Photoaged polystyrene microplastics result in neurotoxicity associated with neurotransmission and neurodevelopment in zebrafish larvae (Danio rerio).

Microplastics (MPs) are emerging pollutants widely distributed in the environment, inducing toxic effects in various organisms. However, the neurotoxicity and underlying mechanisms of simulated sunlight-aged MPs have rarely been investigated. In this study, zebrafish (Danio rerio) were exposed to environmentally relevant concentrations (0, 0.1, 1, 10, and 100 µg/L) of virgin polystyrene (V-PS) and aged polystyrene (A-PS) for 120 hpf to evaluate the neurotoxicity. The results demonstrated that simulated sunlight irradiation altered the physicochemical properties (morphology, functional groups, and chemical composition) of V-PS. Exposure to A-PS causes greater toxicity on locomotor ability in larval zebrafish than V-PS. Motor neuron development was disrupted by transgenic (hb9-GFP) zebrafish larvae exposed to A-PS, with significant alterations in neurotransmitter levels (ACh, DA, 5-HT, and GABA) and enzyme activity (AChE, ChAT, and ChE). Further investigation found that exposure to A-PS had a significantly impact on the expression of neurotransmission and neurodevelopment-related genes in zebrafish. These findings suggest that A-PS induces neurotoxicity by its effects on neurotransmission and neurodevelopment. This study highlights the neurotoxic effects and mechanisms of simulated sunlight irradiation of MPs, providing new insights for assessing the ecological risks of photoaged MPs in the environment.

Environmentally persistent free radicals on photoaged microplastics from disposable plastic cups induce the oxidative stress-associated toxicity.

Microplastics (MPs) are ubiquitous environmental contaminants that exerting multiple toxicological effects. Most studies have focused primarily on the models of unaged MPs and lack environmental relevance. The generation and toxicity of environmentally persistent free radicals (EPFRs) on photoaging MPs from disposable plastic cups (DPC-MPs) have not been well studied. Here, the formation of EPFRs on photoaged DPC-MPs and their toxic effects in nematodes were investigated. UV irradiation generated EPFRs, which influenced the characterization of DPC-MPs. Exposure to photoaged DPC-MPs at environmentally relevant concentrations （100-1000 µg/L） reduced the locomotion behavior, body length, and brood size. The Reactive oxygen species (ROS) production, lipofuscin accumulation, malondialdehyde (MDA), and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels were increased along with the downregulation of the expression levels of associated genes, such as clk-1, clt-1, and gst-4，in nematodes. Moreover, the toxicity and oxidative stress response of nematodes were significantly inhibited due to N-acetyl-l-cysteine (NAC). Pearson's correlation analysis revealed that the oxidative stress was significantly associated with adverse physiological effects. Therefore, EPFRs on photoaged DPC-MPs cause toxicity in nematodes, and oxidative stress is important for regulating toxicity. This study offers novel insights into the potential risks of DPC-MPs under UV irradiation, highlighting the need to consider the role of EPFRs in toxicity assessments of DPC-MPs.

Silk fibroin and hydroxypropyl cellulose composite injectable hydrogel-containing extracellular vesicles for myocardial infarction repair.

Extracellular vesicles (EVs) have been recognized as one of the promising specific drugs for myocardial infarction (MI) prognosis. Nevertheless, low intramyocardial retention of EVs remains a major impediment to their clinical application. In this study, we developed a silk fibroin/hydroxypropyl cellulose (SF/HPC) composite hydrogel combined with AC16 cell-derived EVs targeted modification by folic acid for the treatment of acute myocardial infarction repair. EVs were functionalized by distearoylphosphatidyl ethanolamine-polyethylene glycol (DSPE-PEG-FA) via noncovalent interaction for targeting and accelerating myocardial infarction repair.In vitro, cytocompatibility analyses revealed that the as-prepared hydrogels had excellent cell viability by MTT assay and the functionalized EVs had higher cell migration by scratch assay.In vivo, the composite hydrogels can promote myocardial tissue repair effects by delaying the process of myocardial fibrosis and promoting angiogenesis of infarct area in MI rat model.

Photoaging enhances combined toxicity of microplastics and tetrabromobisphenol A by inducing intestinal damage and oxidative stress in Caenorhabditis elegans.

Microplastics (MPs) are emerging environmental contaminants that often co-exist with tetrabromobisphenol A (TBBPA) in the environment. However, the joint effect of TBBPA and photoaged MPs at ambient concentrations remains unknown largely. In this study, the combined toxicity of ultraviolet-aged polystyrene (UV-PS) and TBBPA was investigated in Caenorhabditis elegans. UV irradiation could change the physical and chemical characteristics of polystyrene (PS), and UV-PS (90.218 µg/g) showed a stronger adsorption capacity than PS of 79.424 µg/g. Toxicity testing showed that 1 µg/L UV-PS enhanced the toxic effect of 1 µg/L TBBPA by reducing body length, locomotion behavior, and brood size in nematodes. Using ROS production, lipofuscin accumulation, and expression of gst-4::GFP as endpoints, the combined exposure of UV-PS and TBBPA induced stronger oxidative stress than TBBPA alone. Joint exposure to UV-PS and TBBPA significantly increased of Nile red and blue food dye in its intestinal tract compared to that in the TBBPA exposure group, indicating that co-exposure enhanced intestinal permeability. After co-exposure to UV-PS and TBBPA, the expression of the associated genes detected increased significantly. Therefore, UV-PS enhances the adverse effects of TBBPA through intestinal damage and oxidative stress in nematodes. These findings suggest that the co-presence of photoaged PS and TBBPA results in high environmental risks.

In situ monitoring of cytoplasmic dopamine levels by noble metals decorated carbon fiber tips.

Dopamine (DA), a catecholamine neurotransmitter, is crucial in brain signal transmission. Monitoring cytoplasmic DA levels can reflect changes in metabolic factors and provide valuable information for researching the mechanisms involved in neurodegenerative diseases. However, the in-situ detection of intracellular DA is constrained by its low contents in small-sized single cells. In this work, we report that noble metal (Au, Pt)-modified carbon fiber micro-nanoelectrodes are capable of real-time detection of DA in single cells with excellent sensitivity, selectivity, and anti-contamination capabilities. Notably, noble metals can be modified on the electrode surface through electrochemical deposition to enhance the conductivity of the electrode and the oxidation current of DA by 50 %. The nanosensors can work stably and continuously in rat adrenal pheochromocytoma cells (PC12) to monitor changes in DA levels upon K+ stimulation. The functionalized carbon fibers based nanosensors will provide excellent prospects for DA analysis in the brains of living animals.

Combined neurotoxicity of aged microplastics and thiamethoxam in the early developmental stages of zebrafish (Daniorerio).

Microplastics (MPs) pollution, together with its consequential effect on aquatic biota, represent a burgeoning environmental concern that has garnered significant scholarly attention. Thiamethoxam (TMX), a prevalently utilized neonicotinoid insecticide, is renowned for its neurotoxic impact and selective action against targeted pests. The aquatic environment serves as a receptacle for numerous pollutants, such as MPs and neonicotinoid insecticides. However, there is currently a lack of comprehensive understanding regarding the toxic effects of co-exposure to aged MPs and neonicotinoid insecticides in aquatic organisms. Therefore, we endeavor to elucidate the deleterious impacts of aged polystyrene (PS) and TMX on zebrafish (Danio rerio) larvae when present at environmentally relevant concentrations, and to reveal the underlying molecular mechanisms driving these effects. Our study showed that exposure to aged PS, TMX, or their combination notably inhibited the heart rate and locomotion of zebrafish larvae, with a pronounced effect observed under combined exposure. Aged PS and TMX were found to diminish the activity of antioxidative enzymes (SOD, CAT, and GST), elevate MDA levels, and disrupt neurotransmitter homeostasis (5-HT, GABA and ACh). Notably, the mixtures exhibited synergistic effects. Moreover, gene expression related to oxidative stress (e.g., gstr1, gpx1a, sod1, cat1, p38a, ho-1, and nrf2b) and neurotransmission (e.g., ache, ChAT, gat1, gabra1, 5ht1b, and 5ht1aa) was significantly altered upon co-exposure to aged PS and TMX in larval zebrafish. In summary, our findings support the harmful effects of aged MPs and the neonicotinoid insecticides they carry on aquatic organisms. Results from this study enhance our understanding of the biological risks of MPs and insecticides, as well as help fill existing knowledge gaps on neonicotinoid insecticides and MPs coexistence toxicity in aquatic environment.

UV-aged microplastics induces neurotoxicity by affecting the neurotransmission in larval zebrafish.

Microplastics (MPs) are nearly ubiquitous in aquatic ecosystems and may affect aquatic organisms. In this study, virgin and aged polystyrene MPs (PS-MPs) of size 1 µm were selected to analyze their adverse effects on larvae zebrafish. Exposure to PS-MPs significantly reduced the average swimming speed of zebrafish, and the behavioral effects caused by aged PS-MPs on zebrafish were more pronounced. Fluorescence microscopy revealed that 10-100 µg/L of PS-MPs accumulated in tissues of zebrafish. As an endpoint of neurotransmitter concentration, exposure to aged PS-MPs at doses ranging from 0.1 to 100 µg/L significantly increased the dopamine (DA), 5-hydroxytryptamine (5-HT), γ-aminobutyric acid (GABA), and acetylcholine (ACh) levels in zebrafish. Similarly, exposure to aged PS-MPs significantly altered the expression of genes related to these neurotransmitters (e.g., dat, 5ht1aa, and gabral genes). According to Pearson correlation analyses, neurotransmissions was significantly correlated with neurotoxic effects of aged PS-MPs. Thus, aged PS-MPs cause neurotoxicity in zebrafish through their effects on DA, 5-HT, GABA, and ACh neurotransmissions. The results highlight the importance of the neurotoxicity of aged PS-MPs in zebrafish, which has important implications for the risk assessment of aged MPs and the conservation of aquatic ecosystems.

Photoaged microplastics induce neurotoxicity via oxidative stress and abnormal neurotransmission in zebrafish larvae (Danio rerio).

Microplastics (MPs) are ubiquitous environmental contaminants and cause neurotoxicity in various organisms. However, previous studies that analyzed the effects of MPs mainly focused on virgin polystyrene (V-PS) as representative models of MPs, and the mechanism underlying the neurotoxicity of photoaged polystyrene (P-PS) remains largely unknown. In this study, zebrafish (Danio rerio) were exposed to environmentally relevant concentrations (0.1-100 µg/L) of V-PS and P-PS(10 µm). The results indicated that UV radiation accelerated the aging process and changed physical and chemical properties of PS. Whereas exposure to both V-PS and P-PS at low concentrations (100 µg/L) significantly reduced the locomotor behavior of zebrafish larvae, P-PS caused more severe neurotoxicity compared to V-PS. The activity of antioxidant enzymes (SOD, CAT, and GST) and MDA content were significantly altered in zebrafish exposed to 10-100 µg/L of P-PS. Similarly, exposure to P-PS significantly increased neurotransmitter (5-HT, GABA, DA, and ACh) levels and activity of AChE, ChAT, and ChE. Star plots based on integrated biomarker response (IBR) values showed more incline toward neurotransmitter biomarkers in response to increasing P-PS concentration, and the behavioral parameters negatively correlated with the neurotransmitter biomarkers. Further investigations revealed that the expression of neurotransmission- (e.g., ache, drd3, 5th2c, and gat1) and oxidative stress- (e.g., cat1, sod1, gpx1a, and gstrl) related genes was significantly affected by PS in larval zebrafish. Thus, this study provides new insights on the potential risks of MPs into the environment.

Photoformation of environmentally persistent free radicals on particulate organic matter in aqueous solution: Role of anthracene and formation mechanism.

Environmentally persistent free radicals (EPFRs) generated under irradiation have been widely detected in soil particles, atmospheric particles and microplastic particles, but the formation of EPFRs in water is not well understood. This study investigated the formation of EPFRs on particulate organic matter (POM) in water contaminated by anthracene (Ant) under irradiation. The photoformation and decay progress of EPFRs was represented with the help of electron paramagnetic resonance (EPR) technique on both actual POM and Fe(III)-montmorillonite simulated samples. EPR signals at the range of 1016 to 1017 spin/g were detected and the half-life time of EPFRs stored in water was at around 16.62 h and 60.80 h, much shorter than those in the air. The g factors were all larger than 2.0040, which indicated the generation of oxygen centered EPFRs. The primary intermediates were identified by gas chromatography-mass spectrometer (GC-MS) and a possible EPFR formation pathway during Ant degradation was proposed. The interaction between Ant and POM, and the hydroxylation and carbonylation of the intermediates made contributions to the generation of EPFRs. Meanwhile, the indirect photodegradation of bisphenol A (BPA) has been demonstrated by analyzing the reactive oxygen species (ROS) and photogenerated electrons in the solution with POM containing EPFRs. It is found that hydroxyl radicals (•OH) and singlet oxygen (1O2) were induced and might promote the photodegration. Overall, our present study provided useful information to understand the photoformation of EPFRs on POM and their fate in aqueous environments.

Microplastics in inland freshwater environments with different regional functions: A case study on the Chengdu Plain.

As an emerging pollutant, microplastic has been demonstrated to widely cover water and sediments in marine and freshwater environments globally. Due to the differences in the regional functions of cities, the abundance and characteristics of microplastic pollution in rivers are different. Taking the Minjiang River as the research object, which flows through the Chengdu Plain, the abundance, composition, shape, and size of microplastics in the water and sediments of the Minjiang River were investigated. The results showed that serious microplastic pollution occurred in the Chengdu section of the Minjiang River, with an abundance ranging from 6.11-44.08 n/L in the water and from 573.84-2878.97 n/kg in the sediments. By using the "regional function index (Q)", the relationships between the characteristics of microplastic pollution and regional functions were analyzed. Areas with a high Q proved to be more polluted by microplastics. Densely populated areas with large construction areas and high human activity intensity tended to generate microplastics with larger sizes and a more fiber-like shapes. Rayon (RA) and nylon (PA) were identified as typical urban microplastics, while polypropylene (PP) and polyethylene (PE) were identified as typical agricultural microplastics. This study elucidated the microplastic pollution in the Chengdu section of the Minjiang River, a tributary in the upper reaches of the Yangtze River. It also provided a new direction for the study of microplastic pollution characteristics of freshwater environments with different regional functions and microplastic pollution source control.