Mo Single-Atom Nanozyme Anchored to the 2D N-Doped Carbon Film: Catalytic Mechanism, Visual Monitoring of Choline, and Evaluation of Intracellular ROS Generation.

Single-atom nanozymes (SANs) have attracted great attention in constructing devices for instant biosensing due to their excellent stability and atom utilization. Here, Mo atoms were immobilized in 2D nitrogen-doped carbon films by cascade-anchored one-pot pyrolysis to obtain Mo single-atom nanozyme (Mo-SAN) with high atomic loading (4.79 wt %) and peroxidase-like activity. The coordination environment and enzyme-like activity mechanism of Mo-SAN were studied by combining synchrotron radiation and density functional theory. The strong oxophilicity of single-atom Mo makes the catalytic center more capable of transferring electrons to free radicals to selectively generate •OH in the presence of H2O2. Choline oxidase and Mo-SAN were used as signal opening unit and signal amplification unit, respectively. Combining the portability and visualization functions of smartphone and test strips, a paper-based visual sensing platform was constructed, which can accurately identify choline at a concentration of 0.5-35 µM with a limit of detection as low as 0.12 µM. The recovery of human serum samples was 96.4-102.2%, with an error of less than 5%. Furthermore, the potential of Mo-SAN to efficiently generate toxic •OH in tumor cells was intuitively confirmed. This work provides a technical and theoretical basis for designing highly active SANs and detecting neurological markers.

Realgar Alleviated Neuroinflammation Induced by High Protein and High Calorie Diet in Rats via the Microbiota-Gut-Brain Axis.

PURPOSE: Gastrointestinal heat retention syndrome (GHRS) often occurs in adolescents, resulting into nervous system injury. Realgar, an arsenic mineral with neuroprotective effect, has been widely used to treat GHRS. However, its mechanism of action remains unknown. METHODS: A GHRS rat model was established using a high protein and high calorie diet. We performed macroscopic characterization by assessing bowel sounds, hot/cold preference, anal temperature, and fecal features. Atomic fluorescence spectroscopy was employed to evaluate brain arsenic level while hippocampal ultrastructural changes were analyzed using transmission electron microscopy. In addition, inflammatory cytokines and BBB breakdown were analyzed by western blotting, immunofluorescence assays, and immunohistochemistry staining. We also evaluated hippocampal metabolites by LC-MS while fecal microorganisms were assessed by 16S rDNA sequencing. RESULTS: Our data showed that the high protein and high calorie diet induced GHRS. The rat model depicted decreased bowel sounds, increased fecal characteristics score, preference for low temperature zone, and increased anal temperature. In addition, there was increase in inflammatory factors IL-6, Iba-1, and NF-κB p65 as well as reduced BBB structural protein Claudin-5 and Occludin. The data also showed appearance of hippocampus metabolites disorder and fecal microbial imbalance. Realgar treatment conferred a neuroprotective effect by inhibiting GHRS-specific characteristics, neuroinflammatory response, BBB impairment, metabolites disorder, and microbial imbalance in the GHRS rat model. CONCLUSION: Taken together, our analysis demonstrated that realgar confers a neuroprotective effect in GHRS rats through modulation of the microbiota-gut-brain axis.

Smartphone-integrated dual-emission fluorescence sensing platform based on carbon dots and aluminum ions-triggered aggregation-induced emission of copper nanoclusters for on-site visual detecting sulfur ions.

A ratiometric fluorescence strategy was proposed based on carbon dots (CDs) and self-assembled copper nanoclusters (CuNCs) driven by Al3+ ions for S2- detection. Si-CDs/CuNCs@Al3+ exhibits blue and red emission under single excitation. Interestingly, the red emission of the CuNCs was regularly quenched while the blue fluorescence emission of the CDs was preserved after continuous addition of S2-. The fluorescence spectrometer-based S2- linear range is from 0.5 to 40 µM, with a low detection limit (LOD) of 0.16 µM. The fluorescence response of Si-CDs/CuNCs@Al3+ to S2- exhibits a distinct color change process (red to pink to blue), implying feasibility of visual analysis. A portable fluorescence sensing platform was established using the color-to-value conversion function of a smartphone for accurate visualization and quantitative identification of S2- without spectrometer. The fluorescent test strips prepared with Si-CDs/CuNCs@Al3+ can conduct on-site visual analysis of S2- in the water environment more conveniently and quickly. The linear range of S2- detection based on the smartphone-integrated test strip sensing platform is 1-40 µM, and the LOD is 0.42 µM. This work provides a new horizon for target on-site analysis in environmental samples.

Polypyrrole-based nanotheranostic agent for MRI guided photothermal-chemodynamic synergistic cancer therapy.

Polypyrrole (PPy) nanoparticles have been widely studied in tumor photothermal therapy (PTT) for their significant photostability, good biocompatibility, and excellent photothermal performance. Herein, we report bovine serum albumin (BSA) stabilized PPy that were mineralized by MnO2 nanozyme on the surface (PPy@BSA-MnO2) to achieve synergistic photothermal and chemodynamic therapy (CDT) for breast cancer. In this multifunctional nanoplatform, the surface-loaded MnO2 undergoes a redox reaction with glutathione (GSH) to generate glutathione disulfide (GSSG) and Mn2+. Then, Mn2+ can convert H2O2 into a highly cytotoxic ˙OH to achieve chemodynamic therapy (CDT) and possess good magnetic resonance (MR) T1-weighted imaging capabilities to realize contrast imaging of the 4T1 tumor-bearing mouse models. In addition, PPy nanoparticles can efficiently convert near-infrared light energy into heat and achieve PTT. Most importantly, PPy@BSA-MnO2 nanoprobes have excellent in vitro 4T1 cell-killing effect and in vivo tumor-suppressive properties. The acute toxicity assessment results indicate that PPy@BSA-MnO2 nanoprobes have good biological safety. Therefore, the as-prepared multifunctional PPy@BSA-MnO2 nanoprobes possess excellent performance to promote MRI-guided PTT/CDT synergistic therapy for breast cancer treatment and have extensive clinical transformation and application prospects.