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A facile electrochemical aptasensor based on a novel signal amplification strategy was employed for sensitive and selective detection of streptomycin for the first time. The aptasensor was prepared by sequentially dripping a gold nanoparticle-functionalized magnetic multi-walled carbon nanotube (Au@MWCNTs-Fe 3 O 4 ) composite and nanoporous PtTi (NP-PtTi) alloy onto a glassy carbon electrode (GCE) surface. The NP-PtTi alloy with a uniform nanoporous structure was successfully fabricated by selectively de-alloying Al from a PtTiAl alloy in HCl solution. The results demonstrated that the Au@MWCNTs-Fe 3 O 4 /NP-PtTi composite not only showed a remarkable synergistic effect towards the aptasensor, but also provided a beneficial immobilization platform for the streptomycin aptamer carrier.Under optimal conditions, a wide linear range from 0.05 to 100 ng mL À1 and a detection limit of 7.8 pg mL À1 were obtained. The designed aptasensor showed an excellent analytical performance with good reproducibility, high selectivity and stability. Finally, the proposed aptasensor was successfully used for the detection of streptomycin in a real sample.

A novel 18-nor-clerodane diterpenoid named sagitone (1) was isolated from the 95% ethanol extract of dry roots of Tinospora sagittata var. yunnanensis together with the five known diterpenoids columbin (2), palmatoside C (3), fibleucin (4), tinophylloloside (5) and epitinophylloloside (6). The structure of the new compound 1 was determined based on MS, IR, 1D and 2D NMR spectral data. The compounds 1~6 did not show significant cytotoxic activity against cancer cell lines K562 and HL-60.