Xuechao Xu,Xiaobo Zou,Shuwen Wu,Linjie Wang,Xiangheng Niu,Xin Li,Jianming Pan,Hongli Zhao,Minbo Lan
As pyrophosphate ion (PPi) and pyrophosphatase (PPase) play crucial roles in the pathological process of arthritis, determination of PPi and PPase in biological fluids turns to be of great importance for clinical diagnosis and therapy of arthritic diseases. In this work, we proposed a new fluorescent assay for PPi and PPase activity detection based on the competitive coordination chemistry of Fe 3+ between PPi and an in situ formed fluorescent polydopamine (PDA). FeCo layered double hydroxide (FeCo-LDH) was explored as a peroxidase mimic to facilitate the in situ formation of fluorescent PDA from dopamine mediated by low-concentration H 2 O 2 within 30 min; The formed fluorescent PDA could be significantly quenched by Fe 3+ through forming a PDA-Fe 3+ complex structure; When PPi existed, it coordinated Fe 3+ competitively against PDA and inhibited the fluorescence quenching of PDA by Fe 3+ ; When PPi was hydrolyzed under the catalysis of PPase, the Fe 3+ ion could quench the fluorescence of the formed PDA again. With these principles, our fluorescent assay was able to detect PPi and PPase activity specifically, providing detection limits down to 54 μM and 0.13 U/L, respectively. Furthermore, accurate determination of PPi and PPase activity in spiked human serum was also demonstrated using the developed assay.
Ran Li,Deliang Zhang,Huamao Chen,Shaozhen Wang,Yunyun Ling,Caihong Fang
Developing high-performance and low-cost electrocatalysts for the oxygen evolution reaction (OER) and urea oxidation reaction (UOR) is essential for hydrogen production. Herein, we prepared Zn,S-incorporated Fe,Co layered double hydroxide (ZnCoFeS–LDH) nanosheets on nickel foam via a two-step hydrothermal reaction. The attractive two-dimensional (2D) nanosheet morphology with ultrathin thickness offers abundant active sites, promotes the adsorption and desorption of intermediates on the surface, and also facilitates mass transportation. The electronic structure of ZnCoFeS–LDH was modified, which thus improves their conductivity, offers high-valence iron ions (Fe3+), and therefore intrinsically enhances their electrocatalytic properties. In particular, the constructed crystalline/amorphous interfaces benefit electron transfer between different phases. As a proof of concept, we examined the electrocatalytic performances of ZnCoFeS–LDH nanostructures to both the OER and UOR. As a result, the ZnCoFeS–LDH nanosheets exhibit excellent catalytic OER activity, with low overpotentials of 202, 217, 238, and 261 mV to achieve current densities of 10, 20, 50, and 100 mA cm–2, respectively, which are remarkably enhanced in comparison with that of commercial RuO2. Furthermore, they also demonstrate outstanding durability after long-term (48 h) and cycling (5000 cycles) measurements. Moreover, the ZnCoFeS–LDH nanosheets also possess superior UOR activity. The potentials were measured to be as low as 1.313, 1.334, 1.366, and 1.398 V to reach current densities of 10, 20, 50, and 100 mA cm–2, respectively, with high long-term stability after 20 h.
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