation and molecular dynamics simulation

Microplastics (MPs) and antibiotics can enter groundwater through the interaction of soil and surface water, and MPs as carriers of antibiotics can promote the migration of antibiotics and thus generate more serious ecological risks. Therefore, this paper used experimental and molecular dynamics (MD) simulation methods to investigate the sorption between four common types of MPs in groundwater, namely polyamide (PA), polystyrene (PS), polyvinyl chloride (PVC), and polyethylene (PE), and oxytetracycline (OTC) with high detection rate in groundwater. Additionally, the impact of environmental factors on sorption was examined. The sorption kinetics of the four types of MPs followed the pseudo-second-order kinetics model, and the sorption isotherms of OTC on PA, PE, and PVC were highly linear, suggesting that the electrostatic interaction was the main sorption mechanism. Both experimental and simulation results indicated that PA had the highest affinity for OTC, due to the effect of the formation of hydrogen bonding between the amide groups of PA and OTC. The primary way pH affected sorption was by altering the form in which OTC exists. The effects of the representative substances of protein-like component (bovine serum albumin) and humus-like component (humic acid) in dissolved organic matter varied but were generally inhibitory. Ions could influence the sorption process by competitive sorption or forming complexes with the OTC.

Sorption of tetracycline antibiotics by microplastics, associated mechanisms, and risk assessments

In this study, we selected polyvinyl chloride (PVC), polyethylene (PE), and polystyrene (PS) as representative microplastics (MPs) to systematically investigate the sorption behavior of tetracycline (TC) antibiotics by MPs. Scanning electron microscopy, X-ray diffraction, Fourier transform-infrared spectroscopy, and adsorption experiments were applied to assess the sorption behavior of MPs. The results demonstrated that the sorption of TC by MPs was most favorable under neutral conditions, where a modest increase in the salt ion concentration enhanced the adsorption of TC by MPs. The saturation adsorption capacities for PVC, PE, and PS for TC were determined as 121.95 μg/g, 81.301 μg/g, and 178.57 μg/g, respectively. The strength of TC sorption by MPs followed the order of: PS > PVC > PE. Analysis of the sorption behavior of TC by MPs showed that the adsorption of TC by PE was weak and it readily desorbed, and thus their interaction will not lead to excessive compound pollution. By contrast, the adsorption of TC was high by PVC and PS, and they were not readily desorbed.

Perfluorobutanoic acid weakens the heterogeneous aggregation of microplastics and microalgae: Perspective from physicochemical properties, extracellular polymeric substances secretion and DLVO theory

Microplastics (MPs) and per- and poly-fluoroalkyl substances extensively coexist in aquatic environments and potentially endanger organisms. Microalgae may decrease the effective concentration of pollutants via hetero-aggregation with MPs and adsorption of emerging contaminants. However, the potential influence of coexistent pollutants on hetero-aggregation of MPs and microalgae remains unknown. This study investigated the hetero-aggregation process involving different sizes of polystyrene (PS, 3.0 and 50.0 μm) with Chlorella sorokiniana (C. sorokiniana) in the presence or absence of perfluorobutanoic acid (PFBA) along settling experiments, scanning electron microscope, and Derjaguin-Landau-Verwey-Overbeek (DLVO) model. We found that the hetero-aggregation between C. sorokiniana and 3 μm PS was more pronounced than with 50 μm PS, while PFBA inhibited this process. ΔOD1 values (reflected hetero-aggregation level) for 3PS-cells and 50PS-cells were 0.189 and 0.087, respectively, and PFBA decreased these values to 0.134 and 0.033. Furthermore, extracellular polymeric substances, known as inducer of hetero-aggregation, increased by 14.33% when exposed to 3 μm PS alone, whereas the co-exposure group showed a decrease of 4.52% compared to 3PS-cells group. PFBA also significantly decreased the protein/polysaccharide ratios in both MPs sizes, reducing hetero-aggregation. DLVO theory revealed that microalgae lowered the energy barrier significantly, while PFBA elevated it, indicating that hetero-aggregation was inhibited by PFBA. This study provides new perspectives for pollutant removal and toxicity variation in aquatic environments.

Impacts of micro/nano plastics on the ecotoxicological effects of antibiotics in agricultural soil: A comprehensive study based on meta-analysis and machine learning prediction

Micro/nano plastics (M/NPs) and antibiotics, as widely coexisting pollutants in environment, pose serious threats to soil ecosystem. The purpose of this study was to systematically evaluate the ecological effects of the co-exposure of M/NPs and antibiotics on soil organisms through the meta-analysis and machine learning prediction. Totally, 1002 data set from 38 articles were studied. The co-exposure of M/NPs significantly promoted the abundance (62.68 %) and migration level (55.22 %) of antibiotic contamination in soil, and caused serious biotoxicity to plants (-12.31 %), animals (-12.03 %), and microorganisms (35.07 %). Using 10 variables, such as risk response categories, basic physicochemical properties, exposure objects, and exposure time of M/NPs, as data sources, Random Forests (RF) and eXtreme Gradient Boosting (XGBoost) models were developed to predict the impacts of M/NPs on the ecotoxicological effects of antibiotics in agricultural soil. The effective R2 values (0.58 and 0.60, respectively) indicated that both models can be used to predict the future ecological risk of M/NPs and antibiotics coexistence in soil. Particle size (13.54 %), concentration (5.02 %), and type (11.18 %) of M/NPs were the key characteristic parameters that affected the prediction results. The findings of this study indicate that the co-exposure of M/NPs and antibiotics in soil not only exacerbates antibiotic contamination levels but also causes severe toxic effects to soil organism. Furthermore, this study provides an effective approach for ecological risk assessment of the coexistence of M/NPs and antibiotics in environment.

Biofilm formation on microplastics and interactions with antibiotics, antibiotic resistance genes and pathogens in aquatic environment

Microplastics (MPs) in aquatic environments easily support biofilm development, which can interact with other environmental pollutants and act as harbors for microorganisms. Recently, numerous studies have investigated the fate and behavior of MP biofilms in aquatic environments, highlighting their roles in the spread of pathogens and antibiotic resistance genes (ARGs) to aquatic organisms and new habitats. The prevalence and effects of MP biofilms in aquatic environments have been extensively investigated in recent decades, and their behaviors in aquatic environments need to be synthesized systematically with updated information. This review aims to reveal the development of MP biofilm and its interactions with antibiotics, ARGs, and pathogens in aquatic environments. Recent research has shown that the adsorption capabilities of MPs to antibiotics are enhanced after the biofilm formation, and the adsorption of biofilms to antibiotics is biased towards chemisorption. ARGs and microorganisms, especially pathogens, are selectively enriched in biofilms and significantly different from those in surrounding waters. MP biofilm promotes the propagation of ARGs through horizontal gene transfer (HGT) and vertical gene transfer (VGT) and induces the emergence of antibiotic-resistant pathogens, resulting in increased threats to aquatic ecosystems and human health. Some future research needs and strategies in this review are also proposed to better understand the antibiotic resistance induced by MP biofilms in aquatic environments.

Adsorption and desorption of parachlormetaxylenol by aged microplastics and molecular mechanism

The addition of active ingredients such as antibacterial agent and non-active ingredients such as plastic microspheres (MPs) in personal care products (PCPs) are the common pollutants in the aquatic environment, and their coexistence poses potential threat to the aquatic ecosystem. As a substitute for the traditional antibacterial ingredients triclosan and triclocarban, the usage of parachlormetaxylenol (PCMX) is on the rise and is widely used in PCPs. In this study, the adsorption and desorption behaviors of PCMX were investigated with two typical MPs, polyvinyl chloride (PVC) and polyethylene (PE), and the effects of different aging modes and molecular mechanisms were explored through batch experiments and density functional theory calculation. Both laboratory aging and field aging resulted in surface wrinkles of MPs, along with an increased proportion of oxygen-containing functional groups (CO, -OH). At the same aging time, the degree of laboratory aging was stronger than that of field aging, and the aging degree of PVC was greater that of PE. The aging process enhanced the adsorption capacity of MPs for PCMX. The equilibrium adsorption capacity of PVC increased from 3.713 mg/g (virgin) to 3.823 mg/g (field aging) and 3.969 mg/g (laboratory aging), while that of PE increased from 3.509 mg/g to 3.879 mg/g and 4.109 mg/g, respectively. Meanwhile, aging also resulted in an increase in the desorption capacity of PCMX from PVC and PE. Oxygen-containing functional groups in aged MPs could serve as adsorption sites for PCMX and improved the electrostatic adsorption capacity. Oxygen-containing groups generated on the surface of aged MPs formed hydrogen bonding with the phenolic hydroxyl groups of PCMX, which became the main driving force for adsorption. Our results reveal the potential impact and mechanism of aging on the adsorption of PCMX by MPs, which provides new insights for the interaction mechanism between environmental MPs and associated contaminants.

Cotransport of 6PPD-Q and pristine/aged microplastics in porous media: An insight based on transport forms and mechanisms

The environmental fate and risks of microplastics (MPs) and their associated contaminants have attracted increasing concern in recent years. In this study, the cotransport of six kinds of pristine and aged MPs and the antiager ozonation product N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPD-Q) were investigated via a series of batch and transport experiments, and characteristic analysis (e.g., SEM, FTIR and XPS). Generally, pristine MPs exhibit higher adsorption ability than aged MPs due to the hydrophobic interaction. The 6PPD-Q usually exhibited both free moving and bond-MPs moving during transport process in presence of MPs, but none free 6PPD-Q was detected in presence of pristine PP MPs. The mobility of 6PPD-Q was generally facilitated in presence of MPs by bond-MPs moving due to the hydrogen bonding, halogen bonding, π-π interaction (the maximum total mass recovery of 84.11%), which efficiency was influenced with the combined effect of adsorption ability and mobility of MPs. The pristine PVC MPs showed highest facilitation on 6PPD-Q transport. The retained 6PPD-Q in porous media also was released by various MPs with different mass recovery ranged from 15.72% to 56.26% via surface moving of MPs around porous media. Both the dissolved and retained 6PPD-Q decreased the MPs mobility with the minimum mass recovery of 34.02%. Findings from this study contribute to the prediction and assessment of the combined risks of MPs and 6PPD-Q.

The adsorption of drugs on nanoplastics has severe biological impact

Micro- and nanoplastics can interact with various biologically active compounds forming aggregates of which the effects have yet to be understood. To this end, it is vital to characterize these aggregates of key compounds and micro- and nanoplastics. In this study, we examined the adsorption of the antibiotic tetracycline on four different nanoplastics, made of polyethylene (PE), polypropylene (PP), polystyrene (PS), and nylon 6,6 (N66) through chemical computation. Two separate approaches were employed to generate relevant conformations of the tetracycline-plastic complexes. In the first approach, we folded the plastic particle from individual polymer chains in the presence of the drug through multiple separate simulated annealing setups. In the second, more biased, approach, the neat plastic was pre-folded through simulated annealing, and the drug was placed at its surface in multiple orientations. The former approach was clearly superior to the other, obtaining lower energy conformations even with the antibiotic buried inside the plastic particle. Quantum chemical calculations on the structures revealed that the adsorption energies show a trend of decreasing affinity to the drug in the order of N66> PS> PP> PE. In vitro experiments on tetracycline-sensitive cell lines demonstrated that, in qualitative agreement with the calculations, the biological activity of tetracycline drops significantly in the presence of PS particles. Preliminary molecular dynamics simulations on two selected aggregates with each plastic served as first stability test of the aggregates under influence of temperature and in water. We found that all the selected cases persisted in water indicating that the aggregates may be stable also in more realistic environments. In summary, our data show that the interaction of micro- and nanoplastics with drugs can alter drug absorption, facilitate drug transport to new locations, and increase local antibiotic concentrations, potentially attenuating antibiotic effect and at the same time promoting antibiotic resistance.

Micro(nano)plastic and Related Chemicals: Emerging Contaminants in Environment, Food and Health Impacts

Microplastic pollution is a problem of increasing concern in food, and while food safety issues around the world are serious, an increasing number of food safety issues related to microplastics have become the focus of people's attention. The presence of microplastics in food is a worldwide problem, and they are present in all kinds of foods, foods of both animal and plant origin, food additives, drinks, plastic food packaging, and agricultural practices. This can cause problems for both humans and the environment. Microplastics have already been detected in human blood, heart, placenta, and breastmilk, but their effects in humans are not well understood. Studies with mammals and human cells or organoids have given perspective about the potential impact of micro(nano)plastics on human health, which affect the lungs, kidneys, heart, neurological system, and DNA. Additionally, as plastics often contain additives or other substances, the potentially harmful effects of exposure to these substances must also be carefully studied before any conclusions can be drawn. The study of microplastics is very complex as there are many factors to account for, such as differences in particle sizes, constituents, shapes, additives, contaminants, concentrations, etc. This review summarizes the more recent research on the presence of microplastic and other plastic-related chemical pollutants in food and their potential impacts on human health.

Polyamide 6 microplastics as carriers led to changes in the fate of bisphenol A and dibutyl phthalate in drinking water distribution systems: The role of adsorption and interfacial partitioning

Microplastics (MPs) co-exist with plastic additives and other emerging pollutants in the drinking water distribution systems (DWDSs). Due to their strong adsorption capacity, MPs may influence the occurrence of additives in DWDSs. The article investigated the occurrence of typical additives bisphenol A (BPA) and dibutyl phthalate (DBP) in DWDSs under the influence of polyamide 6 (PA6) MPs and further discussed the partitioning of BPA/DBP on PA6s, filling a research gap regarding the impact of adsorption between contaminants on their occurrence within DWDSs. In this study, adsorption experiments of BPA/DBP with PA6s and pipe scales were conducted and their interaction mechanisms were investigated. Competitive adsorption experiments of BPA/DBP were also carried out with site energy distribution theory (SEDT) calculations. The results demonstrated that PA6s might contribute to the accumulation of BPA/DBP on pipe scales. The adsorption efficiencies of BPA/DBP with both PA6s and pipe scales were 26.47 and 2.61 times higher than those with only pipe scales. It was noteworthy that BPA had a synergistic effect on the adsorption of DBP on PA6s, resulting in a 26.47 % increase in DBP adsorption. The article provides valuable insights for the compounding effect of different types of additives in water quality monitoring and evaluation.

Impact on sulfadiazine bio-accessibility in soils through organic diffusive gradients in thin films (o-DGT): Differentiation based on microplastic polymers, aging, and soil properties

Due to the similar sources of swage irrigation, organic fertilizer, and sludge application, microplastics (MPs) and antibiotics coexist inevitably in the agriculture soils. However, the impacts of MPs with different polymer types and aging status on the bio-accessibility of co-existing antibiotics in soils remained unclear. Therefore, we using the diffusive gradients films for organic compounds devices (o-DGT) to evaluated the distribution of sulfadiazine (SDZ) in both paddy soil and saline soil amended with 0.5 % (w/w) MPs. Four polymer types (polyethylene: PE, polypropylene: PP, polyamide: PA, and polyethylene terephthalate: PET) and two aging statuses (aged PE and aged PP) of MPs were used in this study. Results showed that soil properties significantly influence the partition of SDZ in soil and soil solution, and SDZ gained a lower degradation rate but higher mobility in saline soil. MPs pose different impacts on partition of SDZ between paddy soil and saline soil. Notably, PP reduced the labile solid phase-solution phase partition coefficient (Kdl) by 17.7 % in paddy soil, while PE, PP, and aPE increased the Kdl value by 2.00, 1.62, and 2.81 times in saline soil. Besides, in saline soil, all the MPs reduced the SDZ concentration in the soil solution, while significantly increased the SDZ in o-DGT phase. Conversely, MPs did not impact the SDZ's o-DGT concentration in paddy soil. Additionally, MPs increased the R value of SDZ in two soils, especially in saline soil. It suggested that MPs could potentially enhance the resupply of SDZ from soil to plants, particularly under saline conditions. Furthermore, aged MPs had a more pronounced effect on these indicators compared to virgin MPs in saline soil. Therefore, MPs in soil poses a potential risk for biota's uptake of SDZ, particularly in fragile environment. Moreover, the risk intensifies with aged MPs.

When antibiotics encounter microplastics in aquatic environments: Interaction, combined toxicity, and risk assessments

Antibiotics and microplastics (MPs), known as emerging pollutants, are bound to coexist in aquatic environments due to their widespread distribution and prolonged persistence. To date, few systematic summaries are available for the interaction between MPs and antibiotics in aquatic ecosystems, and a comprehensive reanalysis of their combined toxicity is also needed. Based on the collected published data, we have analyzed the source and distribution of MPs and antibiotics in global aquatic environments, finding their coexistence occurs in a lot of study sites. Accordingly, the presence of MPs can directly alter the environmental behavior of antibiotics. The main influencing factors of interaction between antibiotics and MPs have been summarized in terms of the characteristics of MPs and antibiotics, as well as the environmental factors. Then, we have conducted a meta-analysis to evaluate the combined toxicity of antibiotics and MPs on aquatic organisms and the related toxicity indicators, suggesting a significant adverse effect on algae, and inapparent on fish and daphnia. Finally, the environmental risk assessments for antibiotics and MPs were discussed, but unfortunately the standardized methodology for the risk assessment of MPs is still challenging, let alone assessment for their combined toxicity. This review provides insights into the interactions and environment risks of antibiotics and MPs in the aquatic environment, and suggests perspectives for future research.

Evaluation of the difference in adsorption of amphetamine-type drugs on deep eutectic solvent-functionalized graphene oxide/ZIF-67 composite: Experiment and theoretical calculations

Herein, the capture and separation properties of the deep eutectic solvent-functionalized magnetic graphene oxide/ZIF-67 composite (ZMG-DES) towards amphetamine-type drugs (MDMA, MAM and AM) from water were investigated. Kinetic and isotherm models showed that the adsorption behaviors were monolayer chemisorption. Batch experiment results showed that the maximal adsorption of MDMA (933.652 μg⋅g-1) was 2.3 and 2.8 times higher than that of MAM (412.849 μg⋅g-1) and AM (328.652 μg⋅g-1), respectively, and this superiority remained consistent under varied environmental influences (pH, background ion and humic acid). Theoretical calculations and characterization analyses demonstrated the methylenedioxy group of MDMA led to the highly selective adsorption. Electrostatic potential (ESP) distribution indicated that the methylenedioxy added electron-rich areas and provided more adsorption sites. The Independent Gradient Model (IGMH) quantified the adsorption contribution of the functional groups in each system, which the contribution of the methylenedioxy reached 25.23%, significantly exceeding that of -NH- (18.80%) and benzene ring (20.76%), and proved that the H-bonds formed methylenedioxy enhanced adsorption. Furthermore, the Hirshfeld surface analysis proved that the methylenedioxy and -NH- of MDMA acted as H-bond acceptor and donor, respectively, which synergistically promoted the adsorption. The present study will help us to understand the structure-property relationship between amphetamine-type drugs and ZMG-DES.

High-sensitive determination of tetracycline antibiotics adsorbed on microplastics in mariculture water using pre-COF/monolith composite-based in-tube solid phase microextraction on-line coupled to HPLC-MS/MS

Microplastics (MPs) act as carriers for organic pollutants (e.g. antibiotics) and microorganisms (e.g. bacteria) in waters, leading to the proliferation of antibiotic resistance genes. Moreover, the antibiotics adsorbed on MPs may exacerbate this process. For further research, it is necessary to understand the types and amounts of antibiotics adsorbed on MPs. However, due to the heavy work of MPs collection and sample pretreatment, there is a lack of analytical methods and relevant data. In this study, an in-tube solid phase microextraction (IT-SPME) on-line coupled to HPLC-MS/MS method based on amorphous precursor polymer of three-dimensional covalent organic frameworks/monolith-based composite adsorbent was developed, which could efficiently capture, enrich and analyze tetracycline (TCs) antibiotics. Under the optimal extraction parameters, the developed method was capable of detecting TCs at levels as low as 0.48-1.76 pg. This method was applied to analyze the TCs adsorbed on MPs of different particle sizes in mariculture water for the first time, requiring a minimum amount of MPs of only 1 mg. Furthermore, it was observed that there could be an antagonistic relationship between algal biofilm and TCs loaded on MPs. This approach could open up new possibilities for analyzing pollutants on MPs and support deeper research on MPs.

The impact of arbuscular mycorrhizal fungi and endophytic bacteria on peanuts under the combined pollution of cadmium and microplastics

It remains unclear how symbiotic microbes impact the growth of peanuts when they are exposed to the pollutants cadmium (Cd) and microplastics (MPs) simultaneously. This study aimed to investigate the effects of endophytic bacteria Bacillus velezens SC60 and arbuscular mycorrhizal fungus Rhizophagus irregularis on peanut growth and rhizosphere microbial communities in the presence of Cd at 40 (Cd40) or 80 (Cd80) mg kg-1 combined without MP or the presence of low-density polyethylene (LDPE) and poly butyleneadipate-co-terephthalate (PBAT). This study assessed soil indicators, plant parameters, and Cd accumulation indicators. Results showed that the application of R. irregularis and B. velezens significantly enhanced soil organic carbon and increased Cd content under the conditions of Cd80 and MPs co-pollution. R. irregularis and B. velezens treatment increased peanut absorption and the enrichment coefficient for Cd, with predominate concentrations localized in the peanut roots, especially under combined pollution by Cd and MPs. Under treatments with Cd40 and Cd80 combined with PBAT pollution, soil microbes Proteobacteria exhibited a higher relative abundance, while Actinobacteria showed a higher relative abundance under treatments with Cd40 and Cd80 combined with LDPE pollution. In conclusion, under the combined pollution conditions of MPs and Cd, the co-treatment of R. irregularis and B. velezens effectively immobilized Cd in peanut roots, impeding its translocation to the shoot.

Microplastics enhance the invasion of exotic submerged macrophytes by mediating plant functional traits, sediment properties, and microbial communities

Plant invasions and microplastics (MPs) have significantly altered the structure and function of aquatic habitats worldwide, resulting in severe damage to aquatic ecosystem health. However, the effects of MPs on plant invasion and the underlying mechanisms remain largely unknown. In this study, we conducted mesocosm experiments over a 90-day period to assess the effects of polystyrene microplastics on the invasion of exotic submerged macrophytes, sediment physicochemical properties, and sediment bacterial communities. Our results showed that PS-MPs significantly promoted the performance of functional traits and the invasive ability of exotic submerged macrophytes, while native plants remained unaffected. Moreover, PS-MPs addition significantly decreased sediment pH while increasing sediment carbon and nitrogen content. Additionally, MPs increased the diversity of sediment bacterial community but inhibited its structural stability, thereby impacting sediment bacterial multifunctionality to varying degrees. Importantly, we identified sediment properties, bacterial composition, and bacterial multifunctionality as key mediators that greatly enhance the invasion of exotic submerged macrophytes. These findings provide compelling evidence that the increase in MPs may exacerbate the invasion risk of exotic submerged macrophytes through multiple pathways. Overall, this study enhances our understanding of the ecological impacts of MPs on aquatic plant invasion and the health of aquatic ecosystems.

Adsorption interactions between typical microplastics and enrofloxacin: Relevant contributions to the mechanism

Microplastics (MPs) are increasingly contaminating the environment and they can combine with antibiotics as carriers to form complex contaminants. In this study, we systematically investigated the interactions between the antibiotic enrofloxacin (ENR) and MPs comprising polyethylene (PE), polyvinyl chloride (PVC), and polystyrene (PS). Characterization was performed by using conventional techniques and the mechanisms involved in interactions were initially explored based on adsorption kinetics, isotherms, and resolution experiments, and the adsorption capacities of the MPs were determined. In addition, the extended Derjaguin-Landau-Verwey-Overbeek theory was used to investigate the interaction mechanisms. The results showed that the interactions were weaker in strong acidic and alkaline environments, and the interactions were also inhibited at higher salt ion concentrations. The saturation adsorption amounts of ENR on PVC, PE, and PS were 74.63 μg/g, 103.09 μg/g, and 142.86 μg/g, respectively. The interactions between MPs and ENR were dominated by hydrophobic interactions, followed by van der Waals forces and acid-base forces. This study provides new insights into the adsorption behavior of ENR by MPs.

Development of calcium phosphate-chitosan composites with improved removal capacity toward tetracycline antibiotic: Adsorption and electrokinetic properties

Two eco-friendly and highly efficient adsorbents, namely brushite-chitosan (DCPD-CS), and monetite-chitosan (DCPA-CS) composites were synthesized via a simple and low-cost method and used for tetracycline (TTC) removal. The removal behavior of TTC onto the composite particles was studied considering various parameters, including contact time, pollutant concentration, and pH. The maximum TTC adsorption capacity was 138.56 and 112.48 mg/g for the DCPD-CS and DCPA-CS, respectively. Increasing the pH to 11 significantly enhanced the adsorption capacity to 223.84 mg/g for DCPD-CS and 205.92 mg/g for DCPA-CS. The antibiotic adsorption process was well-fitted by the pseudo-second-order kinetic and Langmuir isotherm models. Electrostatic attractions, complexation, and hydrogen bonding are the main mechanisms governing the TTC removal process. Desorption tests demonstrated that the (NH4)2HPO4 solution was the most effective desorbing agent. The developed composites were more efficient than DCPD and DCPA reference samples and could be used as valuable adsorbents of TTC from contaminated wastewater.

Adsorption behavior of triclosan on polystyrene nanoplastics: The roles of particle size, surface functionalization, and environmental factors

Nanoplastics (NPs) contribute substantially to the transport of waterborne pollutants. Triclosan (TCS) has a high potential to contact with NPs because of their prevalence in natural waters. Herein, this study investigated the adsorption behavior of TCS on differently sized and functionalized polystyrene (PS) NPs. The effects of environmental factors such as pH, salinity, and dissolved organic matter (DOM) were also evaluated. Results suggest that the adsorption equilibrium constant (kd) of TCS in pristine PSNP suspensions followed the order as: PSNPs-50 nm (4.39 L·g-1) > PSNPs-100 nm (2.78 L·g-1) > PSNPs-200 nm (2.59 L·g-1) > PSNPs-500 nm (1.36 L·g-1) ≈ PSNPs-900 nm (1.36 L·g-1). For the functionalized PSNPs (i.e., PSNPs-COOH, PSNPs-NH2), the values of specific surface area normalized kd called kd, SSA were higher than those of pristine PSNPs. Meanwhile, TCS adsorption on two functionalized PSNPs remained stable and then decreased as salinity increased, while an opposite trend was observed toward pristine PSNPs. All these suggested that physicochemical properties of PSNPs (e.g., particle size and surface functional groups) are important factors influencing their adsorption capacity. When the solution pH raised, the adsorbed amounts of TCS on all tested PSNPs prone to decline. However, DOM only affected the adsorption behavior of PSNPs-50 nm, probably owing to its aggregation with tiny PSNPs and the induced secondary adsorption.

Effects of polyvinylchloride microplastics on the toxicity of nanoparticles and antibiotics to aerobic granular sludge: Nitrogen removal, microbial community and resistance genes

Copper oxide nanoparticles (CuO NPs) and ciprofloxacin (CIP) have ecological risk to humans and ecosystems. Polyvinylchloride microplastics (PVC MPs), as a representative of microplastics, may often coexist with CuO NPs and CIP in wastewater treatment systems due to their widespread application. However, the co-impact of PVC MPs in wastewater systems contained with CuO NPs and CIP on nitrogen removal and ecological risk is not clear. In this work, PVC MPs co-impacts on the toxicity of CuO NPs and CIP to aerobic granular sludge (AGS) systems and potential mechanisms were investigated. 10 mg/L PVC MPs co-addition did not significantly affect the nitrogen removal, but it definitely changed the microbial community structure and enhanced the propagation and horizontal transfer of antibiotics resistance genes (ARGs). 100 mg/L PVC MPs co-addition resulted in a raise of CuO NP toxicity to the AGS system, but reduced the co-toxicity of CuO NPs and CIP and ARGs expression. The co-impacts with different PVC MPs concentration influenced Cu2+ concentrations, cell membrane integrity, extracellular polymeric substances (EPS) contents and microbial communities in AGS systems, and lead to a change of nitrogen removal.

Bioaccessibility of polypropylene microfiber-associated tetracycline and ciprofloxacin in simulated human gastrointestinal fluids

Microplastics residues in natural waters can adsorb organic contaminants owing to their rough surface morphology and high specific surface area, potentially harming human health when ingested. Although humans inevitably ingest microplastics, the bioaccessibility of microplastic-associated chemicals in the human gastric and intestinal fluids remains unresolved. This study investigated the mechanism and primary factor controlling the bioaccessibility of polypropylene (PP) microplastic fiber-associated tetracycline (TC) and ciprofloxacin (CIP) in simulated human gastrointestinal fluids. After mixing 0.1 g of PP microfiber with 10 mg/L of TC (or CIP) for 96 h and exposure to simulated human gastrointestinal fluids, the TC concentrations were 0.440, 0.678, and 1.840 mg/L and the CIP concentrations were 0.700, 1.367, and 3.281 mg/L CIP in the simulated human saliva, gastric, and intestinal fluids after incubation for 60 s, 4 h, and 8 h, respectively. This indicated that the antibiotics TC and CIP adsorbed onto microfiber surface are readily released into human gastrointestinal fluids upon ingestion. Gastric and intestinal fluids showed enhanced bioaccessibility to TC/CIP adhered to PP microfiber. The primary factors affecting the bioaccessibility to TC/CIP adhered to PP microfiber surfaces were found to be pepsin in human gastric fluid and trypsin in human intestinal fluid. Molecular docking and simulated molecular dynamic analyses results showed that pepsin and trypsin stablish connections with TC via hydrogen bonds (reaction sites: pepsin TC: T139, T136, S97, D94, D277 and Y251; trypsin TC: S257, H120, K235, G274, and G276) and CIP via hydrophobic interactions (reaction sites: pepsin CIP: Y137, T136, T139, F173, I362, V353, and I275; trypsin CIP: W273, I161, C253, and C277). Our findings highlight that microplastic ingestion increases the risk of microplastics and the co-contaminants adsorbed to human health; thus, these findings are helpful to assess the risk of microplastics and co-contaminants to human health.

Development and Evaluation of EDTA-Treated Rabbits for Bioavailability Study of Chelating Drugs Using Levofloxacin, Ciprofloxacin, Hemiacetal Ester Prodrugs, and Tetracycline

Laboratory rabbits are fed foods rich with cationic metals, and while fasting cannot empty gastric contents because of their coprophagic habits. This implies that, in rabbits, the oral bioavailability of chelating drugs could be modulated by the slow gastric emptying rates and the interaction (chelation, adsorption) with gastric metals. In the present study, we tried to develop a rabbit model with low amounts of cationic metals in the stomach for preclinical oral bioavailability studies of chelating drugs. The elimination of gastric metals was achieved by preventing food intake and coprophagy and administering a low concentration of EDTA 2Na solution one day before experiments. Control rabbits were fasted but coprophagy was not prevented. The efficacy of rabbits treated with EDTA 2Na was evaluated by comparing the gastric contents, gastric metal contents and gastric pH between EDTA-treated and control rabbits. The treatment with more than 10 mL of 1 mg/mL EDTA 2Na solution decreased the amounts of gastric contents, cationic metals and gastric pH, without causing mucosal damage. The absolute oral bioavailabilities (mean values) of levofloxacin (LFX), ciprofloxacin (CFX) and tetracycline hydrochloride (TC), chelating antibiotics, were significantly higher in EDTA-treated rabbits than those in control rabbits as follows: 119.0 vs. 87.2%, 9.37 vs. 13.7%, and 4.90 vs. 2.59%, respectively. The oral bioavailabilities of these drugs were significantly decreased when Al(OH)₃ was administered concomitantly in both control and EDTA-treated rabbits. In contrast, the absolute oral bioavailabilities of ethoxycarbonyl 1-ethyl hemiacetal ester (EHE) prodrugs of LFX and CFX (LFX-EHE, CFX-EHE), which are non-chelating prodrugs at least in in vitro condition, were comparable between control and EDTA-treated rabbits irrespective of the presence of Al(OH)₃, although some variation was observed among rabbits. The oral bioavailabilities of LFX and CFX from their EHE prodrugs were comparable with LFX and CFX alone, respectively, even in the presence of Al(OH)₃. In conclusion, LFX, CFX and TC exhibited higher oral bioavailabilities in EDTA-treated rabbits than in control rabbits, indicating that the oral bioavailabilities of these chelating drugs are reduced in untreated rabbits. In conclusion, EDTA-treated rabbits were found to exhibit low gastric contents including metals and low gastric pH, without causing mucosal damage. Ester prodrug of CFX was effective in preventing chelate formation with Al(OH)₃ in vitro and in vivo, as well as in the case of ester prodrugs of LFX. EDTA-treated rabbits are expected to provide great advantages in preclinical oral bioavailability studies of various drugs and dosage formulations. However, a marked interspecies difference was still observed in the oral bioavailability of CFX and TC between EDTA-treated rabbits and humans, possibly due to the contribution of adsorptive interaction in rabbits. Further study is necessary to seek out the usefulness of the EDTA-treated rabbit with less gastric contents and metals as an experimental animal.

Revealing the sorption mechanisms of carbamazepine on pristine and aged microplastics with extended DLVO theory

The co-occurrence of microplastics (MPs) and organic contaminants in aquatic environment can complexify their environmental fate via sorption interactions, especially when the properties of MPs can even vary due to the aging effect. Thus, quantitatively clarifying the sorption mechanisms is required to understand their environmental impacts. This study selected popularly occurring carbamazepine (CBZ) and four types of MPs as model systems, including polyethylene, polyvinyl chloride, polyethylene terephthalate and polystyrene in their pristine and aged forms, to investigate the sorption isotherms, kinetics, and desorption. The variation of MPs during the aging process were analyzed with scanning electron microscopy, contact angle, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. It was found that the aging process elevated the sorption capacity and intensified the desorption hysteresis of CBZ on MPs via increasing the surface roughness, decreasing the particle size, and altering the surficial chemistry of all MPs. The extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory was innovatively applied hereby to calculate the interfacial free energies and revealed that the hydrophobic interaction was significantly lessened after aging for all MPs with the slightly enhanced van der Waals interaction. Then the total interfacial free energies were dropped down for all MPs, which resulted in their declined specific sorption capacity. This work reveals the sorption mechanisms of CBZ on pristine and aged MPs with XDLVO and provides a useful reference to study the sorption of other neutral organics onto MPs.