Multicomponent nanohybrids of nickel/ferric oxides and nickel cobaltate spinel (denoted as NiO/Fe2O3/NiCo2O4) have been prepared through pyrolyzing the hierarchical nanostructure of MOF-on-MOF and explored as efficient scaffolds for sensitively determining insulin. As for the MOF-on-MOF preparation, the ultra-thin bimetallic CoNi-zeolitic imidazolate framework (CoNi-ZIF) nanosheets were grown tightly around the bimetallic CoFe Prussian blue analogue (CoFe PBA) nanocube (denoted as CoNi-ZIF@CoFePBA). Basic characterizations revealed the original core-shell structure shape was still maintained in the NiO/Fe2O3/NiCo2O4 pyrolyzed at 300 °C, which was composed of multi-metal oxides and NiCo2O4 spinel, along with low crystallinity. Conversely, the NiO/Fe2O3/NiCo2O4 nanohybrid calcined at 600 °C consisted of large amounts of nanoparticles, while the nanohyrbid obtained at 900 °C demonstrated aggregated NiO and Fe2O3 nanoparticles coexisted with the NiCo2O4 phase. Owing to the porous nanostructure, the synergistic effect among different components, excellently electrochemical conductivity, and good biocompatibility of the NiO/Fe2O3/NiCo2O4 nanohybrid obtained at 600 °C, the relevant aptasensor displayed superior sensing performance for the determination of insulin. It gave an ultra-low detection limit of 9.1 fg mL-1 (0.16 fM) within a wide linear insulin concentration ranging from 0.01 pg mL-1 (0.172 fM) to 100 ng mL-1 (1.72 nM) determined by the electrochemical technique. The constructed aptasensor also had high selectivity, good stability, excellent reproducibility, and acceptable applicability in human serum. By integrating the advantages of aptasensors and electrochemical approach with features of multi-metallic metal-organic frameworks, this work widely broadens the applications of MOF-driven nanohybrids in biosensing fields.

中文翻译：

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源自 MOF-on-MOF 纳米结构的镍/氧化铁和钴酸镍尖晶石的多组分纳米混合物作为灵敏测定胰岛素的有效支架

镍/氧化铁和钴酸镍尖晶石的多组分纳米杂化物（表示为 NiO/Fe2O3/NiCo2O4）已通过热解 MOF-on-MOF 的分级纳米结构制备，并被探索作为灵敏测定胰岛素的有效支架。对于 MOF-on-MOF 制备，超薄双金属 CoNi-沸石咪唑酯骨架（CoNi-ZIF）纳米片紧密生长在双金属 CoFe 普鲁士蓝类似物（CoFe PBA）纳米立方体（表示为 CoNi-ZIF@CoFePBA）周围. 基本表征表明，NiO/Fe2O3/NiCo2O4 在 300°C 热解时仍保持原始核壳结构形状，由多金属氧化物和 NiCo2O4 尖晶石组成，结晶度较低。相反，在 600 °C 下煅烧的 NiO/Fe2O3/NiCo2O4 纳米杂化物由大量纳米颗粒组成，而在 900 °C 下获得的纳米杂化物表明聚集的 NiO 和 Fe2O3 纳米粒子与 NiCo2O4 相共存。由于多孔纳米结构、不同组分之间的协同作用、优异的电化学导电性和在 600°C 下获得的 NiO/Fe2O3/NiCo2O4 纳米杂化物良好的生物相容性，相关适体传感器显示出优异的胰岛素测定传感性能。它在通过电化学技术确定的 0.01 pg mL-1 (0.172 fM) 至 100 ng mL-1 (1.72 nM) 的宽线性胰岛素浓度范围内提供了 9.1 fg mL-1 (0.16 fM) 的超低检测限. 构建的适体传感器还具有选择性高、稳定性好、重现性好、人血清适用性好等特点。