Guizhou University

Chromium predominantly exists as Cr(III) and Cr(VI) in aquatic environments, which differ markedly in physicochemical properties and toxicity. Rapid and direct discrimination of Cr(III) and Cr(VI) remains challenging because conventional chromium speciation methods often require redox pretreatment, multiple recognition elements, or indirect calculation. Herein, a new Ag/Cu-containing metal-organic nanozyme with MOF-like structural characteristics (Ag-BC@Cu) was developed. Ag-BC@Cu exhibited laccase-like and peroxidase-like activities and was used to construct an orthogonal colorimetric sensor for discrimination of Cr(III) and Cr(VI). Cr(III) selectively inhibited the laccase-like pathway, whereas Cr(VI) enhanced the peroxidase-like pathway, producing independent colorimetric responses at 510 and 652 nm, respectively. Generally, both chromium species were directly discriminated and quantified using a single nanozyme without redox pretreatment, multiple probes, or subtraction-based calculations. The detection limits of the orthogonal colorimetric sensor were 0.05 mg·L^-1 for Cr(III) and 0.0047 mg·L^-1 for Cr(VI). Smartphone-assisted analysis further enabled portable visual detection of chromium speciation. The colorimetric sensor exhibited good selectivity and was successfully applied to river-water samples, with results consistent with LC-ICP-MS. This work provides a simple "kill two birds with one stone" strategy for chromium speciation, with potential for portable water-quality monitoring.

Photodynamic therapy (PDT) offers spatiotemporally controlled tumor ablation via photosensitizer-mediated singlet oxygen (¹O₂) generation, yet its application to deep-seated solid tumors remains fundamentally constrained by limited light penetration and tumor hypoxia. Endoperoxides (EPOs), which reversibly capture and release ¹O₂, offer a promising strategy to overcome these constraints. Nevertheless, existing EPO-based systems suffer from uncontrolled half-life-dependent ¹O₂ release and inefficient utilization. Moreover, PDT-induced oxidative stress upregulates inducible nitric oxide synthase (iNOS), leading to nitric oxide (NO) overproduction that quenches ¹O₂ and promote adaptive resistance. Herein, we report a self-assembly nano-prodrug enabling on-demand ¹O₂ release while suppressing NO-mediated resistance. An amphiphilic prodrug, L-NARG-SS-Py, comprising a ¹O₂-storing pyridone moiety and an iNOS inhibitor linked via a glutathione-responsive disulfide bond, co-assembles with protoporphyrin IX to form nano-prodrug (PPIX@L-NARG-SS-Py NPs). Upon irradiation, generated ¹O₂ is captured and stored as EPO intermediates, followed by glutathione-triggered release in tumor microenvironment. Simultaneously, released iNOS inhibitor suppresses NO production, thereby reducing ¹O₂ quenching and amplifying oxidative damage. In deep-seated pancreatic tumor models, the nano-prodrug achieves potent tumor suppression with minimal systemic toxicity. This work establishes a biologically amplified, light-independent PDT strategy for overcoming physical and adaptive resistance in deep-tissue phototherapy.

Salt concentration shapes the growth and metabolism of lactic acid bacteria in vegetable fermentations, yet the effects of salt gradients on the fermentation performance of suansun-derived Lactiplantibacillus plantarum BS3-1, together with associated temporal transcriptional changes in BS3-1 and metabolite variation in the fermentation broth, remain insufficiently characterized. Here, BS3-1 was evaluated across a 0-7% (w/w) salt gradient during suansun fermentation. The 0%, 3%, and 5% treatments were selected for time-series transcriptomic analysis of fermentation-derived cell pellets and untargeted metabolomic analysis of fermentation-broth supernatants. The 3% treatment yielded the highest sensory score (79.0/100 versus 72.2/100 in the no-added-salt treatment). On day 7, total acidity was 8.16 g/L at 1% salt and 3.60 g/L at 7%, and viable cells at 7% fell below the detection limit. BS3-1 transcriptional profiles and fermentation-broth metabolite compositions differed among salt treatments. In the 3% versus 0% comparison, 119 differentially expressed genes were shared across four time points, while an average of 598 differential metabolites was identified per time point. WGCNA identified 17 co-expression modules with significant module-trait associations. Association analysis integrating 126 candidate hub genes from four phenotype-associated modules with 30 shared differential metabolites retained 1100 gene-metabolite associations (|r| ≥ 0.65, global BH-FDR < 0.05). Overall, under the tested conditions, 3% salt provided the most favorable balance among viable-cell persistence, acidification, and sensory quality, while multi-omics analysis revealed covariation among BS3-1 transcriptional responses, fermentation traits, and fermentation-broth metabolite variation.