Magnetically actuated nanomotor, which swims under externally applied magnetic fields, shows great promise for controlled cargo delivery and release in biological fluids. Here, we report an on-demand release of 6-carboxyfluoresceins (FAM), a green fluorescein, from G-quadruplex DNA functionalized magnetically actuated wormlike nanomotors by applying an alternating magnetic field. This field-triggered FAM releasing process can be easily controlled by multiple parameters such as magnetic field, frequency, and exposure time. In addition, the experimental results and the theoretical simulation demonstrate that both a thermal and a nonthermal mechanism are involved in the cargo releasing process.Keywords: cargo delivery; CoFe2O4 nanoparticles; HeLa cells; magnetic actuation; wormlike nanomotor;

•We demonstrate a novel SERS/fluorescence dual-mode nano-sensing system in which the conformational switching of the human telomeric G-quadruplexes results in the signal transduction.•Its SERS/fluorescence dual-modalities nature effectively extends the response range of the nanosensor, leading to significant improvement in the sensing performance.•It exhibits a LOD as low as 5 pM for Hg2+ ions, which is ~100 times more sensitive than conventional optical sensors.DNA-metal nanoparticle conjugates have been increasingly exploited for sensing purposes over the past decades. However, most of the existing strategies are operated with canonical DNA structures, such as single-stranded forms, stem-loop structures, and double helix structures. There is intense interest in the development of nano-system based on high order DNA secondary structures. Herein, we propose a SERS/fluorescence dual-mode nanosensor, where the signal transduction mechanism is based on the conformational switching of the human telomeric G-quadruplex DNA. The nanosensor exhibits excellent SERS/fluorescence responses to the complementary strands of G-quadruplexes. Based on T–Hg2+–T coordination chemistry, this sensor is effectively applied to determination of Hg2+ in buffer solution and real samples. It achieves a limit of detection (LOD) as low as 1 ppt, which is ~100 times more sensitive than conventional optical sensors. We anticipate that the proposed G-quadruplex-based nanosensor could be applied to the analysis of other metal ions and small molecules in environmental samples and biological systems.