CuO nanorod-decorated hemin-graphene with enhanced peroxidase-mimicking performance for the colorimetric and electrochemical determination of 4-aminophenol with a smartphone.

The detection of 4-aminophenol (4-AP) is of critical importance due to its high toxicity, and the development of accurate, sensitive, and portable methods for this purpose is essential. Here, a facile colorimetric and electrochemical dual-mode sensor based on a CuO nanorod-decorated hemin-functionalized graphene nanocomposite (CuO/H-Gr) is successfully constructed for the detection of 4-AP. CuO/H-Gr exhibited superior peroxidase-mimicking activity, catalyzing the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 and generating a colorimetric signal. The catalytic system was found to contain hydroxyl radicals, as revealed by reactive oxygen species trials. Meanwhile, TMB was found to be an electroactive indicator that could be oxidized on a glassy carbon electrode. In the presence of CuO/H-Gr and H2O2, an enhanced electrochemical signal of TMB was generated. Upon the addition of 4-AP, the catalytic performance of CuO/H-Gr in the oxidation of TMB was significantly reduced, leading to a decrease in colorimetric and electrochemical signals. Based on this, a dual-mode sensor for the detection of 4-AP was developed. The linear response ranges for colorimetric and electrochemical sensors are 1.00-200 µM and 0.0100-300 µM, with detection limits of 0.687 µM and 0.00756 µM, respectively. Real water samples were tested to estimate the feasibility of the dual-mode sensor, and the recoveries were found to be consistent with those obtained by high-performance liquid chromatography. In addition, a smartphone-based assay was used to evaluate the levels of 4-AP, which opened a new path for on-site detection.

Fall of PARP3 restrains Lgr5+ intestinal stem cells proliferation and mucosal renovation in intestinal aging.

The regeneration ability of intestinal epithelium is degenerated in aging. The determining factor is leucine-rich repeat-containing G-protein-coupled receptor 5-positive intestinal stem cells (Lgr5+ ISCs). Lgr5-EGFP (enhanced green fluorescence protein) knock-in in transgenic mice at three different ages (young group: 3-6 months; middle group: 12-14 months; old group: 22-24 months) were used to examined Lgr5+ ISCs at three different timepoints. The jejunum samples were collected for histology, immunofluorescence analysis, western blotting and PCR. In tissue, crypt depth, proliferating cells and Lgr5+ ISC numbers were increased in the middle group (12-14 months) and decreased in the old group (22-24 months). The number of proliferating Lgr5+ ISCs gradually decreased as the mice aged. In organoids, the budding number, projected area, and Lgr5+ ISC ratio decreased as the mice aged. The gene expression of poly (ADP-ribose) polymerase 3 (Parp3) and the protein expression of PARP3 were increased in the middle- and old-aged groups. PARP3 inhibitors slowed organoid growth in the middle group. In conclusion, PARP3 is upregulated in aging, and the inhibition of PARP3 reduces the proliferation of aging Lgr5+ ISCs.

Pt-on-Pd Dendritic Nanosheets with Enhanced Bifunctional Fuel Cell Catalytic Performance.

Pd-Pt bimetallic nanocrystals have become appealing in the electrocatalytic field by virtue of their synergy effects derived from the electronic coupling between two metals. Herein, a facile seed-mediated growth approach is reported for synthesis of Pt-on-Pd dendritic nanosheets (DNSs) through the growth of Pt branches on ultrathin Pd nanosheets (NSs). The as-obtained Pt-on-Pd DNSs exhibit superior catalytic activity toward both oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR), with mass activities (MAs) 2.2 times higher for ORR and 3.4 times higher for MOR than commercial Pt/C catalysts. Moreover, these spatially separated Pt branches supported on 2D NSs also endow the Pt-on-Pd DNSs with impressive durability for ORR with only 18.9% loss in MA, whereas the Pt/C catalyst loses 50.0% after 10,000-cycle accelerated durability tests. This 2D DNS architecture can be extended to other 2D metallic NS substrates for constructing Pt-based electrocatalysts with excellent electrocatalytic performance.