Exosomes are extracellular vesicles (50–100 nm) circulating in biofluids as intercellular signal transmitters. Although the potential of cancerous exosomes as tumor biomarkers is promising, sensitive and rapid detection of exosomes remains challenging. Herein, we combined the strengths of advanced aptamer technology, DNA-based nanostructure, and portable electrochemical device to develop a nanotetrahedron (NTH)-assisted aptasensor for direct capture and detection of hepatocellular exosomes. The oriented immobilization of aptamers significantly improved the accessibility of an artificial nucleobase-containing aptamer to suspended exosomes, and the NTH-assisted aptasensor could detect exosomes with 100-fold higher sensitivity when compared to the single-stranded aptamer-functionalized aptasensor. The present study provides a proof-of-concept for sensitive and efficient quantification of tumor-derived exosomes. We thus expect the NTH-assisted electrochemical aptasensor to become a powerful tool for comprehensive exosome studies.

We demonstrate a facile hydrothermal method for growth of ultrathin NiCo2S4 nanosheets on reduced graphene oxide (RGO), which exhibit remarkable electrochemical performance with higher capacitance and longer cycle life than the bare NiCo2S4 hollow spheres (HSs).

. IntroductionOver the last two decades, transition metal chalcogenides have attracted much attention, due to their excellent optical, electrical, magnetic and catalytic properties. [1][2][3][4] These unique properties can lead to wide applications in supercapacitors, lithium-ion batteries, DSCs, et al. [5][6][7][8][9][10][11] As important transition metal sulfi des, CoS 2 showed high capacitances in electrochemical capacitors, due to their high redox activity. In addition, CoS 2 has been demonstrated to be very effective in catalyzing redox electrolytes in DSCs, showing a potential replacement for the noble metal Pt counter electrodes to lower the cost of the DSCs. These superior performances make metal sulfi des, especially CoS 2 , promising in the applications of supercapacitors and DSCs. Stimulated by the attractive properties and promising applications, several methods have been developed to prepare MS 2 (M = Co and Ni) materials with a wide range of nanostructures, including ellipsoids, microspheres, microtubes and microfl owers. [12][13][14][15][16][17] However, there is still much room for progress with regard to the development of MS 2 nanostructures with different morphologies and their energy applications.Recently, extensive attention has been paid to three-dimensional (3D) hollow nanostructures because of their attractive properties of low density, high surface-to-volume ratio, and low coeffi cients of thermal expansion, which make them promising in the applications of energy. [ 18,19 ] Especially for supercapacitors, hollow structures with high surface areas and suitable mesopores (especially 2−5 nm) can provide rich electroactive sites and short diffusion paths for charge carriers, which are required in the Faradaic redox reactions. [ 20,21 ] As for DSCs, the photovoltaic conversion effi ciency can be improved by using counter electrodes with high surface areas. Thus, the porous hollow structure with a high surface area can lead to high catalytic activity for redox electrolytes and fast reaction rate. [ 22,23 ] Furthermore, two-dimensional nanosheet structures have the advantages of enhancing the effective interaction between the active materials and electrolytes and reducing transport lengths for both mass and charge transport. [ 24,25 ] Up to now, a variety of hollow structures with different complex interiors, such as coreshell, yolk-shell, and multi-shell structures, have been successfully fabricated mainly through hard and soft template-assisted approaches. [26][27][28] As compared to the much more common hard-template techniques, soft templates can be easily removed by gentle evaporation or dissolution in solvents. To the best of our knowledge, systematic study for the fabrication of CoS 2 and NiS 2 hollow structures with various interiors constructed by nanosheets are rarely reported. Therefore, it is highly desirable but challenging to synthesize MS 2 (M= Co, Ni) hollow structures and investigate their applications in supercapacitors and DSCs. MS 2 (M = Co and Ni) Hollow Spheres with Tunable...

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