Selective lignin arylation for biomass fractionation and benign bisphenols.

Lignocellulose is mainly composed of hydrophobic lignin and hydrophilic polysaccharide polymers, contributing to an indispensable carbon resource for green biorefineries1,2. When chemically treated, lignin is compromised owing to detrimental intra- and intermolecular crosslinking that hampers downstream process3,4. The current valorization paradigms aim to avoid the formation of new C-C bonds, referred to as condensation, by blocking or stabilizing the vulnerable moieties of lignin5-7. Although there have been efforts to enhance biomass utilization through the incorporation of phenolic additives8,9, exploiting lignin's proclivity towards condensation remains unproven for valorizing both lignin and carbohydrates to high-value products. Here we leverage the proclivity by directing the C-C bond formation in a catalytic arylation pathway using lignin-derived phenols with high nucleophilicity. The selectively condensed lignin, isolated in near-quantitative yields while preserving its prominent cleavable ß-ether units, can be unlocked in a tandem catalytic process involving aryl migration and transfer hydrogenation. Lignin in wood is thereby converted to benign bisphenols (34-48 wt%) that represent performance-advantaged replacements for their fossil-based counterparts. Delignified pulp from cellulose and xylose from xylan are co-produced for textile fibres and renewable chemicals. This condensation-driven strategy represents a key advancement complementary to other promising monophenol-oriented approaches targeting valuable platform chemicals and materials, thereby contributing to holistic biomass valorization.

Environmentally Relevant Concentrations of Microplastic Exposure Cause Cholestasis and Bile Acid Metabolism Dysregulation through a Gut-Liver Loop in Mice.

The massive production of plastics causes the ubiquitous existence of microplastics (MPs) in the biota, therefore, posing exposure risks and potential health concerns to human beings. However, the exact mechanisms of MPs-induced toxicities and abnormalities are largely unknown. In this study, we developed a mouse model of gavage polystyrene microplastics (PS MPs) for 30 days. We found that PS MPs can damage the intestinal barrier, accumulate in the liver tissue, and cause injury. The liver and intestine are both highly associated with bile acid (BA) metabolism. Indeed, we found that PS MPs dysregulate BA synthesis and efflux-related gene expression in the liver, causing cholestasis. Tandemly, PS MPs alter the ratio of primary to secondary BA in the feces by affecting the composition of the intestinal flora. At last, PS MPs alter mice's fecal BA profile, which affects normal BA metabolism. Taken together, the present study provides robust data on the mechanism of toxicity of MPs causing the disturbance of BA metabolism via a 4-step gut-liver loop.

Disposable Polypropylene Face Masks: A Potential Source of Micro/Nanoparticles and Organic Contaminates in Humans.

We have been effectively protected by disposable propylene face masks during the COVID-19 pandemic; however, they may pose health risks due to the release of fine particles and chemicals. We measured micro/nanoparticles and organic chemicals in disposable medical masks, surgical masks, and (K)N95 respirators. In the breathing-simulation experiment, no notable differences were found in the total number of particles among mask types or between breathing intensities. However, when considering subranges, <2.5 µm particles accounted for ∼90% of the total number of micro/nanoparticles. GC-HRMS-based suspect screening tentatively revealed 79 (semi)volatile organic compounds in masks, with 18 being detected in ≥80% of samples and 44 in ≤20% of samples. Three synthetic phenolic antioxidants were quantified, and AO168 reached a median concentration of 2968 ng/g. By screening particles collected from bulk mask fabrics, we detected 18 chemicals, including four commonly detected in masks, suggesting chemical partition between the particles and the fabric fibers and chemical exposure via particle inhalation. These particles and chemicals are believed to originate from raw materials, intentionally and nonintentionally added substances in mask production, and their transformation products. This study highlights the need to study the long-term health risks associated with mask wearing and raises concerns over mask quality control.

Influence of microplastics on the photodegradation of perfluorooctane sulfonamide (FOSA).

PFAS (per- and polyfluoroalkyl substances) are omnipresent in the environment and their transportation and transformation have attracted increased attention. Microplastics are another potential risk substances that can serve as a carrier for ubiquitous pollutants, thus affecting the presence of PFAS in the environment. In this study, the adsorption of perfluorooctane sulfonamide (FOSA) and perfluorooctanoic acid (PFOA) on four microplastics (PE, PVC, PS, and PTFE) and their effect on the photodegradation of FOSA were studied. The adsorption capacity of FOSA by PS was the highest, in similar, PS displayed the highest adsorption capacity in the presence of PFOA. Different effects of pH and salinity on the adsorption of FOSA and PFOA were observed among different microplastics indicating inconsistent interaction mechanisms. Furthermore, FOSA could be photodegraded, with PFOA as the main product, while the presence of microplastics had a negligible effect on the degradation of this contaminant. The results indicated that microplastics could act as PFAS concentrators. Moreover, their photochemical inertias make the pollutants enriched on microplastics more resistant to degradation.

Total Organic Carbon as a Quantitative Index of Micro- and Nano-Plastic Pollution.

The global pollution of micro- and nano-plastics (MNPs) calls for monitoring methods. As diverse mixtures of various sizes, morphologies, and chemical compositions in the environment, MNPs are currently quantified based on mass or number concentrations. Here, we show total organic carbon (TOC) as an index for quantifying the pollution of total MNPs in environmental waters. Two parallel water samples are respectively filtered with a carbon-free glass fiber membrane. Then, one membrane with the collected particulate substances is treated by potassium peroxodisulfate oxidation and Fenton digestion in sequence for quantifying the sum of MNPs and particulate black carbon (PBC) as TOCMNP&PBC using a TOC analyzer, another membrane is treated by sulfonation and Fenton digestion for quantifying PBC as TOCPBC, and the TOC of MNPs is calculated by subtracting TOCPBC from TOCMNP&PBC. The feasibility of our method is demonstrated by determination of various MNPs of representative plastic types and sizes (0.5-100 µm) in tap, river, and sea water samples, with low detection limits (∼7 µg C L-1) and high spiked recoveries (83.7-114%). TOC is a powerful index for routine monitoring of MNP pollution.

The occurrence of per- and polyfluoroalkyl substances (PFASs) in fluoropolymer raw materials and products made in China.

Perfluorooctanoic acid (PFOA), its salts, and related compounds were listed as new persistent organic pollutants by the Stockholm Convention in 2019. In this study, the occurrence of residues of PFOA and other per- and polyfluoroalkyl substances (PFASs) in raw materials and fluoropolymer products from the Chinese fluoropolymer industries are reported for the first time. The PFOA concentrations in raw materials and fluoropolymer products were in the range of 6.7 to 1.1 × 106 ng/g, and

Occurrence and Human Exposure Assessment of Short- and Medium-Chain Chlorinated Paraffins in Dusts from Plastic Sports Courts and Synthetic Turf in Beijing, China.

This study presents the first investigation of concentrations and congener group patterns of short- and medium-chain chlorinated paraffins (SCCPs and MCCPs) in 159 dust samples from plastic sports courts and synthetic turf in Beijing, China. The geometric mean concentration of SCCPs and MCCPs in dusts from plastic tracks (5429 and 15157 µg g-1) and basketball courts (5139 and 11878 µg g-1) were significantly higher than those from plastic tennis courts, badminton courts, and synthetic turf; meanwhile, they were 1-3 orders of magnitude higher than in dusts from other indoor environments. The friction between sneaker soles and plastic track materials may lead to the wear and decomposition of rubber, which may be an important source of chlorinated paraffins (CPs) in the dust from plastic tracks. The mean estimated daily intakes of CPs from plastic tracks and basketball courts are generally higher than those estimated from dietary, breast milk, or other indoor dust sources. The margin of exposure for adults and children was greater than 1000 both at mean and high-exposure scenarios, indicating that no significant health risks were posed by CPs in the dust from plastic sports courts and synthetic turf.

Improved Biocompatibility of Black Phosphorus Nanosheets by Chemical Modification.

Black phosphorus nanosheets (BPs) show great potential for various applications including biomedicine, thus their potential side effects and corresponding improvement strategy deserve investigation. Here, in vitro and in vivo biological effects of BPs with and without titanium sulfonate ligand (TiL4 ) modification are investigated. Compared to bare BPs, BPs with TiL4 modification (TiL4 @BPs) can efficiently escape from macrophages uptake, and reduce cytotoxicity and proinflammation. The corresponding mechanisms are also discussed. These findings may not only guide the applications of BPs, but also propose an efficient strategy to further improve the biocompatibility of BPs.

Brain-targeted distribution and high retention of silver by chronic intranasal instillation of silver nanoparticles and ions in Sprague-Dawley rats.

The wide applications of silver nanoparticles (AgNPs) have been concerned regarding their unintentional toxicities. Different exposure modes may cause distinct accumulation, retention and elimination profiles, which are closely related with their toxicities. Unlike silver accumulation profiles through other regular administration modes, the biodistribution, accumulation and elimination of AgNPs by intranasal instillation are not fully understood. This study conducted intranasal instillation of polyvinylpyrrolidone-coated AgNPs in neonatal Sprague-Dawley rats at doses of 1 and 0.1 mg kg(-1) day(-1) for 4 and 12 weeks, respectively. The 4-week recovery was also designed after the 12-week exposure. Silver concentrations in the main tissues or organs were periodically monitored. Parallel exposures using silver ion were performed for the comparative studies. No physiological alterations were observed in AgNP exposures. In comparison, 1 mg kg(-1) day(-1) silver ions decreased body weight gain and caused mortality of 18.2%, showing ionic silver had a relatively higher toxicity than AgNPs. A relatively higher silver accumulation was observed in silver ion groups than AgNP groups. The silver ion release could not fully explain silver accumulation in AgNP exposures, showing silver distribution caused by particulate silver occurred in vivo. The highest silver concentration was in the liver at week 4, while it shifted to the brain after a 12-week exposure. Dose-related silver accumulation occurred for both AgNP and silver ion groups. The time course revealed a uniquely high concentration and retention of brain silver, implying chronic intranasal instillation caused brain-targeted silver accumulation. These findings provided substantial evidence on the potential neuronal threat from the intranasal administration of AgNPs or silver colloid-based products.

Particle coating-dependent interaction of molecular weight fractionated natural organic matter: impacts on the aggregation of silver nanoparticles.

Ubiquitous natural organic matter (NOM) plays an important role in the aggregation state of engineered silver nanoparticles (AgNPs) in aquatic environment, which determines the transport, transformation, and toxicity of AgNPs. As various capping agents are used as coatings for nanoparticles and NOM are natural polymer mixture with wide molecular weight (MW) distribution, probing the particle coating-dependent interaction of MW fractionated natural organic matter (Mf-NOM) with various coatings is helpful for understanding the differential aggregation and transport behavior of engineered AgNPs as well as other metal nanoparticles. In this study, we investigated the role of pristine and Mf-NOM on the aggregation of AgNPs with Bare, citrate, and PVP coating (Bare-, Cit-, and PVP-AgNP) in mono- and divalent electrolyte solutions. We observed that the enhanced aggregation or dispersion of AgNPs in NOM solution highly depends on the coating of AgNPs. Pristine NOM inhibited the aggregation of Bare-AgNPs but enhanced the aggregation of PVP-AgNPs. In addition, Mf-NOM fractions have distinguishing roles on the aggregation and dispersion of AgNPs, which also highly depend on the AgNPs coating as well as the MW of Mf-NOM. Higher MW Mf-NOM (>100 kDa and 30-100 kDa) enhanced the aggregation of PVP-AgNPs in mono- and divalent electrolyte solutions, whereas lower MW Mf-NOM (10-30 kDa, 3-10 kDa and <3 kDa) inhibited the aggregation of PVP-AgNPs. However, all the Mf-NOM fractions inhibited the aggregation of Bare-AgNPs. For PVP- and Bare-AgNPs, the stability of AgNPs in electrolyte solution was significantly correlated to the MW of Mf-NOM. But for Cit-AgNPs, pristine NOM and Mf-NOM has minor influence on the stability of AgNPs. These findings about significantly different roles of Mf-NOM on aggregation of engineered AgNPs with various coating are important for better understanding of the transport and subsequent transformation of AgNPs in aquatic environment.

Water chemistry controlled aggregation and photo-transformation of silver nanoparticles in environmental waters.

The inevitable release of engineered silver nanoparticles (AgNPs) into aquatic environments has drawn great concerns about its environmental toxicity and safety. Although aggregation and transformation play crucial roles in the transport and toxicity of AgNPs, how the water chemistry of environmental waters influences the aggregation and transformation of engineered AgNPs is still not well understood. In this study, the aggregation of polyvinylpyrrolidone (PVP) coated AgNPs was investigated in eight typical environmental water samples (with different ionic strengths, hardness, and dissolved organic matter (DOM) concentrations) by using UV-visible spectroscopy and dynamic light scattering. Raman spectroscopy was applied to probe the interaction of DOM with the surface of AgNPs. Further, the photo-transformation and morphology changes of AgNPs in environmental waters were studied by UV-visible spectroscopy, inductively coupled plasma mass spectrometry, and transmission electron microscopy. The results suggested that both electrolytes (especially Ca(2+) and Mg(2+)) and DOM in the surface waters are key parameters for AgNP aggregation, and sunlight could accelerate the morphology change, aggregation, and further sedimentation of AgNPs. This water chemistry controlled aggregation and photo-transformation should have significant environmental impacts on the transport and toxicity of AgNPs in the aquatic environments.

Neurotoxicities induced by micro/nanoplastics: A review focusing on the risks of neurological diseases.

Pollution of micro/nano-plastics (MPs/NPs) is ubiquitously prevalent in the environment, leading to an unavoidable exposure of the human body. Despite the protection of the blood-brain barrier, MPs/NPs can be transferred and accumulated in the brain, which subsequently exert negative effects on the brain. Nevertheless, the potential neurodevelopmental and/or neurodegenerative risks of MPs/NPs remain largely unexplored. In this review, we provide a systematic overview of recent studies related to the neurotoxicity of MPs/NPs. It covers the environmental hazards and human exposure pathways, translocation and distribution into the brain, the neurotoxic effects, and the possible mechanisms of environmental MPs/NPs. MPs/NPs are widely found in different environment matrices, including air, water, soil, and human food. Ambient MPs/NPs can enter the human body by ingestion, inhalation and dermal contact, then be transferred into the brain via the blood circulation and nerve pathways. When MPs/NPs are present in the brain, they can initiate a series of molecular or cellular reactions that may harm the blood-brain barrier, cause oxidative stress, trigger inflammatory responses, affect acetylcholinesterase activity, lead to mitochondrial dysfunction, and impair autophagy. This can result in abnormal protein folding, loss of neurons, disruptions in neurotransmitters, and unusual behaviours, ultimately contributing to the initiation and progression of neurodegenerative changes and neurodevelopmental abnormalities. Key challenges and further research directions are also proposed in this review as more studies are needed to focus on the potential neurotoxicity of MPs/NPs under realistic conditions.

Protocol for detecting micro(nano)plastics released from intravenous infusion products.

Approaches for detecting micro(nano)plastics (MNPs) released from intravenous infusion products (IVIPs) are vital for evaluating the safety of both IVIPs and their derived MNPs on human health, yet current understanding is limited. Here, we present a protocol for detecting polyvinyl chloride (PVC) MNPs by combining Raman spectroscopy, scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM-EDS), and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). We describe steps for collecting, pretreating, and measuring PVC MNPs released from IVIPs. For complete details on the use and execution of this protocol, please refer to Li et al.1.

Chronic exposure to polystyrene microplastics increased the chemosensitivity of normal human liver cells via ABC transporter inhibition.

Microplastics (MPs) are ubiquitous in environmental compartments and consumer products. Although liver is frequently reported to be a target organ of MP accumulation in mammals, few studies have focused on MP hepatoxicity in humans. In this study, we used normal human liver cells, THLE-2, to assess the acute and chronic toxicity of polystyrene (PS) MPs with sizes of 0.1 and 1 µm. The results showed that after 48 h of exposure, both kinds of PS MPs could enter THLE-2 cells and cause no obviously acute cytotoxicity at <20 µg/mL. In contrast, metabolomic analysis revealed that 90 days of PS MPs exposure at environmentally relevant dose (0.2 µg/mL) could significantly alter the metabolic profiles of the cells, especially the nanosized MPs. KEGG pathway analysis showed that the ATP-binding cassette (ABC) transporter pathway was the most significantly changed pathway. Cell functional tests confirmed that chronic PS MP treatment could inhibit the activity of the ABC efflux transporter and further increase the cytotoxicity of arsenic, indicating that the PS MPs had a chemosensitizing effect. These findings underline the chronic risk of MPs to human liver.

Polyvinyl pyrrolidone promotes DNA cleavage by a ROS-independent and depurination mechanism.

Polyvinyl pyrrolidone polymer (PVP) has been widely applied in biological and medical fields. A few in vitro studies indicated that PVP might cause toxicity. However, the underlying mechanism is poorly understood. In this work, we found that PVP directly induced strand breakages of various DNA molecules, implicating a cleavage activity. Moreover, reactive oxygen species (ROS) scavenging analysis shows that DNA cleavage activity of PVP is not related to ROS-induced oxidation. As revealed by gel electrophoresis and liquid chromatography/mass spectrometry analysis, the major cleavage products of DNA were identified as two purine bases, guanine and adenine, suggesting that PVPs have a novel depurination activity. The selective depurination and DNA cleavage activity of PVPs were further confirmed by studying the interaction of PVP with four nucleosides and four well-designed oligodeoxynucleotides probes containing specific nucleotides. This study may provide insights into PVP-DNA interactions and resultant genotoxicity and may also open a new way for DNA study.

Quantification of the uptake of silver nanoparticles and ions to HepG2 cells.

The toxic mechanism of silver nanoparticles (AgNPs) is still debating, partially because of the common co-occurrence and the lack of methods for separation of AgNPs and Ag(+) in biological matrices. For the first time, Triton-X 114-based cloud point extraction (CPE) was proposed to separate AgNPs and Ag(+) in the cell lysates of exposed HepG2 cells. Cell lysates were subjected to CPE after adding Na2S2O3, which facilitated the transfer of AgNPs into the nether Triton X-114-rich phase by salt effect and the preserve of Ag(+) in the upper aqueous phase through the formation of hydrophilic complex. Then the AgNP and Ag(+) contents in the exposed cells were determined by ICP-MS after microwave digestion of the two phases, respectively. Under the optimized conditions, over 67% of AgNPs in cell lysates were extracted into the Triton X-114-rich phase while 94% of Ag(+) remained in the aqueous phase, and the limits of detection for AgNPs and Ag(+) were 2.94 µg/L and 2.40 µg/L, respectively. This developed analytical method was applied to quantify the uptake of AgNPs to the HepG2 cells. After exposure to 10 mg/L AgNPs for 24 h, about 67.8 ng Ag were assimilated per 10(4) cells, in which about 10.3% silver existed as Ag(+). Compared to the pristine AgNPs (with 5.2% Ag(+)) for exposure, the higher ratio of Ag(+) to AgNPs in the exposed cells (10.3% Ag(+)) suggests the transformation of AgNPs into Ag(+) in the cells and/or the higher uptake rate of Ag(+) than that of AgNPs. Given that the toxicity of Ag(+) is much higher than that of AgNPs, the substantial content of Ag(+) in the exposed cells suggests that the contribution of Ag(+) should be taken into account in evaluating the toxicity of AgNPs to organisms, and previous results obtained by regarding the total Ag content in organisms as AgNPs should be reconsidered.

The ex vivo and in vivo biological performances of graphene oxide and the impact of surfactant on graphene oxide's biocompatibility.

Graphene oxide (GO) displays promising properties for biomedical applications including drug delivery and cancer therapeutics. However, GO exposure also raises safety concerns such as potential side effects on health. Here, the biological effects of GO suspended in phosphate buffered saline (PBS) with or without 1% nonionic surfactant Tween 80 were investigated. Based on the ex vivo experiments, Tween 80 significantly affected the interaction between GO and peripheral blood from mice. GO suspension in PBS tended to provoke the aggregation of diluted blood cells, which could be prevented by the addition of Tween 80. After intravenous administration, GO suspension with or without 1% Tween 80 was quickly eliminated by the mononuclear phagocyte system. Nevertheless, GO suspension without Tween 80 showed greater accumulation in lungs than that containing 1% Tween 80. In contrast, less GO was found in livers for GO suspension compared to Tween 80 assisted GO suspension. Organs including hearts, livers, lungs, spleens, kidneys, brains, and testes did not reveal histological alterations. The indexes of peripheral blood showed no change upon GO exposure. Our results together demonstrated that Tween 80 could greatly alter GO's biological performance and determine the pattern of its biodistribution in mice.

Distribution and exposure risk assessment of chlorinated paraffins and novel brominated flame retardants in toys.

Chlorinated paraffins (CPs) and novel brominated flame retardants (NBFRs) were examined in children's toys collected from 13 families in China. The concentrations of short-chain CPs (SCCPs), medium-chain CPs (MCCPs) and NBFRs in toys were 32.8-1,220,954 ng/g, not detected-2,688,656 ng/g and 0.08-103,461 ng/g, respectively. Median concentrations of SCCPs and MCCPs in toys were 1355 and 1984 ng/g, respectively, while except for pentabromobenzene (median:0.04 ng/g), the median concentrations of the other 8 NBFRs were below method detection limits. Rubber and foam toys contained higher amounts of CPs and NBFRs. Among the SCCPs and MCCPs monitored, Cl6-8-SCCPs/MCCPs and C14-MCCPs were the most abundant congener groups. On the other hand, decabromodiphenyl ethane was the predominant NBFR in toys. Moreover, to understand the role of toys in children's daily exposure to CPs and NBFRs, hand-to-mouth contact, mouthing, and dermal exposure were assessed for children aged 3 months to 6 years. Hand-to-mouth contact is the primary exposure route for children's exposure to CPs (25.4-536 ng/kg/day) and NBFRs (1.24-26.2 ng/kg/day) through toys. A low deleterious risk associated with children's toys concerning CPs and NBFRs was investigated based on the margin of exposure and hazard quotient values.

Percutaneous absorption and exposure risk assessment of organophosphate esters in children's toys.

The percutaneous penetration and exposure risk of organophosphate esters (OPEs) from children's toys remains largely unknown. Percutaneous penetration of OPEs was evaluated by EPISkin™ model. Chlorinated OPEs (Cl-OPEs) and alkyl OPEs, except tris(2-ethylhexyl) phosphate, exhibited a fast absorption rate and good dermal penetration ability with cumulative absorptions of 57.6-127 % of dosed OPEs. Cumulative absorptions of OPEs through skin cells were inversely associated with their molecular weight and log octanol-water partition coefficient. Additionally, a quantitative structure-activity relationship model indicated that topological charge and steric features of OPEs were closely related to the transdermal permeability of these chemicals. With the clarification of the factors affecting the transdermal penetration of OPEs, the level and exposure risk of OPEs in actual toys were studied. The summation of 18 OPE concentrations in 199 toy samples collected from China ranged from 6.82 to 228,254 ng/g, of which Cl-OPEs presented the highest concentration. Concentrations of OPEs in toys exhibited clear type differences. Daily exposure to OPEs via dermal, hand-to-mouth contact, and mouthing was evaluated, and dermal contact was a significant route for children's exposure to OPEs. Hazard quotients for noncarcinogenic risk assessment were below 1, indicating that the health risk of OPEs via toys was relatively low.

Single-particle analysis of micro/nanoplastics by SEM-Raman technique.

Micro/nanoplastics (MNPs) have received global concern due to their widespread contamination, ingestion in organisms, and the ability to cross the biological barrier. Although MNPs have been detected in a variety of ecosystems, the identification of single MNPs remains an unsolved challenge. Herein, for the first time, scanning electron microscope (SEM) coupled with surface-enhanced Raman spectroscopy (SERS), which combined the advantages of ultrahigh spatial resolution of SEM and structural fingerprint of Raman spectroscopy, was proposed to identify MNPs at single-particle level. Under the optimum conditions, the polystyrene (PS) MNPs with sizes of 500 nm and 1 µm were identified by the image of SEM and fingerprint peaks of Raman spectroscopy. Additionally, the applicability of the method in different sample matrices and for other types of MNPs such as poly-methyl methacrylate (PMMA) with the sizes of 300 nm, 1 µm were validated. This method is simple, rapid and effective and is likely to provide an essential tool to identify other micro/nanoparticles in addition to MNPs.