Aqueous photodegradation of okadaic acid and dinophysistoxin-1: Persistence, kinetics, photoproducts, pathways, and toxicity evaluation

Responses of the intestinal microbiota to exposure of okadaic acid in marine medaka Oryzias melastigma

It is still limited that how the microalgal toxin okadaic acid (OA) affects the intestinal microbiota in marine fishes. In the present study, adult marine medaka Oryzias melastigma was exposed to the environmentally relevant concentration of OA (5 μg/L) for 10 days, and then recovered in fresh seawater for 10-days depuration. Analysis of taxonomic composition and diversity of the intestinal microbiota, as well as function prediction analysis and histology observation were carried out in this study. Functional prediction analysis indicated that OA potentially affected the development of colorectal cancer, protein and carbohydrate digestion and absorption functions, and development of neurodegenerative diseases like Parkinson's disease, which may be associated with changes in Proteobacteria and Firmicutes in marine medaka. Significant increases of C-reactive protein (CRP) and inducible nitric oxide synthase (iNOS) levels, as well as the changes of histology of intestinal tissue demonstrated that an intestinal inflammation was induced by OA exposure in marine medaka. This study showed that the environmental concentrations of OA could harm to the intestinal microbiota thus threatening the health of marine medaka, which hints that the chemical ecology of microalgal toxins should be paid attention to in future studies.

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.

Competitive near-infrared PEC immunosorbent assay for monitoring okadaic acid based on a disposable flower-like WO3-Modified screen-printed electrode

The long-term toxic effects of okadaic acid (OA) in shellfish pose a serious threat to public health, negatively impacting the development of the shellfish aquaculture industry. In this study, a novel competitive near-infrared-mediated photoelectrochemical immunosorbent assay (cNIR-PECIA) was developed for ultrasensitive and highly selective detection of OA based on NaYF₄:Yb, Tm upconversion nanophosphors (UCNPs) and a flower-like WO₃-modified screen-printed electrode (FL-WO₃ SPE). The UCNPs function as a self-powder to convert NIR excitation into visible emissions. FL-WO₃ fully utilizes the visible illumination and induces the separation of electron-hole pairs, thus generating a photocurrent. After conjugating monoclonal antibodies against OA on UCNPs (UCNPs-Ab), the bright PEC immunoprobe selectively captured OA molecules, which were then determined by a competitive indirect immunosorbent assay. Under optimal conditions, the 50% inhibitory concentration of the immunosensor was 0.09 ng mL^-1. The OA concentration had a linear relationship with the antibody binding rate in the range of 0.01-60 ng mL^-1 with an extremely low detection limit of 0.007 ng mL^-1. Finally, the proposed cNIR-PECIA was successfully utilized to analyze OA content in mussel samples. This study affords new ideas for constructing NIR PEC sensors by using upconversion luminescent materials to match semiconductors. The superior sensing properties indicate their potential applicability in food safety analysis.