Chenxi Wei

Effects of silica nanoparticles on growth and photosynthetic pigment contents of Scenedesmus obliquus

To assess the aquatic ecosystem safety for silica (SiO2) nanoparticles (NPs), the growth inhibition and photosynthetic pigment contents of Scenedesmus obliquus in logarithm growth phase exposed to SiO2 NPs and SiO2 bulk particles (BPs) suspensions were measured. SiO2 NPs with 10-20 nm diameters were found to be toxic. The 20% effective concentration (EC20) values for 72 and 96 hr were 388.1 and 216.5 mg/L, respectively. The contents of chlorophyll decreased significantly under moderate and high concentration (50, 100, and 200 mg/L) of SiO2 NPs after 96-hr exposure, but the carotenoids did not. SiO2 BPs were found to be nontoxic up to 200 mg/L. The toxicity of SiO2 NPs probablely due to their sorption to algal cells surface. The results imply that there is potential harm to aquatic environment by using SiO2 NPs, and it should deserve special concern.

Single-walled carbon nanotube induction of rat aortic endothelial cell apoptosis: Reactive oxygen species are involved in the mitochondrial pathway

The use of nano-sized materials offers exciting new options in technical and medical applications. Single-walled carbon nanotubes are emerging as technologically important in different industries. However, adverse effects on cells have been reported and this may limit their use. We previously found that 200μg/mL of single-walled carbon nanotubes induce apoptosis in rat aorta endothelial cells. The current study aimed to determine the signaling pathway involved in this process. We found that reactive oxygen species generation was involved in activation of the mitochondria-dependent apoptotic pathway. The finding of apoptosis was supported by a number of morphological and biochemical hallmarks, including chromatin condensation, internucleosomal DNA fragmentation, and caspase-3 activation. In conclusion, our results demonstrate that single-walled carbon nanotubes induce apoptosis in rat aorta endothelial cells and that reactive oxygen species are involved in the mitochondrial pathway.

Pulmonary Toxicity and Adjuvant Effect of Di-(2-exylhexyl) Phthalate in Ovalbumin-Immunized BALB/c Mice

Background Asthma is a complex pulmonary inflammatory disease, which is characterized by airway hyperresponsiveness, variable airflow obstruction and inflammation in the airways. The majority of asthma is allergic asthma, which is a disease caused by type I hypersensitivity mediated by IgE. Exposures to a number of environmental chemicals are suspected to lead to asthma, one such pollutant is di-(2-ethylheyl) phthalate (DEHP). DEHP is a manufactured chemical that is commonly added in plastic products to make them flexible. Epidemiological studies have revealed a positive association between DEHP exposure and asthma prevalence. Methodology/Principal Findings The present study was aimed to determine the underlying role of DEHP exposure in airway reactivity, especially when combined with allergen exposure. The biomarkers include pulmonary histopathology, airway hyperresponsiveness (lung function), IgE, IL-4, IFN-γ and eosinophils. Healthy balb/c mice were randomly divided into eight exposure groups (n = 8 each): (1) saline control, (2) 30 µg/(kg•d) DEHP, (3) 300 µg/(kg•d) DEHP, (4) 3000 µg/(kg•d) DEHP, and (5) ovalbumin (OVA)-sensitized group, (6) OVA-combined with 30 µg/(kg•d) DEHP, (7) OVA-combined with 300 µg/(kg•d) DEHP, and (8) OVA-combined with 3000 µg/(kg•d) DEHP. Experimental tests were conducted after 52-day DEHP exposure and subsequently one week of challenge with aerosolized OVA. The principal findings include: (1) Strong postive associations exist between OVA-combined DEHP exposure and serum total IgE (T-IgE), as well as histological findings. These positive associations show a dose-dependent low dose sensitive effect of DEHP. (2) IL-4, eosinophil recruitment and lung function are also indicators for adjuvant effect of DEHP. Conclusions/Significance Our results suggest that except the significant changes of immunological and inflammatory biomarkers (T-IgE, IL-4, IFN-γ and eosinophils), the pulmonary histological (histopathological examination) and physiological (lung function) data also support that DEHP may promote and aggravate allergic asthma by adjuvant effect.

Inhaled formaldehyde induces DNA-protein crosslinks and oxidative stress in bone marrow and other distant organs of exposed mice.

Formaldehyde (FA), a major industrial chemical and ubiquitous environmental pollutant, has been classified as a leukemogen. The causal relationship remains unclear, however, due to limited evidence that FA induces toxicity in bone marrow, the site of leukemia induction, and in other distal organs. Although induction of DNA–protein crosslinks (DPC), a hallmark of FA toxicity, was not previously detected in the bone marrow of FA‐exposed rats and monkeys in studies published in the 1980s, our recent studies showed increased DPC in the bone marrow, liver, kidney, and testes of exposed Kunming mice. To confirm these preliminary results, in the current study we exposed BALB/c mice to 0, 0.5, 1.0, and 3.0 mg m−3 FA (8 hr per day, for 7 consecutive days) by nose‐only inhalation and measured DPC levels in bone marrow and other organs of exposed mice. As oxidative stress is a potential mechanism of FA toxicity, we also measured glutathione (GSH), reactive oxygen species (ROS), and malondialdehyde (MDA), in the bone marrow, peripheral blood mononuclear cells, lung, liver, spleen, and testes of exposed mice. Significant dose‐dependent increases in DPC, decreases in GSH, and increases in ROS and MDA were observed in all organs examined (except for DPC in lung). Bone marrow was among the organs with the strongest effects for DPC, GSH, and ROS. In conclusion, exposure of mice to FA by inhalation induced genotoxicity and oxidative stress in bone marrow and other organs. These findings strengthen the biological plausibility of FA‐induced leukemogenesis and systemic toxicity. Environ. Mol. Mutagen. 54:705–718, 2013.

Approach to distribution and accumulation of dibutyl phthalate in rats by immunoassay

Dibutyl phthalate (DBP) is mainly taken up by the general population from food intake. To estimate intake of phthalates, determining distribution and accumulation of DBP in biological materials was a critical need. In this work, we set up two novel approaches with a monoclonal antibody specific to DBP to determine the distribution and accumulation of DBP in vivo. The contents of DBP in liver, kidney, stomach and testes were detected by immunofluorescence assays and indirect competitive ELISA. This data give directly evidence that indicates the distribution and accumulation of DBP in vivo. Double-label immunofluorescence assay provides with a visual approach to determination of the distribution and accumulation of DBP. It indicated that DBP accumulated in subcutaneous tissue such as sweat gland, hair follicle. Both of immunofluorescence assay and ELISA can be used to detect the content of DBP in biological materials. Our assays showed that DBP accumulated in viscera being rich in fat, such as liver, kidney and could overcome physiological barriers to penetrate testes. The date suggested that the accumulations of DBP exposed through dermal route were less than that of oral route and most of DBP was metabolized in 2 or 3 days.

An Immunoassay for Dibutyl Phthalate Based on Direct Hapten Linkage to the Polystyrene Surface of Microtiter Plates

Background Dibutyl phthalate (DBP) is predominantly used as a plasticizer inplastics to make them flexible. Extensive use of phthalates in both industrial processes and other consumer products has resulted in the ubiquitous presence of phthalates in the environment. In order to better determine the level of pollution in the environment and evaluate the potential adverse effects of exposure to DBP, immunoassay for DBP was developed. Methodology/Principal Findings A monoclonal antibody specific to DBP was produced from a stable hybridoma cell line generated by lymphocyte hybridoma technique. An indirect competitive enzyme-linked immunosorbent assay (icELISA) employing direct coating of hapten on polystyrene microtiter plates was established for the detection of DBP. Polystyrene surface was first oxidized by permanganate in dilute sulfuric acid to generate carboxyl groups. Then dibutyl 4-aminophthalate, which is an analogue of DBP, was covalently linked to the carboxyl groups of polystyrene surface with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC). Compared with conjugate coated format (IC50 = 106 ng/mL), the direct hapten coated format (IC50 = 14.6 ng/mL) improved assay sensitivity after careful optimization of assay conditions. The average recovery of DBP from spiked water sample was 104.4% and the average coefficient of variation was 9.95%. Good agreement of the results obtained by the hapten coated icELISA and gas chromatography-mass spectrometry further confirmed the reliability and accuracy of the icELISA for the detection of DBP in certain plastic and cosmetic samples. Conclusions/Significance The stable and efficient hybridoma cell line obtained is an unlimited source of sensitive and specific antibody to DBP. The hapten coated format is proposed as generally applicable because the carboxyl groups on modified microtiter plate surface enables stable immobilization of aminated or hydroxylated hapten with EDC. The developed hapten coated icELISA can be used as a convenient quantitative tool for the sensitive and accurate monitoring DBP in water, plastic and cosmetic samples.

Neurobehavioral changes induced by di(2-ethylhexyl) phthalate and the protective effects of vitamin E in Kunming mice

Di(2-ethylhexyl) phthalate (DEHP) is a plasticizer commonly used in PVC that may leach into the environment, and has been shown to adversely affect the health of humans and animals. We undertook a study to ascertain the neurotoxicity of DEHP in Kunming mice. This study included three rounds of testing. In the first round, Kunming mice were exposed to different concentrations of DEHP (0, 5, 50, 500 mg kg−1 per day) after which their cognitive ability was assessed using the Morris water maze (MWM) test. The reactive oxygen species (ROS) content in tissue and the malondialdehyde (MDA) content of brains were also measured. In the second round, vitamin E (50 mg kg−1 per day) was given daily as an anti-oxidant via the intragastric route. Cognitive deficits and locomotor activity, as well as ROS and MDA contents were tested employing the same methods. In the third round, the depressive mood of mice after DEHP exposure (500 mg kg−1 per day) was measured using the open field test, the tail suspension test, and the forced swim test. The main findings of this study include: (1) a statistical association exists between DEHP oral exposure and spatial learning (DEHP 500 mg kg−1 per day) and memory (DEHP 50 mg kg−1 per day) dysfunction as ascertained by an MWM test of Kunming mice. (2) A statistical association was also found between DEHP oral exposure (50 and 500 mg kg−1 per day) and oxidative stress (ROS and MDA) of mouse brain tissue. (3) Co-administration of vitamin E (50 mg kg−1 per day) diminishes the elevation of ROS and MDA induced by DEHP (50 mg kg−1 per day) from significant levels to non-significant levels. (4) Co-administration of vitamin E (50 mg kg−1 per day) protects against mouse memory dysfunction induced by DEHP (50 mg kg−1 per day) from being significant to being not significant. (5) In the 5 mg kg−1 per day DEHP exposure groups, oxidative stress in brain tissue, and neurobehavioral changes were not found. (6) High dose DEHP exposure (500 mg kg−1 per day) may induce behavioral despair in mice. Conclusions: These data suggest that DEHP is neurotoxic with regard to cognitive ability and locomotor activity.

Ecotoxicological Effect of Nano-silicon Dioxide Particles on Daphnia Magna

Engineering nanoparticles (ENPs) have been widely used in many areas in virtue of its special physical and chemical properties. And ENPs are one of the major innovative scientific and economic growth things, which may present a variety of questions for organisms and environment. This paper analyzed the ecotoxicological effect of the nanosized silicon dioxide (Nano-SiO2) and the normal sized silicon dioxide (Nor-SiO2) within 24 hours as its bulk counterpart to Daphnia magna with different concentration. To assess the aquatic ecosystem safety, EC50 value for immobilization and LC50 value for mortality were measured respectively. The results show that the toxicity of Nano-SiO2 has obviously dose-dependent effect but the Nor-SiO2 has not, evidently. The optical microscope and digital camera also been used to observe and record the biological form of Daphnia magna during the exposure and in this study we found that D. magna can uptake and adsorb Nano-SiO2 but only apparently show uptaking to its bulk counterpart. The conclusions of results suggest that there is potential harm to aquatic environment in using Nano-SiO2, and it should deserve special concern.

Cytotoxicity Effects of Nano-Fe3O4 on HeLa Cells

In order to study the cytotoxicity effects of Nano-Fe3O4 Particles on HeLa Cells, 50µg/mL, 100µg/mL and 200µg/mL concentrations of Nano-Fe3O4 were exposed to HeLa cells, twelve hours later&#65292;single cell gel electrophoresis (SCGE) was used to detect HeLa cell DNA molecule damage, the content of the malondialdehyde (MDA) were determined by thiobarbiturie acid reactive substance method and the activity of super oxide dismutase (SOD) was determined by xanthine oxldase method. The results shown that under the 50µg/mL Nano-Fe3O4 exposure, compared with the control group, neither the tail moment nor the tail DNA% increased (P>0.05), the increase content of MDA also not significant (P>0.05), but the reduce activity of SOD is significant (P<0.05); under the 100µg/mL and 200µg/mL Nano-Fe3O4 exposure, compared with the control group, the increase of tail moment and tail DNA% both significant (P<0.05 or P<0.01), the increase content of MDA also significant&#65288;P<0.05 or P<0.01&#65289;&#65292;the reduce activity of SOD is significant (P<0.01). The results suggest that Nano-Fe3O4 could induce the cytotoxicity on HeLa cells.

Anti-bensulfuron methyl monoclonal antibody production and BSM-detecting indirect competitive enzyme-linked immunoassay establishment

Bensulfuron methyl (BSM) is widely used for agricultural purposes and has raised health concerns, as well as ecological problems. Immunoassay would be one of the most advantaged measurements compared with traditional methods for BSM detection and measurement. In order to develop indirect competitive enzyme-linked immunoassay (icELISA), the anti-BSM monoclonal antibody (anti-BSM MAb) was produced. For the MAb production, BSM was conjugated to OVA and injected to mice with Freuds adjuvant for immunisation. Antiserum screening has revealed successful immunising. One stable hybridoma cell line (2H1) was obtained through cell fusion between spleen cells of immunised mouse and SP 2/0 cells. The MAb secreted by 2H1 cells was of high affinity and sensitivity, as well as specificity to BSM. Then the protocol of the icELISA and standard curve for BSM measurement was made and examined by controlled application. Significantly, the application has exhibited 96.530%–107.2% recovery of BSM. The produced MAb and established immunoassay may facilitate the measurement of BSM and herein help to ensure food safety and regulate environmental protection.