Mechanisms of Se(IV) Co-precipitation with Ferrihydrite at Acidic and Alkaline Conditions and Its Behavior during Aging

Understanding the form of Se­(IV) co-precipitated with ferrihydrite and its subsequent behavior during phase transformation is critical to predicting its long-term fate in a range of natural and engineered settings. In this work, Se­(IV)-ferrihydrite co-precipitates formed at different pH were characterized with chemical extraction, transmission electron microscopy (TEM), and X-ray absorption spectroscopy (XAS) to determine how Se­(IV) is associated with ferrihydrite. Results show that despite efficient removal, the mode and stability of Se­(IV) retention in the co-precipitates varied with pH. At pH 5, Se­(IV) was removed dominantly as a ferric selenite-like phase intimately associated with ferrihydrite, while at pH 10, it was mostly present as a surface species on ferrihydrite. Similarly, the behavior of Se­(IV) and the extent of its retention during phase transformation varied with pH. At pH 5, Se­(IV) remained completely associated with the solid phase despite the phase change, whereas it was partially released back into solution at pH 10. Regardless of this difference in behavior, TEM and XAS results show that Se­(IV) was retained within the crystalline post-aging products and possibly occluded in nanopore and defect structures. These results demonstrate a potential long-term immobilization pathway for Se­(IV) even after phase transformation. This work presents one of the first direct insights on Se­(IV) co-precipitation and its behavior in response to iron phase transformations

Relationship between DOX, p53, and ORAI1 in CFs.

DOX increased the expression of p53 and induced apoptosis, cell cycle arrest, and ROS production. In addition, DOX increased the expression of ORAI1, not STIM1. Furthermore, the inhibition of ORAI1 negated the DOX-induced expression of p53, suggesting that the DOX-ORAI1-p53 pathway induces cardiotoxicity. (TIF)</p

Western blotting analysis for four groups to evaluate the effects of store-operated Ca²⁺ entry (SOCE) inhibition; CTRL group, DOX group, YM group, and YM+DOX group.

(A) YM-58483 significantly attenuated the DOX-induced upregulation of p53 protein. (B) YM-58483 significantly attenuated the DOX-induced upregulation of p21 protein. (one-way ANOVA followed by Tukey’s test, n = 6, *** p < 0.001, NS: no significant difference).</p

Fig 1 -

1A and 1B. Western blotting analysis comparing doxorubicin (DOX) samples with control (CTRL) samples. (A) Human cardiac fibroblasts (HCFs) were exposed to 0.1 to 1.0 μM DOX for 24 h. DOX increased the expression of p53 protein in a dose-dependent manner (one-way ANOVA followed by Tukey’s test, n = 4, *** p p p 1C. Apoptosis assay comparing DOX samples with CTRL samples. Flow cytometry analysis showed that DOX significantly increased early apoptosis (Q3) (unpaired t-test, n = 4, ** p 1D and 1E. Cell cycle analysis comparing DOX samples with CTRL samples. (D) Western blotting analysis. HCFs were exposed to 0.5 μM DOX for 1 to 24 h. DOX increased the expression of p21 protein in a time-dependent manner (one-way ANOVA followed by Tukey’s test, n = 4, *** p p p 1F. ROS production measured by fluorescence 24 h after administration of DOX. DOX increased ROS production significantly in the samples with 5.0 μM DOX (one-way ANOVA followed by Tukey’s test, n = 6, * p < 0.05, NS: no significant difference).</p

Original data (data shown in Fig 4).

(PDF)</p

Western blotting analysis to evaluate the effects of ORAI1 gene knockdown.

(A) Expression of ORAI1 mRNA by qPCR. The expression level of ORAI1 mRNA was reduced in samples with siRNA against ORAI1. In samples with control siRNA, DOX significantly upregulated the expression level of ORAI1 mRNA (two-way ANOVA followed by Bonferroni’s post hoc test, n = 6, *** p p p p p p p p < 0.01, NS: no significant difference).</p

Original data (data shown in Fig 1).

(PDF)</p

Original data (data shown in Fig 2).

(PDF)</p

Protocol for western blotting.

(DOCX)</p

Cell cycle assays for evaluating the effects of SOCE inhibition.

There were four groups: the CTRL group, DOX group, YM group, and YM+DOX group. DOX decreased the proportion of cells in the G1 and S phases. In contrast, DOX increased the proportion of cells in the G2 phase. This suggests that DOX induced cell cycle arrest in the G2/M phase. YM-58483 attenuated the changes induced by DOX. (TIF)</p