Qiqing Chen

Adsorption of cadmium(II) on humic acid coated titanium dioxide

The rapid increase in nanotechnology has led to growing concerns on environmental effects and health risks of nanoparticles (NPs). Many studies investigated the adsorption of toxic pollutants on NPs; however, the interaction between heavy metals and natural organic matter (NOM) coated metal oxide NPs was scarcely studied. In this study, using humic acid (HA) as model NOM, the adsorption of Cd(II) on humic acid coated titanium dioxide (HA-TiO(2)) NPs was investigated. Solution parameters such as pH and salinity were investigated to exploit the mechanisms. Our results demonstrated that the adsorption isotherms of Cd(II) to both TiO(2) and HA-TiO(2) complied well with Freundlich model. q(e) values increased with pH increase, mainly due to electrostatic attraction, whereas q(e) values increased initially and then decreased at 100 mmol L(-1) with salinity increase, mainly due to complexation and electrostatic effects. It is noteworthy that an overall trend of higher Cd(II) adsorption was observed on HA-TiO(2) compared to that on TiO(2), implying that HA coating might modify bioavailability of heavy metals in aquatic environment. The possible adsorption mechanisms in views of electrostatic interactions and covalent effects were interpreted, and the X-ray photoelectron spectroscopy (XPS) results also verified the possible mechanisms.

Combined effects of titanium dioxide and humic acid on the bioaccumulation of cadmium in Zebrafish.

The combined effects of titanium dioxide (TiO2) nanoparticles and humic acid (HA) on the bioaccumulation of cadmium (Cd) in Zebrafish were investigated. Experimental data on the equilibrium Cd bioaccumulation suggest that only the dissolved Cd effectively contributed to Cd bioaccumulation in HA solutions whereas both the dissolved and TiO2 associated Cd were accumulated in TiO2 or the mixture of HA and TiO2 solutions, due likely to the additional intestine uptake of the TiO2-bound Cd. The equilibrium Cd bioaccumulation in the mixed system was comparable to that in the corresponding HA solutions, and significantly lower than that in the corresponding TiO2 solutions (n=3, p<0.05). The presence of either HA or TiO2 (5-20 mg L(-1)) in water slightly increased the uptake rate constants of Cd bioaccumulation whereas combining HA and TiO2 reduced the uptake rate constants.

The effects of humic acid on the uptake and depuration of fullerene aqueous suspensions in two aquatic organisms

The authors investigated the uptake and depuration of fullerene aqueous suspensions (nC(60)) in 2 aquatic organisms: Daphnia magna and zebrafish. The effects of humic acid were examined to elucidate its possible mechanisms in the aquatic environment. The uptake was concentration-dependent in both organisms, and the maximum uptake concentration of nC(60) in Daphnia (2268 ± 158 mg/kg) was approximately 1 order of magnitude higher than that in zebrafish (222 ± 30 mg/kg) because of the larger gut volume ratio to the mass of Daphnia or its high uptake efficiency. Humic acid reduced the uptake of nC(60) in Daphnia and zebrafish as a result of the size effect and the polarity alternation of nC(60). The depuration patterns were rapid for Daphnia and slow for zebrafish, and the differences were most likely the result of different water exchange frequencies between organisms. The remaining nC(60) percentages were approximately 20% for Daphnia and 30% for zebrafish after 48-h depuration, suggesting that a large nC(60) burden still existed for both aquatic organisms and that there is a need for further studies on the potential for trophic transfer.

Dietary selenium protect against redox-mediated immune suppression induced by methylmercury exposure

The antagonism between selenium (Se) and mercury (Hg) has been widely recognized, however, the protective role of Se against methylmercury (MeHg) induced immunotoxicity and the underlying mechanism is still unclear. In the current study, MeHg exposure (0.01 mM via drinking water) significantly inhibited the lymphoproliferation and NK cells functions of the female Balb/c mice, while dietary Se supplementation (as Se-rich yeast) partly or fully recovered the observed immunotoxicity, indicating the protective role of Se against MeHg-induced immune suppression in mice. Besides, MeHg exposure promoted the generation of the reactive oxygen species (ROS), reduced the levels of nonenzymic and enzymic antioxidants in target organs, while dietary Se administration significantly diminished the MeHg-induced oxidative stress and subsequent cellular dysfunctions (lipid peroxidation and protein oxidation). Two possible mechanisms of Ses protective effects were further revealed. Firstly, the reduction of mercury concentrations (less than 25%, modulated by Se supplementation) in the target organs might contribute, but not fully explain the alleviated immune suppression. Secondly and more importantly, Se could help to maintain/or elevate the activities of several key antioxidants, therefore protect the immune cells against MeHg-induced oxidative damage.

Enhanced uptake of BPA in the presence of nanoplastics can lead to neurotoxic effects in adult zebrafish

Plastic particles have been proven to be abundant in the aquatic environment, raising concerns about their potential toxic effects. In the present study, we determined the bioaccumulation potential of bisphenol A (BPA) in adult zebrafish (Danio rerio) in the absence and presence of nano-sized plastic particles (nanoplastics, NPPs). Results show that BPA can accumulate in the viscera, gill, head and muscle of zebrafish with 85, 43, 20, and 3μg/g ww after 1d exposure. NPPs were also found to accumulate in different tissues of the fish. Relative equilibrium was reached after 1d exposure in different tissues with 39 to 636mg/kg ww. Co-exposure of NPPs and BPA led to a 2.2 and 2.6-fold significant increment of BPA uptake in the head and viscera, if compared with BPA alone treatment after 3d exposure. As such, we further investigated several neurotoxic biomarker alterations in the fish head. It was found that either BPA or NPPs can cause myelin basic protein (MBP)/gene up-regulation in the central nervous system (CNS); meanwhile, both contaminants exhibited significant inhibition of acetylcholinesterase (AChE) activity, which is a well-known representative biomarker for neurotoxicity. Moreover, for the co-exposure treatment, biomarkers of myeline and tubulin protein/gene expressions, dopamine content, and the mRNA expression of mesencephalic astrocyte derived neurotrophic factor (MANF) were all significantly up-regulated, suggesting that an enhanced neurotoxic effects in both CNS and dopaminergic system occurred. However, AChE activity was no more inhibited in the co-exposure treatment, which implies that solely AChE measurement may not be sufficient to identify neurotoxic effects in the cholinergic system. Overall, the present study demonstrates that the presence of NPPs can increase BPA bioavailability and cause neurotoxicity in adult zebrafish.

Combined effects of aqueous suspensions of fullerene and humic acid on the availability of polycyclic aromatic hydrocarbons: Evaluated with negligible depletion solid-phase microextraction

The wide application of engineered carbon nanomaterials, such as fullerene (C60), will inevitably result in their introduction into the aqueous environment. Interactions of C60 with abundant natural organic matter (NOM) will likely alter the bioavailability of organic compounds to aquatic organisms. The availability of 12 types of polycyclic aromatic hydrocarbons (PAHs) in various aqueous suspensions of fullerene (nC60) prepared by different methods, e.g., in humic acid (HA) and particularly in combined systems of nC(60) and HA, was investigated by negligible depletion solid-phase microextraction (nd-SPME). The results showed that HA accelerated the rate constants (k2) of almost all PAH uptakes to the nd-SPME fibers compared with the solutions without the matrix; the combined matrices of nC(60) and HA significantly promoted the k2 of highly hydrophobic PAHs (logKOW 5.81-6.20), whereas they retarded that of less hydrophobic ones (logKOW 3.82-4.63) (p<0.05). Remarkable or minor reduction of free concentration of PAH was observed in the combined system of nC(60) and HA depending on the properties of individual PAHs. Sorption coefficients (KHA, K(C60) and K(C60+HA)) of various PAHs in different matrices were provided, and matrix concentrations showed no significant effects. For highly hydrophobic PAHs (logKOW 5.16-6.20), the logK(C60+HA) >= logKHA > logK(C60), whereas for less hydrophobic PAHs (logKOW 3.8-4.63), the Kmatrix values in various matrices showed no noticeable trend. In addition, higher K(C60) values were obtained for aqu/nC(60) than for son/nC(60) for most highly hydrophobic PAHs. The above results suggest that hydrophobicity plays an important role in determining Kmatrix in addition to the matrix effects. The interactions between nC(60) and HA have critical or minor impacts on availability, and thus bioavailability, of PAHs. This paper contributes to the understanding of the bioavailability mechanisms of organic pollutants in the aquatic environment with both nC(60) and NOM.

The effect of nC60 on tissue distribution of ibuprofen in Cyprinus carpio

UNLABELLED The potential transfer of fullerene aqueous suspension (nC₆₀) associated contaminants in vivo is one of the most significant and currently not well-understood environmental risks. In this study, the carrier function of nC₆₀ for ibuprofen (IBU) was examined through whole-body and tissue distribution determination of nC₆₀ and IBU in Cyprinus carpio. The results showed that the presence of nC₆₀ only slightly increased the whole-body burden of IBU, because the amount of soluble IBU far exceeds that of nC₆₀ associated form of IBU; while the presence of nC₆₀ activated the catalase activity and enhanced the lipid peroxidation in the liver, suggesting an obviously induced oxidative damage to fish. With the presence of nC₆₀, the uptake of IBU in both gill and digestive tract tissues increased obviously: the uptake of IBU in the gill was mainly from the desorption of nC₆₀ associated IBU, and that in the digestive tract was both from nC₆₀ associated IBU and soluble IBU. On the contrary, the nC₆₀ reduced IBU uptake in the brain, probably due to the high accumulation of nC₆₀ which blocked the blood brain barrier. Moreover, there was no significant increase in the muscle, which implies that the soluble form should be the main source of IBU accumulation in the muscle. The carrier function of nC₆₀ observed in the present study indicates the potential transportation of other contaminants and the subsequently enhanced environmental risks. CAPSULE Fullerene aqueous suspension functioned as a carrier to alter the tissue distribution of ibuprofen in Cyprinus carpio.

Fullerene inhibits benzo(a)pyrene Efflux from Cyprinus carpio hepatocytes by affecting cell membrane fluidity and P-glycoprotein expression

P-Glycoprotein (P-gp) can protect cells by pumping out toxic compounds, and has been found widely expressed in fish tissues. Here, we illustrate the P-gp efflux ability for benzo(a)pyrene (BaP) in the hepatocytes of common carp (Cyprinus carpio) after exposing to fullerene aqueous suspension (nC60). The results revealed that nC60 increased the membrane fluidity by decreasing the ratio of saturated to unsaturated fatty acids, and increased the cholesterol contents. These findings, combined with 10-38% and 70-75% down-regulation of P-gp mRNA and protein respectively, suggested that nC60 caused inhibition on P-gp efflux transport system. Therefore, we further investigated the cellular efflux ability for BaP. Results showed unequivocally that nC60 is a potent P-gp inhibitor. The retaining BaP amounts after efflux were elevated by 1.7-2.8 fold during the 10 day exposure. Meanwhile, 5mg/L humic acid (one of the important fractions of natural organic matter, which is ubiquitous in aquatic environment) alleviated the nC60 damage to hepatocytes in terms of oxidative damage, cholesterol increment, and P-gp content reduction; and finally attenuated the suppressed P-gp efflux ability. Collectively, this study provides the first evidence of nC60 toxicity to P-gp functionality in fish and illustrates the possible mechanism of the suppressed P-gp efflux ability for BaP.

Genomic cloning, characterization and statistical analysis of an antitumor-analgesic peptide from Chinese scorpion Buthus martensii Karsch.

The genomic DNA sequence encoding an antitumor-analgesic peptide was amplified from the genome of Chinese scorpion Buthus martensii Karsch (BmKAGAP), then cloned and sequenced. An intron, with a high A + T content (61.6%), splits a glycine codon near the end of the precursor signal peptide and the consensus GT/AG splice junction was identified in the BmKAGAP gene. Using PCR amplification, we confirmed the identity of our cloned cDNA, and found that the BmKAGAP gene contained an intron of 506 bp in length, which was almost identical to that of the characterized scorpion sodium channel ligands in size, consensus junctions, putative branch point and A + T content. This is the first report of using a statistical method for Chinese scorpion B. martensii Karsch genomic sequence analysis, involving the extraction of some putative transcription regulatory factors. Moreover, it establishes a theoretical foundation for studying the relationship between scorpion evolution, gene expression and protein function.

Effect-based and chemical analyses of agonistic and antagonistic endocrine disruptors in multiple matrices of eutrophic freshwaters

In the present study, both bioanalytical and instrumental tools were employed to examine the endocrine-disruptive potentials of water samples, cyanobloom samples, and sediment samples collected from in the northern region of Taihu Lake (China) during cyanobloom season. Results from cell-based bioassays suggested the occurrence of estrogenic, anti-estrogenic, anti-androgenic, and anti-glucocorticogenic activities, while no androgenic and glucocorticogenic activities were observed in the collected samples. Using an UPLC-MS/MS system, 29 endocrine disrupting compounds including seven estrogens, seven androgens, six progestogens, and five adrenocortical hormones and four industrial pollutants were simultaneously detected. 17, 20 and 12 chemicals were detected at least in one of the water samples, cyanobloom samples and sediment samples, respectively. Since both agonistic and antagonistic endocrine-disruptive activities were detected in the present study, commonly used receptor-based in vitro bioassays resulted in net effects, suggesting that the hormone receptor agonistic potentials might be underestimated with this practice. The EDCs detected in cyanobloom samples also highlight the necessity to consider the phytoplankton matrix for understanding the mass fluxes of endocrine disruptors in eutrophic freshwaters and to consider it in monitoring strategies.