The effect of polystyrene nanoplastics on arsenic-induced apoptosis in HepG2 cells.

Microplastics are detrimental to the environment. However, the combined effects of microplastics and arsenic (As) remain unclear. In this study, we investigated the combined effects of polystyrene (PS) microplastics and As on HepG2 cells. The results showed that PS microplastics 20, 50, 200, and 500 nm in size were taken up by HepG2 cells, causing a decrease in cellular mitochondrial membrane potential. The results of lactate dehydrogenase release and flow cytometry showed that PS microplastics, especially those of 50 nm, enhanced As-induced apoptosis. In addition, transcriptome analysis revealed that TP53, AKT1, CASP3, ACTB, BCL2L1, CASP8, XIAP, MCL1, NFKBIA, and CASP7 were the top 10 hub genes for PS that enhanced the role of As in HepG2 cell apoptosis. Our results suggest that nano-PS enhances As-induced apoptosis. Furthermore, this study is important for a better understanding of the role of microplastics in As-induced hepatotoxicity.

Polystyrene nanoplastics promote the apoptosis in Caco-2 cells induced by okadaic acid more than microplastics.

Microplastics (MPs) are widespread in the environment and can be ingested through food, water, and air, posing a threat to human health. In addition, MPs can have a potential combined effect with other toxic compounds. Polystyrene (PS) has been shown to enhance the cytotoxicity of okadaic acid (OA). However, it remains unclear whether this enhancement effect is related to the size of PS particles. In this study, we investigated the mechanism of the combined effect of PS microplastics (PS-MPs) or PS nanoplastics (PS-NPs) and OA on Caco-2 cells. The results indicated that PS-NPs enhanced the cytotoxicity of OA and induced endoplasmic reticulum (ER) stress-mediated apoptosis in Caco-2 cells, compared to PS-MPs. Specifically, PS-NPs and OA cause more severe oxidative stress, lactate dehydrogenase (LDH) release, and mitochondrial membrane depolarization. Furthermore, it induced intracellular calcium overload through store-operated channels (SOCs) and activated the PERK/ATF-4/CHOP pathway to cause ER stress. ER stress promoted mitochondrial damage and finally activated the caspase family to induce apoptosis. This study provided an indirect basis for the assessment of the combined toxicity of MPs or NPs with OA.

High sensitivity in quantitative analysis of mixed-size polystyrene micro/nanoplastics in one step.

As emerging environmental pollutants, microplastics (MPs) and nanoplastics (NPs) pose a serious threat to human health. Owing to the lack of feasible and reliable analytical methods, the separation and identification of MPs and NPs of different sizes remains a challenge. In this study, a hyphenated method involving filtration and surface-enhanced Raman spectroscopy (SERS) for the separation and identification of MPs and NPs is reported. This method not only avoids the loss of MPs and NPs during the transfer process but also provides an excellent SERS substrate. The SERS substrate was fabricated by electrochemically depositing silver particles onto the reduced graphene oxide layer coated on stainless steel mesh. Results show that polystyrene (PS) MPs and NPs are efficiently separated on the SERS substrate via vacuum filtration, resulting in high retention rates (74.26 % ± 1.58 % for 100 nm, 81.06 % ± 1.49 % for 500 nm, and 97.73 % ±0.11 % for 5 µm) and low limit of detection (LOD). The LOD values of 100 nm, 500 nm, and 5 µm PS are 8.89 × 10-5, 3.39 × 10-5, and 1.57 × 10-4 µg/mL, respectively. More importantly, a linear relationship for uniform quantification of 100 nm, 500 nm, 3 µm and 5 µm PS was established, and the relationship is Y = 225.61 lgX + 1076.36 with R2 = 0.980. The method was validated for the quantitative analysis of a mixture of 100 nm, 500 nm PS NPs, 3 µm and 5 µm PS MPs in a ratio of 1:1:1:1, which successfully approaches the evaluation of evaluated PS NPs in the range of 10-4-10 µg/mL with an LOD value of approximately 7.82 × 10-5 µg/mL. Moreover, this method successfully detected (3.87 ± 0.06) × 10-5 µg MPs and NPs per gram of oyster tissue.

Differences in toxicity induced by the various polymer types of nanoplastics on HepG2 cells.

The problem of microplastics (MPs) contamination in food has gradually come to the fore. MPs can be transmitted through the food chain and accumulate within various organisms, ultimately posing a threat to human health. The concentration of nanoplastics (NPs) exposed to humans may be higher than that of MPs. For the first time, we studied the differences in toxicity, and potential toxic effects of different polymer types of NPs, namely, polyethylene terephthalate (PET), polyvinyl chloride (PVC), and polystyrene (PS) on HepG2 cells. In this study, PET-NPs, PVC-NPs, and PS-NPs, which had similar particle size, surface charge, and shape, were prepared using nanoprecipitation and emulsion polymerization. The results of the CCK-8 assay showed that the PET-NPs and PVC-NPs induced a decrease in cell viability in a concentration-dependent manner, and their lowest concentrations causing significant cytotoxicity were 100 and 150 µg/mL, respectively. Moreover, the major cytotoxic effects of PET-NPs and PVC-NPs at high concentrations may be to induce an increase in intracellular ROS, which in turn induces cellular damage and other toxic effects. Notably, our study suggested that PET-NPs and PVC-NPs may induce apoptosis in HepG2 cells through the mitochondrial apoptotic pathway. However, no relevant cytotoxicity, oxidative damage, and apoptotic toxic effects were detected in HepG2 cells with exposure to PS-NPs. Furthermore, the analysis of transcriptomics data suggested that PET-NPs and PVC-NPs could significantly inhibit the expression of DNA repair-related genes in the p53 signaling pathway. Compared to PS-NPs, the expression levels of lipid metabolism-related genes were down-regulated to a greater extent by PET-NPs and PVC-NPs. In conclusion, PET-NPs and PVC-NPs were able to induce higher cytotoxic effects than PS-NPs, in which the density and chemical structure of NPs of different polymer types may be the key factors causing the differences in toxicity.

Distribution and risk assessment of microplastics in typical ecosystems in the South China Sea.

Microplastic pollution in the marine environment has attracted worldwide attention. The South China Sea is considered a hotspot for microplastic pollution due to the developed industries and high population density around the South China Sea. The accumulation of microplastics in ecosystems can adversely affect the health of the environment and organisms. This paper reviews the recent microplastic studies conducted in the South China Sea, which novelty summarizes the abundance, types, and potential hazards of microplastics in coral reef ecosystems, mangrove ecosystems, seagrass bed ecosystems, and macroalgal ecosystems. A summary of the microplastic pollution status of four ecosystems and a risk assessment provides a more comprehensive understanding of the impact of microplastic pollution on marine ecosystems in the South China Sea. Microplastic abundances of up to 45,200 items/m3 were reported in coral reef surface waters, 5738.3 items/kg in mangrove sediments, and 927.3 items/kg in seagrass bed sediments. There are few studies of microplastics in the South China Sea macroalgae ecosystems. However, studies from other areas indicate that macroalgae can accumulate microplastics and are more likely to enter the food chain or be consumed by humans. Finally, this paper compared the current risk levels of microplastics in the coral reef, mangrove, and seagrass bed ecosystems based on available studies. Pollution load index (PLI) ranges from 3 to 31 in mangrove ecosystems, 5.7 to 11.9 in seagrass bed ecosystems, and 6.1 to 10.2 in coral reef ecosystems, respectively. The PLI index varies considerably between mangroves depending on the intensity of anthropogenic activity around the mangrove. Further studies on seagrass beds and macroalgal ecosystems are required to extend our understanding of microplastic pollution in marine environments. Recent microplastic detection in fish muscle tissue in mangroves requires more research to further the biological impact of microplastic ingestion and the potential food safety risks.

Occurrence of antibiotic resistance genes carried by plastic waste from mangrove wetlands of the South China Sea.

Plastic waste can carry organisms such as bacterial pathogens and antibiotic resistance genes (ARGs) over long distances. However, only few studies have been conducted on the occurrence of ARGs in plastic waste from mangrove wetlands. This study evaluated the distribution characteristics and ecological risks of plastic waste from mangroves in the coastal areas of the South China Sea. The correlation between anthropogenic activity levels and abundance of ARGs in mangroves was evaluated. Transparent and white were the common colors of plastic waste in mangroves. The main shapes of plastic waste were foam and film. The predominant types of plastic waste order were as follows: polyethylene (30.18 %) > polypropylene (27.51 %) > polystyrene (23.59 %). The living area (LA) mangroves had the highest polymer hazard and pollution load indices of 329.09 and 10.03, respectively. The abundance of ARGs (5.08 × 108 copies/g) on the plastic surface in LA mangroves was significantly higher than that of the other mangrove areas. Furthermore, there was a significant correlation between ARGs and intI1 on the plastic surface in mangroves. Correlation analysis between the ARGs and intI1 showed that most of the ARGs were correlated with intI1 except for msbA. In LA mangroves, sociometric and environmental factors showed significant correlations with the absolute abundances of the four ARGs and intI1, indicating that anthropogenic activities may lead to changes in the amount of ARGs on plastic surfaces. Furthermore, the ARG storage of plastic waste from different mangroves was as follows: protected areas (3.12 × 1017 copies) > living areas (2.99 × 1017 copies) > aquaculture pond areas (2.88 × 1017 copies). The higher ARG storage of LA mangroves, with the smallest area, greatly increased its ecological risk. The results of this study can provide basic data for processes that influence the distribution of plastic waste and ARGs in mangroves.

Exosomal miRNA analysis provides new insights into exposure to nanoplastics and okadaic acid.

As an emerging environmental pollutant, nanoplastics (NPs) have attracted wide attention in terms of their impact on the ecological environment and human health. Currently, researches on the cytotoxicity of NPs mainly focus on oxidative stress, damage to the cell membrane and organelles, induction of immune response and genotoxicity. Okadaic acid (OA) is the main component of diarrheal shellfish toxin. Based on the previous combined toxicity exploration of polystyrene (PS) NPs and (OA) to human gastric adenocarcinoma (AGS) cells, cell-derived exosomes were extracted and exosomal miRNA profiles were analyzed for the first time in this study. The results showed that the composition of miRNAs varied after the exposure of NPs and OA. Specifically, the expression of miR-1-3p in both PS-Exo and PS-OA-Exo was significantly reduced. And the expression of miR-1248 was upregulated most significantly by comparing the DE miRNAs between PS-Exo and PS-OA-Exo. MiR-1-3p and miR-1248 may be the key genes for the combined toxicity of NPs and OA. After analysis, we found that both the decreased expression of miR-1-3p and the increased expression of miR-1248 can increase the expression of FN1 and affect DNA replication, which was surprisingly consistent with the results of our previous cytotoxicity studies. Since exosomal miRNAs are selectively encapsulated by donor cell, we speculate that the changes of exosomal miRNAs may due to the synchronous changes of intracellular environment and the downregulation of intracellular FN1 may be attributed to decreased expression of miR-1-3p and increased expression of miR-1248 in donor cells. Accordingly, we come to the conclusion that the changes of miRNAs in the exosomes derived from AGS cells after environmental stimulation could reflect the biological effects of donor cells.

Impact of the surrounding environment on antibiotic resistance genes carried by microplastics in mangroves.

The pollution of antibiotic resistance genes (ARGs) carried by microplastics (MPs) is a growing concern. Mangroves are located at the intersection of land and sea and are seriously affected by MP pollution. However, few studies have systematic research evaluating the transmission risk of ARGs carried by MPs in mangroves. We conducted in situ experiments by burying five different MPs (polypropylene, high-density polyethylene, polystyrene, polyethylene glycol terephthalate, and polycaprolactone particles) in mangroves with different surrounding environments. A total of 10 genes in the MPs of mangroves were detected using quantitative real-time polymerase chain reactions, including eight ARGs and two mobile genetic elements (MGEs). The abundance of ARGs in Guanhai park mangroves in living areas (GH) was higher than that of Gaoqiao mangroves in protected areas (GQ) and Beiyue dike mangroves in aquaculture pond areas (BY). Pathogenic bacteria, such as Acinetobacter, Bacillus, and Vibrio were found on the MP surfaces of the mangroves. The number of ARGs carried by multiple drug-resistant bacteria in the GH mangroves was greater than that in the GQ and BY mangroves. Moreover, the ARGs carried by MPs in GH mangroves had the highest potential transmission risk by horizontal gene transfer. Sociometric and environmental factors were the main drivers shaping the distribution characteristics of ARGs and MGEs. Polypropylene and high-density polyethylene particles are preferred substrates for obtaining diffuse ARGs. This study investigated the drivers of ARGs in the MPs of mangroves and provided essential guidance on the use and handling of plastics.

Microplastics accumulation in mangroves increasing the resistance of its colonization Vibrio and Shewanella.

The enrichment of various pollutants in mangrove has attracted widespread attention. Especially, microplastics accumulation in mangrove may provide a more challenging ecological colonization site by enriching pollutants, thus affecting the change of microplastics antibiotic resistance and increasing the risk of antibiotic failure. Herein, the antibiotic-resistant of microplastics and sediment from mangrove were investigated. The results show that isolates are mainly colonized by Vibrio parahemolyticus (V. parahemolyticus), Vibrio alginolyticus (V. alginolyticus), and Shewanella. 100% mangrove microplastics isolates are resistant to chloramphenicol, cefazolin, and tetracycline, especially amoxicillin clavulanate and ampicillin. Meanwhile, the multiple antibiotics resistance (MAR) indexes of V. parahaemolyticus, Shewanella, and V. alginolyticus in mangrove microplastics are 0.72, 0.77, and 0.77, respectively, which are far higher than the MAR index standard (0.2) and that of mangrove sediment isolates. Furthermore, compared with V. parahaemolyticus isolated from the same mangrove microplastics, Shewanella and V. alginolyticus show stronger drug resistance. It should be noted that there is a closely related relationship between the type of microplastics and the antibiotics resistance of isolated bacteria. For the antibiotics sensitivity test of norfloxacin, streptomycin, amoxicillin, and chloramphenicol, V. parahaemolyticus have the lower antibiotics resistance than that of V. alginolyticus isolated from the same mangrove microplastics. However, Vibrio isolated from PE has stronger antibiotics resistance. Results reveal that mangrove may be one of the potential risks for emergence and spread of bacterial antibiotics-resistant and multidrug-resistant, and microplastic biofilms may act as promoters of bacterial antibiotic resistance.

Separation of false-positive microplastics and analysis of microplastics via a two-phase system combined with confocal Raman spectroscopy.

In the field of microplastics research, more accurate standardised methods and analytical techniques still need to be explored. In this study, a new method for the microplastics quantitatively and qualitatively analysis by two-phase (ethyl acetate-water) system combined with confocal Raman spectroscopy was developed. Microplastics can be separated from false-positive microplastics in beach sand and marine sediment, attributing to the hydrophobic-lipophilic interaction (HLI) of the two-phase system. Results show that the recovery rates of complex environment microplastics (polypropylene (PP), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyamide 66 (PA 66), polycarbonate (PC) and polyethylene (PE)) are higher than 92.98%. Moreover, the new technique can also be used to detect hydrophobic and lipophilic antibiotics, such as sulfamethoxazole (SMX), erythromycin (EM), madimycin (MD), and josamycin (JOS), which adsorbed on microplastics and are extracted based on the dissolving-precipitating mechanism. This innovative research strategy provides a new scope for further detection of marine environment microplastics and toxic compounds adsorbed on its surface.

A portable dual-mode sensor based on a TiO2 nanotube membrane for the evaluation of telomerase activity.

A portable dual-mode sensing platform based on a self-standing TiO2 nanotube membrane is developed for simultaneously performing both qualitative analysis by the naked eye and quantitative analysis by ionic current. This dual-mode diagnosis strategy exhibits a high performance in telomerase detection in urine specimens from patients with bladder cancer.