质子交换膜燃料电池铂基催化剂研究进展

燃料电池是一种将化学能直接转化为电能的能量转换装置,具有能量密度高、利用率高、清洁安静等优点。在不同类型的燃料电池中,质子交换膜燃料电池(PEMFC)不仅能量密度高,而且具有在近常温条件下工作的特点,因此受到广泛关注。目前,商业化PEMFC仍采用铂基纳米材料作为催化剂,其中缺乏低成本、高效的阴极催化剂是限制PEMFC性能提升和成本降低的关键因素之一。本文综述PEMFC催化剂的结构可控制备及其对阴极氧还原反应和膜电极性能的影响,阐述调控催化剂结构提高PEMFC性能的方法,特别是提高贵金属催化剂的利用率,降低膜电极中贵金属用量的研究进展。

玻璃体腔注射康柏西普联合激光光凝治疗糖尿病性黄斑水肿的效果分析

目的:分析玻璃体腔注射康柏西普联合视网膜激光光凝治疗糖尿病性黄斑水肿(diabetic macular edema,DME)的临床疗效。方法:选取2015-06/2016-12我院确诊的DME患者73例80眼,根据治疗方式不同分为对照组和治疗组,对照组采用视网膜激光光凝治疗,治疗组采用玻璃体腔注射康柏西普联合激光光凝治疗。观察治疗前和治疗后3mo两组患者最佳矫正视力(BCVA)、视网膜厚度及并发症发生情况。结果:治疗后3mo,两组患者BCVA均较治疗前显著改善,且治疗组患者BCVA显著优于对照组;两组患者黄斑上方、下方、颞侧、鼻侧环状区的视网膜厚度和平均视网膜厚度均低于治疗前,且治疗组患者的平均视网膜厚度显著低于对照组,差异均有统计学意义(P<0.05)。随访期间,所有患者均未出现角膜水肿、前房炎性反应、视网膜出血、新生血管性青光眼、眼内炎等严重眼部并发症及全身不良反应。结论:与单纯视网膜激光治疗相比,玻璃体腔注射康柏西普联合视网膜激光光凝治疗DME在改善视力、恢复视网膜功能方面效果更佳,且具有良好的安全性。

The cultivation and identification of tumor stem cells from neuroblastoma derived tumor spheres

Background and Objective: Since the proposal of the tumor stem cell hypothesis, considerable interest has been devoted to the isolation and purification of tumor stem cells. Tumor stem cell enrichment from primary tumor derived cell spheres has been demonstrated in specific, serum-free media. This goal of this study is to establish a method of cultivating floating tumor spheres from neuroblastoma cells and to confirm that neuroblastoma spheres are rich in tumor stem cells. Methods: Bone marrow aspirates were obtained from pediatric patients diagnosed with stage IV neuroblastoma. Primary tumor cells were isolated and cultivated in serum-free, stem cell-selective medium. Single sphere-forming cells were cultivated under serum-free conditions; their cloning efficiency and monoclonal tumor sphere formation rates were calculated. The expression of stem cell marker genes Oct-4 and Bmi-1 was detected by RT-PCR in sphere-forming cells and parental neurolastoma cells. Sphere-forming cells were injected into the armpit of nude mice with subsequent assessment for tumor growth. Sphere-forming cells were cultivated in differentiation medium containing 5 μmol/L 13-cis retinoic acid; changes in cell morphology were observed. Results: Neuroblastoma cells formed non-adherent neurospheres under serum-free, stem cell-selective conditions after a period of 4 to 6 days. A single cell dissociated from a neurosphere could reform a monoclonal sphere; cloning efficiency and monoclonal sphere formation rates were 55.3% and 26.3%, respectively. RT-PCR results revealed heightened tumor sphere expression of Oct-4 and Bmi-1 as compared with parental tumor cells. Fourteen days after injection of 104 sphere-forming cells into nude mice, a neuroblastoma xenograft formed. Treatment of sphere-forming cells with 13-cis retinoic acid induced a gradual differentiation to neuronal cell morphology. Conclusions: Neuroblastoma derived tumor spheres enrich tumor stem cells and the cultivation of primary neuroblastoma cells in serum-free, stem cell-selective medium is an effective method to dissociate and purify tumor stem cells in vitro.

Inhibition of smoothened decreases proliferation of Synoviocytes in rheumatoid arthritis

Fibroblast-like synoviocytes （FLSs） contribute to synovial hyperplasia in rheumatoid arthritis （RA）. Smoothened （Smo） is a key component of sonic hedgehog （Shh） signaling and contributes to tumor cell proliferation. The objective of this study was to investigate the role of Smo in RA synoviocyte proliferation. FLSs were isolated from RA synovium. Shh signaling was studied using a Smo antagonist （GDC-0449） and small interfering RNA （siRNA） targeting the Smo gene in FLSs. Cell proliferation was quantified by using kit-8 assay and cell cycle distribution and apoptosis were evaluated by flow cytometry. Cell cycle-related genes and proteins were detected by real-time PCR and western blot. FLSs treated with GDC-0449 or Smo-siRNA showed significantly decreased proliferation compared to controls （P〈0.05）. Incubation with GDC-0449 or transfection with Smo-siRNA resulted in a significant increase of G1 phase cells compared to controls （P 〈 0.05）. Cell cycle arrest was validated by the significant increase in cyclin D1 and E1 mRNA expression, decrease in cyclin-dependent kinase p21 mRNA expression in Smo-siRNA transfected cells （P 〈 0.05）. Protein expression of cyclin D1 was also downregulated after Smo gene knockdown （P 〈0.05）.The results suggest that Shh signaling plays an important role in RA-FLSs proliferation in a Smo-dependent manner and may contribute to synovial hyperplasia. Targeting Shh signaling may help control joint damage in patients with RA.

Highly efficient electroreduction of CO_(2) by defect single-atomic Ni-N_(3) sites anchored on ordered micro-macroporous carbons

Microporous supports typically fail to fully expose active sites for electrolytes and CO_(2) molecules,and this usually results in low current density for the electrocatalytic CO_(2) reduction reaction(CO_(2)RR).To overcome the biggest obstacle and facilitate commercial applications,defective single-atomic Ni-N_(3) sites anchored to ordered micro-macroporous N-doped carbon(Ni-N/OMC)have been prepared by the pyrolysis of the Ni-ZIF-8@PS(ZIF=zeolitic imidazolate framework)and are intended to provide enhanced CO_(2)RR with a current density at an industrial level.This Ni-ZIF-8@PS is constructed of nickel-based ZIF-8 embedded in the three-dimensional(3D)highly ordered polystyrene spheres(PS).The 3D ordered micro-macroporous architecture of Ni-N/OMC could facilitate the mass transfer of substrates to the accessible defective single-atomic Ni-N_(3) sites through micropores(0.6 nm)and macropores(~200 nm)interconnected by 50 nm channels.In a flow cell,Ni-N/OMC exhibits almost 100.0%CO Faraday efficiency(FECO)between−0.2 and−1.1 V vs.RHE and an industrial level CO partial current density of 208 mA cm^(−2).It has a turnover frequency of 1.5×10^(5) h^(−1) at−1.1 V vs.RHE in 1 M KOH electrolyte,which exceeds that of most reported nickel-based electrocatalysts.This excellent CO_(2)RR performance for Ni-N/OMC makes it a state-of-the-art electrocatalyst for CO_(2)RR.Theoretical calculations show that the defective Ni-N_(3) site can lower the energy of*COOH formation compared with that of the Ni-N4 site,thereby accelerating CO_(2)RR.Ni-N/OMC can also be utilized as a cathodic catalyst in Zn-CO_(2) battery,exhibiting high CO selectivity in the discharge process and excellent stability.This work paves a pathway to rational design of highly efficient electrocatalysts with 3D hierarchically ordered micro-macroporous architecture for CO_(2)RR towards industrial production and commercial applications.

Ni single-atom sites supported on carbon aerogel for highly efficient electroreduction of carbon dioxide with industrial current densities

Finding highly efficient electrocatalysts for the CO_(2)electroreduction reactions(CO_(2)RR)that have high selectivity and appreciable current density to meet commercial application standards remains a challenge.Because their reduction potentials are similar to that of the associated competitive hydrogen evolution reaction and the CO_(2)activation kinetics are sluggish.Although single-atom catalysts(SACs)with high atom efficiency are one class of promising candidates for the CO_(2)RR to produce CO,single-atom active sites supported on microporous carbons are not fully exposed to substrates and thus lead to low current density.Carbon aerogels with interconnected channels and macropores can facilitate mass transport.But few reports describe utilizing them as supports to anchor SACs for efficient electrocatalysis.Herein,N-doped carbon aerogels supporting Ni single atomic catalyst sites(denoted as Ni-NCA-X,X¼10,20)were fabricated by pyrolyzing Ni/Zn bimetallic zeolitic imidazolate framework(Ni/Zn-ZIF-8)/carboxymethylcellulose composite gels.Owing to abundant hierarchical micro-,meso-,and macropores and high CO_(2)adsorption,the Ni single active sites in the optimal Ni-NCA-10 were readily accessible for the electrolyte and CO_(2)molecules and thus achieved an industrial-level CO partial current density of 226 mA cm?2,a high CO Faradaic efficiency of 95.6%at?1.0 V vs.the reversible hydrogen electrode,and a large turnover frequency of 271810 h?1 in a flow-cell reactor at?1.0 V.Such excellent CO_(2)RR performance makes Ni-NCA-10 a rare state-of-the-art electrocatalyst for CO_(2)-to-CO conversion.This work provides an effective strategy for designing highly efficient electrocatalysts toward the CO_(2)RR to achieve industrial current density via anchoring single-atom sites on carbon aerogels.