[Self-made metal freezing plate for cryopreservation of human epididymal sperm: An experimental study].

OBJECTIVE: To study the effect of a new human sperm freezing method on the sperm recovery rate and search for an optimal method for cryopreservation of human epididymal sperm. METHODS: We collected semen samples from 76 men with obstructive azoospermia by percutaneous epididymal sperm aspiration and divided each sample into two parts to be cryopreserved with a self-made metal freezing plate (the experimental group) or by slow freezing (the control group), respectively. We measured the percentage of progressively motile sperm (PMS) with the computer-assisted semen analysis system and compared the membrane function, DNA fragmentation index (DFI), acrosin activity and morphological abnormality of the sperm between the two groups before and after cryopreservation. RESULTS: After thawing, both the percentages of PMS and hypotonically swollen sperm were significantly higher in the experimental than in the control group (ï¼»12.0 ± 7.5ï¼½% vs ï¼»8.0 ± 5.1ï¼½%, P < 0.05; ï¼»22.0 ± 17.5ï¼½% vs ï¼»18.0 ± 20.5ï¼½%, P < 0.05), though both decreased in comparison with the pre-freezing parameters (ï¼»20.7 ± 8.8ï¼½% and ï¼»30.0 ± 13.5ï¼½%) (P < 0.05). The sperm acrosin activity was remarkably higher in the experimental than in the control group after thawing (ï¼»75.2 ± 9.5ï¼½ vs ï¼»55.7 ± 8.3ï¼½ µIU/106sperm, P < 0.05), though decreased as compared with the baseline (ï¼»120.0 ± 10.5ï¼½ µIU/106 sperm, P < 0.05). No statistically significant differences were observed between the experimental and the control groups after thawing in the percentage of morphologically abnormal sperm (ï¼»98.7 ± 8.8ï¼½% vs ï¼»98.5±9.2ï¼½%, P > 0.05) or sperm DFI ï¼»38.2 ± 8.5ï¼½% vs ï¼»39.5 ± 10.2ï¼½%, P > 0.05), though both markedly elevated in comparison with the pre-freezing parameters (ï¼»97.2 ± 9.5ï¼½% and ï¼»30.8 ± 9.7ï¼½%) (P < 0.05). The post-thaw recovery rate of sperm was significantly higher in the experimental than in the control group (ï¼»65.2 ± 12.0ï¼½% vs ï¼»52.3 ± 18.0ï¼½%, P < 0.05). CONCLUSIONS: The self-made metal freezing plate, with its advantages of low cost, high efficiency, and easy operation, can be used as an effective method for cryopreservation of human sperm to achieve a high post-thaw sperm recovery rate, progressive sperm motility, and sperm acrosin activity.

Hydrogenated Boride-Assisted Gram-Scale Production of Platinum-Palladium Alloy Nanoparticles on Carbon Black for PEMFC Cathodes: A Study from a Practical Standpoint.

Platinum-palladium (PtPd) alloy catalysts with high durability are viable substituents to commercial Pt/C for proton exchange membrane fuel cells (PEMFCs). Herein, a facile approach for gram-scale preparation of PtxPd100-x alloy nanoparticles on carbon black is developed. The optimized Pt54Pd46/B-C catalyst shows a mass activity (MA) of 0.549 A mgPt-1 and a specific activity (SA) of 0.463 mA cm-2 at the rotating disk electrode (RDE) level, which are 3.4 and 1.9 times those of commercial Pt/C, respectively. In H2/O2 and H2/air PEMFCs, the membrane electrode assembly (MEA) with Pt54Pd46/B-C achieves peak power densities of 2.33 and 1.04 W cm-2, respectively, and shows negligible performance degradation after 100 h of running in H2/O2 conditions. Moreover, the MA of MEA with Pt54Pd46/B-C in H2/O2 PEMFC reaches 0.978 A mgPt+Pd-1 beyond the 2020 target of the Department of Energy (DOE) of 0.44 A mgPt-1. After 30k cyclic voltammetry cycles in PEMFC, the MA loss and cell voltage loss of MEA with Pt54Pd46/B-C are well within the DOE 2020 target. Density functional theory calculations reveal that the PtPd(111) surface can weaken the adsorption of *OOH and *OH compared to the Pt(111) surface, indicating that Pt54Pd46/B-C is more energetically favorable for the oxygen reduction reaction (ORR) than commercial Pt/C. This study offers a new approach for batch preparation of PtPd alloy-based catalysts for PEMFCs.

Localized surface plasmon enhanced electrocatalytic methanol oxidation of AgPt bimetallic nanoparticles with an ultra-thin shell.

AgPt bimetallic hollow nanoparticles (AgPt-BHNPs) with an ultra-thin shell were synthesized. They show obvious localized surface plasmon resonance (LSPR) effects on electrocatalytic activity and CO poisoning tolerance in the methanol oxidation reaction (MOR) in alkaline media, which is attributed to the LSPR-induced localized photothermal effects and LSPR induced surface charge heterogeneity.

Structural and Electronic Stabilization of PtNi Concave Octahedral Nanoparticles by P Doping for Oxygen Reduction Reaction in Alkaline Electrolytes.

The enhancement in the catalytic activity of PtM (transition metals, TMs) alloy nanoparticles (NPs) results from the electronic structure of Pt being modified by the TM. However, the oxidation of the TM would lead to the electronegativity difference between Pt and TM being much lowered, which induces a decrease in the number of electrons transferred from the TM to Pt, resulting in excessive oxygenated species accumulating on the surface of Pt, thus deteriorating their performance. In this work, the oxygen reduction reaction (ORR) performance of PtNi (Pt68Ni32) concave octahedral NPs (CONPs) in alkaline electrolytes is much improved by doping small amounts of phosphorus. The P-doped PtNi CONPs (P-PtNi) show about 2 and 10 times enhancement for ORR compared to PtNi and commercial Pt/C catalysts. The high-angle annular dark-field scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy mapping characterizations reveal that the P dopant uniformly distributes throughout the CONPs, Pt mainly locates at the edges and corners, whereas Ni situates at the center, forming a P-doped Pt-frame@Ni quasi-core-shell CONP. The X-ray photoelectron spectroscopy spectra indicate that the P dopant obviously increases the electron density of Pt compared with that of PtNi NPs, which contributes to the stabilization of the electronic structure of PtNi CONPs, thus restraining the excessive HO2- species produced on the catalysts, which endow them with a high catalytic performance in the ORR. In addition, the P attached to the Ni sites in the PtNi NPs partially prevents the Ni atoms being oxidized by the external O species, which is conducive to the structural and electrochemical stability of the PtNi NPs during the ORR. The present results provide a new insight into the development of ORR catalysts with low utilization of Pt.

Zinc ion mediated synthesis of cuprous oxide crystals for non-enzymatic glucose detection.

Morphology control is expected to be an effective method to enhance the electrochemical properties of materials. In this work, zinc cation-mediated growth of Cu2O crystals was achieved via an aqueous chemical route at room temperature. Thus, by simply increasing the concentration of Zn2+, concave cube-like (C-Cu2O), porous (P-Cu2O), and hierarchical (H-Cu2O) Cu2O crystals were selectively obtained. The morphologies and structures of the as-prepared Cu2O crystals were characterized by SEM, TEM, XRD and XPS. The three materials were subsequently employed as active materials for the non-enzymatic detection of glucose. The H-Cu2O-based electrode exhibited the highest sensitivity (3076 µA mM-1 cm-2) in virtue of its highest surface area, while the P-Cu2O-based electrode showed the widest linear range (up to 24 mM). The reliability of the Cu2O-based glucose sensors was proved by determining their detection limit, response time, selectivity, and stability characteristics on human serum samples. This work provides a novel strategy for the morphology-controlled Zn2+-mediated fabrication of Cu2O crystals with different glucose sensing performances depending on their structures.