Gold–Nickel Nanowires as Nanomotors for Cancer Marker Biodetection and Chemotherapeutic Drug Delivery

Future biomedical applications of nanomachines require elimination of fuel requirements since most of the fuels have potential toxic effects. Herein, we report fuel-free magnetically powered gold–nickel (Au–Ni) nanowires as nanomotors for multipurpose biomedical applications. Fabrication of the nanowire-based nanomotors developed in this study is unique, and this protocol was dependent on the electrochemical preparation of Au nanowires followed by the direct current (DC) magnetron sputtering of Ni part. DC magnetron sputtering-based preparation used for the first time in the literature not only ensured homogeneous distribution and rapid deposition of the metal directly but also provided reproducible thin layers of magnetic Ni resulting in a significant improvement at nanomotor speeds. Besides magnetic propulsion, acoustic propulsion was also successfully applied. The effects of both propusion mechanisms were tested on the speed and direction of Au–Ni nanomotors. Biomedical applications of the motors accomplished in this study are rapid and sensitive detection of an important cancer biomarker microRNA-21 (miRNA-21) and pH-dependent and near-infrared (NIR) triggered release of a commonly used chemotherapeutic drug doxorubicin (DOX). Sensitive and selective miRNA-21 detection was achieved by using dye-labeled single-stranded DNA (ssDNA probe) modified Au–Ni nanomotors with a wide linear concentration range of 0.01 nM to 25 nM. Low detection limits of 2.9 pM and 1.6 pM were obtained for fluorescence and speed-based detection, respectively (n = 3). In addition, magnetically powered DOX-loaded Au–Ni nanomotors were guided on cancer cells (human breast cancer cell lines, MCF-7) in a controllable way for the efficient and controlled delivery of DOX. Cytotoxicity studies of the nanomotors presented negligible influence on the cell viability.