Reaction mechanism and detecting properties of a novel molecularly imprinted electrochemical sensor for microcystin based on three-dimensional AuNPs@MWCNTs/GQDs.

Microcystins with leucine arginine (MC-LR) is a virulent hepatotoxin, which is commonly present in polluted water with its demethylated derivatives [Dha7] MC-LR. This study reported a low-cost molecularly imprinted polymer network-based electrochemical sensor for detecting MC-LR. The sensor was based on a three-dimensional conductive network composed of multi-walled carbon nanotubes (MWCNTs), graphene quantum dots (GQDs), and gold nanoparticles (AuNPs). The molecularly imprinted polymer was engineered by quantum chemical computation utilizing p-aminothiophenol (p-ATP) and methacrylic acid (MAA) as dual functional monomers and L-arginine as a segment template. The electrochemical reaction mechanism of MC-LR on the sensor was studied for the first time, which is an irreversible electrochemical oxidation reaction involving an electron and two protons, and is controlled by a mixed adsorption-diffusion mechanism. The sensor exhibited a great detection response to MC-LR in the linear range of 0.08-2 µg/L, and the limit of detection (LOD) is 0.0027 µg/L (S/N = 3). In addition, the recoveries of the total amount of MC-LR and [Dha7] MC-LR in the actual sample by the obtained sensor were in the range from 91.4 to 116.7%, which indicated its great potential for environmental detection.

Adverse effects of plastic leachate and its component 2,4-DTBP on the early development of zebrafish embryos.

Plastic waste has become a global environmental problem threatening the health of aquatic organisms especially via leachate. In this study, the test of zebrafish embryo showed adverse effects of leachate from some agricultural mulching films after UV light aging for 60 h. A typical phenolic antioxidant 2,4-di-tert-butylphenol (2,4-DTBP) was detected in the leachate and tested further for the zebrafish embryo biotoxicity. The microplastic leachate (6, 8 g/L, mass concentration measured by weight of plastic) increased the death and malformation rates, and reduced the hatching rate, heart rate, and body length of zebrafish larvae in the 96-hour early development period. Similar adverse effects were also caused by the 2,4-DTBP (0.01, 0.1, 1.0 mg/L, corresponding to 0.049, 0.49, and 4.85 µM) to some degree but could not completely explain the significant influences caused by the plastic leachate. Transcriptome analysis of zebrafish embryos exposed to the 2,4-DTBP for 96 h showed that the protein, fat, and carbohydrate digestion and absorption pathways, pancreatic secretion, PPAR signaling pathway, tryptophan metabolism, and adipocytokine signaling pathway were considerably down-regulated, but the cholesterol metabolism pathway was up-regulated in larval zebrafish. The altered transcriptional expression of mRNA at early development stage (96 h post fertilization) of zebrafish suggested that the 2,4-DTBP caused reduction of digestive capacity and pancreatic secretory function, and adversely affected processes associated with energy metabolism and glycolipid metabolism of larval zebrafish. This study helps us further understanding the effects of plastic leachate on the early development of fishes.

Effects of Polystyrene Microplastics on Growth and Toxin Production of Alexandrium pacificum.

Microplastics (MP) widely distributed in aquatic environments have adverse effects on aquatic organisms. Currently, the impact of MP on toxigenic red tide microalgae is poorly understood. In this study, the strain of Alexandrium pacificum ATHK, typically producing paralytic shellfish toxins (PST), was selected as the target. Effects of 1 and 0.1 µm polystyrene MP with three concentration gradients (5 mg L-1, 25 mg L-1 and 100 mg L-1) on the growth, chlorophyll a (Chl a), photosynthetic activity (Fv/Fm) and PST production of ATHK were explored. Results showed that the high concentration (100 mg L-1) of 1 µm and 0.1 µm MP significantly inhibited the growth of ATHK, and the inhibition depended on the size and concentration of MP. Contents of Chl a showed an increase with various degrees after MP exposure in all cases. The photosynthesis indicator Fv/Fm of ATHK was significantly inhibited in the first 11 days, then gradually returned to the level of control group at day 13, and finally was gradually inhibited in the 1 µm MP treatments, and promotion or inhibition to some degree also occurred at different periods after exposure to 0.1 µm MP. Overall, both particle sizes of MP at 5 and 25 mg L-1 had no significant effect on cell toxin quota, and the high concentration 100 mg L-1 significantly promoted the PST biosynthesis on the day 7, 11 and 15. No significant difference occurred in the cell toxin quota and the total toxin content in all treatments at the end of the experiment (day 21). All MP treatments did not change the toxin profiles of ATHK, nor did the relative molar percentage of main PST components. The growth of ATHK, Chl a content, Fv/Fm and toxin production were not affected by MP shading. This is the first report on the effects of MP on the PST-producing microalgae, which will improve the understanding of the adverse impact of MP on the growth and toxin production of A. pacificum.

An efficient preparative procedure for main flavonoids from the peel of Trichosanthes kirilowii Maxim. using polyamide resin followed by semi-preparative high performance liquid chromatography.

In this study, a simple and efficient preparative procedure was developed for preparation of seven flavonoids from the peel of Trichosanthes kirilowii Maxim. using polyamide resin followed by semi-preparative high performance liquid chromatography (SPHPLC). First, the ethyl acetate fraction from the peel of T. kirilowii Maxim. obtained "prefractionation" using polyamide resin, which yielded two subfractions. And then the two subfractions were isolated by SPHPLC with an isocratic elution of methanol-water. Finally, seven known flavonoids were purified from 35 g of ethyl acetate extract including quercetin-3-O-[α-l-rhamnose (1→2)-ß-d-glucopyranosyl]-5-O-ß-d-glucopyranoside (19 mg), quercetin-3-O-rutinoside (24 mg), apigenin-7-O-ß-d-glucopyranoside (10mg), diosmetin-7-O-ß-d-glucopyranoside (45 mg), luteolin (21 mg), apigenin (15 mg), and diosmetin (56 mg). The purities of the compounds were determined by HPLC and the chemical structures were confirmed by UV and NMR analysis. In the present study, a simple, effective, and rapid procedure was established for preparative separation of multiple components from the peel of T. kirilowii Maxim. Furthermore, it was scalable and economical, so it was a promising basis for large-scale preparation of flavonoids from other plant extracts.

Effect of seawater salinity on pore-size distribution on a poly(styrene)-based HP20 resin and its adsorption of diarrhetic shellfish toxins.

In the present study, okadaic acid (OA) and dinophysistoxin-1 (DTX1) were spiked into artificial seawater at low, medium and high estuarine salinities (9‰, 13.5‰ and 27‰). Passive samplers (HP20 resin) used for solid phase adsorption toxin tracking (SPATT) technology were exposed in these seawaters for 12-h periods. Adsorption curves well fitted a pseudo-secondary kinetics model. The highest initial sorption rates of both toxins occurred in the seawater of medium salinity, followed by seawater of low and high estuarine salinity. Pore volumes of micropores (<2 nm) and small mesopores (2 nm